Authors: J. E. Hirsch
The Meissner effect, the expulsion of magnetic field from the interior of a metal entering the superconducting state, is arguably the most fundamental property of superconductors, discovered in 1933. The conventional theory of superconductivity developed in 1957 is generally believed to fully explain the Meissner effect. We will review the arguments that support this consensus, rooted in the concept of emergence. However, recent work has shown that there are questions related to momentum conservation in the process of magnetic field expulsion that have not been addressed within the conventional theory. Within a reductionist approach, it has been proposed that those questions can only be resolved by introducing physics that is not part of the conventional theory, namely that there is radial motion of electric charge in the transition process. This is consistent with the behavior of classical plasmas, where motion of magnetic field lines is always associated with motion of charges. We review how this approach explains puzzles associated with momentum transfer between electrons and ions in the Meissner effect. Whether or not radial charge motion is associated with the Meissner effect has fundamental implications regarding superconductivity mechanisms in materials and regarding strategies to search for new materials with higher superconducting transition temperatures. Therefore, adjudication of this question is urgent and important.
Authors: Samudra Sur, Thierry Giamarchi
Persistent current is a hallmark of quantum phase coherence. We study the fate of the persistent current in a non-equilibrium setting, where a tight-binding ring is subjected to stochastic disorder as well as a fermionic reservoir attached to each site. We evaluate the current using Keldysh technique and find that it exhibits non-monotonic behavior, suggesting two distinct mechanisms of decoherence. While coupling to the reservoirs introduces a coherence length scale given by the inverse of the coupling strength, the other mechanism is more subtle and driven by the ratio of noise strength to reservoir coupling. The interplay of noise and reservoir constitutes a purely non-equilibrium steady state with a flatter distribution function that we effectively describe using classical rate equations. We discuss possibilities of realizing our findings in ultracold-atom experiments.
Authors: Bastian Castorene, Francisco J. Peña, Eric Suarez, Caio Lewenkopf, Martin HvE Groves, Natalia Cortés, Patricio Vargas
In this work, quantum Stirling engines based on monolayer, AB-stacked bilayer, and ABC-stacked trilayer graphene under perpendicular magnetic fields are analyzed. Performance maps of the useful work \((\eta W)\) reveal a robust optimum at low magnetic fields and moderately low temperatures, with all stackings capable of reaching Carnot efficiency under suitable configurations. The AB bilayer achieves this across the broadest parameter window while sustaining finite work, the monolayer exhibits highly constrained regimes, and the trilayer shows smoother trends with sizable \(\eta W\). These results identify multilayer graphene, particularly the AB bilayer, as a promising platform for efficient Stirling engines, while also highlighting the versatility of the monolayer in realizing all four operational regimes of the Stirling cycle.
Authors: Sakineh Vosoughi-nia, Michał P. Nowak
Altermagnets provide a new route to engineer superconducting circuits without magnetic fields. We theoretically study the Andreev bound state (ABS) spectrum of a finite-width altrmagnet-based Josephson junction and show how the $d$-wave altermagnetic symmetry and geometric confinement shape its low-energy excitations. We find a clear distinction between the two $d$-wave symmetries: $d_{x^2-y^2}$ order produces spin splitting, whereas $d_{xy}$ order preserves spin degeneracy and exhibits splitting of the ABS spectrum induced by intermode hybridization. Leveraging these novel features, we propose applying a transverse electric field to tune the system and realize a magnetic-field-free, parity-protected superconducting qubit that we call altermon.
Authors: Lucy L. Hale, Daniele De Bernardis, Stephan Lempereur, Lianhe H. Li, A. Giles Davies, Edmund H. Linfield, Trevor Blaikie, Chris Deimert, Zbigniew R. Wasilewski, Iacopo Carusotto, Jean-Michel Manceau, Mathieu Jeannin, Raffaele Colombelli, Jérôme Faist, Giacomo Scalari
We investigate the coupling of a multi-mode metal-insulator-metal cavity to a two-dimensional electron gas (2DEG) in a quantum well in the presence of a strong magnetic field. The TM cavity mode is strongly hybridized with an intersubband transition of the 2DEG, forming a polaritonic mode in the ultrastrong coupling regime, while the TE mode remains an almost purely cavity mode. The magnetoplasmon excitation emerging from the presence of the magnetic field couples with both TM and TE modes, exhibiting different coupling strengths and levels of spatial field inhomogeneity. While the strong homogeneity of the bare TE mode gives rise to the standard anticrossing of strong coupling, the inhomogeneous polaritonic TM mode is shown to activate an observable Coulombic effect in the spectral response, often referred to as non-locality. This experiment demonstrates a cavity-induced modification of the 2DEG response and offers a new route to probing the effect of Coulomb interactions in ultrastrongly coupled systems via reshaping of their cavity mode profiles.
Authors: Sonu Prasad Keshri, Guang-Yu Guo
We investigate the superconducting (SC) properties of experimentally realised $\gamma$-BiPd by solving the anisotropic Migdal-Eliashberg equations in conjunction with {\it ab initio} relativistic calculations of the electron and phonon band structures as well as electron-phonon coupling (EPC) matrix elements. Our study reveals that $\gamma$-BiPd possesses a complex Fermi surface (FS), consisting of two electron pockets and one hole pocket, each characterised by distinct atomic orbitals. Our key finding is that the superconductivity in $\gamma$-BiPd is primarily orbital-selective, arising from Bi $p$-orbitals, and distributed anisotropically on the FS, although contribution from Pd $d$-orbitals, particularly on the hole pocket, is also discernable. While our results show an anisotropic nature of the {\bf k}-dependent SC gap $\Delta_{\bf k}$ and EPC strength $\lambda_{\bf k}$ across the FS, calculated superconducting quasiparticle density of states $N_S$ spectra exhibit a U-shaped gap and $\Delta_{\bf k}$ distribution forms a single peak, being consistent with the spin-singlet $s$-wave superconductivity observed in this material. The calculated $T_c$ is $\sim$2.0 K, agreeing in order of magnitude with the experimental value of 3.3 K in $\gamma$-BiPd thin films. The predicted EPC-enhanced Sommerfeld coefficient $\gamma_n$ of $0.141$ mJ/K$^2$cm$^3$ is similar to the experimental $\gamma_n$ value ($0.119$ mJ/K$^2$cm$^3$) of the isoelectronic and isostructural Bi(Pd$_{0.5}$Pt$_{0.5}$) alloy.
Authors: Yeri Lee, Juseung Oh, Kyung Yeol Ma, Seung Jin Lee, Eui Young Jung, Yani Wang, Kenji Watanabe, Takashi Taniguchi, Hailin Peng, Hiroki Ago, Ki Kang Kim, Hyeon Suk Shin, Sunmin Ryu
Hexagonal boron nitride (hBN) supports a wide range of two-dimensional (2D) technologies, yet assessing its crystalline quality over large areas remains a fundamental challenge. Both antiparallel domains, an intrinsic outcome of epitaxy on high-symmetry substrates, and associated structural defects have long evaded optical detection. Here, we show that interferometric second-harmonic generation (SHG) imaging provides a powerful, nondestructive probe of lattice orientation and structural integrity in chemical vapor deposition-grown hBN. This approach reveals the ubiquitous formation of antiparallel domains and quantifies their impact on crystalline order. SHG intensity also emerges as a direct optical metric of domain disorder, spanning three orders of magnitude across films produced by ten different growth routes. Correlation with Raman spectroscopy establishes a unified framework for evaluating crystalline quality. Beyond hBN, this method offers a high-throughput route to wide-area structural imaging in various non-centrosymmetric materials, advancing their deployment in electronics, photonics, and quantum technologies.
Authors: Dhruv Srinivasan, Alex Beyer, Daiwei Zhu, Pranav Srikanth, Spencer Churchill, Kushagra Mehta, Sashank Kaushik Sridhar, Kushal Chakrabarti, David W. Steuerman, Nikhil Chopra, Avik Dutt
The Fermi-Hubbard model (FHM) is a simple yet rich model of strongly interacting electrons with complex dynamics and a variety of emerging quantum phases. These properties make it a compelling target for digital quantum simulation. Trotterization-based quantum simulations have shown promise, but implementations on current hardware are limited by noise, necessitating error mitigation techniques like circuit optimization and post-selection. A mapping of the FHM to a Z2 LGT was recently proposed that restricts the dynamics to a subspace protected by additional symmetries, and its ability for post-selection error mitigation was verified through noisy classical simulations. In this work, we propose and demonstrate a suite of algorithm-hardware co-design strategies on a trapped-ion quantum computer, targeting two key aspects of NISQ-era quantum simulation: circuit compilation and error mitigation. In particular, a novel combination of iteratively preconditioned gradient descent (IPG) and subsystem von Neumann Entropy compression reduces the 2-qubit gate count of FHM quantum simulation by 35%, consequently doubling the number of simulatable Trotter steps when used in tandem with error mitigation based on conserved symmetries, debiasing and sharpening techniques. Our work demonstrates the value of algorithm-hardware co-design to operate digital quantum simulators at the threshold of maximum circuit depths allowed by current hardware, and is broadly generalizable to strongly correlated systems in quantum chemistry and materials science.
Authors: Livia Correa McCormack, Lei Tang, Mathieu Francoeur
The enhancement and attenuation of near-field radiative heat transfer between polaritonic SiC, SiN and SiO2 subwavelength membranes is analyzed. Fluctuational electrodynamics simulations combined with a modal analysis show that all membranes support corner and edge modes, which can induce a large 5.1-fold enhancement for SiC and a 2.1-fold attenuation for SiO2 of the heat transfer coefficient with respect to that between infinite surfaces. The enhancement or attenuation is directly related to material losses which reduce the density of available electromagnetic states between the membranes.
Authors: Avijit Barua, Kartik Gaur, Leo J. Roche, Suk In Park, Priyabrata Mudi, Sven Rodt, Jin-Dong Song, Stephan Reitzenstein
The controlled integration of quantum dots (QDs) as single-photon emitters into quantum light sources is essential for the implementation of large-scale quantum networks. In this study, we employ the deterministic in-situ electron-beam lithography (iEBL) nanotechnology platform to integrate individual QDs with high accuracy and process yield into circular Bragg grating (CBG) resonators. Notably, CBG devices comprising just 3 to 4 rings exhibit photon extraction efficiencies comparable to those of structures with more rings. This facilitates faster fabrication, reduces the device footprint, and enables compatibility with electrical contacting. To demonstrate the scalability of this process, we present results of 95 optically active QD-CBG devices fabricated across two lithography sessions. These devices exhibit bright, narrow-linewidth single-photon emission with excellent optical quality. To evaluate QD placement accuracy, we apply a powerful characterization technique that combines cathodoluminescence (CL) mapping and scanning electron microscopy. Statistical analysis of these devices reveals that our iEBL approach enables high alignment accuracy and a process yield of over >90% across various CBG geometries. Our findings highlight a reliable route toward the scalable fabrication of high-performance QD-based single-photon sources for use in photonic quantum technology applications.
Authors: Mohsen Yarmohammadi, Libor Šmejkal, James K. Freericks
Altermagnets feature antiparallel spin sublattices with $d$-, $g$-, or $i$-wave spin order, yielding nonrelativistic spin splitting without net magnetization. We show that embedding a two-dimensional $d$-wave altermagnet in a driven optical cavity induces a finite, tunable magnetization. Coherent photon driving couples selectively to electronic sublattices, and the resulting altermagnets' symmetry-broken spin texture yields a pronounced steady-state spin imbalance -- coherent magnetization -- absent in conventional antiferromagnets for the same lattice configuration. A mean-field Lindblad analysis reveals the dominance of quadratic over linear couplings. In the strong-coupling regime, distinct polariton signatures emerge in the steady state of induced magnetization. This work demonstrates cavity control of altermagnets for spintronic applications.
Authors: Adel Ali, Alexey Belyanin
We study fermionic and bosonic systems coupled to a real or synthetic static gauge field that is quantized, so the field itself is a quantum degree of freedom and can exist in coherent superposition. A natural example is electrons on a quantum ring encircling a quantized magnetic flux (QMF) generated by a superconducting current. We show that coupling to a common QMF gives rise to an emergent interaction between particles with no classical analog, as it is topological and nonlocal (independent of interparticle distance). Moreover, the interaction persists even when the particles lie in a nominally field-free region, with the vector potential mediating the interaction. We analyze several one- and two-dimensional model systems, encompassing both real and synthetic gauge fields. These systems exhibit unusual behavior, including strong nonlinearities, non-integer Chern numbers, and quantum phase transitions. Furthermore, synthetic gauge fields offer high tunability and can reach field strengths that are difficult to realize with real magnetic fields, enabling engineered nonlinearities and interaction profiles.
Authors: Haoyuan Zhong, Xuanxi Cai, Changhua Bao, Fei Wang, Tianyun Lin, Yudong Chen, Sainan Peng, Lin Tang, Chen Gu, Zhensheng Tao, Hongyun Zhang, Shuyun Zhou
High-quality ultrafast light sources are critical for developing advanced time- and angle-resolved photoemission spectroscopy (TrARPES). While the application of high harmonic generation (HHG) light sources in TrARPES has increased significantly over the past decade, the optimization of the HHG probe beam size and selective control of the light polarization, which are important for TrARPES measurements, have been rarely explored. In this work, we report the implementation of high-quality HHG probe source with an optimum beam size down to 57 $\mu$m $\times$ 90 $\mu$m and selective light polarization control, together with mid-infrared (MIR) pumping source for TrARPES measurements using a 10 kHz amplifier laser. The selective polarization control of the HHG probe source allows to enhance bands with different orbital contributions or symmetries, as demonstrated by experimental data measured on a few representative transition metal dichalcogenide materials (TMDCs) as well as topological insulator Bi$_2$Se$_3$. Furthermore, by combining the HHG probe source with MIR pumping at 2 $\mu$m wavelength, TrARPES on a bilayer graphene shows a time resolution of 140 fs, allowing to distinguish two different relaxation processes in graphene. Such high-quality HHG probe source together with the MIR pumping expands the capability of TrARPES in revealing the ultrafast dynamics and light-induced emerging phenomena in quantum materials.
Authors: M. Q. Dong, B. Liu, Z. H. Dai, Zhi-Xin Guo, Hongjun Xiang, Xin-Gao Gong
Multiferroics, which combine ferroelectric and magnetic order, offer a transformative platform for next-generation electronic devices. However, the intrinsic competition between the mechanisms driving ferroelectricity and magnetism in single-phase materials severely limits their performance, typically resulting in weak magnetoelectric coupling at room temperature. Here, we propose a solution to this long-standing challenge through the novel concept of fractional quantum multiferroics (FQMF), where strong magnetoelectric coupling is naturally realized by coupling fractional quantum ferroelectricity (FQFE) with altermagnetism (AM). Symmetry analysis shows that reversing the FQFE polarization necessarily inverts the AM spin splitting under parity-time ($\mathcal{PT}$) or time-reversal ($\mathcal{T}\tau$) operations. A minimal tight-binding model reproduces this effect, demonstrating electrically driven spin control without rotating the Néel vector. First-principles calculations further identify a broad family of candidate materials in two and three dimensions including bulk MnTe, Cr$_2$S$_3$, Mn$_4$Bi$_3$NO$_{15}$ and two-dimensional AB$_2$ bilayers such as MnX$_2$ (X=Cl, Br, I), CoCl$_2$, CoBr$_2$, and FeI$_2$. Notably, MnTe exhibits a high Néel temperature ($\sim$300 K) and a large electrically switchable spin splitting ($\sim$0.8 eV), demonstrating room-temperature magnetoelectric performance that surpasses that of conventional multiferroics. To further showcase the technological potential, we propose an electric-field-controlled FQMF tunnel junction based on MnTe that achieves tunneling magnetoresistance exceeding 300\%. This work establishes FQMF as a distinct and promising route to achieving room-temperature strong magnetoelectric coupling, opening a new avenue for voltage-controlled spintronics.
Authors: Bin Jin, Bin Han, Wei Feng, Kuang Yu, Shenzhen Xu
Exact characterization of phase transitions requires sufficient configurational sampling, necessitating efficient and accurate potential energy surfaces. Molecular force fields with computational efficiency and physical interpretability are desirable but challenging to refine for complex interactions. To address this, we propose a force field refinement strategy with phase diagrams as top-down optimization targets based on automatic differentiation. Using gas-liquid co-existence as a paradigm, we employ an enhanced sampling technique and design a differentiable loss function to evaluate force fields' depiction of phase diagrams. The refined force fields produce gas-liquid phase diagrams matching well with targets for two modeling systems, which confirms our approach as an effective automated force field development framework for phase transition studies.
Authors: Yanling Pan, Qi Li, Gongping Zheng, Yongping Zhang
We propose the realization of a spin-2 Floquet spinor Bose-Einstein condensate via Floquet engineering of the quadratic Zeeman energy. In the Floquet system, the coupling strengths of all angular-momentum-conserving spin-flip processes are renormalized by driving-parameter-dependent Bessel functions. Such Floquet-engineered interactions significantly enriches possible ground states in homogeneous gases. The resulting phase diagrams, which map the distributions of these possible ground states, are presented in the space of the driving parameters.
Authors: Shah Hussain, Sikander Azam, Umme Habiba, Qaiser Rafiq, Amin Ur Rahman, Hamada H. Amer, Yasir Saeed
Rare earth doping is an effective way to convert chemically stable oxides into multifunctional materials with coupled electronic, optical, and magnetic properties. We present first principles calculations of pristine and Tm3+ doped Ca2SnO4 to understand how localized 4f states change the structural, electronic, magnetic, and optical behavior of the host. Pristine Ca2SnO4 is a mechanically stable, wide band gap insulator with mostly ionic covalent bonding and diamagnetic character. Replacing Ca2+ with Tm3+ introduces several key changes: (i) localized Tm 4f states create intermediate levels inside the wide gap, reducing the optical band gap; (ii) exchange and spin orbit interactions generate strong local magnetic moments and spin asymmetry near the conduction band; (iii) electron localization function analysis shows enhanced covalency and electron pockets that stabilize luminescent centers; and (iv) the optical response shows visible range absorption, refractive index features, and low energy plasmon peaks while maintaining high energy dielectric stability. These effects make Tm doped Ca2SnO4 a mechanically robust, optically tunable, and magnetically active oxide phosphor suitable for red emission, intermediate band photovoltaics, and spin photon coupling. More broadly, our results show how targeted rare earth substitution can enable multifunctionality in wide gap stannates and guide the design of next generation spintronic photonic oxides.
Authors: V. E. Timofeev, D. N. Aristov
A regular lattice of magnetic skyrmions is the ground state of thin ferromagnetic films with Dzyaloshinskii-Moriya interaction in a relatively wide range of external magnetic fields. It was previously theoretically shown that upon the increase of magnetic field a topological transition in the magnon spectrum of such skyrmion crystal (SkX) may occur. Non-uniform magnetic field may lead to localized magnon states emerging at the interface between two half-planes of SkX. Using semiclassical quantization and the stereographic projection approach, we study such appearing edge states both in a full band structure calculation and in simplified effective model. The latter effective model described by extended Dirac equation is applicable to two relevant magnon bands near $\Gamma$ point. We show that both the chirality of emerging edge states and the degree of its localization at the interface is controlled by magnetic field profile. We demonstrate that the localization length may be as small as a few inter-skyrmion distances.
Authors: Maniesha Singh, Anter El-Azab
A comprehensive analysis is presented for the diffusivity of oxygen defects and oxygen self-diffusion in ThO$-2$. The migration energy and diffusivity of oxygen defects with nominal charges have been investigated using density functional theory and phonon simulations. The pathway for the lowest migration energy barrier of oxygen vacancies was found to be along the $\langle 100 \rangle$ direction. Neutral and non-neutral oxygen interstitials exhibited direct (interstitial) and indirect (interstitialcy) migration, respectively. The vacancy migration barrier was found to be lowest for the highest charge, while for interstitials, it is lowest when the charge is lowest. The attempt frequencies of defects were calculated using the Eyring and Vineyard theories. These frequencies displayed a similar dependence on the defect charge as the activation barriers. The charge-averaged diffusivity of vacancies and interstitials were also computed. Across all temperatures, the average vacancy diffusivity was found to be greater than that of interstitial, indicating that oxygen vacancies are more mobile than interstitials. Oxygen self- and chemical diffusion coefficients were analyzed by combining the defect diffusivities with the concentrations computed using an equilibrium defect thermodynamics. The self-diffusion coefficient of oxygen was found to rise with temperatures and lower oxygen pressures. The contributions of various defects to self-diffusion of oxygen were subsequently examined. In the normal to high oxygen pressure range, at all temperatures, it is found that interstitials contribute most to oxygen diffusion in ThO2. At low oxygen pressures, vacancies with highest charge state were found to dominate oxygen diffusion. The chemical diffusion coefficient of oxygen was further computed, which was found to increase with temperature and decrease with hypo-stoichiometry in ThO2 to a plateau value.
Authors: Batyr Ilyas, Tianchuang Luo, Honglie Ning, Emil Vinas Bostrom, Alexander von Hoegen, Jaena Park, Junghyun Kim, Je-Geun Park, Angel Rubio, Nuh Gedik
The crystal lattice governs the emergent electronic, magnetic, and optical properties of quantum materials, making structural tuning through strain, pressure, or chemical substitution a key approach for discovering and controlling novel quantum phases. Beyond static modifications, driving specific lattice modes with ultrafast stimuli offers a dynamic route for tailoring material properties out of equilibrium. However, achieving dynamic coherent control of the nonequilibrium phases via resonant excitation of lattice coherences remains largely unexplored. Such manipulation enables non-volatile, on demand amplification and suppression of order parameters on femtosecond timescales, necessary for next generation optoelectronic ultrafast computation. In this study, we demonstrate coherent phononic control of a newly discovered, light-induced metastable magnetization in the van der Waals antiferromagnet FePS3. By using a sequence of terahertz (THz) pulses, we modulate the magnetization amplitude at the frequencies of phonon coherences, whose infrared-active nature and symmetries are further revealed by polarization- and field-strength-dependent measurements. Furthermore, our two-dimensional THz spectroscopy, in tandem with first-principles numerical simulations, shows that these phonons nonlinearly displace a Raman active phonon, which induces the metastable net magnetization. These findings not only clarify the microscopic mechanism underlying the metastable state in FePS3 but also establish vibrational coherences in solids as a powerful tool for ultrafast quantum phase control, enabling manipulation of material functionalities far from equilibrium.
Authors: Zhiyi Zhang, Gang Cui, Kai Jiang, An-Chang Shi, Pingwen Zhang, Jianyuan Yin, Lei Zhang
The Landau-Brazovskii model provides a theoretical framework for describing various phases arising from competing short- and long-range interactions in many physical systems. In this work, we investigate phase transitions among various ordered phases within the three-dimensional Landau-Brazovskii model. We construct the phase diagram of this model, which encompasses eight distinct phases, and systematically compute the transition pathways connecting various metastable and stable states using the Landau-Brazovskii saddle dynamics. Along each transition pathway, the critical nucleus is identified with some detailed analyses of its shape, energy barrier, and Hessian eigenvalues. Furthermore, we explore how the transition state is influenced by model parameters, revealing systematic trends in critical nucleus sizes and energy barrier heights. Our results provide a comprehensive characterization of the nucleation mechanisms within the Landau-Brazovskii model and offer valuable insights into the structural transformations of modulated-phase systems.
Authors: Caroline N. Cappetto, Penelope Messinger, Kaitlyn S. Yasumura, Miro Rothman, Tuan K. Do, Gao Wang, Liyu Liu, Robert H. Austin, Shengkai Li, Trung V. Phan
We present a minimal model for autonomous robotic swarms in one- and higher-dimensional spaces, where identical, field-driven agents interact pairwise to self-organize spacing and independently follow local gradients sensed through quantized digital sensors. We show that the collective response of a multi-agent train amplifies sensitivity to weak gradients beyond what is achievable by a single agent. We discover a fractional transport phenomenon in which, under a uniform gradient, collective motion freezes abruptly whenever the ratio of intra-agent sensor separation to inter-agent spacing satisfies a number-theoretic commensurability condition. This commensurability locking persists even as the number of agents tends to infinity. We find that this condition is exactly solvable on the rationals -- a dense subset of real numbers -- providing analytic, testable predictions for when transport stalls. Our findings establish a surprising bridge between number theory and emergent transport in swarm robotics, informing design principles with implications for collective migration, analog computation, and even the exploration of number-theoretic structure via physical experimentation.
Authors: Fan-Shun Meng, Shuhei Shinzato, Zhiqiang Zhao, Jun-Ping Du, Lei Gao, Zheyong Fan, Shigenobu Ogata
A neuroevolution potential (NEP) for the ternary $\alpha$-Fe--C--H system was developed based on a database generated from spin-polarized density functional theory (DFT) calculations, achieving empirical potential efficiency with DFT accuracy. At the same power consumption, simulation speeds using NEP are comparable to, or even faster than, those with bond order potentials. The NEP achieves DFT-level accuracy across a wide range of scenarios commonly encountered in studies of $\alpha$-Fe- and $\alpha$-Fe--C under hydrogen environments. The NEP enables large-scale atomistic simulations with DFT-level accuracy at the cost of empirical potentials, offering a practical tool to study hydrogen embrittlement in steel.
Authors: A. Aligayev, U. Jabbarli, U. Samadova, F. J. Dominguez-Gutierrez, S. Papanikolaou, Qing Huang
In this study, we employ a multi-scale computational modeling approach, combining density functional theory (DFT) and self-consistent charge density functional tight binding (SCC-DFTB), to investigate hydrogen (H2) production and dissociation mechanisms from ammonia (NH3) and methane (CH4) on pristine and nickel-doped graphene. These two-dimensional materials hold significant potential for applications in advanced gas sensing and catalysis. Our analysis reveals that Ni-doped graphene, validated through work function calculations, is a promising material for gas separation and hydrogen production. The samples with adsorbed molecules are characterized by calculating chemical potential, chemical hardness, electronegativity, electrophilicity, vibrational frequencies, adsorbtion and Gibbs energies by DFT calculations. Methane molecules preferentially adsorb at the hexagonal ring centers of graphene, while ammonia inter-acts more strongly with carbon atoms, highlighting distinct molecular doping mechanisms for CH4 and NH3. Dynamic simulations show that CH4 splits into CH3+H, with Ni-doped graphene facilitating enhanced hydrogen transmission, while NH3 dissociates into NH2+H, which may lead to N2H4 formation. Our non-equilibrium Green's function (NEGF) simulations demonstrate increased H-atom transmission on Ni-doped graphene during gas interactions. These findings suggest that Ni-doped graphene is superior to pristine graphene for applications in gas separation, hydrogen production, and high-sensitivity sensors.
Authors: Babak Benam, Abolfazl Ramezanpour
Human mobility, enabled by diverse transportation modes, is fundamental to urban functionality. Studying these movements across scales-from microscopic to macroscopic-yields valuable insights into urban dynamics. Local adaptation and (self-)organization in such systems are expected to result in dynamical behaviors that are represented by stationary trajectories of an appropriate effective action. In this study we develop a Lagrangian dynamical model for movement processes, using local population functions as the coordinate variables. An efficient gradient descent algorithm is introduced to estimate the optimal Lagrangian parameters minimizing a local error function of the dynamical process. We show that even a quadratic Lagrangian, incorporating dissipation, effectively captures the dynamics of synthetic and empirical movement data. The inferred models reveal that inertia and dissipation are of comparable importance, while interactions and randomness in the movements induce significant qualitative changes in model parameters. Our results provide an interpretable and generative model for human mobility, with potential applications in movement prediction.
Authors: James P. Connolly (GeePs), Ahmed Nejim, Alexandre Jaffré (GeePs), J Alvarez (IPVF, GeePs), Kleider J.P. (GeePs), Denis Mencaraglia (GeePs), Laurie Dentz (C2N), Geraldine Hallais (C2N), Frédéric Hamouda (C2N), Laetitia Vincent (C2N), Daniel Bouchier (C2N), Charles Renard (C2N)
This work reports optical and electronic numerical modelling of a novel emerging structure which is the GaAs nanocrystal on Si tandem solar cell by epitaxial lateral overgrowth, a technique which allows defect free material growth. The techniqueconsists of creating nucleation sites in a silicon surface SiO2 layer and initiating growth of nanoscalescale seeds, whereby strain energy remains below the Matthews-Blakeslee strain relaxation limit. This leads to AlxGaAs growth in micro-crystals without generation of material defects. The focus of this presentation is optical and electrical modelling of nanocrystals for applications in the very active field of silicon based multijunction solar cells, and design of a AlxGaAs/Si two terminal tandem, for compositions ranging from x=0 to x=30% in absorber layers. We present a model of the complete structure in two dimensions, consisting of a Al xGaAs high bandgap subcell connected with a tunnel junction to the low bandgap Si junction. The elaboration of models is described, with an emphasis on the AlxGaAs crystal featuring a non-planar pn-junction, and a focus on the optical properties of this lattice of micrometric AlGaAs crystals and in particular their light trapping properties from the resulting surface texture. The question of AlxGaAs surface coverage is addressed, given that neighbouring AlxGaAs crystals have different crystal orientations on a (111) Si surface, such that any coalescence of neighbour AlxGaAs crystals leads to crippling defects at their interface. The result is that some high energy incident light above the AlxGaAs bandgap is nevertheless transmitted directly to the Si cell, such that the resulting photogenerated carriers thermalise to the Silicon bandgap, and result in a loss of efficiency. The interface between AlxGaAs and Si subcells is addressed, with an emphasis on current transport efficiency through the nanoseeds and tunnelling currents through appropriately designed SiO2 buffer layers. This work therefore presents a theoretical framework for evaluating the potential of AlxGaAs nanocrystal growth on Si for light trapping, for GaAs silicon two terminal tandem cell performance including tunnel junctions, and provides models and design rules for efficient AlxGaAs microcrystal arrays as high bandgap subcells for tandem solar cells on silicon.
Authors: O. Goisot, H. vanLandeghem, R. Haettel, F. Robaut, O. Robach, L. Porcar, M. Verdier
Improvement of functional and structural fatigue endurance for applications of ferroelastic materials requires an optimization of their composition. A strategy for finding alloy compositions that minimize the transformation hysteresis is necessary. We propose an experimental high throughput methodology to explore the model \b{eta}-Cu-Zn-Al system. It is based on an original route to process bulk gradient composition single crystals to investigate fine variation of composition range coupled with local measurements of the austenite-martensite microstructure by light microscopy during the transformation. The latter method is compared with differential scanning calorimetry measurements. The methodology is applied in an Al-richer range of composition of standard CuZnAl SMA where a minimum of transformation hysteresis is observed.
Authors: Pooja Bhat, Wafa Maftuhin, Michael Walter
Bond rupture under the action of external forces is induced by temperature fluctuations. We show that measured forces from single molecule force spectroscopy experiments can be predicted from two quantities describing the bond that are the barrier to break the bond in absence of force as well as the maximal force the bond can withstand. The former can be obtained by a force free transition state calculation and the latter is determined by a simple constrained ge- ometry simulates forces (COGEF) calculation. Considering experimental temperature and force loading rate allows the prediction of measured bond rupture forces from a closed expression with very good accuracy.
Authors: Pierre Gosselin (IF), Aïleen Lotz
In a previous paper, we applied a field formalism to analyze capital allocation and accumulation within a microeconomic framework of investors and firms. The financial connections were modeled by a field of stakes, representing the links between agents. We showed that the resulting collective states were composed of interconnected groups of agents defined by their connections, their returns and disposable capital. However, within this framework, the collective states exhibited structural instability, as capital shortages in specific sectors could trigger cascades of defaults. The present model refines this framework by introducing a third type of agent, banks, a type of investor that can create money through loans. We show that money creation neither eliminates systemic instability nor prevents the emergence of defaults. In fact, the effect of banks on system stability and defaults is ambiguous: When banks favor firms over investors, money creation stabilizes the system by providing the necessary capital to prevent initial defaults, whereas when banks favor investors over firms, investors' influence is strengthened, potentially amplifying instability and defaults. Moreover, regardless of whether they favor investors or firms, banks may facilitate the propagation of defaults once they have started. Ultimately, because banks are themselves investors, the emergence of highly capitalized, high-return banks can directly generate instability in the system. Beyond these mechanisms, the analysis reveals the structural limits of macroprudential regulation. Highly capitalized, high-return investors and banks may appear more diversified and resilient, yet they constitute the primary source of endogenous instability. The model thus highlights that systemic fragility is inherent to the very structure of financial interdependence and capital flows.
Authors: Claude Godrèche, Jean-Marc Luck
The distribution of the first positive position reached by a random walker starting at the origin is central to the analysis of extremes and records in one-dimensional random walks. In this work, we present a detailed and self-contained analytical study of this distribution for symmetric finite-range lattice walks, whose steps are drawn from a distribution supported on finitely many integers.
Authors: Christina Gasper, Nisa Ulumuddin, Siyuan Zhang, Sang-Hyeok Lee, Christina Scheu, Benjamin Berkels, Zhuocheng Xie, Sandra Korte-Kerzel
Intermetallics often exhibit complex crystal structures, which give rise to intricate defect structures that critically influence their mechanical and functional properties. Despite studies on individual defect types, a comprehensive understanding of the defect landscape in {\mu}-phases, a class of topologically close-packed phases, remains elusive. In this study, we investigated the planar defect structures in the Ta-Fe {\mu}-phase across a compositional range of 46 to 58 at.% Ta using electron microscopy and density functional theory calculations. Electron backscatter diffraction and high-resolution scanning transmission electron microscopy reveal a transition from basal twin boundaries and planar faults containing C14 TaFe2 Laves phase layers at a low Ta content to pyramidal {1\bar{1}02} twins at a higher Ta content. Density functional theory calculations of defect formation energies confirm a chemical potential-driven stabilisation of Laves phase lamellae. The prevalence of pyramidal twins in Ta-rich {\mu}-phase samples is attributed to the competitive nature of different planar defects during solidification. A defect landscape for {\mu}-phases is proposed, illustrating the interplay between site occupancy, dislocation types and planar faults across the chemical potential space. These findings provide fundamental insights into defect engineering in structurally complex intermetallics and open pathways for optimising material properties through chemical tuning.
Authors: Gijin Kim, Purun-hanul Kim, Suk Gyu Hahm, Myongjong Kwon, Byungha Park, Changho Hong, Seungwu Han
Area-selective atomic layer deposition (AS-ALD) is an emerging technology in semiconductor manufacturing. However, accurately understanding inhibitor reactivity on surfaces remains challenging, particularly when the substrate is amorphous. In this study, we employ density functional theory (DFT) to investigate reaction pathways and quantify the reactivity of (N,N-dimethylamino)trimethylsilane (DMATMS) and ethyltrichlorosilane (ETS) at silanol (-OH), siloxane (-O-), amine (-NH2), and imide (-NH-) sites on both amorphous and crystalline silicon oxide and silicon nitride surfaces. Notably, both molecules exhibit greater reactivity toward terminal sites (-OH and -NH2) on amorphous surfaces compared to crystalline counterparts. For bridge sites, -O- and -NH-, multiple reaction pathways are identified, with bridge-cleavage reactions being the predominant mechanism, except for DMATMS reactions with nitride surfaces. The reactivity of DMATMS with -NH- sites is comparable to that with -NH2, with both reactions yielding volatile products. This study underscores the importance of amorphous surface modeling in reliably predicting inhibitor adsorption and reactivity on realistic surfaces. Moreover, we outline a computational screening approach that accounts for site-specific precursor-inhibitor interactions, enabling efficient and rational theoretical design of AS-ALD precursor-inhibitor pairs.
Authors: Bogdan R. Bułka, Tadeusz Domański, Karol I. Wysokiński
We investigate a hybrid device, consisting of two quantum dots proximized by a BCS superconductor and coupled to two external normal electrodes. Assuming charge tunneling between quantum dots through the spin-flip processes, we study the molecular Andreev bound states appearing in the proximized quantum dots. We show that the spin-orbit coupling induces four quasiparticle states. For the appropriate set of model parameters, two of these internal quasiparticles merge, forming the zero-energy state. Under such circumstances, we obtain fully spin-polarized versions of the Majorana quasiparticles, localized on different quantum dots. This situation occurs solely when the spin-orbit interaction is equally strong to the magnitude of crossed Andreev reflections, i.e. in the sweet spot. Otherwise, these processes are competitive, as indicated in expectation values of the corresponding order parameters. We analyze signatures of such competition manifested under the nonequilibrium conditions, for various configurations of bias voltage. In particular, for the symmetric bias voltage between the normal electrodes and the Cooper pair splitter bias configuration we reveal duality in the transport properties. Charge transport through the zero-energy state at the sweet spot is contributed by perfectly entangled electrons with an (almost) ideal transmission. Transport studies would thus enable empirical detection of the molecular quasiparticle states and the efficiency of dissipation processes caused by the external normal electrodes.
Authors: Seyed Mahdi Mastoor, Amirhossein Ahmadkhan Kordbacheh
Theoretical research has been conducted to study how geometry affects charge and spin transport in $\beta\mathrm{12}$ borophene quantum dots, which are confined systems. The study examined two distinct central regions, which included a circular disc and a regular hexagonal area that connected to semi-infinite zigzag and armchair borophene nanoribbon leads. The system was described by a five-band tight-binding Hamiltonian parameterized using first-principles data, and the transport properties were calculated within the non-equilibrium Green's function framework. Spin resolved transmissions and spin polarization were computed for a range of lead widths and proximity-induced exchange field strengths. The analysis revealed distinct transport characteristics determined by geometry and edge configuration: armchair-connected structures exhibited broader and more stable fully spin-polarized windows compared with zigzag-connected counterparts. Furthermore, critical lead-width thresholds ($\approx 1.01$ nm for zigzag and $\approx 0.87$ nm for armchair) and a moderate exchange field above which complete spin filtering occurs were identified. The results highlight the strong influence of edge termination and confinement geometry on transport properties and provide useful design guidelines for developing borophene-based nanoscale spintronic devices.
Authors: D. Pecchio, S. Sahoo, V. Scagnoli, L. J. Heyderman
Artificial spin ices (ASIs) provide a versatile platform to explore magnetic frustration and emergent phenomena. However, in kagome ASI, experimental access to the ground state remains elusive due to dynamical freezing. Here, we demonstrate a deterministic and rewritable approach to attain the ground state using ultrafast, site-selective laser annealing. By engineering sublattice-dependent optical absorption through selective capping of the nanomagnets with Cr or utilizing different nanomagnet thicknesses, we achieve selective partial demagnetization of one sublattice under a sub-coercive magnetic field, driving the system into the ground state in a single switching step. Magnetic force microscopy reveals nearly perfect long-range ordering, while heat-transfer simulations confirm the sublattice-selective excitation mechanism. This work establishes an ultrafast method to attain the kagome ASI ground state, which does not require a modification of the geometry of the ASI or the materials used for the individual nanomagnets. Beyond ground-state writing, this site-selective activation provides an important tool for controlling the magnetic states, which is important for applications such as reconfigurable magnonic crystals, neuromorphic computing and programmable nanomagnetic logic.
Authors: Taras Holovatch, Yuri Kozitsky, Krzysztof Pilorz, Yurij Holovatch
The following model is studied analytically and numerically: point particles with masses $m,\mu,m, \dots$ ($m\geq\mu$) are distributed over the positive half-axis. Their dynamics is initiated by giving a positive velocity to the particle located at the origin; in its course the particles undergo elastic collisions. We show that, for certain values of $m/\mu$, starting from the initial state where the particles are equidistant the system evolves in a hydrodynamic way: (i) the rightmost particle (blast front) moves as $t^{\delta}$ with $\delta < 1$; (ii) recoiled particles behind the front enter the negative half-axis; (iii) the splatter -- the particles with locations $x\leq 0$ -- moves in the ballistic way and eventually takes over the whole energy of the system. These results agree with those obtained in S. Chakraborti et al, SciPost Phys. 2022, 13, 074, for $m/\mu=2$ and random initial particle positions. At the same time, we explicitly found the collection of positive numbers $\{\mathcal{M}_i, i \in \mathbf{N} \}$ such that, for $m/\mu = \mathcal{M}_i$, $i\leq 700$, the following holds: (a) the splatter is absent; (b) the number of simultaneously moving particles is at most three; (c) the blast front moves in the ballistic way. However, if, similarly as in S. Chakraborti et al, the particle positions are sampled from a uniformly distributed ensemble, for $m/\mu = \mathcal{M}_i$ the system evolves in a hydrodynamic way.
Authors: T.B. Charikova, A.Yu. Pavlova, M.R. Popov, A.V. Pozdin, L.N. Maskaeva
We present the results of measurements of bulk current-voltage (I-V) characteristics and local surface I-V characteristics by atomic force microscopy (AFM) of iodine-doped PbS films. It is established that bulk I-V curves of both undoped and iodine-doped PbS films demonstrate a linear (ohmic) U(I) dependence. The tipe of local surface I-V characteristics is ohmic at the concentration range of the dopant 0<[NH4I]<=0.10 M and becomes rectifying at [NH4I]>=0.15 M, which is determined by a decrease in the size and a change in the shape of the film grains, as well as a decrease in the surface roughness of the film. An increase in the iodine content in the PbS(I) films leads to nonlinear dependences of the microscopic characteristics and photoelectric parameters of the PbS(I) films. A sharp decrease in the diffusion coefficient, the beginning of an increase in the charge carrier lifetime, a maximum in voltage sensitivity and specific detectability are observed in the PbS(I) film chemically deposited from a reaction mixture containing [NH4I] = 0.15 M. This indicates that the optimalconcentration of iodine in the film is 2.7 at.%.
Authors: Vaishnavi Gajendragad, Suropriya Saha
We explore the concept of memory in scalar active matter systems, focusing on the collective dynamics of particles whose interactions depend on their evolutionary history rather than on their present configuration. We do so by introducing the idea of an active particle whose velocity acquires an active contribution that depends on its past trajectory suitably weighted by a memory kernel. The memory kernel is unrelated to the thermal noise acting on the particle, meaning that the particle breaks detailed balance at the microscopic level. The number density of these active particles is described by a Cahn-Hilliard equation, which typically describes passive phase separation, suitably modified to account for this particular non-equilibrium effect. Through theory and simulations we establish the novel emergent features of the model and use the example of time delayed interactions to highlight the novel pattern-forming abilities of the model.
Authors: Kai Chen, Pavan Hosur
The superconducting diode effect (SDE), characterized by a nonreciprocal supercurrent, has attracted significant attention in recent years due to its potential applications. However, most studies have focused on weakly correlated models, leaving the impact of strong electron-electron interactions on the SDE largely unexplored. In this work, we bridge this gap by investigating the SDE in asymmetric band metals with Hatsugai-Kohmoto (HK) interaction, which are exactly solvable due to their locality in Bloch momentum space. Through a combination of low-energy analysis and a numerical self-consistent approach, we demonstrate that HK interaction can enhance the SDE's quality factor. Our findings shed light on the role of strong electron-electron correlations in shaping the SDE.
Authors: Hongwen Zhang, Bowen Ai, Zekun Gong, Tianyi Sui, Zuzanna S. Siwy, Yinghua Qiu
Nanoporous membranes, leveraging their high-throughput characteristics, have been widely applied in fields such as molecular separation and energy conversion. Due to interpore interactions, besides the applied voltage and solution environment, the ion transport properties in porous membranes are influenced by the pore number and spacing. Here, to understand and control the transport properties of nanopore arrays, we systematically investigate the ion transport characteristics through membranes with different charge properties, pore numbers, and interpore distances. Using numerical simulations, we analyzed local ionic concentrations and electric potential in nanopore arrays containing nanopores with uniformly charged walls as well as unipolar diodes i.e., pores containing a junction between a charged zone and a neutral zone, and showed significant ion concentration polarization (ICP) for all studied cases. As the number of pores increased and the interpore spacing decreased, the enhanced interpore interactions through ICP led to a greater deviation of the total ionic current from the linear superposition of single-pore currents. Conversely, in bipolar nanopores whose walls contain a junction between positively and negatively charged zones ICP becomes negligible, and interpore interactions are substantially reduced. Furthermore, for membranes with various charge properties, the total current through nanopore arrays presents different quantitative dependence on the pore number under varying pore spacings. Our findings clarify the mechanism of interpore interactions in modulating ion transport through porous membranes, providing critical insights for designing nanofluidic devices based on nanopore arrays, such as nanopore-array sensors.
Authors: Meryem Bouaziz, Samir El Masaoudi, Aymen Mahmoudi, Eva Desgue, Marco Pala, Pavel Dudin, Mathieu G. Silly, Julien Chaste, Fabrice Oehler, Pierre Legagneux, Jose Avila, Iann C. Gerber, Abdelkarim Ouerghi
Van der Waals (vdW) heterostructures, which combine bi-dimensional materials of different properties, enable a range of quantum phenomena. Here, we present a comparative study between the electronic properties of mono- and bi-layer of platinum diselenide (PtSe2) grown on hexagonal boron nitride (h-BN) and graphene substrates using molecular beam epitaxy (MBE). Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), the electronic structure of PtSe2/graphene and PtSe2/h-BN vdW heterostructures are investigated in systematic manner. In contrast to PtSe2/h-BN, the electronic structure of PtSe2/graphene reveals the presence of interlayer hybridization between PtSe2 and the graphene, which is evidenced by minigap openings in the {\pi}-band of graphene. Furthermore, our measurements show that the valence band maximum (VBM) of monolayer PtSe2 is located at the {\Gamma} point with different binding energies of about -0.9 eV and -0.55 eV relative to the Fermi level on h-BN and graphene and substrates, respectively. Our results represent a significant advance in the understanding of electronic hybridization between TMDs and different substrates, and they reaffirm the crucial role of the substrate in any nanoelectronic applications based on van der Waals heterostructures.
Authors: Xin Chen, Jin Zou, Lipeng Song, Wei Sun, Yiwen Wu, Luyao Zhu, Xu Cheng, Duo Wang, Biplab Sanyal
Altermagnets combine zero net magnetization with giant spin splitting, enabling spin-polarized transport without strong spin-orbit coupling (SOC). Deterministically selecting the conducting spin channel, however, requires breaking the 90 degree rotation and time-reversal antisymmetry (C4zT). Using standard axial vector transformation rules as preliminaries, we show that in monolayer Ta2TeSeO this can be achieved naturally and tuned in a symmetry efficient way by rotating the Neel vector. Without considering the Neel vector, Ta2TeSeO has one pair of mirror protected spin polarized Weyl points in each spin channel. Aligning the Neel vector along the crystallographic x or y direction breaks the mirror symmetry Mx or My, inducing selective mirror symmetry breaking that keeps one spin sector gapless and opens a gap in the opposite spin, yielding fully spin polarized transport. The C2z symmetry breaking makes the preserved two Weyl points inequivalent, turning the half semimetal into a half metallic state. The same orientation selective symmetry reduction applies to lattice vibrations, implying phonon chirality splitting. Owing to the near degenerate in plane anisotropy, reversible zero moment switching is achievable with minute in plane strain or weak magnetic fields, and the lattice coupling suggests control by circularly polarized light. The mechanism extends to other two dimensional decorated Lieb altermagnets lacking horizontal mirror Mz, providing a general low power route to spin filtering and logic.
Authors: Dezhong Tong, Andrew Choi, Jiaqi Wang, Weicheng Huang, Zexiong Chen, Jiahao Li, Xiaonan Huang, Mingchao Liu, Huajian Gao, K. Jimmy Hsia
Flexible slender structures such as rods, ribbons, plates, and shells exhibit extreme nonlinear responses bending, twisting, buckling, wrinkling, and self contact, that defy conventional simulation frameworks. Discrete Differential Geometry (DDG) has emerged as a geometry first, structure preserving paradigm for modeling such behaviors. Unlike finite element or mass spring methods, DDG discretizes geometry rather than governing equations, allowing curvature, twist, and strain to be defined directly on meshes. This approach yields robust large deformation dynamics, accurate handling of contact, and differentiability essential for inverse design and learning based control. This review consolidates the rapidly expanding landscape of DDG models across 1D and 2D systems, including discrete elastic rods, ribbons, plates, and shells, as well as multiphysics extensions to contact, magnetic actuation, and fluid structure interaction. We synthesize applications spanning mechanics of nonlinear instabilities, biological morphogenesis, functional structures and devices, and robotics from manipulation to soft machines. Compared with established approaches, DDG offers a unique balance of geometric fidelity, computational efficiency, and algorithmic differentiability, bridging continuum rigor with real time, contact rich performance. We conclude by outlining opportunities for multiphysics coupling, hybrid physics data pipelines, and scalable GPU accelerated solvers, and by emphasizing DDG role in enabling digital twins, sim to real transfer, and intelligent design of next generation flexible systems.
Authors: Urmimala Dey, Natalya S. Fedorova, Jorge Íñiguez-González, Hugo Aramberri
Chirality in solids is attracting growing attention as a potential ferroic order, yet virtually no paradigmatic example of a soft-mode achiral-to-chiral phase transition has been firmly established to date. Here we identify ferroelectric bubble domains as a model system that undergoes a strain-driven achiral-to-chiral transition exhibiting the hallmarks of spontaneous symmetry breaking. Using second-principles atomistic simulations, we uncover chiral phonon modes in ferroelectric/dielectric superlattices that soften under epitaxial strain following textbook soft-mode behaviour. The transition is accompanied by a change in topological character, highlighting an interplay between chirality and topology in these systems. This work provides a concrete step towards establishing chirality as a genuine ferroic order in solids.
Authors: Timur Aslyamov, Krzysztof Ptaszyński, Massimiliano Esposito
Gaussian macroscopic fluctuation theory underpins the understanding of noise in a broad class of nonequilibrium systems. We derive exact fluctuation-response relations linking the power spectral density of stationary fluctuations to the linear response of stable nonequilibrium steady states. Both of these can be determined experimentally and used to reconstruct the kernel of the linearized dynamics and the diffusion matrix, and thus any features of the Gaussian theory. We apply our theory to gene regulatory networks with negative feedback, and derive an explicit internal-external noise decomposition of the power spectral density for any networks, including cross-correlations.
Authors: A.Ya. Maltsev
We investigate the probability of detecting the most nontrivial conductivity behavior regimes in metals whose electron spectrum is described by the tight-binding approximation. These regimes are associated with the emergence of highly complex electron trajectories on the Fermi surface and correspond to a nontrivial (scaling) behavior of the conductivity tensor in strong magnetic fields. The geometry of such trajectories, as well as the corresponding conductivity regimes, have been well studied theoretically; however, they have not yet been observed experimentally. The results of our study allow us, in particular, to estimate the probability of their occurrence and to indicate the conditions for their possible detection for a wide class of conductors.
Authors: Claudio Bellani, Simon Mellaerts, Wei-Fan Hsu, Koen Schouteden, Alberto Binetti, Arno Annys, Zezhong Zhang, Nicolas Gauquelin, Johan Verbeeck, Jesús López-Sánchez, Adolfo del Campo, Soon-Gil Jung, Tuson Park, Michel Houssa, Jean-Pierre Locquet, Jin Won Seo
Ordered corundum oxides introduce new prospects in the field of functional oxides thin films, complementing the more widely studied class of ABO$_3$ perovskites. In this work, we take advantage of the layer-by-layer growth regime to fabricate epitaxial CrVO$_3$ superlattice thin films with atomic-scale accuracy on the periodic arrangement of Cr and V layers. By means of X-ray diffraction, scanning transmission electron microscopy and Raman spectroscopy, we confirm the thickness control in the sub-unit cell scale, alternating 3, 2 or 1 single atomic layers of Cr$_2$O$_3$ and V$_2$O$_3$. For the first time, we stabilize the ilmenite phase of CrVO$_3$ (space group R-3) and compare the functional properties of the thin film with those calculated by density functional theory. This novel approach to the growth of ordered corundum oxides opens the path towards the stabilization of new complex oxides with tailored properties by varying the composition and the superlattice period, ultimately broadening the family of functional rhombohedral oxides.
Authors: Hui-Min Zhang, Cheng-Ao Ji, Tong Zhu, Hongjun Xiang, Hiroshi Kageyama, Shuai Dong, James M. Rondinelli, Xue-Zeng Lu
We present a comprehensive theoretical investigation of magnetoelectric (ME) coupling mechanisms in 19 altermagnetic and 4 ferrimagnetic Type-I multiferroics using electronic band structure calculations with spin-orbit coupling, a first-principles ME response framework, and spin-space-group theory analysis. We formulate a universal scheme for realizing nonvolatile ME coupling in Type-I multiferroics, where two distinct pathways emerge, each dictated by spin-space symmetry. The first pathway is associated with switching of the spin splitting or the now familiar spin-momentum locking in reciprocal space, characteristic of some altermagnetic mul-tiferroics that exhibit coexisting antiferromagnetism and ferroelectricity. The second pathway involves real-space magnetization switching via electric polarization reversal, characterized by switchable components of the linear ME tensor, despite the traditionally weak coupling in Type-I systems due to the independent origins of magnetism and ferroelectricity. We demonstrate that these two intrinsic ME coupling mechanisms are mutually exclusive and propose thermodynami-cally stable compounds for experimentation. Our findings establish general design principles for controlling robust nonvolatile ME effects in multiferroic materials.
Authors: Landon Johnson, Walter Malone, Jason Rizk, Renai Chen, Tammie Gibson, Michael W. D. Cooper, Galen T. Craven
The formation and subsequent growth of structural defects in an irradiated material can strongly influence the material's performance in technological and industrial applications. Predicting how the growth of defects affects material performance is therefore a pressing problem in materials science. One common computational approach that is used to examine defect growth is cluster dynamics, a method which employs a system of mean-field rate equations to track the time evolution of concentrations of individual defect types. However, the computational complexity of performing cluster dynamics can limit its practical implementation, specifically in the context of exploring a broad set of physical conditions corresponding to, for example, different temperatures and pressures. Here, we present a machine learning approach to circumvent the computational challenges of performing cluster dynamics while maintaining high accuracy in the prediction of defect concentrations. The method is illustrated on the nuclear material uranium nitride but is broadly applicable to other materials. The developed data-driven method is shown to accurately capture complex correlations between material properties, temperature, irradiation conditions, and the concentration of defects.
Authors: Andrea Pelissetto, Ettore Vicari
A fundamental issue in the renormalization-group (RG) theory of critical phenomena concerns the allowed values of critical exponents that are consistent with the continuous nature of a phase transition. Here we conjecture a lower bound for the length-scale exponent $\nu$ that should hold at continuous transitions associated with $d$-dimensional Landau-Ginzburg-Wilson (LGW) $\Phi^4$ theories with a multicomponent scalar field $\varphi_i$ (including some extensions with fermionic and gauge fields). If $\Delta_\varphi=(d-2+\eta)/2$ is the dimension of the order parameter -- $\varphi_i$ in LGW models -- and $\Delta_\varepsilon=d-1/\nu$ is the RG dimension of the energy operator $\varepsilon$, which can be identified with $[\sum_i \varphi_i^2]$ (the squared field with a proper subtraction of the mixing with the identity), we conjecture the inequality $\Delta_\varepsilon - 2 \Delta_\varphi\ge 0$, which implies $1/\nu \le 2-\eta$ and $\gamma = (2-\eta)\nu\ge 1$. These inequalities are supported by general arguments for lattice models, exact relations for two-dimensional minimal conformal field theories, and are consistent with all known (numerical, perturbative, and exact) results for LGW $\Phi^4$ theories. In particular, since unitarity requires $\eta\ge 0$, the above inequality implies $\nu\ge 1/2$ for unitary theories. This lower bound is more restrictive than the bound $\nu > 1/d$, which is derived by noting that $\nu=1/d$ is the expected behavior at first-order transitions.
Authors: Júlio P. A. Santos, Margarida M. Telo da Gama, Rodrigo C. V. Coelho
We investigate the dynamics of elastic capsules suspended in two-dimensional active nematic fluids using lattice Boltzmann simulations. The capsules, modeled as flexible membranes enclosing active internal regions, exhibit a rich variety of behaviors shaped by their geometry and the interplay between internal and external activity. Circular capsules with active interiors undergo persistent rotation driven by internally confined +1/2 topological defects. Axisymmetric capsules, such as boomerangs, develop directed motion along their axis of symmetry due to unbalanced active forces generated by defect distributions near their boundaries. We further show that capsule flexibility suppresses motility and rotation, as active stresses are dissipated into shape deformations. These findings reveal how shape, deformability, and defect dynamics cooperate to produce emergent motility in soft active matter, with potential applications in the design of microswimmers and drug delivery vehicles.
Authors: Hidekazu Kurebayashi, Giovanni Finocchio, Karin Everschor-Sitte, Jack C. Gartside, Tomohiro Taniguchi, Artem Litvinenko, Akash Kumar, Johan Åkerman, Eleni Vasilaki, Kemal Selçuk, Kerem Y. Çamsarı, Advait Madhavan, Shunsuke Fukami
Spin-based computing is emerging as a powerful approach for energy-efficient and high-performance solutions to future data processing hardware. Spintronic devices function by electrically manipulating the collective dynamics of the electron spin, that is inherently non-volatile, nonlinear and fast-operating, and can couple to other degrees of freedom such as photonic and phononic systems. This review explores key advances in integrating magnetic and spintronic elements into computational architectures, ranging from fundamental components like radio-frequency neurons/synapses and spintronic probabilistic-bits to broader frameworks such as reservoir computing and magnetic Ising machines. We discuss hardware-specific and task-dependent metrics to evaluate the computing performance of spin-based components and associate them with physical properties. Finally, we discuss challenges and future opportunities, highlighting the potential of spin-based computing in next-generation technologies.
Authors: Soumyaditya Das, Soumyajyoti Biswas, Muktish Acharyya, Bikas K. Chakrabarti
We briefly review the early development of the mean-field dynamics for cooperatively interacting quantum many-body systems, mapped to pseudo-spin (Ising-like) systems. We start with (Anderson, 1958) pseudo-spin mapping of the BCS (1957) Hamiltonian of superconductivity, reducing it to a mean-field Hamiltonian of XY (or effectively Ising) model in a transverse field. Then we get the mean-field estimate for the equilibrium gap in the ground state energy at different temperatures (gap disappearing at the transition temperature), which fits Landau's (1949) phenomenological theory of superfluidity. We then present in detail a general dynamical extension of the mean-field theory of quantum Ising systems (in a transverse field), following de Gennes' (1963) decomposition of the mean field into orthogonal classical cooperative (longitudinal) component and the quantum (transverse) component, with each of the components following Suzuki-Kubo (1968) mean-field dynamics. Next we discuss its applications to quantum hysteresis in Ising magnets (in presence of oscillating transverse field), to quantum heat engines (employing transverse Ising model as working fluid), and to the quantum annealing of the Sherrington-Kirkpatrick (1975) spin glass by tuning down (to zero) the transverse field which provided us a very fast computational algorithm leading to ground state energy values converging to the best known analytic estimate for the model. Finally, we summarize the main results obtained and conclude about the effectiveness of the de Gennes-Suzuki-Kubo mean-field equations for the study of various dynamical aspects of quantum condensed matter systems.
Authors: Katelyn Lazareno, Christopher Chae, Becky Haight, Shams Jabin, Rachel Steinhardt, John J. Plombon, Siddharth Rajan, Patrick M. Woodward, Jinwoo Hwang, Fengyuan Yang
To investigate the scope of ferroelectric behavior in La-substituted BiFeO3 films, LaxBi1-xFeO3 epitaxial films were synthesized using off-axis co-sputtering on SrTiO3(001) and DyScO3(110) substrates with a SrRuO3 bottom electrode layer. A digital-doping deposition method was used to enable precise control and continuous tuning of La concentration in high-quality LaxBi1-xFeO3 films across a wide range of x = 0.05-0.60, which was systematically investigated using piezoresponse force microscopy. Robust and reversible out-of-plane ferroelectric switching has been observed up to x = 0.35, while films with x $\geq$ 0.37 exhibit no measurable ferroelectric behavior, indicating a sharp ferroelectric-to-paraelectric phase transition between x = 0.35 and 0.37. This represents the highest reported La concentration in LaxBi1-xFeO3 films that retains ferroelectric ordering, highlighting opportunities to engineer ferroelectric and multiferroic properties in complex oxide heterostructures.
Authors: Hao Wang, Jiayu Yuan, Hongkai Shi, Haojie Li, Xiaoqing Jia, Xiaohui Song, Liyu Shi, Tianyi Wu, Li Yue, Yangmu Li, Kui Jin, Dong Wu, Jianlin Luo, Xinbo Wang, Tao Dong, Nanlin Wang
Detection of the Higgs mode in superconductors using nonlinear terahertz spectroscopy is a key area of interest in condensed matter physics. We investigate the influence of disorder on the nonlinear terahertz response and the Higgs mode in NbN thin films with varying Ioffe-Regel parameters ($k_Fl$). In strongly disordered films near the superconductor-insulator transition (SIT), we observe an anomalous third-harmonic generation (THG) signal above $T_c$, which is absent in both cleaner superconducting and non-superconducting counterparts. The persistence of this normal-state THG signal in a high magnetic field excludes superconducting fluctuations as its origin. Below $T_c$, the THG intensity increases sharply, indicating a dominant contribution from the driven Higgs mode. The THG spectrum of the strongly disordered sample exhibits a broadened, multi-peak structure, which we attribute to quantum path interference between distinct channels involving unpaired electrons and Cooper pairs within emergent superconducting islands. Our findings not only demonstrate how disorder tunes the nonlinear terahertz response but also uncover a strong coupling between electrons responsible for normal-state THG and the superconducting Higgs mode below $T_c$ in strongly disordered samples.
Authors: Livia A. J. Guttieres, Ryan K. Krueger, Remi Drolet, Michael P. Brenner
Designing heterogeneous, self-assembling systems is a central challenge in soft matter and biology. We present a framework that uses gradient-based optimization to invert an analytical yield calculation, tuning systems toward target equilibrium yields. We design systems ranging from simple dimers to temperature-controlled shells to polymerizing systems, achieving precise control of self- and non-self-limiting assemblies. By operating directly on closed-form calculations, our framework bypasses trajectory-based instabilities and enables efficient optimization in otherwise challenging regimes.
Authors: Sebastiano Battisti, Matteo Pioldi, Alessandro Paghi, Giorgio De Simoni, Alessandro Braggio, Giulio Senesi, Lucia Sorba, Francesco Giazotto
We present a groundbreaking demonstration of thermal modulation in a field-effect-controllable semiconductor-superconductor hybrid structure, wherein the heating mechanism is exclusively radiative. The architecture comprises two reservoirs separated by $\sim 1$ mm and interconnected via a completely non-galvanic electrical circuit, enabling the transfer of black-body radiation from the hot to the cold reservoir. Our device utilizes a superconducting Josephson field-effect transistor to achieve magnetic-field-free gate-tunable regulation of heat currents within the circuit. While prior studies have indicated the potential for electrostatic modulation of thermal transport properties, our framework demonstrates a temperature modulation of up to $\sim 45$ mK, exceeding prior findings by more than an order of magnitude. Furthermore, it proves a thermal transimpedance of $\sim 20$ mK/V at a bath temperature of $30$ mK. The development of such systems holds substantial promise for advancing heat management and routing in quantum chips and radiation sensors, as it enables precise nonlocal control of heat flow towards a designated structure, even when the heat source is distant and non-galvanically coupled.
Authors: Gökhan Altıner, Jons Bolding, Yiğit Mert Kaplan, Floor Souren, Hindrik de Vries, Raşit Turan, Hisham Nasser
Tandem solar cells offer a promising alternative to exceed the efficiency limits of single-junction silicon photovoltaics, yet they require high-performance recombination junctions that are transparent, passivating, and electrically efficient. Indium tin oxide (ITO), which is conventionally used as a recombination junction material, faces challenges related to indium scarcity and sputter-induced damage. This work investigates hydrogenated aluminum-doped zinc oxide (AZO:H) deposited by spatial atomic layer deposition (s-ALD) as a viable indiumfree alternative for TOPCon-based bottom cells. The deposited AZO:H films demonstrate excellent transparency, exceeding 90% in the 380-1200 nm wavelength range. When applied to n-TOPCon surfaces with an AlOx capping layer, the stack achieves an outstanding passivation quality, indicated by implied open-circuit voltage (iVoc) values up to 734 mV after annealing. The AlOx capping layer proved crucial for enhancing thermal stability by preventing hydrogen effusion at higher temperatures. While the contact resistivity was high for the 20 nm thick films tested, the combination of superior optical and passivation properties establishes spatial ALD-deposited AZO:H as a highly promising material for creating efficient and indiumfree recombination junctions in next-generation tandem solar cells.
Authors: Kristiana Mihali, Dennis Wörthmüller, Pierre Sens
Cell shape changes are largely controlled by the actin cytoskeleton, a dynamic filament network beneath the plasma membrane. Several cell types can form extended free-standing protrusions not supported by an extracellular substrate or matrix, and regulated by proteins that modulate cytoskeletal dynamics in a way sensitive to the curvature of the cell membrane. We develop a theoretical model for the mechanics of a free-standing viscous actin network growing on a corrugated membrane. The model couples the dynamics of the viscous active gel with membrane deformation and the recruitment of curvature-sensitive actin nucleators. We show that an actin layer polymerising uniformly on the membrane always exerts a stabilising effect that reduces membrane deformation. However, curvature-sensitive actin nucleator proteins can render the membrane linearly unstable, depending on the interplay between membrane and actin dynamics, giving rise to spontaneous membrane deformation which could initiate extended free-standing cellular protrusion.
Authors: E. Bortchagovsky, A.V. Chumak, V. Lozovski
Brillouin light scattering (BLS) is a key technique in studying magnonic systems, but its sensitivity is often limited. While nanoplasmonic systems can enhance BLS through near-field effects, we propose a novel approach for additional amplification. In this conceptual paper, we show how to actively supply energy to a surface collective electromagnetic resonance (SCR) supported by a sparse layer of metal nanoparticles on a magnetic film. Proposed methods are designed to significantly amplify the efficiency of surface-enhanced Brillouin light scattering without increasing the intensity of the primary excitation. In the proposed scheme, the pump extends the propagation length of the SCR, leading directly to BLS amplification. We analyze the conditions for such amplification, with numerical estimates indicating a potential gain of more than an order of magnitude in the surface-wave amplitude. This gain far surpasses the modest increase achievable through passive enhancement alone. These findings outline a practical pathway to achieving BLS amplification in integrated magnonic platforms.
Authors: K. R. Prathyusha, Paulami Sarkar, Justin Xu, Saad Bhamla
Living organisms employ diverse strategies to navigate confined environments. Inspired by translocation observations on California blackworms (\textit{Lumbriculus variegatus}), we combine biological experiments and active-polymer simulations to examine how confinement and stiffness govern translocation. Active filaments translocate fastest when the channel width is comparable to their diameter, with escape time determined by propulsion speed, filament length, and channel geometry. In wider channels, activity and flexibility induce reorientation-dominated conformational changes that prolong escape. A single dimensionless ratio linking confinement to stiffness captures the transition from axis-aligned escape with short wall deflections for stiffer filaments, to reorientation-controlled motion with blob-like shapes for flexible filaments. These results provide a unified physical framework for active translocation in confinement and suggest design principles for flexible robotic filaments in complex environments.
Authors: Nicolas Harmand, Julien Dervaux, Christophe Poulard, Sylvie Hénon
We measured the thickness of MDCK epithelia grown on substrates with a sinusoidal profile. We show that while at long wavelength the profile of the epithelium follows that of the substrate, at short wavelengths cells are thicker in valleys than on ridges. This is reminiscent of the so-called « healing length » in the case of a thin liquid film wetting a rough solid substrate. We explore the ability of continuum mechanics models to account for these observations. Modeling the epithelium as a thin liquid film, with surface tension, does not fully account for the measurements. Neither does modeling the epithelium as a thin incompressible elastic film. On the contrary, the addition of an apical active stress gives satisfactory agreement with measurements, with one fitting parameter, the ratio between the active stress and the elastic modulus.
Authors: Brenden W. Hamilton, Alexander R. Muñoz, Travis E. Jones, Benjamin T. Nebgen
The cerium iso-structural phase transition (gamma to alpha) is dominated by f-electron localization changes that results in a magnetic ordering change and a volume collapse. Generally, these physics are difficult to capture with ab initio and first principles methods. However, previous works have shown various methods to be successful in predicting at least some of the physics of the gamma to alpha phase transition. Therefore, here, we perform a broad survey of density functional based methods across three levels of theory and types of functions (GGA, MetaGGA, and Hybrid functionals) and compare the results, focusing on hydrostatic compression across the phase boundary at zero Kelvin. For the methods that best reproduce experimental results, we directly probe the predicted mechanisms and frame the results in the Mott/Kondo debate, assessing how the underlying methods and assumptions of different functionals can assess the physical drivers in the phase transition, providing insight into the governing dynamics of this unique phase transition.
Authors: Sana Kordoghli, Abdelhakim Settar, Oumayma Belaati, Mohammad Alkhatib
This work contributes to advancing sustainable energy and waste management strategies by investigating the thermochemical conversion of food-based biomass through pyrolysis, highlighting the role of artificial intelligence (AI) in enhancing process modelling accuracy and optimization efficiency. The main objective is to explore the potential of underutilized biomass resources, such as spent coffee grounds (SCG) and date seeds (DS), for sustainable hydrogen production. Specifically, it aims to optimize the pyrolysis process while evaluating the performance of these resources both individually and as blends. Proximate, ultimate, fibre, TGA/DTG, kinetic, thermodynamic, and Py-Micro GC analyses were conducted for pure DS, SCG, and blends (75% DS - 25% SCG, 50% DS - 50% SCG, 25% DS - 75% SCG). Blend 3 offered superior hydrogen yield potential but had the highest activation energy (Ea: 313.24 kJ/mol), while Blend 1 exhibited the best activation energy value (Ea: 161.75 kJ/mol). The kinetic modelling based on isoconversional methods (KAS, FWO, Friedman) identified KAS as the most accurate. These approaches provide a detailed understanding of the pyrolysis process, with particular emphasis on the integration of artificial intelligence. An LSTM model trained with lignocellulosic data predicted TGA curves with exceptional accuracy (R^2: 0.9996-0.9998).
Authors: Martin Ryzy, Guqi Yan, Clemens Grünsteidl, Georg Watzl, Kevin Sequoia, Pavel Lapa, Haibo Huang
In inertial confinement fusion experiments hollow, spherical mm-sized capsules are used as a container for nuclear fuel. To achieve maximum implosion efficiency, a perfect capsule geometry is required. This paper presents a wall thickness measurement method based on zero-group velocity guided elastic wave resonances. They are measured with a non-destructive, contactless frequency domain laser ultrasound microscopy system. Wall thickness measurements along the equator of a high-density carbon capsule with a diameter of around 2 mm and a wall thickness of around 80 $\unicode{x00B5}$m excellently agree with infrared interferometry reference measurements. In addition, the multi-resonant nature of a spherical shell is studied by complementing experimental observations with plate dispersion calculations and finite element wave propagation simulations. The presented method is scalable and can be applied to a broad range of target materials, including metals, or metal-doped targets.
Authors: Martin Ryzy, Guqi Yan, István Veres, Thomas Berer, Ivan Alić, Clemens Grünsteidl, Georg Watzl, Georg Gramse, Susanne Kreuzer
Nanometric layer thickness imaging is crucial for fundamental research and characterization of micro fabricated devices. Here, we assess the potential of a non-contact opto-acoustic frequency domain laser ultrasound (FreDomLUS) microscopy technique for imaging nanometric thickness variations via GHz zero-group velocity (ZGV) elastic plate resonances. The method exploits the ZGV's lateral energy confinement that leads to sharp resonance peaks which can be effectively probed with the FreDomLUS technique at GHz acoustic frequencies. For demonstration purposes we introduced sub-10 nm height variation patterns in the topmost layer of solidly mounted bulk-acoustic wave resonators with a design frequency of around 1.7 GHz. They are raster-scanned to retrieve ZGV-frequencies from local acoustic spectra as a contrast quantity for imaging. We show how to retrieve quantitative height information by numerically calibrating the factor which inversely relates ZGV frequency change with the layer thickness change. Height variations in stacks with nominal thickness changes of 8 nm, 4 nm, and 1 nm can be resolved and indicate sub-nanometer depth resolution capabilities. The lateral resolution is studied by measuring the method's step edge function and it is found to be in the micrometer range. Atomic force microscopy imaging is used to validate the results.
Authors: Fanmeng Wang, Shan Mei, Wentao Guo, Hongshuai Wang, Qi Ou, Zhifeng Gao, Hongteng Xu
Polymers, macromolecules formed from covalently bonded monomers, underpin countless technologies and are indispensable to modern life. While deep learning is advancing polymer science, existing methods typically represent the whole polymer solely through monomer-level descriptors, overlooking the global structural information inherent in polymer conformations, which ultimately limits their practical performance. Moreover, this field still lacks a universal foundation model that can effectively support diverse downstream tasks, thereby severely constraining progress. To address these challenges, we introduce PolyConFM, the first polymer foundation model that unifies polymer modeling and design through conformation-centric generative pretraining. Recognizing that each polymer conformation can be decomposed into a sequence of local conformations (i.e., those of its repeating units), we pretrain PolyConFM under the conditional generation paradigm, reconstructing these local conformations via masked autoregressive (MAR) modeling and further generating their orientation transformations to recover the corresponding polymer conformation. Besides, we construct the first high-quality polymer conformation dataset via molecular dynamics simulations to mitigate data sparsity, thereby enabling conformation-centric pretraining. Experiments demonstrate that PolyConFM consistently outperforms representative task-specific methods on diverse downstream tasks, equipping polymer science with a universal and powerful tool.
Authors: Karol Sajnok, Michał Matuszewski
Backpropagation learning algorithm, the workhorse of modern artificial intelligence, is notoriously difficult to implement in physical neural networks. Equilibrium Propagation (EP) is an alternative with comparable efficiency and strong potential for in-situ training. We extend EP learning to both discrete and continuous complex-valued wave systems. In contrast to previous EP implementations, our scheme is valid in the weakly dissipative regime, and readily applicable to a wide range of physical settings, even without well defined nodes, where trainable inter-node connections can be replaced by trainable local potential. We test the method in driven-dissipative exciton-polariton condensates governed by generalized Gross-Pitaevskii dynamics. Numerical studies on standard benchmarks, including a simple logical task and handwritten-digit recognition, demonstrate stable convergence, establishing a practical route to in-situ learning in physical systems in which system control is restricted to local parameters.
Authors: Leopoldo A. Pando Zayas, Jingchao Zhang
Near-extremal black holes are known to contain strong quantum fluctuations in their near-horizon near-AdS$_2$ throat region governed by an effective action that includes Schwarzian modes. These fluctuations lead to one-loop corrections in the gravitational path integral that are essential in understanding the thermodynamics of near-extremal black holes at low temperatures where they become more dominant that the semi-classical answer. We explore the implications of these quantum fluctuations for near-extremal asymptotically AdS$_4$ black branes in the context of the AdS/CFT correspondence. We note that at one-loop level there is a coupling of the shear gravitational fluctuations to one of the would-be zero modes. This coupling affects the retarded Green's function in a way that leads to a low temperature violation of the shear viscosity to entropy density bound.
Authors: Charles Rhys Campbell, Aldo H. Romero, Kamal Choudhary
Generative models have become significant assets in the exploration and identification of new materials, enabling the rapid proposal of candidate crystal structures that satisfy target properties. Despite the increasing adoption of diverse architectures, a rigorous comparative evaluation of their performance on materials datasets is lacking. In this work, we present a systematic benchmark of three representative generative models- AtomGPT (a transformer-based model), Crystal Diffusion Variational Autoencoder (CDVAE), and FlowMM (a Riemannian flow matching model). These models were trained to reconstruct crystal structures from subsets of two publicly available superconductivity datasets- JARVIS Supercon 3D and DS A/B from the Alexandria database. Performance was assessed using the Kullback-Leibler (KL) divergence between predicted and reference distributions of lattice parameters, as well as the mean absolute error (MAE) of individual lattice constants. For the computed KLD and MAE scores, CDVAE performs most favorably, followed by AtomGPT, and then FlowMM. All benchmarking code and model configurations will be made publicly available at this https URL.
Authors: Felix Kogel, Tatsam Garg, Phillip Groß, Lukas Leczek, Marian Rockenhäuser, Neil Shah, Jakob Weiß, Andreas Schindewolf, Tim Langen
Optical Bloch equations and rate equations serve as powerful tools to model light-matter interactions from textbook-like two-level atoms to the complex internal dynamics of molecules. A particular challenge in this context is posed by molecular laser cooling, where many dozens or hundreds of levels need to be taken into account for a comprehensive modeling. Here, we present MoleCool, a numerically efficient Python toolbox to implement and solve the corresponding differential equation systems. We illustrate both the capabilities of the toolbox and some of the intricacies of molecular laser cooling by educational examples, which range from simple Rabi oscillations to spontaneous and coherent cooling schemes for various currently studied or considered molecular species. This includes, in particular, a comprehensive modeling of laser cooling dynamics with full hyperfine structure resolution in radioactive radium monofluoride (RaF), as well as studies of other complex species such as barium monofluoride (BaF) and ytterbium monohydroxide (YbOH).
Authors: Rajesh Asapanna, Clément Hainaut, Alberto Amo, Álvaro Gómez-León
We study the noisy dynamics of periodically driven, discrete-step quantum walks in a one-dimensional photonic lattice. We find that in the bulk, temporal noise that is constant within a Floquet period leads to decoherence-free momentum subspaces, whereas fully random noise destroys coherence in a few time-steps. When considering topological edge states, we observe decoherence no matter the type of temporal noise. To explain these results, we derive a non-perturbative master equation to describe the system's dynamics and experimentally confirm our findings in a discrete mesh photonic lattice implemented in a double-fibre ring setup. Surprisingly, our results show that a class of bulk states can be more robust to a certain type of noise than topological edge states.
Authors: Paulo R. A. Campos, Sandro M. Reia, José F. Fontanari
The standard Axelrod model of cultural dissemination, based on discrete cultural traits, exhibits a non-equilibrium phase transition but is inherently limited by its inability to continuously probe the critical behavior. We address this limitation by introducing a generalized Axelrod model utilizing continuous cultural traits confined to the interval $[0,1]$, and a similarity threshold, $d$, that serves as a continuous control parameter representing cultural tolerance. This framework allows for a robust analysis of the model's critical properties and its dynamics under cultural drift (copying noise). For the perfect copying scenario, we precisely locate the critical threshold $d_c$, which separates the disordered (fragmented) and ordered (polarized) phases. Through Finite-Size Scaling, we find that the mean domain density vanishes continuously at $d_c$ with the exponent $\beta = 1/3$. Simultaneously, the largest domain fraction displays a surprising discontinuous jump at $d_c$. We find that the finite size effects in the critical region are governed by the exponent $\nu=2$ for both the continuous and discontinuous transitions. Under imperfect copying, persistent noise introduces a powerful selective pressure on the trait space, leading to the emergence of two symmetry-related attractors at the trait values $d$ and $1-d$. However, these noise-induced attractors prove fragile in the thermodynamic limit, becoming unstable at large lattice sizes, which directly accounts for the observed failure of the dynamics to freeze under sustained cultural drift. This suggests that in large, continuously evolving societies, true cultural convergence is highly unlikely, leading instead to sustained fragmentation and nonstationary dynamics where cultural domains never fully stabilize.
Authors: Ning Sun, Peng Zhang, Pengfei Zhang
Understanding the emergence of complex correlations in strongly interacting systems remains a fundamental challenge in quantum many-body physics. One fruitful approach is to develop solvable toy models that encapsulate universal properties shared by realistic systems. In this work, we introduce the Brownian SYK-Hubbard model, which combines the all-to-all random interactions of the Sachdev-Ye-Kitaev (SYK) model with on-site Hubbard-type interactions. This hybrid construction enables the study of the interplay between nonlocal random dynamics and local correlation effects: (1) As the interaction strength increases, the single-particle spectrum exhibits a transition from a single peak to a two-peak structure, signaling the onset of Mottness. (2) The spectral form factor undergoes a sequence of dynamical transitions as the evolution time increases before reaching the plateau in the long-time limit under strong Hubbard interactions. (3) The out-of-time-order correlator is computed by summing a series of modified ladder diagrams, which determines the quantum Lyapunov exponent and reveals a violation of the bound on branching time. Our results establish a new analytically tractable platform for exploring the effects of Hubbard interactions in chaotic many-body systems.
Authors: Arkaprava Sil, Sudipto Singha Roy
Kinetic constraints in quantum many-body systems give rise to quantum states, whose behavior strongly depends on the choice of initial conditions. In recent years, these systems have drawn increasing interest because they provide insight into the mechanisms of thermalization and the situations where it can fail. In this work, we study a family of kinetically constrained models, including the celebrated Quantum Game of Life, from the perspective of quantum complexity, with a focus on entanglement, nonstabilizerness, and signatures of quantum chaos. By applying spectral diagnostics such as level statistics and spectral form factors, we demonstrate that these models show robust chaotic behavior while also supporting Hilbert space fragmentation and quantum many-body scar states. Remarkably, we find that even certain symmetry-resolved fragmented sectors can themselves host scarred eigenstates, highlighting the unexpected coexistence of chaos, scars, and fragmentation within the same family of Hamiltonians. To better understand these fragmented subspaces, we further characterize them using their quantum resource generation ability. In particular, we demonstrate that characterization of entanglement and the ability to generate nonstabilizerness can be instrumental in distinguishing different dynamically disconnected sectors.
Authors: Cassidy Ashworth, Pietro Liò, Francesco Caso
Deep learning models have proven enormously successful at using multiple layers of representation to learn relevant features of structured data. Encoding physical symmetries into these models can improve performance on difficult tasks, and recent work has motivated the principle of parameter symmetry breaking and restoration as a unifying mechanism underlying their hierarchical learning dynamics. We evaluate the role of parameter symmetry and network expressivity in the generalisation behaviour of neural networks when learning a real-space renormalisation group (RG) transformation, using the central limit theorem (CLT) as a test case map. We consider simple multilayer perceptrons (MLPs) and graph neural networks (GNNs), and vary weight symmetries and activation functions across architectures. Our results reveal a competition between symmetry constraints and expressivity, with overly complex or overconstrained models generalising poorly. We analytically demonstrate this poor generalisation behaviour for certain constrained MLP architectures by recasting the CLT as a cumulant recursion relation and making use of an established framework to propagate cumulants through MLPs. We also empirically validate an extension of this framework from MLPs to GNNs, elucidating the internal information processing performed by these more complex models. These findings offer new insight into the learning dynamics of symmetric networks and their limitations in modelling structured physical transformations.
Authors: Seyed Mohammad Hosseiny, Abolfazl Pourhashemi Khabisi, Jamileh Seyed-Yazdi, Milad Norouzi, Somayyeh Ghorbani, Asad Ali, Saif Al-Kuwari
Quantum thermometry leveraging quantum sensors is investigated with an emphasis on fundamental precision bounds derived from quantum estimation theory. The proposed sensing platform consists of two dissimilar qubits coupled via capacitor, which induce quantum oscillations in the presence of a thermal environment. Thermal equilibrium states are modeled using the Gibbs distribution. The precision limits are assessed through the Quantum Fisher Information (QFI) and the Hilbert-Schmidt Speed (HSS), serving as stringent criteria for sensor sensitivity. Systematic analysis of the dependence of QFI and HSS on tunable parameters -such as qubit energies and coupling strengths- provides optimization pathways for maximizing temperature sensitivity. Furthermore, we explore two distinct quantum thermometry paradigms: (I) local temperature estimation directly performed by Alice, who possesses the quantum sensor interfacing with the thermal bath, and (II) remote temperature estimation conducted by Bob, facilitated via quantum teleportation. In the latter scenario, temperature information encoded in the qubit state is transmitted through a single-qubit quantum thermal teleportation protocol. Our findings indicate that direct measurement yields superior sensitivity compared to remote estimation, primarily due to the inherent advantage of direct sensor-environment interaction. The analysis reveals that increasing Josephson energies diminishes sensor sensitivity, whereas augmenting the mutual coupling strength between the qubits enhances it.
Authors: Pierre Coulombel, Fabian Denner
While it is well known that cavitation occurs in liquids under tension, no universally accepted criterion for its onset in transient pressure fields exists. We propose a precise definition of the critical tension for cavitation in transient pressure fields that bridges the gap between quasi-static and dynamic regimes, identifying cavitation as the transition of the bubble radius to a dynamically unstable state. This threshold depends on the instantaneous state of the gas-liquid system and, when combined with an appropriate set of dimensionless parameters, yields a self-similar description of cavitation onset. Phase maps for different liquids reveal a minimum tension required for the onset of cavitation, determined by the duration of the tension event and the initial bubble size, whereby the well-known Blake threshold is the lower bound for cavitation across all conditions.
Authors: Giovanni Miano, Loris Maria Cangemi, Carlo Forestiere
The control of interactions among quantum emitters through nanophotonic structures offers significant potential for quantum technologies. However, a rigorous theoretical description of the interaction of multiple quantum emitters with complex dispersive dielectric objects remains highly challenging. Here we introduce an approach based on the modified Langevin noise formalism that unveils the roles of both the noise polarization currents of the dielectrics and the vacuum fluctuations of the electromagnetic field scattered by the dielectrics. This extends Refs. \cite{miano_quantum_2025}, \cite{miano_spectral_2025} to the general case of an arbitrary number of emitters. The proposed approach allows us to describe the dynamics of the quantum emitters for arbitrary initial quantum states of the electromagnetic environment consisting of two independent bosonic reservoirs, a medium-assisted reservoir and a scattering-assisted reservoir, each characterized by its own spectral density matrix. Understanding how these reservoirs shape emitter dynamics is crucial to understanding light-matter interactions in complex electromagnetic environments and to enhancing intrinsic emitter properties in structured environments.
Authors: Anbang Yang, Xiaoyu Nie, Hao Lin Yu, Yiming Liu, Victor Avalos, Canming He, Jacek Klos, Svetlana Kotochigova, Kai Dieckmann
The narrow transition from the lowest rovibrational level of the $\mathrm{X}^{1}\Sigma^{+}$ electronic ground state to the lowest vibrational level of the $\mathrm{b}^{3}\Pi_{0}$ potential provides opportunities for achieving magic-wavelength trapping of ultracold bialkali molecules for enhancing their rotational coherence times. Guided by existing spectroscopic data of several perturbed and deeply-bound rovibrational states of the $\mathrm{A}^{1}\Sigma^{+}$ potential [Grochola et al., Chem. Phys. Lett., 2012, 535, 17-20], we conducted a targeted spectroscopic search and report the first observation of the lowest vibrational level of the $\mathrm{b}^{3}\Pi_{0}$ state in $^{6}\mathrm{Li}^{40}\mathrm{K}$. The transition frequency from $|\mathrm{X}^{1}\Sigma^{+},\,v=0,\,J=0>$ to $|\mathrm{b}^{3}\Pi_{0},\,v'=0,\,J'=1>$ is determined to be 314,230.5(5)GHz. Assisted by microwave spectroscopy, we resolved the rotational structure of $|\mathrm{b}^{3}\Pi_{0},\,v'=0>$ and extracted a rotational constant of $h\times8.576(44)$ GHz for the $\mathrm{b}^{3}\Pi_{0}$ state. From this, we deducted an energy separation between $|\mathrm{b}^{3}\Pi_{0},v'=0,J'=0>$ and $|\mathrm{X}^{1}\Sigma^{+},v=0,J=0>$ of $hc\times$10,481.03(2) $\mathrm{cm}^{-1}$. Our work provides timely and precise information on the deeply-bound region of the $\mathrm{b}^{3}\Pi_{0}$ triplet excited potential of LiK, and benefits future applications of ultracold LiK isotopologues in quantum simulation and quantum computation that demand long coherence times.
Authors: Mu Qiao, Romain Martin, Lukas Homeier, Ivan Morera, Bastien Gély, Lukas Klein, Yuki Torii Chew, Daniel Barredo, Thierry Lahaye, Eugene Demler, Antoine Browaeys
Understanding how particles bind into composite objects is a ubiquitous theme in physics, from the formation of molecules to hadrons in quantum chromodynamics and the pairing of charge carriers in superconductors. The formation of bound states usually originates from attractive interactions between particles. However, the binding can also arise purely from the motion of dopants due to kinetic frustration, which is potentially related to unconventional pairing in moiré materials. Here, we report the first direct observation of kinetically-induced bound states between holes and magnons using a Rydberg atom array quantum simulator of the bosonic $t$-$J$ model in frustrated ladders and 2D lattices. First, we demonstrate the formation of mobile one-hole-one-magnon bound states. We then construct three-particle one-hole-two-magnon bound states and reveal the underlying binding mechanism by observing kinetically-induced singlet correlations. Finally, we investigate how mobile dopants structure their magnetic environment in a spin-balanced 2D triangular lattice, showing that a hole induces $120^\circ$ antiferromagnetic order, while a doublon dopant generates in-plane ferromagnetic correlations. Our results demonstrates compelling evidence of kinetically-induced binding, opening a new avenue to understand novel pairing mechanisms in correlated quantum materials like superconductors in moiré superlattices.
Authors: Bin Sui, Yihao Wang, Jiaju Zhang
We investigate the short-interval expansion of the subsystem fidelity in two-dimensional conformal field theories (2D CFTs) using the operator product expansion (OPE) of twist operators. We obtain universal contributions from general quasiprimary operators valid for arbitrary 2D CFTs, along with specific results in free massless boson and fermion theories. The analytical predictions demonstrate excellent agreement with established analytical results in field theories and numerical calculations in integrable models. Furthermore, we extend the method to holographic CFTs, where subsystem fidelity serves to analyze the distinguishability of black hole microstates through the AdS/CFT correspondence. This work establishes a unified framework for quantifying quantum state distinguishability across various 2D CFTs, bridging quantum information techniques with applications in quantum gravity.
Authors: Eduard Naichuk, Jeroen van den Brink, Flavio S. Nogueira
In quantum optics and condensed matter physics non-Hermitian phenomena are often studied under the assumption of an open physical system. However, there are examples of intrinsically non-Hermitian, though often $\mathcal{PT}$ (parity-time) symmetric, not necessarily open systems, in which case the concept of gain and loss relative to an underlying environment is not primordial. A particularly intriguing example with experimental consequences in the literature is QCD at finite density. Motivated by the existence of such inherently non-Hermitian systems, here we study the critical behavior of a $U(1)$-invariant Lagrangian perturbed by a complex, $\mathcal{PT}$ symmetric $Z_{4}$ anisotropy. We find real critical exponents both in the region of unbroken and broken $\mathcal{PT}$ symmetry. In the former the coupling constants for fixed points or lines are real, whereas in the latter they become complex. Importantly, the most stable fixed point corresponds to the flow at large distances towards an effectively Hermitian $U(1)$ symmetric system. This constitutes an example where both the $U(1)$ and the Hermitian character are emergent features of the theory. This tells us about the importance and physical meaning of some non-Hermitian systems beyond interpretations involving gain and loss.
Authors: Cătălin Paşcu Moca, Doru Sticlet, Balázs Dóra
We investigate non-stabilizerness, also known as ``magic,'' to understand criticality and exceptional points in non-Hermitian quantum many-body systems. Our focus is on parity-time ($\mathcal{PT}$) symmetric spin chains, specifically the non-Hermitian transverse-field Ising and XX models. We calculate stabilizer Rényi entropies in their ground states using non-Hermitian matrix product state methods. Our findings show that magic exhibits unique and model-specific signs of phase transitions. In the Ising chain, it peaks along the regular Hermitian-like critical line but disappears across exceptional points. In contrast, in the XX chain, it reaches its maximum at the exceptional line where $\mathcal{PT}$ symmetry is broken. Finite-size scaling reveals that these effects become more pronounced with larger systems, highlighting non-stabilizerness as a sensitive marker for both quantum criticality and non-Hermitian spectral degeneracies. We also investigate magic in momentum space for the XX model analytically and find that is reaches a minimum around exceptional points. Our results indicate that magic takes extremal values at the exceptional points and serves as a valuable tool for examining complexity, criticality, and symmetry breaking in non-Hermitian quantum matter.
Authors: Pei-Yao Liu
We prove an entanglement sum rule for $(d{-}1)$-dimensional quantum lattice models with finite abelian higher-form symmetries, obtained by minimally coupling a sector on $p$-simplices carrying a $p$-form $G$ symmetry to a sector on $(p{+}1)$-simplices carrying the dual $(d{-}p{-}2)$-form $\widehat G$ symmetry (with $\widehat G$ the Pontryagin dual of $G$). The coupling is introduced by conjugation with a symmetry-preserving operator $\mathcal{U}$ that dresses symmetry-invariant operators with appropriate Wilson operators. On the symmetry-invariant subspace, $\mathcal{U}$ is well-defined and unitary, and the coupled Hamiltonian is obtained from the decoupled one by conjugation with $\mathcal{U}$. Our main result concerns symmetric eigenstates of the coupled model that arise by acting with $\mathcal{U}$ on direct-product, symmetric eigenstates of the decoupled model: provided a topological criterion formulated via the Mayer--Vietoris sequence holds for the chosen bipartition, $\mathcal{U}$ factorizes across the cut when acting on the symmetric state, and the bipartite entanglement entropy equals the sum of the entropies of the two sectors. The framework explains and generalizes known examples in fermion-$\mathbb{Z}_2$ gauge theory, identifies when topology obstructs the factorization, and provides a procedure to construct new examples by gauging higher-form symmetries.
Authors: Ling-Zheng Xia, Lixin Xu, Wei-Jia Li
Fractonic phases of matter, a class of states in which collective excitations with constrained mobility exist, have recently emerged as a novel avenue for ergodicity breaking and garnered broad interest in condensed matter physics. In this work, we consider a (3+1)-dimensional holographic model of fractonic solids and investigate the low-energy collective dynamics systematically. By computing the quasinormal modes of black holes, we obtain all the hydrodynamic excitations on the boundary, including two acoustic phonons, a longitudinal diffusive mode as well as a fractonic subdiffusive mode with the dispersion $\omega \sim-ik^4$. In addition, it is found that the fracton mode remains gapless when translational symmetry is explicitly broken. These results suggest that fractonic excitations are inherently protected by the crystal-dipole symmetry in solids and are qualitatively unaffected by broken spacetime symmetries.
Authors: Zhichang Fu, Yunhai Li, Weiqing Zhou, Shengjun Yuan
The $O(N)$ stochastic propagation method, which relies on the numerical solution of the time-dependent Schrödinger equation using random initial states, is widely used in large-scale first-principles calculations. In this work, we eliminate the conventional sequential computation of intermediate states by introducing a concurrent strategy that minimizes information redundancy. The new method, in its state-, moment-, and energy-based implementations, not only surpasses the time step constraint of sequential propagation but also maintains precision within the framework of the Nyquist-Shannon sampling theorem. Systematic benchmarking on one billion atoms within the tight-binding model demonstrates that our new concurrent method achieves up to an order-of-magnitude speedup, enabling the rapid computation of a wide range of electronic, optical, and transport properties. This performance breakthrough offers valuable insights for enhancing other time-propagation algorithms, including those employed in large-scale stochastic density functional theory.
Authors: Pierre Mergny, Lenka Zdeborová
We provide a rigorous random matrix theory analysis of spiked cross-covariance models where the signals across two high-dimensional data channels are partially aligned. These models are motivated by multi-modal learning and form the standard generative setting underlying Partial Least Squares (PLS), a widely used yet theoretically underdeveloped method. We show that the leading singular values of the sample cross-covariance matrix undergo a Baik-Ben Arous-Peche (BBP)-type phase transition, and we characterize the precise thresholds for the emergence of informative components. Our results yield the first sharp asymptotic description of the signal recovery capabilities of PLS in this setting, revealing a fundamental performance gap between PLS and the Bayes-optimal estimator. In particular, we identify the SNR and correlation regimes where PLS fails to recover any signal, despite detectability being possible in principle. These findings clarify the theoretical limits of PLS and provide guidance for the design of reliable multi-modal inference methods in high dimensions.
Authors: Sudipta Kundu, Indrajit Maity, Robin Bajaj, H. R. Krishnamurthy, Manish Jain
Strain-induced lattice mismatch leads to moiré patterns in homobilayer transition metal dichalcogenides (TMDs). We investigate the structural and electronic properties of such strained moiré patterns in TMD homobilayers. The moiré patterns in strained TMDs consist of several stacking domains which are separated by tensile solitons. Relaxation of these systems distributes the strain unevenly in the moiré superlattice, with the maximum strain energy concentrating at the highest energy stackings. The order parameter distribution shows the formation of aster topological defects at the same sites. In contrast, twisted TMDs host shear solitons at the domain walls, and the order parameter distribution in these systems shows the formation of vortex defects. The strained moiré systems also show the emergence of several well-separated flat bands at both the valence and conduction band edges, and we observe a significant reduction in the band gap. The flat bands in these strained moiré superlattices provide platforms for studying the Hubbard model on a triangular lattice as well as the ionic Hubbard model on a honeycomb lattice. Furthermore, we study the localization of the wave functions corresponding to these flat bands. The wave functions localize at different stackings compared to twisted TMDs, and our results are in excellent agreement with spectroscopic experiments.
Authors: Olivia Liebman, Jonathan Curtis, Ioannis Petrides, Prineha Narang
The unusual magnetoelectric transport present in Weyl semimetals and 3D topological insula- tors can be compactly understood as manifestations of a background axion field, which itself is determined by the microscopic band structure. In the presence of correlations, an additional axion quasiparticle may emerge as the collective excitations on top of the mean background field. Such modes couple nonlinearly to electric and magnetic fields, giving rise to a dynamical magnetoelectric response. However, unambiguous identification of this collective axion mode is challenging due to its inherent nonlinear dynamics. Here, we propose an all-optical protocol that utilizes a pump-probe setup for verifying and characterizing the transient dynamics of axion fields in three-dimensional insulator systems. In particular, we show that nonlinear Raman processes induce dynamical oscillations of the axion field that depend on the geometry of the incident electromagnetic fields. These oscillations manifest in the polarization and magnetization of the material, hence, can be subsequently measured using time-resolved Kerr rotation spectroscopy. Our results open a pathway towards using multi-photon and quantum pair spectroscopies to identify new correlated phases of quantum matter.
Authors: Marie-Eve Boulanger, Lu Chen, Vincent Oliviero, David Vignolles, Gaël Grissonnanche, Kejun Xu, Zhi-Xun Shen, Cyril Proust, Jordan Baglo, Louis Taillefer
It has recently become clear that phonons generate a sizable thermal Hall effect in cuprates, whether they are undoped, electron-doped or hole-doped (inside the pseudogap phase). At higher doping, where cuprates are reasonably good metals, mobile electrons also generate a thermal Hall effect, the thermal equivalent of the standard electrical Hall effect. Here we show that in the cleanest crystals of the electron-doped cuprate Nd$_{2-x}$Ce$_{x}$CuO$_{4}$, at high doping, the phonon and electron contributions to the thermal Hall conductivity $\kappa_{\rm {xy}}$ are of comparable magnitude, but of opposite sign. In samples of lower quality, phonons dominate $\kappa_{\rm {xy}}$, resulting in a negative $\kappa_{\rm {xy}}$ at all temperatures. The fact that the negative phononic $\kappa_{\rm {xy}}$ in the metallic state is similar in magnitude and temperature dependence to that found in the insulating state at lower doping rules out any mechanism based on skew scattering of phonons off charged impurities, since a local charge should be screened in the metallic regime. The phononic $\kappa_{\rm {xy}}$ is found to persist over the entire doping range where antiferromagnetic correlations are known to be significant, suggesting that such correlations may play a role in generating the phonon thermal Hall effect in electron-doped cuprates. If the same mechanism is also at play in hole-doped cuprates, the presence of a phononic $\kappa_{\rm {xy}}$ below (and only below) the critical doping $p^{\star}$ would be evidence that spin correlations are a property of the pseudogap phase.
Authors: Masashi Hashimoto, Yasuhiro Yamada, Yoichi Tanaka, Yoshimichi Teratani, Takuro Kemi, Norio Kawakami, Akira Oguri
We study the nonlocal magnetotransport through a strongly correlated quantum dot, connected to multiple terminals consisting of two normal and one superconducting (SC) leads. Specifically, we present a comprehensive view on the interplay between the crossed Andreev reflection (CAR), the Kondo effect, and the Zeeman splitting at zero temperature in the large SC gap limit. The ground state of this network shows an interesting variety, which varies continuously with the system parameters, such as the coupling strength $\Gamma_S^{}$ between the SC lead and the quantum dot, the Coulomb repulsion $U$, the impurity level $\varepsilon_d^{}$, and the magnetic field $b$. We show, using the many-body optical theorem which is derived from the Fermi-liquid theory, that the nonlocal conductance is determined by the transmission rate of the Cooper pairs $\mathcal{T}_{\mathrm{CP}}^{} = \frac{1}{4} \sin^2 \Theta\, \sin^2 \bigl(\delta_{\uparrow}+ \delta_{\downarrow})$ and that of the Bogoliubov particles $\mathcal{T}_{\mathrm{BG}}^{}= \frac{1}{2}\sum_{\sigma} \sin^2 \delta_{\sigma}^{}$. Here, $\delta_\sigma^{}$ is the phase shift of the renormalized Bogoliubov particles, and $\Theta \equiv \cot^{-1} (\xi_d^{}/ \Gamma_S^{})$ is the Bogoliubov-rotation angle in the Nambu pseudo spin space, with $\xi_d^{} =\varepsilon_d^{}+U/2$. It is also demonstrated, using Wilson's numerical renormalization group approach, that the CAR is enhanced in the crossover region between the Kondo regime and the SC-proximity-dominated regime at zero magnetic field. The magnetic fields induce another crossover between the Zeeman-dominated regime and the SC-dominated regime. We find that the CAR is enhanced and becomes less sensitive to magnetic fields in the SC-dominated regime close to the crossover region spreading over the angular range of $\pi/4 \lesssim \Theta \lesssim 3\pi/4$.
Authors: Peter Zalom, Kacper Wrześniewski, Tomáš Novotný, Ireneusz Weymann
This work systematically investigates the phase diagram of a parallel double-quantum-dot Andreev molecule, where the two quantum dots are coupled to a common superconducting lead. Using the numerical renormalization group method, we map out the evolution of the ground state across a wide parameter space of level detunings, size of the superconducting gap, lead couplings, and inter-dot coupling strength. The intricate phase diagrams feature singlet, doublet, and a relatively uncommon triplet ground states, with the latter being a distinct signature of strong lead-mediated interactions between the quantum dots. We benchmark the applicability of simplified effective models, including the atomic limit and zero-bandwidth approximations, in capturing the complex behavior of this parallel configuration. Our analysis reveals severe limitations of these models, underscoring the necessity for maximal caution when extrapolating beyond their tested validity. In particular, all effective models except for the extended version of the zero-bandwidth approximation failed in reproducing the triplet ground state and made several false predictions. These findings provide crucial insights for interpreting experimental observations and designing superconducting devices based on quantum-dot architectures.
Authors: Shinsuke Haze, Jinglun Li, Dominik Dorer, José P. D'Incao, Paul S. Julienne, Eberhard Tiemann, Markus Deiß, Johannes Hecker Denschlag
Gaining control over chemical reactions on the quantum level is a central goal of the modern field of cold and ultracold chemistry. Here, we demonstrate a novel method to coherently steer reaction flux of a three-body recombination process across different product spin channels. For this, we employ a magnetically-tunable Feshbach resonance to admix, in a controlled way, a specific spin state to the reacting collision complex. This allows for the control of the reaction flux into the admixed spin channel, which can be used to significantly change the reaction products. Furthermore, we also investigate the influence of an Efimov resonance on the reaction dynamics. We find that while the Efimov resonance can be used to globally enhance three-body recombination, the relative flux between the reaction channels remains unchanged. Our control scheme is general and can be extended to other reaction processes. It also provides new opportunities in combination with other control schemes, such as quantum interference of reaction paths.
Authors: Archak Purkayastha, Giacomo Guarnieri, Janet Anders, Marco Merkli
Thermalization of isolated and open quantum systems has been studied extensively. However, being the subject of investigation by different scientific communities and being analysed using different mathematical tools, the connection between the isolated (IQS) and open (OQS) approaches to thermalization has remained opaque. Here we demonstrate that the fundamental difference between the two paradigms is the order in which the long time and the thermodynamic limits are taken. This difference implies that they describe physics on widely different time and length scales. Our analysis is carried out numerically for the case of a double quantum dot (DQD) coupled to a fermionic lead, also known as the interacting resonant level model in quantum impurity physics. We show how both OQS and IQS thermalization can be explored in this model on equal footing, allowing a fair comparison between the two. We find that while the quadratically coupled (free) DQD experiences no isolated thermalization, it of course does experience open thermalization. For the non-linearly interacting DQD coupled to a fermionic lead, the many-body interaction in the DQD breaks the integrability of the whole system. We find that this system shows strong evidence of both OQS and IQS thermalization in the same dynamics, but at widely different time scales, consistent with reversing the order of the long time and the thermodynamic limits.
Authors: Juno Nam, Sulin Liu, Gavin Winter, KyuJung Jun, Soojung Yang, Rafael Gómez-Bombarelli
Atomic transport underpins the performance of materials in technologies such as energy storage and electronics, yet its simulation remains computationally demanding. In particular, modeling ionic diffusion in solid-state electrolytes (SSEs) requires methods that can overcome the scale limitations of traditional ab initio molecular dynamics (AIMD). We introduce LiFlow, a generative framework to accelerate MD simulations for crystalline materials that formulates the task as conditional generation of atomic displacements. The model uses flow matching, with a Propagator submodel to generate atomic displacements and a Corrector to locally correct unphysical geometries, and incorporates an adaptive prior based on the Maxwell-Boltzmann distribution to account for chemical and thermal conditions. We benchmark LiFlow on a dataset comprising 25-ps trajectories of lithium diffusion across 4,186 SSE candidates at four temperatures. The model obtains a consistent Spearman rank correlation of 0.7-0.8 for lithium mean squared displacement (MSD) predictions on unseen compositions. Furthermore, LiFlow generalizes from short training trajectories to larger supercells and longer simulations while maintaining high accuracy. With speed-ups of up to 600,000$\times$ compared to first-principles methods, LiFlow enables scalable simulations at significantly larger length and time scales.
Authors: Tu Hong, Xiao Yan Xu
Non-Fermi liquids are an important topic in condensed matter physics, as their characteristics challenge the framework of traditional Fermi liquid theory and reveal the complex behavior of electrons in strongly interacting systems. Both the experimentally observed smeared region and the theoretically predicted marginal Fermi liquid suggest that spatial disorder seems to be an important driver of these phenomena. By performing large-scale determinant quantum Monte Carlo (DQMC) simulations in the ferromagnetic spin-fermion model at finite $N$, beyond the large-$N$ used in previous theoretical work, we investigated the role of spatial disorder in the critical Fermi surface (FS) of this model. We proposed a corrected theory of our system, which is based on a modified Eliashberg theory and a universal theory of strange metals. This theory agrees well with the data obtained from DQMC, particularly in capturing the $\omega \ln \omega$ type self-energy characteristic of marginal Fermi liquid behavior, and observing the linear-in-temperature resistivity. Our findings offer strong and unbiased validation of the universal theory of strange metals, broaden the applicability of the modified Eliashberg theory, and provide insights for numerically searching for marginal Fermi liquid and linear-in-temperature resistivity.
Authors: Godwill Mbiti Kanyolo, Titus Masese
Motivated by a recent pseudo-spin model for monolayer-bilayer phase transitions in silver-based honeycomb layered materials, we propose that the critical pseudo-magnetic fields in such systems correspond to both the infinite-channel Feshbach resonance widths of a (Fermi-Dirac/Bose-Einstein/etc.) condensate in 2 dimensions, and equivalently to the Lee-Yang zeros of the Ising model of two pseudo-spins with a partition function corresponding to a class of functions that must include the Riemann Xi function. Identifying the quantum-mechanical operator that yields the discontinuous/random/topological spectrum of the critical pseudo-magnetic fields in such systems offers a tenable realisation of the Hilbert-Pólya conjecture.
Authors: Joaquin Garcia-Suarez
We study the fluid-mediated approach of a deformable axisymmetric object towards a rigid substrate, focusing on how its shape influences contact formation. For low approach velocities and large Stokes numbers, we show that sharper profiles (e.g., conical) maximize contact at the center and avoid fluid entrapment, while blunter ones form central dimples that trap bubbles. We also find that the resulting pressure distributions in the presence of thin viscous films can be predicted remarkably well by classical (dry) contact mechanics. These findings reveal shape as a design parameter for contact optimization in soft matter, adhesion, and elastohydrodynamics. Finally, we also theorize the possibility of a mechanical equivalence between shape and approach velocity.
Authors: Juan Polo, Wayne J. Chetcuti, Anna Minguzzi, Andreas Osterloh, Luigi Amico
We investigate the effects of a static impurity, modeled by a localized barrier, in a one-dimensional mesoscopic system comprised of strongly correlated repulsive SU($N$)-symmetric fermions. For a mesoscopic sized ring under the effect of an artificial gauge field, we analyze the energy spectrum, the particle density and the current flowing through the impurity at varying interaction strengths, barrier heights, and number of components. We find that the physics of the system is governed by the competition between effective single-particle process and the formation of a high-stiffness spin-correlated state associated to the phenomenon of fractionalization of the flux quantum characterizing the $N$-component fermionic system. Our findings provide a route to probe the response of SU($N$) fermions to effective magnetic fields; at the same time, they hold significance for fundamental understanding of localized impurity problems.
Authors: Changyu Yao, Yue Yu, Yinyao Shi, Ji-In Jung, Zoltan Vaci, Yizhou Wang, Zhongyuan Liu, Chuanwei Zhang, Sonia Tikoo-Schantz, Chong Zu
Understanding intricate magnetic structures in materials is essential for advancing materials science, spintronics, and geology. Recent developments of quantum-enabled magnetometers, such as nitrogen-vacancy (NV) centers in diamond, have enabled direct imaging of magnetic field distributions across a wide range of magnetic profiles. However, reconstructing the magnetization from an experimentally measured magnetic field map is a complex inverse problem, further complicated by measurement noise, finite spatial resolution, and variations in sample-to-sensor distance. In this work, we present a novel and efficient GPU-accelerated method for reconstructing spatially varying magnetization density from measured magnetic fields with minimal prior assumptions. We validate our method by simulating diverse magnetic structures under realistic experimental conditions, including multi-domain ferromagnetism and magnetic spin textures such as skyrmion, anti-skyrmion, and meron. Experimentally, we reconstruct the magnetization of a micrometer-scale Apollo lunar mare basalt (sample 10003,184) and a nanometer-scale twisted double-trilayer CrI3. The basalt exhibits soft ferromagnetic domains consistent with previous paleomagnetic studies, whereas the CrI3 system reveals a well-defined hexagonal magnetic Moire superlattice. Our approach provides a versatile and universal tool for investigating complex magnetization profiles, paving the way for future quantum sensing experiments.
Authors: Carlo Danieli, Laura Pilozzi, Claudio Conti, Valentina Brosco
Non-Abelian gauge symmetries are cornerstones of modern theoretical physics, underlying fundamental interactions and the geometric structure of quantum mechanics. However, their potential to control quantum coherence, entangle- ment, and transport in engineered quantum systems remains to a large extent unexplored. In this work, we propose utilizing non-Abelian Thouless pumping to realize one-dimensional discrete-time quantum walks on topological lattices char- acterized by degenerate flat bands. Through carefully designed pumping cycles, we implement different classes of holonomic coin and shift operators. This frame- work allows for the construction of quantum walks that encode the topological and geometric properties of the underlying system. Remarkably, the resulting evolution exhibits parity symmetry breaking and gives rise to a dynamical pro- cess governed by a Weyl-like equation, highlighting the deep connection between parity and time-reversal symmetry breaking in the system.
Authors: D. Beretta
This article presents an open-source Python package for simulating micro-thermoelectric generators, based on the work by D. Beretta et al. (Sustainable Energy Fuels, 2017). Featuring a user-friendly graphical user interface and robust computational capabilities, the tool is designed for use by scientists, researchers, and engineers to analyze and optimize device designs. The software calculates key performance metrics such as power, efficiency, electrical resistance, open circuit voltage, and short circuit current per unit of device area, based on the device design and material properties. The full source code is available for download on GitHub, enabling further customization.
Authors: Tymoteusz Tula, Jorge Quintanilla, Gunnar Möller
Recently, a direct connection between static structure factors and quantum ground states for two-spin interaction Hamiltonians was proven. This suggests the possibility of quantum state tomography from neutron scattering. Here, we investigate the associated fitness landscape numerically. We find a linear relationship between the mean square distances of the structure factors and the associated state overlaps, implying a well-behaved fitness landscape. Furthermore, we find evidence suggesting that the approach can be generalized to thermal equilibrium states. We also extend the arguments to the cases of applied magnetic fields and finite clusters.
Authors: Jan Barański, Magdalena Barańska, Tomasz Zienkiewicz, Tadeusz Domański
We study the quasiparticle spectrum of a hybrid system, comprising a correlated (Anderson-type) quantum dot coupled to a topological superconducting nanowire hosting the Majorana boundarymodes. From the exact solution of the low-energy effective Hamiltonian, we uncover a subtle interplay between Coulomb repulsion and the Majorana mode. Our analytical expressions show that the spectral weight of the leaking Majorana mode is sensitive to both the quantum dot energy level and the repulsive potential. We compare our results with estimations by L.S. Ricco et al. Phys. Rev. B 99, 155159 (2019) obtained for the same hybrid structure using the Hubbard-type decoupling scheme, and analytically quantify the spectral weight of the zero-energy (topological) mode coexisting with the finite-energy (trivial) states of the quantum dot. We also show that empirical verification of these spectral weights could be feasible through spin-polarized Andreev spectroscopy.
Authors: Anton Romen, Johannes Knolle, Michael Knap
Prethermalization phenomena in driven systems are generally understood via a local Floquet Hamiltonian obtained from a high-frequency expansion. Remarkably, recently it has been shown that a driven Kitaev spin liquid with fractionalized excitations can realize a quasi-stationary state that is not captured by this paradigm. Instead distinct types of fractionalized excitations are characterized by vastly different temperatures-a phenomenon dubbed "fractionalized prethermalization". In our work, we analyze fractionalized prethermalization in a driven one-dimensional Hubbard model at strong coupling which hosts spin-charge fractionalization. At intermediate frequencies quasi-steady states emerge which are characterized by a low spin and high charge temperature with lifetimes set by two competing processes: the lifetime of the quasiparticles determined by Fermi's Golden rule and the exponentially long lifetime of a Floquet prethermal plateau. We classify drives into three categories, each giving rise to distinct (fractional) prethermalization dynamics. Resorting to a time-dependent variant of the Schrieffer-Wolff transformation, we systematically analyze how these drive categories are linked to the underlying driven Hubbard model, thereby providing a general understanding of the emergent thermalization dynamics. We discuss routes towards an experimental realization of this phenomenon in quantum simulation platforms.
Authors: Sergei D. Liazhkov
We consider unsteady ballistic heat transport in a semi-infinite Hooke chain with a free end and an arbitrary heat source. An analytical description of the evolution of the kinetic temperature is proposed in both discrete (exact) and continuum (approximate) formulations. The continualization of the discrete solution for kinetic temperature is performed through a large-time asymptotic estimate of the fundamental solution of the dynamical problem for the instantly perturbed conservative semi-infinite chain at the fronts of the incident and reflected thermal waves. By analyzing the continuum solution, we observe that any instantaneous heat supply (i.e., a heat pulse) results in the anti-localization of the reflected thermal wave. We demonstrate that sudden point heat supply leads to a transition to a non-equilibrium steady state, which, unexpectedly, may exist even in the non-dissipative case. The results of this paper are expected to provide insight into the continuum description of nanoscale heat transport.
Authors: Rahil N. Valani, David M. Paganin
Active particles are non-equilibrium entities that uptake energy and convert it into self-propulsion. A dynamically rich class of inertial active particles having features of wave-particle coupling and wave memory are walking/superwalking droplets. Such classical, active wave-particle entities (WPEs) have previously been shown to exhibit hydrodynamic analogs of many single-particle quantum systems. Inspired by the rich dynamics of strongly interacting superwalking droplets in experiments, we numerically investigate the dynamics of WPE clusters using a stroboscopic model. We find that several interacting WPEs self-organize into a stable bound cluster, reminiscent of an atomic nucleus. This active cluster exhibits a rich spectrum of collective excitations, including shape oscillations and chiral rotating modes, akin to vibrational and rotational modes of nuclear excitations, as the spatial extent of the waves and their temporal decay rate (memory) are varied. Dynamically distinct excitation modes create a common time-averaged collective wave field potential, bearing qualitative similarities with the nuclear shell model and the bag model of hadrons. For high memory and rapid spatial decay of waves, the active cluster becomes unstable and disintegrates; however, within a narrow regime of the parameter space, the cluster ejects single particles whose decay statistics follow exponential laws, reminiscent of radioactive nuclear decay. Our study uncovers a rich spectrum of dynamical behaviors in clusters of active particles, opening new avenues for exploring hydrodynamic quantum analogs in active matter systems.
Authors: Yuxuan Guo, Sheng Yang, Xue-Jia Yu
Symmetry breaking has been a central theme in classifying quantum phases and phase transitions. Recently, this concept has been extended to the mixed states of open systems, attracting considerable attention due to the emergence of novel physics beyond closed systems. In this work, we reveal a new type of phase transition in mixed states, termed \emph{quantum} strong-to-weak spontaneous symmetry breaking (SWSSB). Using a combination of field theory calculations and large-scale matrix product state simulations, we map out the global phase diagram of the XXZ critical spin chain under local strong symmetry preserving decoherence, which features an SWSSB phase and a trivial Luttinger liquid phase, separated by a straight critical line that belongs to the boundary Berezinskii-Kosterlitz-Thouless universality class with a varying effective central charge. Importantly, we analyze this transition from two complementary perspectives: on one hand, through the behavior of order parameters that characterize the symmetry breaking; on the other hand, from a quantum information viewpoint by studying entropic quantities and the concept of quantum recoverability. Remarkably, the SWSSB transition in our case is \emph{purely quantum} in the sense that it can only be driven by tuning the Hamiltonian parameter even under arbitrary decoherence strength, fundamentally distinguishing it from the decoherence-driven SWSSB transitions extensively discussed in previous literature. Importantly, our unified theoretical framework is applicable to a broad class of one-dimensional quantum systems, including spin chains and fermionic systems, whose low-energy physics can be described by Luttinger liquid theory, under arbitrary symmetry-preserving decoherence channels. Finally, we also discuss the experimental relevance of our theory on quantum simulator platforms.
Authors: Karim I. Elghazawy, Chris H. Greene
Three-body loss resonances associated with heavy-heavy-light Efimov states have been observed for over a decade in ultracold mixtures tuned near interspecies Feshbach resonances. For light-light-heavy systems, observing such resonances has been far more challenging due to the substantially large Efimov spacing. In these Efimov-unfavored systems, the intraspecies scattering length $a_\text{BB}$ has been shown to significantly affect the overall Efimov scenario, namely, the positions of the Efimov resonances $a_{-}^{(n)}$ and the three-body parameter (3BP) $a_{-}^{(0)}$. The present article explains the origin behind this influence by highlighting two primary mechanisms via which both the magnitude and sign of $a_\text{BB}$ govern the Efimov spectrum and set the resulting 3BP $a_{-}^{(0)}$. By employing van der Waals interactions for $^{23}$Na$_2{}^{40}$K, we attribute the vital role of $a_\text{BB}$ in Efimov-unfavored systems to the large difference between the Efimov scaling parameters for two and three resonant interactions, $s_0$ and $s_0^*$. In particular, we account for the unusually large $a_{-}^{(0)}$ obtained in light-light-heavy systems with $a_\text{BB}>0$ (e.g., $^{41}$K$_2{}^{87}$Rb), and show that the first Efimov resonance can still occur at an experimentally accessible value when $a_\text{BB}<0$.
Authors: Chaebin Kim, Martin Mourigal
We simulate the dynamical spin structure factor (DSSF) S(q,w) of the spin-1/2 Heisenberg antiferromagnetic chain using classical simulations. By employing Landau-Lifshitz Dynamics, we emulate quantum correlations through temperature-dependent corrections, including rescaling of magnetic dipoles and renormalization of exchange interactions. Our results demonstrate that the quantum-equivalent DSSF closely matches Quantum Monte-Carlo calculations for kBT/J ~ 1, extending the applicability of classical dynamics to the challenging case of gapless excitations. At higher temperatures, our simulations comply with general predictions for uncorrelated paramagnetic fluctuations in the infinite temperature limit. Entanglement witnesses derived from the quantum-equivalent DSSF act as sensitive diagnostics for the quantum-to-classical crossover. Their reliability stems from their dependence on spectral features alone, enabling classical dynamics to emulate quantum thresholds without genuine entanglement. This framework also reproduces transverse spin correlations in finite magnetic fields, in agreement with quantum simulations. Together, our results establish quantum-corrected classical dynamics as a scalable and predictive tool for interpreting scattering experiments and exploring quantum correlations in strongly correlated spin systems.
Authors: Cyprien Daix, Maxime Dixmerias, Yuan-Yao He, Joris Verstraten, Tim de Jongh, Bruno Peaudecerf, Shiwei Zhang, Tarik Yefsah
In this work, we explore two-dimensional attractive Fermi gases at the microscopic level by probing spatial charge and spin correlations in situ. Using atom-resolved continuum quantum gas microscopy, we directly observe fermion pairing and study the evolution of two- and three-point correlation functions as inter-spin attraction is increased. The precision of our measurement allows us to reveal nonlocal anticorrelations in the pair correlation function, fundamentally forbidden by the mean-field result based on Bardeen-Cooper-Schrieffer (BCS) theory but whose existence we confirm in exact auxiliary-field quantum Monte Carlo calculations. We demonstrate that the BCS prediction is critically deficient not only in the superfluid crossover regime but also deep in the weakly attractive side. Guided by our measurements, we find a remarkable relation between two- and three-point correlations that establishes the dominant role of pair-correlations. Finally, leveraging local single-pair losses, we independently characterize the short-range behavior of pair correlations, via the measurement of Tan's Contact, and find excellent agreement with numerical predictions. Our measurements provide an unprecedented microscopic view into two-dimensional Fermi gases and constitute a paradigm shift for future studies of strongly-correlated fermionic matter in the continuum.
Authors: Carlos Payá, F.J. Matute-Cañadas, A. Levy Yeyati, Ramón Aguado, Pablo San-Jose, Elsa Prada
We introduce a new type of supercurrent valve based on full-shell nanowires. These hybrid wires consist of a semiconductor core fully wrapped in a thin superconductor shell and subjected to an axial magnetic field. Due to the tubular shape of the shell, the superconductor phase acquires an integer number $n$ of $2\pi$ twists or \textit{fluxoids} that increases in steps with applied flux. By connecting two such hybrid wires, forming a Josephson junction (JJ), a flux-modulated supercurrent develops. If the two superconducting sections of the JJ have different radii $R_1$ and $R_2$, they can develop equal or different fluxoid numbers $n_1,n_2$ depending on the field. If $n_1\neq n_2$ the supercurrent is blocked, while it remains finite for $n_1=n_2$. This gives rise to a fluxoid valve effect controlled by the applied magnetic field or a gate voltage at the junction. We define a fluxoid-valve quality factor that is perfect for cylindrically symmetric systems and decreases as this symmetry is reduced. We further discuss the role of Majorana zero modes at the junction when the full-shell nanowires are in the topological superconducting regime.
Authors: Giovanni Alberto Ummarino, Alessio Zaccone, Alessandro Braggio, Francesco Giazotto
Superconducting thin metallic films, functioning as supercurrent gate-tunable transistors, have considerable potential for future quantum electronic devices. Despite extensive research, a comprehensive microscopic quantitative mechanism that elucidates the control or suppression of supercurrents in thin films remains elusive. Focusing on NbN, a prototypical material, and starting from a phenomenological ansatz that links the critical electric field with the kinetic energy parameter needed to break Cooper pairs, we provide a quantitative analysis of the critical current using Eliashberg theory in the dirty limit without adjustable parameters. The critical kinetic energy value is identified, corresponding to the maximum supercurrent that can flow in the thin film. The peak in supercurrent density as a function of the Cooper pairs' kinetic energy arises from the interplay between the increase in supercurrent due to increased kinetic energy and the depairing effect when the kinetic energy becomes sufficiently large. The critical value of the pair's kinetic energy is subsequently employed to estimate the critical value of an external electric field required to suppress superconductivity in the sample. This estimation is in parameter-free agreement with the experimental observations. Although the disorder reduces the temperature dependence of the gating effect on the critical current, at the same time, it increases the unscreened critical electric field needed to suppress superconductivity. This enables the proposal of methods to control and reduce the critical field value necessary to suppress superconductivity in superconducting electronics.
Authors: Alexis Pecheux (SATIE, ENS Paris Saclay, CNRS), Robin Salvatore (INSP, SU, CNRS), Laura Thevenard (INSP, SU, CNRS), Jon Ander Arregi (CEITEC MU), Vojt{ě}ch Uhlí{ř} (CEITEC MU), Morgan Almanza (ENS Paris Saclay, CNRS, SATIE), Danièle Fournier (INSP, SU, CNRS), Catherine Gourdon (INSP, SU, CNRS), Martino Lobue (SATIE, ENS Paris Saclay, CNRS)
With its huge entropy change and a strong interplay between magnetic order, structural and electrical properties, the first-order antiferromagnetic/ferromagnetic phase transition is a paradigmatic example of the multicaloric effect. The unraveling of the physics underlying the phase transition needs a better understanding of the thermal hysteresis of FeRh within the AF-FM phase coexistence region. In this work, we compare the effect of two very different types of thermal cycling on the hysteresis of the magnetic order: quasi-static heating, and cooling of the entire 195 nm thick film, and a f =100 kHz modulated heating driven by a laser focused down to a spot of about ten microns squared at the film surface. Taking advantage of the reflectivity difference between both phases to probe optically their respective fraction, we show that whereas only temperature-driven reflectivity variations ($dR/dT$, thermoreflectance) are detected in the pure phases, a huge modulation of the phase-dependent reflectance at the driving frequency $f$ is detected in the phase coexistence temperature range. This is quantitatively described as resulting from a substantial modulation of the FM fraction (up to 90% with increasing laser power. A simplified rate-independent hysteresis model with return-point-memory (RPM), represented in terms of bistable units that undergo a temperature excursion corresponding to a given laser power, reproduces very well the optically measured FM phase modulation characteristics for a broad range of temperature excursions. This offers an insight into the leading role of quenched disorder in defining thermal hysteresis in FeRh under high excitation frequency, when the material is periodically driven out-of-equilibrium.
Authors: Roberto Verdel, Devendra Singh Bhakuni, Santiago Acevedo
The intrinsic dimension (ID) is a powerful tool to detect and quantify correlations from data. Recently, it has been successfully applied to study statistical and many-body systems in equilibrium, yet its application to systems away from equilibrium remains largely unexplored. Here we study the ID of nonequilibrium growth dynamics data, and show that even after reducing these data to binary form, their binary intrinsic dimension (BID) retains essential physical information. Specifically, we find that, akin to the surface width, it exhibits Family-Vicsek dynamical scaling -- a fundamental feature to describe universality in surface roughness phenomena. These findings highlight the ability of the BID to correctly discern key properties and correlations in nonequilibrium data, and open an avenue for alternative characterizations of out-of-equilibrium dynamics.
Authors: Hanning Zhang, Oleg V. Yazyev, Ruslan Yamaletdinov
Electrode morphology critically determines the stability and efficiency of lithium metal anodes, yet no predictive framework has explained how measurable parameters control deposition. Here we introduce the first theoretical model of electrochemical Ostwald ripening, capturing the competition between electroplating and surface-energy-driven redistribution and identifying it as the governing process behind morphology evolution in the non-dendritic regime. The framework explicitly incorporates SEI resistance, electrolyte conductivity, electrode wettability, and current density revealing the transition from 2D SEI-limited to 3D electrolyte-limited growth. The model yields analytical expressions for nucleus size, density and distribution that quantitatively reproduce independent experimental results and establishes a direct link between plating conditions, morphology, and Coulombic efficiency. By providing experimentally accessible relationships between key parameters and deposition outcomes, the framework enables predictive understanding of lithium plating and provides a broadly applicable basis for controlling electrodeposition morphology across diverse electrochemical systems.
Authors: Xiao-Jue Zhang, Rong Lü, Qi-Bo Zeng
We introduce a new type of one-dimensional Kitaev chain with staggered $p$-wave superconducting pairing. We find three physical regimes in this model by tuning the $p$-wave pairing and the chemical potential of the system. In the topologically nontrivial phase, there are two Majorana zero modes localized at the opposite ends of the lattice, which are characterized and protected by nonzero topological invariants. More interestingly, we also find a regime where the system can hold four unprotected nonzero-energy edge modes in the trivial phase, which is analogous to a weak topological phase. The third regime is also trivial but holds no edge modes. The emergence of zero- and nonzero-energy edge modes in the system are analyzed by transforming the lattice model into a ladder consisting of Majorana fermions, where the competition between the intra- and inter-leg couplings leads to different phases. We further investigate the properties of edge modes under the influences of dissipation, which is represented by introducing a imaginary part in the chemical potential. Our work unveils the exotic properties induced by the staggered $p$-wave pairing and provides a new platform for further exploration of Majorana edge modes.
Authors: Junyao Wu, Rui-Chang Shen, Li Zhang, Fujia Chen, Bingbing Wang, Hongsheng Chen, Yihao Yang, Haoran Xue
The interplay between band topology and material nonlinearity gives rise to a variety of novel phenomena, such as topological solitons and nonlinearity-induced topological phase transitions. However, most previous studies fall within the Hermitian regime, leaving the impact of nonlinearity on non-Hermitian topology seldom explored. Here, we investigate the effects of nonlinearity on the non-Hermitian skin effect, a well-known non-Hermitian phenomenon induced by the point-gap topology unique to non-Hermitian systems. Interestingly, we discover a nonlinearity-induced point-gap topological phase transition accompanied by a reversal of the skin mode localization, which is distinct from previous nonlinearity-induced line-gap topological phases. This phenomenon is experimentally demonstrated in a nonlinear microwave metamaterial, where electromagnetic waves are localized around one end of the sample under a low-intensity pump, whereas at a high-intensity pump, the waves are localized around the other end. Our results open a new route towards nonlinear topological physics in non-Hermitian systems and are promising for reconfigurable topological wave manipulation.
Authors: P.A. Aksentsev, V.A. Khlebnikov, I.S. Cojocaru, A.E. Rudnev, I.A. Pyrkh, D.A. Kumpilov, P.V. Trofimova, A.M. Ibrahimov, O.I. Blokhin, K.O. Frolov, S.A. Kuzmin, A.K. Zykova, D.A. Pershin, V.V. Tsyganok, A.V. Akimov
Optical lattices play a significant role in the field of cold atom physics, particularly in quantum simulations. Varying the lattice period is often a useful feature, but it presents the challenge of maintaining lattice phase stability in both stationary and varying-period regimes. Here, we report the realization of a low frequency feedback loop for a tunable optical lattice. Our scheme employs a CCD camera, a computer, and a piezoelectric actuator mounted on a mirror. Using this setup, we significantly improved the long-term stability of an optical lattice over durations exceeding 10 seconds. More importantly, we demonstrated a rapid change in the optical lattice period without any loss of phase. The developed phase stabilization algorithm can be extended to more complicated 2D latices, than just periodic lattice.
Authors: Eugene A. Eliseev, Anna N. Morozovska, Sergei V. Kalinin, Long-Qing Chen, Venkatraman Gopalan
Proximity ferroelectricity is a novel paradigm for inducing ferroelectricity, where a non-ferroelectric polar material, which is unswitchable with an external field below the dielectric breakdown field, becomes a practically switchable ferroelectric in direct contact with a thin switchable ferroelectric layer. Here, we develop a Landau-Ginzburg-Devonshire approach to study the proximity effect of local piezoelectric response and polarization reversal in wurtzite ferroelectric multilayers under a sharp electrically biased tip. Using finite element modeling we analyze the probe-induced nucleation of nanodomains, the features of local polarization hysteresis loops and coercive fields in the Al1-xScxN/AlN bilayers and three-layers. Similar to the wurtzite multilayers sandwiched between two parallel electrodes, the regimes of "proximity switching" (where the multilayers collectively switch) and the regime of "proximity suppression" (where they collectively do not switch) are the only two possible regimes in the probe-electrode geometry. However, the parameters and asymmetry of the local piezo-response and polarization hysteresis loops depend significantly on the sequence of the layers with respect to the probe. The physical mechanism of the proximity ferroelectricity in the local probe geometry is a depolarizing electric field determined by the polarization of the layers and their relative thickness. The field, whose direction is opposite to the polarization vector in the layer(s) with the larger spontaneous polarization (such as AlN), renormalizes the double-well ferroelectric potential to lower the steepness of the switching barrier in the "otherwise unswitchable" polar layers. Tip-based control of domains in otherwise non-ferroelectric layers using proximity ferroelectricity can provide nanoscale control of domain reversal in memory, actuation, sensing and optical applications.
Authors: Lumen Eek, Esra D. van 't Westende, Dennis J. Klaassen, Harold J. W. Zandvliet, Pantelis Bampoulis, Cristiane Morais Smith
Reversible, all-electric control of symmetry-protected zero-dimensional modes has been a long-standing goal. In buckled honeycomb lattices, a perpendicular field couples to the staggered sublattice potential providing the required handle. We combine scanning tunneling microscopy and tight-binding theory to switch zero-dimensional topological end states reversibly on and off in ultranarrow germanene nanoribbons by tuning the electric field in the tunnel junction. Increasing the field switches off the end modes of topological two-hexagon wide ribbons, while the same field switches on zero-dimensional states in initially trivial three- and four-hexagon wide ribbons. This atomic scale platform realizes a proof-of-principle for a zero-dimensional topological field effect device, opening a path for ultrasmall memory, controllable qubits, and neuromorphic architectures.
Authors: Martín Pinto-Goldberg, Rodrigo Soto
In the high persistence regime of non-inertial active Brownian particles (ABP), polarization becomes a relevant dynamical field. Based on a recently proposed kinetic description for ABP, we derive Navier-Stokes-like equations for the density and polarization fields in this regime. Using the Chapman-Enskog method, all transport coefficients in the equations are obtained entirely in terms of the microscopic dynamics. A linear stability analysis of the homogeneous and isotropic state shows that the derived equations correctly describe the density instability associated to the motility induced phase separation. Numerical solutions of the equations in one spatial dimension show the need of an additional regularizing pressure term to saturate the system at high densities. With the inclusion of this term, the solutions illustrate in detail the clustering dynamics, with the formation of polarized regions at the interfaces, and the subsequent coarsening of domains, as well as particle accumulation in presence of gravity. Finally, the derived equations imply that, as an effect of the coupling with the polarization, damped density wave modes appear in the system which were verified with numerical simulations.
Authors: Arnaldo Spalvieri
The paper demonstrates that the canonical probability distribution of the occupancy numbers of a bosonic system is multinomial and shows how the thermodynamics of the canonical system descends from this distribution. The categorical distribution (i.e. the one-particle distribution) of the multinomial distribution should be derived from constrained maximization of the entropy of the multinomial distribution, but, being the multinomial distribution intractable, the paper proposes to take instead the one-particle Boltzmann distribution. After this, the imposition of Clausius' equation on the Shannon entropy of the multinomial-Boltzmann distribution leads to an unexpected result: in general, the Lagrange multiplier $\beta$ that imposes the energy constraint in constrained entropy maximization turns out to be substantially different from the inverse temperature. To disprove that $\beta$ should be equal to the inverse temperature, the paper presents an example where, with $\beta$ equal to the inverse temperature, the thermodynamic entropy (i.e. the entropy at a given temperature) of the multinomial-Boltzmann distribution is greater than the Bose-Einstein thermodynamic entropy. But this would contradict the principle of maximum entropy.
Authors: Vincenzo Fiorentini, Paola Alippi, Gianaurelio Cuniberti
Ab initio density-functional calculations show that orthorhombic Pca21 hafnia HfO2 mixed with vanadium at low concentration is a ferroelectric and ferromagnetic insulator. The multiorbital degeneracy of singly-occupied V states in the nominally 4+ ionic state is broken by magnetism, reduced symmetry, and local distortion, causing a single one-electron majority state per V atom to be occupied. A gap of order 1 eV thus survives at all V concentrations, and intrinsic polarization is preserved, at the level of two-thirds the hafnia value. Ferromagnetic magnetization is found to increase linearly with V content, with values of 30-40 emu/cm3 at concentrations near the end of the stability range.
Authors: Indrashish Saha, Lori Graham-Brady
Developing materials with tailored mechanical performance requires iteration over a large number of proposed designs. When considering dynamic fracture, experiments at every iteration are usually infeasible. While high-fidelity, physics-based simulations can potentially reduce experimental efforts, they remain computationally expensive. As a faster alternative, key dynamic properties can be predicted directly from microstructural images using deep-learning surrogate models. In this work, the spallation of ductile polycrystals under plate-impact loading at strain rates of O(10^6 s^-1) is considered. A physics-based numerical model that couples crystal plasticity and a cohesive zone model is used to generate data for the surrogate models. Three architectures - 3D U-Net, 3D Fourier Neural Operator (FNO-3D), and U-FNO were trained on the particle-velocity field data from the numerical model. The generalization of the models was evaluated using microstructures with varying grain sizes and aspect ratios. U-FNO and 3D U-Net performed significantly better than FNO-3D across all datasets. Furthermore, U-FNO and 3D U-Net exhibited comparable accuracy for every metric considered in this study. However, training the U-FNO requires almost twice the computational effort compared to the 3D U-Net, making it a desirable option for a surrogate model.
Authors: Olga Vasiljevic, Nicolas Harmand, Antoine Hubert, Lydia Kebbal, Volker Bormuth, Clara Hayn, Jonathan Fouchard, Marie Anne Breau, Lea-Laetitia Pontani
Mechanical contributions are crucial regulators of diverse biological processes, yet their \textit{in vivo} measurement remains challenging due to limitations of current techniques, that can be destructive or require complex dedicated setups. This study introduces a novel method to synthesize biocompatible, self-functionalizing stress sensors based on inverted emulsions, that can be used to probe stresses inside tissues but can also locally perturb the biological environment through specific binder presentation or drug delivery. We engineered an optimal design for these inverted emulsions, focusing on finding the balance between the two contradictory constraints: achieving low surface tension for deformability while maintaining emulsion instability for efficient self-functionalization and drug release. Proof-of-concept experiments in both agarose gels and complex biological systems, including brain organoids and zebrafish embryos, confirm the droplets ability to deform in response to mechanical stress applied within the tissue, to self-functionalize and to release encapsulated molecules locally. These versatile sensors offer a method for non-invasive stress measurements and targeted chemical delivery within living biological tissues, giving the potential to overcome current technical barriers in biophysical studies.
Authors: Feulefack Ornela Claire, Tsague Fotio Carlos, Keumo Tsiaze Roger Magloire, Serges Eric Mkam Tchouobiap, Mahouton Norbert Hounkonnou
In this study, we present theoretical investigations of phase transitions and critical phenomena in materials through the lens of second-order Ginzburg-Landau theory, in conjunction with considerations of symmetry groups and thermal fluctuations. By addressing the residual effects after a renormalization process, a small number of macroscopic degrees of freedom can effectively replace the infinite number of microscopic degrees of freedom, emphasizing the significant role of dimensionality and the intrinsic characteristics of the system in understanding and analyzing transitions. We highlight several non-universal characteristics of continuous phase transitions near the transition temperature, including the non-monotonic relationship between the critical temperature and dimensionality, as well as the enhancement or disappearance of the specific heat jump in complex superconductors. While the resulting expressions for thermodynamic quantities are complex for one-dimensional systems, obeying Mermin-Wagner's theorem, they are considerably simplified for two-dimensional and three-dimensional systems.
Authors: Qi Gao, Yuan Wan
We study numerically the real time dynamics of lattice polarons by combining the Feynman path integral and the matrix product state (MPS) approach. By constructing and solving a flow equation, we show that the integrand, viewed as a multivariable function of polaron world line parameters, can be compressed as a low bond dimension MPS, thereby allowing for efficient evaluation of various dynamical observables. We establish the effectiveness of our method by benchmarking the calculated polaron spectral function in one dimension against available results. We further demonstrate its potential by presenting the polaron spectral function in two dimensions and simulating polaron diffusion in both one and two dimensions.
Authors: Xiyin Ye, Tao Yu
Thermal and electrical injection and transport of magnon spins in magnetic insulators is conventionally understood by the non-equilibrium population of magnons. However, this view is challenged by several recent experiments in noncollinear antiferromagnets, which urge a thorough theoretical investigation at the fundamental level. We find that the magnon spin in antiferromagnets is described by a matrix, so even when the diagonal terms -- spins carried by population -- vanish, the off-diagonal correlations transmit magnon spins. Our quantum theory shows that a net spin-flip of electrons in adjacent conductors creates quantum coherence between magnon states, which transports magnon spins in canted antiferromagnets, even without a definite phase difference between magnon modes in the incoherent process. It reveals that the pumped magnon correlation is not conserved due to an intrinsic spin torque, which causes dephasing and strong spatial spin oscillations during transport; both are enhanced by magnetic fields. Spin transfer to proximity conductors can cause extrinsic dephasing, which suppresses spin oscillations and thereby gates spin transport.
Authors: Yi Xia
Higher-order phonon scatterings beyond fourth order remain largely unexplored despite their potential importance in strongly anharmonic materials at elevated temperatures. We develop a theoretical formalism for first-principles calculation of five- and six-phonon scatterings using Green's function techniques based on a diagrammatic formalism, and systematically investigate multi-phonon interactions in Si, MgO, and BaO from room temperature to near melting points. Our calculations reveal dramatically different material-dependent behaviors: while five- and six-phonon processes remain negligible in Si even at high temperatures, they become increasingly important in MgO near its melting point (3100~K) and in BaO at intermediate temperatures (1200~K). Most remarkably, five- and six-phonon scatterings surpass three- and four-phonon scattering intensity in BaO near its melting point (2100~K), reducing lattice thermal conductivity by over 50\%. We demonstrate that the strength of higher-order interactions is primarily governed by interatomic force constants, with BaO exhibiting five- and six-phonon scattering rates over one order of magnitude stronger than MgO despite identical crystal structures, due to large scattering phase space arising from softened harmonic interactions. Our work provides theoretical insights into the lattice dynamics and thermal transport in strongly anharmonic materials and at elevated temperatures.
Authors: Jihyung Kim, Dongchang Kim, Seung-Gi Lee, Yung-Cheng Li, Jae-Chun Jeon, Jiho Yoon, Sachio Komori, Ryotaro Arakawa, Tomoyasu Taniyama, Stuart S. P. Parkin, Kun-Rok Jeon
We report a significant reduction of low-temperature damping losses in tensile-strained, ultrathin Y3Fe5O12 (YIG) films grown by pulsed laser deposition, exhibiting ultralow damping constants and tunable magnetic anisotropy. Comparative broadband FMR measurements show that tensile-strained YIG films on Gd3Sc2Ga3O12 (GSGG) retain low damping even at nanometer thicknesses and cryogenic temperatures (down to 2 K), outperforming relaxed films on Gd3Ga5O12. Based on static magnetometry measurements along with microstructural and compositional analyses, we attribute these enhanced dynamic properties to the suppression of interdiffusion across the YIG/GSGG interface, resulting from enhanced chemical stability and favorable growth kinetics by the presence of Sc. Our findings highlight the importance of chemical and kinetic factors in achieving few-nanometer-thick YIG film with negligible low-temperature damping dissipation and perpendicular magnetic anisotropy for cryogenic spintronic applications.
Authors: Irakli Titvinidze, Julian Stobbe, Marvin Leusch, Georg Rohringer
In this paper, we investigate the impact of nonlocal correlations on charge fluctuations in the two-dimensional single-band Hubbard model close to the Mott metal-to-insulator transition, employing the ladder dynamical vertex approximation. At half filling and for interaction strengths and temperatures where the system is in the Mott insulating phase, charge fluctuations are strongly suppressed. Under these conditions, dynamical mean-field theory (DMFT) calculations predict a strong enhancement of the charge susceptibility at small (electron or hole) doping. However, these DMFT results include only the effects of purely local correlations despite the importance of nonlocal correlations in two-dimensional systems. We have, hence, carried out ladder dynamical vertex approximation (lD$\Gamma$A) simulations which allow for the inclusion of such nonlocal correlation effects while retaining the local ones of DMFT. Our lD$\Gamma$A numerical data show that close to half filling the large uniform charge susceptibility of DMFT is strongly suppressed by nonlocal fluctuations but gradually increases with (electron) doping. At a certain doping value, charge fluctuations eventually become larger in lD$\Gamma$A with respect to DMFT, indicating that the absence of nonlocal correlations underestimates the mobility of the charge carriers in this parameter regime. This metallization effect is also reflected in an enhancement of the lD$\Gamma$A kinetic and potential energies and a corresponding reduction of the (absolute value of the) lD$\Gamma$A Matsubara self-energy with respect to DMFT.
Authors: Abhik Samui, Manoj Gopalakrishnan
We study the stationary states of an active Brownian particle (ABP) and run-and-tumble particle (RTP) in two dimensional power-law potentials, in the limit where translational diffusion is negligible. The potential energy of the particle has the form $U(r)\propto r^{n}$, where $n\geq 2$ and even. In two dimensions, we derive the exact equations for the positional probability distribution $\phi({\bf r})$ of ABP ($n\geq 2)$ and RTP ($n=2$), whose solutions are obtained under the assumption that the particle's orientation angle is Gaussian. Both analytical and numerical results show that, in all cases, $\phi({\bf r})$ has compact support and undergoes a phase transition-like shape change as a function of the trap strength. For ABP, our theory predicts a continuous transition in shape for $n=2$ and a discontinuous transition for $n>2$, both of which agree with the simulation results. Simulations suggest the existence of both types of shape transition in the case of RTP as well. For ABP, in the strongly active regime, the orientational probability distribution is unimodal near the outer boundary but becomes bimodal towards the interior, signifying a transition from predominantly radial orientation to orbiting motion. In RTP, the analogous shape transition in the orientational distribution is almost absent.
Authors: Steven T. Bramwell
The common observation of anomalous `$1/f^\alpha$' relaxation with $\alpha<2$ constitutes one of the enduring mysteries of condensed matter physics. Here it is shown that a $1/f^{\alpha}$ spectral density, with $\alpha = 3/2$, can arise in the response of an ensemble of two--level systems coupled to a heat bath by means of a system of Bosonic quasiparticles. The model considered is the classic model of Faughnan and Strandberg of the phonon bottleneck, and the anomalous response is associated with an approximate non-equilibrium steady state of the phonons maintained by slow spin relaxation. The frequency dependence of the response to an applied field is calculated analytically, revealing the emergence, in the limit of a strong bottleneck, of $\alpha=3/2$ behaviour over a diverging range of frequencies. The application of this result to experimental systems is discussed and comparisons are drawn with other systems that exhibit anomalous relaxation.
Authors: Xuan Guo, Meng-Han Zhang, Dao-Xin Yao
We theoretically explore higher-order topological magnons in collinear altermagnets, encompassing a dimensional hierarchy ranging from localized corner modes to propagating hinge excitations. By employing antiferromagnetic interlayer coupling in bosonic Bogoliubov-de Gennes (BdG) Hamiltonian, our work reveals anisotropic surface states and spatially distributed hinge modes propagating along facet intersections. We track the adiabatic evolution of Wannier centers to identify the bulk-polarization with second-order topological magnon insulator (SOTMI), where various magnon spectra demonstrate symmetry-protected band structure beyond conventional topology. Leveraging the stability and propagative properties of hinge modes, these unconventional magnons demonstrate manipulability in atomic-scale modifications of termination. Our study integrate altermagnetism with higher-order topology, which advance magnon-based quantum computing processing energy-efficient integrated architectures and information transfer.
Authors: Kateryna Korshynska, Sebastian Ulbricht
BEC-based quantum sensors offer a huge, yet not fully explored potential in gravimetry and ac- celerometry. In this paper, we study a possible setup for such a device, which is a weakly interacting Bose gas trapped in a double-well potential. In such a trap, the gas is known to exhibit Josephson oscillations, which rely on the coherence between the potential wells. Applying the density matrix approach, we consider transitions between the coherent, partially incoherent, and fully incoherent states of the Bose gas. We provide an analytical description of the collisional decoherence due to weak interactions, causing the Josephson oscillations to decay with time. In particular, we give the mathematical link between that decay in the density matrix approach and its interpretation in terms of phase fluctuations. To investigate the potential of the double-well setup as a quantum sensor we apply additional external acceleration to the system. The interplay of collisional interaction and ac- celeration leads to an additional shift of the oscillation frequency. We give the analytical expression for this shift and estimate the sensitivity of a hypothetical BEC double-well accelerometer based on that effect.
Authors: S. Siva Nasarayya Chari, Bharat Kumar
A two-dimensional system consisting a mixture of highly coarse-grained saturated (S-type), unsaturated (U-type) lipid molecules, and cholesterol (C-type) molecules is considered to form a model lipid monolayer. All the S-, U- and C-type particles are spherical in shape, with distinct interaction strengths. The phase behavior of the system is studied for various compositions ($x$) of the C-type particles, ranging from $x = 0.1$ to $0.9$. The results show that a structurally ordered complex is formed with the S- and C-types in the fluid-like environment of U-type particles, for $x \in \lbrace 0.5 - 0.6\rbrace$. The time-averaged hexatic order parameter $\left\langle \Psi_{6} \right\rangle$ indicates that the dynamical segregation of S- and C-types exhibits a positional order, that is found to be maximum for $x$ in the range of 0.5 - 0.6. The mean change in the free energy ($\Delta G(x)$) obtained from the mean change in enthalpy ($\Delta H$) and entropy ($\Delta S$) calculations suggests that $\Delta G$ is minimum for $x \sim 0.6$. A phenomenological expression for the Gibbs free energy is formulated by explicitly accounting for the individual free energies of S-,U- and C-type particles and the mutual interactions between them. Minimizing this phenomenological $G$ with respect to the C-type composition results in the optimal value, $x^* = 0.564 \pm 0.001$ for stable coexistence of phases; consistent with the simulation results and also the previous experimental observations \cite{raghavendra_effect_2023}. All these observations signify the optimal C-type composition, $x \sim 0.5 - 0.6$.
Authors: Dilipkumar N. Asthagiri, Thiago Pinheiro dos Santos, Thomas L. Beck
We simulate TIP4P/2005 water in the temperature range of 257 K to 318 K with time-steps $\delta =$ 0.25, 0.50, 2.00, and 4.00 fs. The density-temperature behavior obtained using 0.25 or 0.50 fs are in excellent agreement with each other but differ from those obtained using time-steps that have been shown earlier to lead to a breakdown of equipartition. The temperature of maximum density (TMD) is 277.15 K with $\delta t = 0.25\;\mathrm{or}\; 0.50$ fs, but is shifted to progressively lower values for longer time-steps, a trend that holds for different thermostat/barostat combinations. Enhancing the water-water dispersion interaction, as has been recommended for simulating disordered proteins in TIP4P/2005, degrades the description of the liquid-vapor phase envelope. A key takeaway from this study is that using sufficiently short time-steps ($\leq 0.5$ fs) to preserve equipartition is essential for obtaining meaningful liquid water properties and for producing reliable data to parametrize biomolecular simulation models, as correct-ensemble sampling is fundamental to ensure reproducibility across codes and simulation alogrithms.
Authors: Tomoya Nakatani, Nattamon Suwannaharn, Taisuke Sasaki
CoSn kagome metal is a pseudo-one-dimensional electronic conductor, exhibiting low resistivity (\r{ho}) along the [0001] direction (c-axis) and significantly higher \r{ho} along other crystallographic directions. Such anisotropic conduction is expected to mitigate resistivity increases in narrow interconnect wires at advanced semiconductor technology process nodes, making CoSn a promising candidate for future interconnect applications. In this study, CoSn thin films were fabricated by magnetron sputtering, and their resistivity anisotropy was investigated with respect to crystallographic orientation. Epitaxial growth of single-crystalline CoSn(10-10) films was achieved on a Ru(10-10) buffer layer at deposition temperatures above 350 °C. The CoSn films exhibited relatively low \r{ho} along [0001], reaching 13 micro{\Omega} cm for films thickner than 50 nm, and an approximately tenfold anisotropy of \r{ho} between [0001] and [2-1-10] (a-axis), consistent with previous reports on bulk CoSn single crystals. However, the CoSn(10-10) surface exhibited pronounced roughness, attributed to three-dimensional crystal growth during sputtering, which hinders accurate evaluation of the thickness dependence of resistivity. Scanning transmission electron microscopy revealed the growth of a CoSn(10-10) single-crystal with (11-20) and (01-10) side wall facets, as well as domain boundaries within the films. These results highlight both the potential and challenges of employing CoSn kagome metal in future interconnect technologies.
Authors: Deepak Dhar, Sanjib Sabhapandit
We provide an overview of studies of hysteresis in models of magnets. We discuss the shape of the hysteresis loop, dynamical symmetry breaking, and the dependence of the area of the loop on the amplitude and frequency of the driving field. We also discuss Barkhausen noise in the hysteresis loops, where the wide distribution of sizes of jumps in the magnetization may be modeled by the random-field Ising model. We discuss the distribution of sizes of these jumps in the random field Ising model on the Bethe lattice.
Authors: Fei Tan, Yuzhu Wang, Xinghao Wang, Bo Yang
We analytically compute the thermal Hall conductance (THC) of fractional quantum Hall droplets under realistic conditions that go beyond the idealized linear edge theory with conformal symmetry. Specifically, we consider finite-size effects at low temperature, nonzero self-energies of quasiholes, and general edge dispersions. We derive measurable corrections in THC that are consistent with the experimental observables. Although the quantized THC is commonly regarded as a topological invariant that is independent of edge confinement, our results show that this quantization remains robust only for arbitrary edge dispersion in the thermodynamic limit. Furthermore, the THC contributed by Abelian modes can become extremely sensitive to finite-size effects and irregular confining potentials in any realistic experimental system. In contrast, non-Abelian modes show robust THC signatures under perturbations, indicating an intrinsic stability of non-Abelian anyons.
Authors: A.M. Shentsev, M.M. Glazov
We present a theoretical study of terahertz radiation-induced transitions between attractive and repulsive Fermi polaron states in monolayers of transition metal dichalcogenides. Going beyond the simple few-particle trion picture, we develop a many-body description that explicitly accounts for correlations with the Fermi sea of resident charge carriers. We calculate the rate of the direct optical conversion process which has a threshold where the terahertz photon energy equals to the Fermi polaron binding energy. This process features a characteristic frequency dependence near the threshold, due to final-state electron-exciton scattering related to the trion correlation with the Fermi sea hole. Furthermore, we demonstrate that intense terahertz pulses can significantly heat the electron gas via Drude absorption enabling an additional, indirect conversion mechanism through collisions between hot electrons and polarons, which exhibits a strong exponential dependence on the electron temperature. Our results reveal the important role of many-body correlations and thermal effects in the terahertz-driven dynamics of excitonic complexes in two-dimensional semiconductors.
Authors: Sromona Nandi, Vineeta Yadav, Sheetal, C. S. Yadav, Bikash Das, Subhadeep Datta, Kapildeb Dolui, Rudra Sekhar Manna
The La$_2$CoIr$_{1-x}$Ti$_x$O$_6$ double perovskite series serves as an effective platform for investigating the evolution of magnetic and electronic properties as a function of chemical pressure (doping) or hydrostatic pressure due to the interplay between the electrons correlation and spin-orbit coupling. In this study, the substitution of nonmagnetic Ti$^{4+}$ at the magnetic Ir$^{4+}$-site leads to a systematic decrease in unit cell volume keeping the monoclinic symmetry throughout, reflecting the effect of chemical pressure along with a gradual suppression of magnetic interactions. The parent compound ($x =$ 0) exhibits a ferromagnetic-like state with a Curie temperature of 92 K, which continuously evolves into an antiferromagnetic ground state upon full Ti substitution ($x =$ 1) with a Neel temperature of 14.6 K. Isothermal magnetization measurements reveal a hysteresis behavior with step-like feature at zero field, indicative of a noncollinear magnetic ordering. Additionally, the enhancement of magnetization under hydrostatic pressure on La$_2$CoIrO$_6$ suggests the presence of piezomagnetic behavior. Thermal expansion measurements on La$_2$CoIrO$_6$ highlight a coupling between spin and lattice degrees of freedom. The pressure dependence of the transition temperature in the zero-pressure limit, calculated using Ehrenfest's relation, shows good agreement with magnetization data under applied pressure. First-principles density functional theory (DFT) calculations preformed for $x =$ 0, 0.5 and 1, further reveal that strong SOC associated with Ir plays a decisive role in shaping the electronic band structure, with the insulating gap progressively widening as Ti content increases from 0.28 eV ($x =$ 0), 0.44 eV ($x =$ 0.5), and 1.01 eV ($x =$ 1). The magnetic moment decreased more than 50\% for $x =$ 0.5, showing the decrease in magnetic exchange pathways.
Authors: Xin Lu, Yuanfan Yang, Zhongqing Guo, Jianpeng Liu
Moiré superlattices host a rich variety of correlated topological states, including interaction-driven integer and fractional Chern insulators. A common approach to study interacting ground states at integer fillings is the Hartree-Fock mean-field method. However, this method neglects dynamical correlations, which often leads to an overestimation of spontaneous symmetry breaking and fails to provide quantitative descriptions of single-particle excitations. This work introduces a general many-body perturbation framework for moiré systems, combining all-band Hartree-Fock calculations with random phase approximation (RPA) correlation energies and $GW$ quasiparticle corrections. We apply this framework to hexagonal boron nitride aligned rhombohedral pentalayer graphene and magic-angle twisted bilayer graphene. We show that incorporating RPA correlation energy and $GW$ self-energy corrections yields phase diagrams and single-particle spectra that quantitatively align with experimental measurements. Our versatile framework provides a systematic beyond-mean-field approach applicable to generic moiré systems.
Authors: Twan Hooijschuur, Ehsan Irani, Antoine Deblais, Sara Jabbari-Farouji
Active semiflexible filament collectives, ranging from motor-driven cytoskeletal filaments to slender organisms such as cyanobacteria and worm aggregates, abound in nature. Yet how activity and flexibility jointly govern their organization, especially Isotropic-Nematic (I-N) transition, remains poorly understood. Performing large-scale Brownian dynamics simulations of 3D active semiflexible polymers with varying flexibility degrees, we show that tangential active forces systematically shift the I-N transition to higher densities, with the shift controlled by the flexibility degree and activity strength. Strikingly, activity alters the nature of the transition: discontinuous at low strengths, continuous at moderate strengths, and ultimately suppressed at high activity levels. The delayed I-N transition originates from enhanced collective bending fluctuations, resulting in chain shrinkage and enlargement of effective confinement tube. At moderate activity levels, these fluctuations can trigger large-scale excitations that stochastically drive temporal transitions between nematic and isotropic states, indicating an activity-induced instability of the nematic field. We summarize this behavior in non-equilibrium state diagrams of density and activity for different flexibility degrees.
Authors: Xichen Huang, Saisai He, Jize Zhao, Zhong-Bing Huang
By employing the density-matrix renormalization group method, we study an extended checkerboard Hubbard model on the two-leg ladder, which includes an intraplaquette nearest-neighbour attraction V. The simulated results show that V plays a significant role in enhancing the d-wave superconductivity when the electron density is close to half-filling. In the homogeneous case t'=t (t and t' are the intraplaquette and interplaquette hopping integrals), large critical |Vc| is required to induce the superconducting ground state. With decreasing t', |Vc| is substantially diminished and the pair state has a nearly C4 symmetry. In the extremely inhomogeneous case t'<0.2t, the system transits to the d-wave superconducting phase at V\sim-0.3t and V\sim-0.4t for U=8t and U=12t, respectively, accompanying with a shift of spin and single-particle excitations from gapless to gapped type.
Authors: Feng He, Arthur Hutsalyuk, Giuseppe Mussardo, Andrea Stampiggi
Integrability is a cornerstone of classical mechanics, where it has a precise meaning. Extending this notion to quantum systems, however, remains subtle and unresolved. In particular, deciding whether a quantum Hamiltonian - viewed simply as a matrix - defines an integrable system is far from obvious, yet crucial for understanding non-equilibrium dynamics, spectral correlations, and correlation functions in many-body physics. We develop a statistical framework that approaches quantum integrability from a probabilistic standpoint. A key observation is that integrability requires a finite probability of vanishing energy gaps. Building on this, we propose a two-step protocol to distinguish integrable from non-integrable Hamiltonians. First, we apply a systematic Monte Carlo decimation of the spectrum, which exponentially compresses the Hilbert space and reveals whether level spacings approach Poisson statistics or remain mixed. The termination point of this decimation indicates the statistical character of the spectrum. Second, we analyze $k$-step gap distributions, which sharpen the distinction between Poisson and mixed statistics. Our procedure applies to Hamiltonians of any finite size, independent of whether their structure involves a few blocks or an exponentially fragmented Hilbert space. As a benchmark, we implement the protocol on quantum Hamiltonians built from the permutation group $\mathcal{S}_N$, demonstrating both its effectiveness and generality.
Authors: Hongkun Chen, Daohong Xu, Grace M. Sommers, David A. Huse, Jeff D. Thompson, Sarang Gopalakrishnan
Decoding stabilizer codes such as the surface and toric codes involves evaluating free-energy differences in a disordered statistical mechanics model, in which the randomness comes from the observed pattern of error syndromes. We study the statistical distribution of logical failure rates across observed syndromes in the toric code, and show that, within the coding phase, logical failures are predominantly caused by exponentially unlikely syndromes. Therefore, postselecting on not seeing these exponentially unlikely syndrome patterns offers a scalable accuracy gain. In general, the logical error rate can be suppressed from $p_f$ to $p_f^b$, where $b \geq 2$ in general; in the specific case of the toric code with perfect syndrome measurements, we find numerically that $b = 3.1(1)$. Our arguments apply to general topological stabilizer codes, and can be extended to more general settings as long as the decoding failure probability obeys a large deviation principle.
Authors: Md Hasan Shahriar Rifat, Tanvir Khan, Md Arafat Hossain Shourov, Md Sahat Bin Sayed, Md Saiful Islam
The electronic and optical properties of CdGa2Te4 and ZnGa2Te4 were studied using first-principles DFT calculations. Band gaps were calculated using the GGA-PBESol functional. Both materials show promise for photovoltaic applications because of their large, near-unity absorption efficiencies (10^4 cm^-1) in the visible region. They exhibit low exciton binding energies (18.85-26.81 meV), large Bohr radii (23-34.3 Angstrom), and moderate exciton temperatures (218-311 K), which are favorable for photovoltaic applications. Their performance as solar cells was simulated using the SCAPS-1D tool for thin-film devices with Pt/CdS/CdGa2Te4/Cu2O/Ti and Pt/CdS/ZnGa2Te4/Cu2O/Ti structures. We investigated the effects of layer thickness, donor and acceptor concentrations (shallow donors/acceptors), and defect density on device performance. The ideal absorber thickness for XGa2Te4 (X = Cd, Zn) was found to be 1000-1800 nm, and the CdS buffer layer around 100 nm. To obtain an efficiency above 20%, the defect density in the CdGa2Te4 and ZnGa2Te4 absorber layers should be kept below 1.772 x 10^13 cm^-3. The best simulations show efficiencies of 18.46% and 17.35% for CdGa2Te4- and ZnGa2Te4-based solar cells, respectively.
Authors: Bao-Zong Wang, Zi-Kai Li, Zhong-Da Li, Xiong-Jun Liu
We theoretically predict the giant and robust Josephson diode effect in quasi-one-dimensional topological Majorana nanowires in the regime with multiple subbands, which is expected to be relevant for the real experiment. In the multiband regime, the Majorana bound states and conventional Andreev bound states can naturally coexist, and respectively contribute to the fractional and conventional parts in the Josephson effect, with the former/latter having 4$\pi$/2$\pi$-periodicity. We show that the interplay between the two types of bound modes can produce a robust and giant diode effect in the deep topological phase regime. Notably, we unveil a novel spin parity exchange mechanism, occurring only in the multiband regime, which leads to a robust high efficiency plateau of the giant diode effect. This effect is a nontrivial consequence of the balanced Fermi moment shifts of the multiple subbands in tuning the external magnetic field. Our finding highlights the subband engineering as a powerful tool to optimize the Josephson diode effect realistically and provides a new feasible signature to identify topological phase regime in superconducting nanowires.
Authors: He-Da Wang, Bo Wang, Qun-Li Lei, Yu-Qiang Ma
The jamming transition is traditionally regarded as a geometric transition governed by static contact networks. Recently, dynamic phase transitions of athermal particles under periodic shear provide a new lens on this problem, leading to a conjecture that jamming transition corresponds to an absorbing-state transition within the Manna (conserved directed percolation) universality class. Here, by re-examining the biased random organization model, a minimal model for particles under periodic shearing that the conjecture is based on, we uncover several criticality anomalies at high density at odds with Manna universality class. In three-dimensional monodisperse systems, we find crystallization disrupts the absorbing transition, while in dense binary mixtures, a distinct transition from absorbing to active-glass states emerges, signifying a new universality class of dynamic phase transition. Closer to the jamming point, the quenched heterogeneity in the contact network smears the dynamic transition via Griffiths effects and drives the system toward heterogeneous directed percolation. We propose a field theory with fractional time dynamics that unifies these phenomena, establishing a theoretical framework linking jamming, disorder, and dynamic criticality.
Authors: M. Boboqambarova (1), A.V. Nazarov (1,2) ((1) National Research Nuclear University MEPhI, Moscow, Russia (1), (2) National Research Center "Kurchatov Institute")
We have created an innovative natural thermostat algorithm to mimic the direct impact of temperature on interatomic distances in both a perfect crystal and a system containing a vacancy. Unlike previous research, our findings demonstrate that in a system with a defect, the radii of the initial ten coordination spheres increase almost linearly with temperature. However, the coefficients defining these dependencies, unlike those for interatomic distances farther from the vacancy, do not equal the linear thermal expansion coefficient of the perfect crystal. Knowing the atomic coordinates and their temperature evolution, we calculated the temperature dependence of the vacancy formation energy and the vacancy relaxation volume in bcc iron. The significance of these effects for the accurate calculation of atomic diffusion coefficients is analyzed and discussed.
Authors: Xin-Feng Zhang, Huan-Bo Luo, Josep Batle, Bin Liu, Yongyao Li
The present contribution explores phase transitions that occur in the ground state (GS) of spin-1 Bose-Einstein condensates (BECs) with spin-orbit coupling (SOC) under the action of gradient magnetic fields. By solving the corresponding linearized system in an exact fashion, we identify the conditions under which the GS phase transitions occur, thus transforming excited states into GS. The study of the full nonlinear system, including both density-density and spin-spin interactions, is numerically analyzed. For the case of repulsive spin-spin interactions, the results resemble the linear case, while attractive spin-spin interactions lead to the formation of mixed-states near the GS phase-transition points. Additionally, higher-order vortex solitons are found to be stable even in the nonlinear regime. These findings demonstrate that arbitrary winding numbers can be achieved as corresponding to stable GS and thus contributing to the understanding of topological properties in SOC BECs.
Authors: Edgar Guzmán-González, Isaac Pérez Castillo
We develop a theoretical framework based on the cavity and replica methods to analyze the spectral properties of sparse asymmetric correlation matrices of the form $\boldsymbol{F} = (\boldsymbol{X}\boldsymbol{Y}^\top + \omega \boldsymbol{Y}\boldsymbol{X}^\top)/2T$, where $\boldsymbol{X}$ and $\boldsymbol{Y}$ are adjacency matrices of weighted Erdős--Rényi random graphs. We examine how the spectral density evolves as the asymmetry parameter $\omega$ varies from $0 < \omega < 1$ (nearly symmetric matrices) to $-1 < \omega \le 0$ (nearly antisymmetric matrices). Analytical predictions are validated through exact numerical diagonalization, showing excellent agreement with theoretical results in the thermodynamic limit.
Authors: Zhehao Ge, Conor Smith, Zehao He, Yubo Yang, Qize Li, Ziyu Xiang, Jianghan Xiao, Wenjie Zhou, Salman Kahn, Melike Erdi, Rounak Banerjee, Takashi Taniguchi, Kenji Watanabe, Seth Ariel Tongay, Miguel A. Morales, Shiwei Zhang, Feng Wang, Michael F. Crommie
Electron Wigner solids (WSs)1-12 provide an ideal system for understanding the competing effects of electron-electron and electron-disorder interactions, a central unsolved problem in condensed matter physics. Progress in this topic has been limited by a lack of single-defect-resolved experimental measurements as well as accurate theoretical tools to enable realistic experiment-theory comparison. Here we overcome these limitations by combining atomically-resolved scanning tunneling microscopy (STM) with quantum Monte Carlo (QMC) simulation of disordered 2D electron WSs. STM was used to image the electron density ($n_e$) dependent evolution of electron WSs in gate-tunable bilayer MoSe$_2$ devices with varying long-range ($n_\mathrm{LR}$) and short-range ($n_\mathrm{SR}$) disorder densities. These images were compared to QMC simulations using realistic disorder maps extracted from experiment, thus allowing the roles of different disorder types to be disentangled. We identify two distinct physical regimes for disordered electron WSs that depend on the magnitude of $n_\mathrm{SR}$. For $n_\mathrm{SR} \lesssim n_e$ the WS behavior is dominated by long-range disorder and features extensive mixed solid-liquid phases, a new type of re-entrant melting-crystallization, and prominent Friedel oscillations. In contrast, when $n_\mathrm{SR} \gg n_e$ these features are suppressed and a more robust amorphous WS phase emerges that persists to higher $n_e$, highlighting the importance of short-range disorder in this regime. Our work establishes a new framework for studying disordered quantum solids via a combined experimental-theoretical approach.
Authors: Jinpeng Xiao, Qianglin Hu, Zuodong Yu, Weipeng Chen, Xiaobing Luo
Higher-order topological superconductivity typically depends on spin-orbit interaction, and often necessitates well designed sample structures, nodal superconducting pairings or complex magnetic order. In this work, we propose a model that incorporates a Zeeman field, antiferromagnetic order, and $s$-wave superconducting pairing, all without the need for spin-orbit interaction. In a two-dimensional system, we realize a second-order topological superconductor by utilizing a staggered flux, provided that the Zeeman field is oriented perpendicular to the magnetic order moments. In three-dimensional systems, we achieve second- and third-order topological superconductors in theory, through stacking the two-dimensional second-order topological superconductor.
Authors: M. Aguilar-Janita, V. Martin-Mayor, J. Moreno-Gordo, J.J. Ruiz-Lorenzo
We study the critical behavior of the Ising spin glass in five spatial dimensions through large-scale Monte Carlo simulations and finite-size scaling analysis. Numerical evidence for a phase transition is found both with and without an externally applied magnetic field. The critical exponents are computed in both cases. We compute with a 10\% accuracy the lower critical dimension at zero magnetic field, finding a result consistent with estimates obtained with entirely different methods, by combining our estimates of critical exponents in five dimensions with previous results for other spatial dimensions. When the results in a magnetic field are compared with previous results in six spatial dimensions, qualitative differences emerge in the scaling behavior of the correlation functions at zero external momentum. This anomalous scaling does not extend to other wavevectors. We do not find indications of a quasi first-order phase transition in a magnetic field.
Authors: Dominik S. Kufel, Jack Kemp, DinhDuy Vu, Simon M. Linsel, Chris R. Laumann, Norman Y. Yao
We propose and analyze a family of approximately-symmetric neural networks for quantum spin liquid problems. These tailored architectures are parameter-efficient, scalable, and significantly outperform existing symmetry-unaware neural network architectures. Utilizing the mixed-field toric code and PXP Rydberg Hamiltonian models, we demonstrate that our approach is competitive with the state-of-the-art tensor network and quantum Monte Carlo methods. Moreover, at the largest system sizes (N = 480 for toric code, N=1584 for Rydberg PXP), our method allows us to explore Hamiltonians with sign problems beyond the reach of both quantum Monte Carlo and finite-size matrix-product states. The network comprises an exactly symmetric block following a non-symmetric block, which we argue learns a transformation of the ground state analogous to quasiadiabatic continuation. Our work paves the way toward investigating quantum spin liquid problems within interpretable neural network architectures.
Authors: Ken Kikuchi, Kah-Sen Kam, Fu-Hsiang Huang
We discuss anyon condensation in mixed-state topological order. The phases were recently conjectured to be classified by pre-modular fusion categories. Just like anyon condensation in pure-state topological order, a bootstrap analysis shows condensable anyons are given by connected étale algebras. We explain how to perform generic anyon condensation including non-invertible anyons and successive condensations. Interestingly, some condensations lead to pure-state topological orders. We clarify when this happens. We also compute topological invariants of equivalence classes.
Authors: Carlo Orientale Caputo, Elias Seiffert, Enrico Frausin, Matteo Marsili
Abstraction is the process of extracting the essential features from raw data while ignoring irrelevant details. It is well known that abstraction emerges with depth in neural networks, where deep layers capture abstract characteristics of data by combining lower level features encoded in shallow layers (e.g. edges). Yet we argue that depth alone is not enough to develop truly abstract representations. We advocate that the level of abstraction crucially depends on how broad the training set is. We address the issue within a renormalisation group approach where a representation is expanded to encompass a broader set of data. We take the unique fixed point of this transformation -- the Hierarchical Feature Model -- as a candidate for a representation which is absolutely abstract. This theoretical picture is tested in numerical experiments based on Deep Belief Networks and auto-encoders trained on data of different breadth. These show that representations in neural networks approach the Hierarchical Feature Model as the data get broader and as depth increases, in agreement with theoretical predictions.
Authors: Hai-Long Shi, Augusto Smerzi, Luca Pezzè
Multipartite entanglement is a crucial resource for advancing quantum technologies, with considerable research efforts directed toward achieving its rapid and scalable generation. In this work, we derive an analytical expression for the time-averaged quantum Fisher information (QFI), enabling the detection of scalable multipartite entanglement dynamically generated by all quantum chaotic systems governed by Dyson's ensembles. Our approach integrates concepts of randomness and quantum chaos, demonstrating that the QFI is universally determined by the structure and dimension of the Krylov space that confines the chaotic dynamics. In particular, the QFI ranges from $N^2/3$ for $N$ qubits in the permutation-symmetric subspace (e.g. for chaotic kicked top models with long-range interactions), to $N$ when the dynamics extend over the full Hilbert space with or without bit reversal symmetry or parity symmetry (e.g. in chaotic models with short-range Ising-like interactions). In the former case, the QFI reveals multipartite entanglement among $N/3$ qubits and highlights the power of chaotic collective spin systems in generating scalable multipartite entanglement. Interestingly this result can be related to isotropic substructures in the Wigner distribution of chaotic states and demonstrates the efficacy of quantum chaos for Heisenberg-scaling quantum metrology. Finally, our general expression for the QFI agrees with that obtained for random states and, differently from out-of-time-order-correlators, it can also distinguish chaotic from integrable unstable spin dynamics.
Authors: Joan Hernàndez Tey, Emanuele Cozzo
We study the transition between layer-localized and delocalized regimes in a general contact-based contagion model on multiplex networks. Using the inverse participation ratio, we characterize how activity shifts from being confined to a single layer to spreading across the entire system. Through a first-order perturbative analysis of the leading eigenvector of the supra-contact probability matrix, we derive an analytical expression for the fictive coupling $p^*$ that marks the crossover between the two regimes. This result reproduces and explains previously observed numerical scalings and extends them to a broad class of contact-based processes beyond the Susceptible-Infected-Susceptible model. We also obtain an analytical expression for the IPR of the non-dominant layer in the localized regime, confirming its power-law dependence on the coupling with exponent $\alpha=4$. Finally, we study the transition between non-dominant and dominant layers as a function of the intra-layer activity parameter $\gamma$. Our analytical findings are supported by dynamical simulations that highlight distinct susceptibility patterns across regimes. Altogether, this work provides a unified spectral framework for understanding localization and dominance transitions in multiplex contagion dynamics.
Authors: Feiyi Liu, Ming Guo, Mingyang Liu, Ruanjing Zhang, Yang Wang
Topological insulator Bi$_2$Se$_3$ thin films exhibit unique electronic properties arising from their topologically protected surface states. In a theoretical model capturing the essential physics of Dirac electrons in Bi$_2$Se$_3$, we study excitations and dissipation in two infinite parallel metallic plates undergoing relative motion. The degrees of freedom of the electrons in both plates are modeled using the 1+2 dimensional Dirac field, and a nonlocal potential is selected to describe the interaction between the two plates. The internal relative motion is introduced via a Galilean boost, with one plate assumed to slide relative to the other. We then calculate the effective action of the system and derive the vacuum occupation number in momentum space using a perturbative method. Numerical plots reveal that the vacuum occupation number, as a function of momentum, is isotropic for a motion speed $v = 0$ and anisotropic for nonzero $v$. The relative motion induces energy transfer between the plates, leading to on-shell excitations in a manner analogous to the dissipative process of the Schwinger effect. Consequently, we study the motion-induced dissipation effects and the dissipative forces through the quantum action. By using experimental Fermi velocities of Bi$_2$Se$_3$, our results demonstrate that both the imaginary part of the quantum action due to the motion boost and the dissipative force exhibit a threshold as functions of $v$, and both are positively correlated with $v$.
Authors: Gionni Marchetti
A data-driven approach based on unsupervised machine learning is proposed to infer the intrinsic dimension $m^{\ast}$ of the high-dimensional trajectories of the Fermi-Pasta-Ulam-Tsingou (FPUT) model. Principal component analysis (PCA) is applied to trajectory data consisting of $n_s = 4,000,000$ datapoints, of the FPUT $\beta$ model with $N = 32$ coupled oscillators, revealing a critical relationship between $m^{\ast}$ and the model's nonlinear strength. By estimating the intrinsic dimension $m^{\ast}$ using multiple methods (participation ratio, Kaiser rule, and the Kneedle algorithm), it is found that $m^{\ast}$ increases with the model nonlinearity. Interestingly, in the weakly nonlinear regime, for trajectories initialized by exciting the first mode, the participation ratio estimates $m^{\ast} = 2, 3$, strongly suggesting that quasi-periodic motion on a low-dimensional Riemannian manifold underlies the characteristic energy recurrences observed in the FPUT model.
Authors: Jan de Boer, Giuseppe Di Giulio, Esko Keski-Vakkuri, Erik Tonni
In quantum resource theory, one is often interested in identifying which states serve as the best resources for particular quantum tasks. If a relative comparison between quantum states can be made, this gives rise to a partial order, where states are ordered according to their suitability to act as a resource. In the literature, various different partial orders for a variety of quantum resources have been proposed. In discrete variable systems, vector majorization of Wigner functions in discrete phase space provides a natural partial order between quantum states. In the continuous variable case, a natural counterpart would be continuous majorization of Wigner functions in quantum phase space. Indeed, this concept was recently proposed and explored (mostly restricting to the single-mode case) in Van Herstraeten, Jabbour, Cerf, Quantum 7, 1021 (2023). In this work, we develop the theory of continuous majorization in the general $N$-mode case. In addition, we propose extensions to include states with finite Wigner negativity. For the special case of the convex hull of $N$-mode Gaussian states, we prove a conjecture made by Van Herstraeten, Jabbour and Cerf. We also prove a phase space counterpart of Uhlmann's theorem of majorization.
Authors: Clayton Shonkwiler, Kandin Theis
We present an algorithm for sampling tightly confined random equilateral closed polygons in three-space which has runtime linear in the number of edges. Using symplectic geometry, sampling such polygons reduces to sampling a moment polytope, and in our confinement model this polytope turns out to be very natural from a combinatorial point of view. This connection to combinatorics yields both our fast sampling algorithm and explicit formulas for the expected distances of vertices to the origin. We use our algorithm to investigate the expected total curvature of confined polygons, leading to a very precise conjecture for the asymptotics of total curvature.
Authors: Lata Kh Joshi, Filiberto Ares, Manoj K. Joshi, Christian F. Roos, Pasquale Calabrese
In quantum mechanics, the probability distribution function (PDF) and full counting statistics (FCS) play a fundamental role in characterizing the fluctuations of quantum observables, as they encode the complete information about these fluctuations. In this letter, we measure these two quantities in a trapped-ion quantum simulator for the transverse and longitudinal magnetization within a subsystem. We utilize the toolbox of classical shadows to postprocess the measurements performed in random bases. The measurement scheme efficiently allows access to the FCS and PDF of all possible operators on desired choices of subsystems of an extended quantum system.
Authors: Antonio D'Abbruzzo, Vittorio Giovannetti, Vasco Cavina
We derive an exact master equation that captures the dynamics of a quadratic quantum system linearly coupled to a Gaussian environment of the same statistics: the Gaussian Master Equation (GME). Unlike previous approaches, our formulation applies universally to both bosonic and fermionic setups, and remains valid even in the presence of initial system-environment correlations, allowing for the exact computation of the system's reduced density matrix across all parameter regimes. Remarkably, the GME shares the same operatorial structure as the Redfield equation and depends on a single kernel - a dressed environment correlation function accounting for all virtual interactions between the system and the environment. This simple structure grants a clear physical interpretation and makes the GME easy to simulate numerically, as we show by applying it to an open system based on two fermions coupled via superconductive pairing.
Authors: Qiyu Zeng, Xiaoxiang Yu, Bo Chen, Shen Zhang, Kaiguo Chen, Dongdong Kang, Jiayu Dai
Extreme electron-ion non-equilibrium states, generated by ultrafast laser excitation, lead to melting processes that are fundamentally different from those under conventional thermal equilibrium and remain not fully understood. Through neural network-enhanced multiscale simulations of tungsten and gold nanofilms, we identify electronic pressure relaxation as critical to heterogeneous phase transformations. This nonthermal expansion generates a density decrease that enable surface-initiated melting far below equilibrium melting temperatures, creating electronic pressure-driven solid-liquid interface propagation at a high speed of 2500 m/s -- tenfold faster than that of thermal heterogeneous melting mechanisms. Simulated time-resolved X-ray diffraction signatures distinguish this nonthermal expansion from thermal expansion dynamics driven by thermoelastic stress. These results establish hot-electron-mediated lattice destabilization as a universal pathway for laser-induced structural transformations, providing new insights for interpreting time-resolved experiments and controlling laser-matter interactions.
Authors: Jun-Kun Zhao, Li Li
We investigate the shear viscosity and butterfly velocity of a magnetic field-induced quantum phase transition in five dimensional Einstein-Maxwell-Chern-Simons theory, which is holographically dual to a class of strongly coupled quantum field theories with chiral anomalies. Our analysis reveals that the ratio of longitudinal shear viscosity to entropy density $\eta_\parallel/s$ exhibits a pronounced non-monotonic dependence on temperature $T$ when the magnetic field $B$ is slightly below the critical value $B_c$ of the quantum phase transition. In particular, it can develop a distinct minimum at an intermediate temperature. This contrasts sharply with the monotonic temperature scaling observed at and above $B_c$, where $\eta_\parallel/s$ follows the scaling $T^{2/3}$ at $B=B_c$ and transitions to $T^2$ for $B>B_c$ as $T\to0$. The non-vanishing of $\eta_\parallel/s$ for $B
Authors: Gennaro Zanfardino, Stefano Paesani, Luca Leuzzi, Raffaele Santagati, Fabio Sciarrino, Fabrizio Illuminati, Giancarlo Ruocco, Marco Leonetti
In the present work, we introduce, develop, and investigate a connection between multiphoton quantum interference, a core element of emerging photonic quantum technologies, and Hopfieldlike Hamiltonians of classical neural networks, the paradigmatic models for associative memory and machine learning in systems of artificial intelligence. Specifically, we show that combining a system composed of Nph indistinguishable photons in superposition over M field modes, a controlled array of M binary phase-shifters, and a linear-optical interferometer, yields output photon statistics described by means of a p-body Hopfield Hamiltonian of M Ising-like neurons +-1, with p = 2Nph. We investigate in detail the generalized 4-body Hopfield model obtained through this procedure and show that it realizes a transition from a memory retrieval to a memory black-out regime, i.e. a spin-glass phase, as the amount of stored memory increases. The mapping enables novel routes to the realization and investigation of disordered and complex classical systems via efficient photonic quantum simulators, as well as the description of aspects of structured photonic systems in terms of classical spin Hamiltonians.
Authors: Victor Pires, Arilson Silva, Cleber L. Rodrigues, Nemitala Added, Manfredo H. Tabacniks, Tiago F. Silva, Flávio Matias, Helio Yoriyaz, Julian Shorto
Accurate determination of electronic stopping cross sections is critical for ion beam analysis and related applications. While transmission methods are well established, backscattering approaches remain less explored from a metrological perspective, often lacking a systematic treatment of uncertainties. In this work, we present a quantitative framework to optimize experimental geometry in backscattering-based stopping measurements, explicitly accounting for both statistical and systematic errors. Applying the method to helium ions in gold thin films, we identify angular conditions that balance precision and accuracy, achieving total uncertainties below 3\% over a wide energy range. The results, benchmarked against SRIM and ICRU-49, demonstrate that our approach improves the reliability of RBS-derived stopping data and strengthens their use for reference purposes and model validation.
Authors: Yongwei Guo, Wenliang Li
We investigate the $\phi^{2n}$ deformations of the O($N$)-symmetric (generalized) free theories with a flat boundary, where $n\geqslant 2$ is an integer. The generalized free theories refer to the $\Box^k$ free scalar theories with a higher-derivative kinetic term, which is related to the multicritical generalizations of the Lifshitz type. We assume that the (generalized) free theories and the deformed theories have boundary conformal symmetry and O($N$) global symmetry. The leading anomalous dimensions of some boundary operators are derived from the bulk multiplet recombination and analyticity constraints. We find that the $\epsilon^{1/2}$ expansion in the $\phi^6$-tricritical version of the special transition extends to other multicritical cases with larger odd integer $n$, and most of the higher derivative cases involve a noninteger power expansion in $\epsilon$. Using the analytic bootstrap, we further verify that the multiplet-recombination results are consistent with boundary crossing symmetry.
Authors: Xie-Hang Yu, Wen Wei Ho, Pavel Kos
We introduce the notion of the mixed state projected ensemble (MSPE), a collection of mixed states describing a local region of a quantum many-body system, conditioned upon measurements of the complementary region which are incomplete. This constitutes a generalization of the pure state projected ensemble in which measurements are assumed ideal and complete, and which has been shown to tend towards limiting pure state distributions depending only on symmetries of the system, thus representing a new kind of universality in quantum equilibration dubbed deep thermalization. We study the MSPE generated by solvable (1+1)d dual-unitary quantum circuit evolution, and identify the limiting mixed state distributions which emerge at late times depending on the size of the incomplete measurement, which we assume to be lossy, finding that they correspond to certain random density matrix ensembles known in the literature. We also derive the rate of the emergence of such universality. Furthermore, we investigate the quantum information properties of the states composing the ensemble, specifically their capacity to teleport quantum information between the ends of the system. The teleportation fidelity is upper bounded by the quantum conditional entropy, which we find exhibits a sharp transition from zero to maximal when the number of measurements lost matches of that the number of degrees of freedom to be teleported. Our results initiate the first investigation of deep thermalization for mixed state ensembles, which are relevant for present-day quantum simulation experiments wherein measurements are typically not perfect, and also amount to a physical and natural way of sampling from hitherto abstract random density matrix ensembles.
Authors: Muhammad Sajid, Rozhin Yousefjani, Abolfazl Bayat
Many-body localization is a profound phase of matter affecting the entire spectrum which emerges in the presence of disorder in interacting many-body systems. Recently, the stability of many-body localization has been challenged by the avalanche mechanism, in which a small thermal region can spread, destabilizing localization and leading to global thermalization of the system. A key unresolved question is the critical competition between the thermal region's influence and the disorder strength required to trigger such an avalanche. Here, we numerically investigate many-body localization stability in an isolated Heisenberg spin chain of size $L$ subjected to a disordered magnetic field. By embedding a tunable thermal region of size $P$, we analyze the system's behavior in both static and dynamical regimes using entanglement entropy and the gap ratio. Our study yields two main findings. Firstly, for strong disorder, the avalanche only occurs if the thermal region scales with system size, specifically when $P/L$ exceeds a threshold value. Secondly, at strong disorder, we identify an intermediate phase between many-body localization and ergodic behavior as $P$ increases. This intermediate phase leaves its finger print in both static and dynamic properties of the system and tends to vanish in the thermodynamic limit. Although our simulations are restricted to finite system sizes, the analysis suggests that these results hold in the thermodynamic limit for isolated many-body systems.
Authors: Pier Giuseppe Ledda, Hemanshul Garg, Vitus Østergaard-Clausen, Lucas Krumenacker Rudzki, Ahmad Madary, Matteo Pezzulla
We study the snapping instability of a spherical elastic shell induced by a viscous flow, the umbrella flipping problem when life is at low Reynolds numbers. We combine precision desktop-scale experiments, fluid-structure simulations, shell theory, fluid mechanics, and scaling analysis to determine the instability threshold as a function of the geometrical and material parameters of the system. Building on these findings, we devise a snapping-based valve that passively and abruptly alters the hydraulic resistance of a channel, offering robust flow control without active components. Beyond the application, our study presents what we believe to be a prototypical example of fluid-induced elastic instability in viscous flow, providing a foundation for future explorations in soft hydraulics and flow-responsive structures.
Authors: Pablo Jara, Arthur Goetschy, Hui Cao, Alexey Yamilov
Imaging techniques such as functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT) achieve deep, non-invasive sensing in turbid media, but they are constrained by the photon budget. Wavefront shaping (WFS) can enhance signal strength via interference at specific locations within scattering media, enhancing light-matter interactions and potentially extending the penetration depth of these techniques. Interpreting the resulting measurements rests on the knowledge of optical sensitivity - a relationship between detected signal changes and perturbations at a specific location inside the medium. However, conventional diffusion-based sensitivity models rely on assumptions that become invalid under coherent illumination. In this work, we develop a microscopic theory for optical sensitivity that captures the inherent interference effects that diffusion theory necessarily neglects. We analytically show that under random illumination, the microscopic and diffusive treatments coincide. Using our microscopic approach, we explore WFS strategies for enhancing optical sensitivity beyond the diffusive result. We demonstrate that the input state obtained through phase conjugation at a given point inside the system leads to the largest enhancement of optical sensitivity but requires an input wavefront that depends on the target position. In sharp contrast, the maximum remission eigenchannel leads to a global enhancement of the sensitivity map with a fixed input wavefront. This global enhancement equals to remission enhancement and preserves the spatial distribution of the sensitivity, making it compatible with existing DOT reconstruction algorithms. Our results establish the theoretical foundation for integrating wavefront control with diffuse optical imaging, enabling deeper tissue penetration through improved signal strength in biomedical applications.
Authors: Hikaru Watanabe, Rikuto Oiwa, Ryotaro Arita
Multipolar order, such as octupolar order, is a key concept in condensed matter physics, particularly in light of elusive hidden orders. However, its experimental identification remains challenging due to the absence of direct coupling to conventional external stimuli. In this study, we propose that dual-circular Raman scattering serves as a probe of multipolar anisotropies. By combining symmetry analysis with microscopic calculations, we demonstrate that both time-reversal-even ($\theta$-even) and time-reversal-odd ($\theta$-odd) axial multipolar phases exhibit the Raman optical activity as a direct consequence of mirror symmetry breaking. Furthermore, we demonstrated that a multipolar phonon, a three-dimensional and alternating displacement resembling the chiral phonon, plays a vital role in the proposed optical phenomena. Our findings open a pathway for identifying multipolar orders in various materials through dual-circular Raman spectroscopy as a sensitive and versatile probe.
Authors: Stefan Löffler, Peter Schattschneider
Elastic electron scattering is one of the primary means of investigating materials on the atomic scale. It is usually described by modeling the sample as a fixed, static, perturbative potential, thereby completely neglecting the quantum nature of the atoms inside. In this work, we present a quantum treatment of elastic electron scattering. We show that the interaction of the probe beam and the sample results in entanglement between the two systems, which can have far-reaching consequences, particularly on coherence and image contrast. As a timely example, we discuss decoherence in Bragg scattering on nanoparticles. We also investigate under which conditions the conventional scattering theory is recovered.
Authors: Bayan Karimi, Xuntao Wu, Andrew N. Cleland, Jukka P. Pekola
The quantum form of the Poincaré recurrence theorem stipulates that a system with a time-independent Hamiltonian and discrete energy levels returns arbitrarily close to its initial state in a finite time. Qubit systems, being highly isolated from their dissipative surroundings, provide a possible experimental testbed for studying this theoretical construct. Here we investigate a $N$-qubit system, weakly coupled to its environment. We present quantitative analytical and numerical results on both the revival probability and time, and demonstrate that the system indeed returns arbitrarily close to its initial state in a time exponential in the number of qubits $N$. The revival times become astronomically large for systems with just a few tens of qubits. Given the lifetimes achievable in present-day superconducting multi-qubit systems, we propose a realistic experimental test of the theory and scaling of Poincaré revivals. Our study of quantum recurrence provides new insight into how thermalization emerges in isolated quantum systems.
Authors: Wanchen Ma, Junjie Liu
The quantum Mpemba effect (QMPE), an anomalous relaxation phenomenon, has been demonstrated in both closed and open Hermitian quantum systems. While some studies have linked the QMPE to Liouvillian exceptional points--non-Hermitian features emerged at the Liouvillian level--in open Hermitian quantum systems, it remains largely unexplored whether the QMPE can occur in intrinsic non-Hermitian systems, where non-Hermiticity is inherent at the Hamiltonian level. Here, we demonstrate unequivocally the occurrence of QMPE in experimentally realizable parity-time-symmetric qubit systems immersed in a bosonic bath. Using established quantifiers for QMPE, we show numerically that the QMPE persists across parameter regimes both near and far from Hamiltonian and Liouvillian exceptional points, but disappears entirely when Hermitian Hamiltonian is restored. Interestingly, neither Hamiltonian nor Liouvillian exceptional points demarcate the boundaries of the QMPE regime. To complement numerical results, we develop an analytical description based on a long-time approximation of the relaxation dynamics of quantifiers. This approach allows us to decipher the number of intersections between two dynamical trajectories of quantifier starting from two initial conditions in the validity regime of the long-time approximation, thereby providing additional information that delineate the parameter regimes supporting the genuine QMPE. We further demonstrate the robustness of QMPE against increasing the number of qubits and dephasing effect. Our findings not only broaden the scope of the QMPE but also suggest its intricate interplay with non-Hermitian features beyond exceptional points.
Authors: Alberto Giuseppe Catalano, Sven Benjamin Kožić, Gianpaolo Torre, Carola Ciaramelletti, Simone Paganelli, Fabio Franchini, Salvatore Marco Giampaolo
We pursue the identification of quantum resources carried by topological order, by evaluating quantum magic, quantified through the rank-$2$ Stabilizer Rényi entropy $\mathcal{M}_2$, in one-dimensional systems hosting symmetry-protected topological phases (SPTP). Focusing on models with an exact duality between an SPTP and a trivial one, namely the dimerized XX and the Cluster-Ising chains, we show that dual points exhibit identical amounts of magic, even thought they belong to distinct topological sectors. A subextensive asymmetry arises only under open boundary conditions, where edge effects break the duality, but this correction is non-topological and depends on microscopic parameters. These results stand in contrast to the case of topological frustration, where delocalized excitations enhance the magic logarithmically with system size. They also complement recent analyses in the literature, showing that the total magic is largely insensitive to the presence of topological order, hence suggesting that topological order is not necessarily a genuine computational resource.
Authors: Akhil Premkumar
We draw a connection between diffusion models and the Kelly criterion for maximizing returns in betting games. We find that conditional diffusion models store additional information to bind the signal $X$ with the conditioning information $Y$, equal to the mutual information between them. Classifier-free guidance effectively boosts the mutual information between $X$ and $Y$ at sampling time. This is especially helpful in image models, since the mutual information between images and their labels is low, a fact which is intimately connected to the manifold hypothesis. Finally, we point out some nuances in the popular perspective that diffusion models are infinitely deep autoencoders. In doing so, we relate the denoising loss to the Fermi Golden Rule from quantum mechanics.
Authors: Hisham Sati, Urs Schreiber
In the practice of physics model building, the process of renormalization, resummation, and anomaly cancellation is to incrementally repair initially ill-defined Lagrangian quantum field theories. Impressive as this is, one would rather have concisely defined complete theories to begin with, and understand these choices as emergent from fundamental principles. As an instructive example, we recall renormalization choices for Wilson loop observables in abelian Chern-Simons theory. Then we show that these emerge in a novel non-Lagrangian topological completion of 5D Maxwell-Chern-Simons QFT, by means of proper flux quantization in 2-Cohomotopy. This result is a modest cousin, with applications to topologically ordered quantum materials, of the more ambitious flux quantization of 11D supergravity in 4-Cohomotopy ("Hypothesis H").
Authors: Zhao-Fan Cai, Tao Liu
The well-established non-Bloch band theory predicts exponential localization of skin-mode eigenstates in one-dimensional (1D) non-Hermitian systems. Recent studies, however, have uncovered anomalous algebraic localization in higher dimensions. Here, we extend these ideas to Hermitian bosonic quadratic Hamiltonians incorporating quantum squeezing, offering a genuine quantum framework to explore non-Hermitian phenomena without external reservoirs. We construct a two-dimensional (2D) bosonic lattice model with two-mode squeezing and study its spectral properties of bosonic excitation within the Bogoliubov-de Gennes (BdG) formalism. We demonstrate an algebraic non-Hermitian skin effect (NHSE), characterized by quasi-long-range power-law localization of complex eigenstates. The system shows ultra spectral sensitivity to double infinitesimal on-site and long-range hopping impurities, while remaining insensitive to single impurities. Analytical treatment via the Green's function reveals that this sensitivity originates from the divergence of the nonlocal Green's function associated with the formation of nonlocal bound states between impurities. Our study establishes a framework for realizing novel higher-dimensional non-Hermitian physics in Hermitian bosonic platforms such as superconducting circuits, photonic lattices, and optomechanical arrays, with the demonstrated ultraspectral sensitivity enabling quantum sensing and amplification via bosonic squeezing.
Authors: Isobel C. Clarke, Virginia Ciriano-Tejel, David J. Ibberson, Grayson M. Noah, Thomas H. Swift, Mark A. I. Johnson, Ross C. C. Leon, Alberto Gomez-Saiz, John J. L. Morton, M. Fernando Gonzalez-Zalba
Constructing a quantum computer capable of broad and important applications is likely to require millions of addressable physical qubits, posing the challenge of large-scale integration of quantum systems with classical electronics. Fully depleted silicon-on-insulator CMOS technology has been used to develop a range of cryogenic electronic components for the control and readout of different qubit modalities interfaced on separate chips. However, recent measurements of quantum dots on this technology raise the tantalising prospect of realising control electronics and spin qubits on the same manufacturing platform, within a single integrated circuit (IC). Here, we demonstrate single-shot spin readout in addressable quantum dot devices within an IC fabricated using industry-standard 22 nm fully depleted silicon-on-insulator technology. We achieve spin-to-charge conversion via a ramped energy-selective measurement, detected using a radio-frequency single-electron transistor and addressed by on-chip cryogenic electronics. The observation of consistent readout visibilities exceeding 90% and millisecond spin relaxation times in two nominally identical devices within the addressable array supports the reproducibility of the unit cell. The successful observation of spin readout using this CMOS process marks a key step towards realising highly scalable and integrated spin qubits.
Authors: Chih-Yu Lee, Yi-Siou Huang, Felix Adams, Chuanyu Lian, Hongyi Sun, Jie Zhao, Zichao Ye, Nathan Youngblood, Juejun Hu, Leslie H Allen, Yifei Mo, Ichiro Takeuchi, Carlos A Rios Ocampo
Chalcogenide-based optical phase change materials (OPCMs) exhibit a large contrast in refractive index when reversibly switched between their stable amorphous and crystalline states. OPCMs have rapidly gained attention due to their versatility as nonvolatile amplitude or phase modulators in various photonic devices. However, open challenges remain, such as achieving reliable response and transparency spanning into the visible spectrum, a combination of properties in which current broadband OPCMs (e.g., Ge2Sb2Se4Te1, Sb2Se3, or Sb2S3) fall short. Discovering novel materials or engineering existing ones is, therefore, crucial in extending the application scope of OPCMs. Here, we use magnetron co-sputtering to study the effects of Si doping into Sb2Se3. We employ ellipsometry, X-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy to investigate the effects of Si doping on the optical properties and crystal structure and compare these results with those from first principles calculations. Moreover, we study the crystallization and melt-quenching of thin films via nano-differential scanning calorimetry (NanoDSC). Our experiments demonstrate that 20% Si doping increases the transparency window in both states, specifically to 800 nm (1.55 eV) in the amorphous phase, while reducing power consumption by lowering the melting temperature. However, this reduction comes at the cost of reducing the refractive index contrast between states and slowing the kinetics of the phase transition.
Authors: Hui Liu, Raul Perea-Causin, Zhao Liu, Emil J. Bergholtz
The discovery of zero-field fractional Chern insulators (FCIs) in moiré materials has attracted intense interest in the interplay between topology and correlations. Here, we demonstrate that fractionalized topological order can emerge under realistic conditions even within a topologically trivial moiré band. By projecting long-range Coulomb interactions into a trivial band of twisted multilayer graphene, we identify a set of incompressible FCI ground states exhibiting fractional quantized Hall conductance. Their Laughlin-like behavior is further confirmed through the particle-cut entanglement spectrum. We trace the origin of this phase to the strongly inhomogeneous distribution of quantum geometry within the moiré Brillouin zone, which reshapes interaction effects independently of the band topology. Extending this heuristic quantum geometric mechanism, we demonstrate that similarly unexpected Laughlin-like FCIs can also be stabilized in higher-Chern-number moiré bands under experimentally accessible conditions. Our results establish realistic scenarios under which many-body topological order can emerge independently of single-particle band topology.
Authors: Mrinal Kanti Sarkar, Saranyo Moitra, Rajdeep Sensarma
We show that odd order Rényi entropies $S^{(2q+1)}$ of a system of interacting scalar fields can be calculated as the free energy of $2q+1$ replicas of the system with additional quadratic inter-replica couplings in the subsystem at the time of measurement of the entropy. These couplings replace boundary field matching conditions. This formalism works both in and out of thermal equilibrium, for closed as well as open quantum systems, and provides a general dictionary between measurable correlation functions and entanglement entropy. $S^{(2q+1)}$ can be analytically continued to calculate the von Neumann entropy $S^{\mathrm{vN}}$. We provide an exact formula relating $S^{(2q+1)}$ and $S^{\mathrm{vN}}$ with correlation functions in a non-interacting theory. For interacting theories, we provide rules for constructing all possible Feynman diagrams for $S^{(2q+1)}$. We show that the boundary matching conditions cannot be completely eliminated while calculating Rényi entropies of even order due to presence of zero modes in replica space.
Authors: Jinming Yang, Zheting Jin, Siqi Wang, Camilla Moir, Mingyu Xu, Brandon Gunn, Xian Du, Zhibo Kang, Keke Feng, Makoto Hashimoto, Donghui Lu, Jessica McChesney, Shize Yang, Wei-Wei Xie, Alex Frano, M. Brian Maple, Sohrab Ismail-Beigi, Yu He
The mechanism behind superconductivity suppression induced by Pr substitutions in YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) has been a mystery since its discovery: in spite of being isovalent to Y$^{3+}$ with a small magnetic moment, it is the only rare-earth element that has a dramatic impact on YBCO's superconducting properties. Using angle-resolved photoemission spectroscopy (ARPES) and DFT+$U$ calculations, we uncover how Pr substitution modifies the low-energy electronic structure of YBCO. Contrary to the prevailing Fehrenbacher-Rice (FR) and Liechtenstein-Mazin (LM) models, the low energy electronic structure contains no signature of any $f$-electron hybridization or new states. Yet, strong electron doping is observed primarily on the antibonding Fermi surface. Meanwhile, we reveal major electronic structure modifications to Cu-derived states with increasing Pr substitution: a pronounced CuO$_2$ bilayer decoupling and an enhanced CuO chain hopping, implying indirect electron-release pathways beyond simple 4$f$ state ionization. Our results challenge the long-standing FR/LM mechanism and establish Pr substituted YBCO as a potential platform for exploring correlation-driven phenomena in coupled 1D-2D systems.
Authors: Xiangyu Luo, Ludovica Zullo, Sahaj Patel, Dongjin Oh, Qian Song, Asish K. Kundu, Anil Rajapitamahuni, Elio Vescovo, Natalia Olszowska, Rafal Kurleto, Dawid Wutke, Giorgio Sangiovanni, Riccardo Comin
Flat electronic bands, which amplify electron correlations by quenching kinetic energy, provide an ideal foundation for exotic quantum phases. However, prevailing strategies -- including geometrically frustrated lattices, moire superlattices and heavy-fermion physics -- suffer from inherent trade-offs among robustness, tunability and orbital selectivity, limiting their broad applicability. Here, we unveil an intrinsic orbital-selective flat-band mechanism in the van der Waals materials NbOCl2 and TaOCl2, directly observed by angle-resolved photoemission spectroscopy (ARPES) and understood through density functional theory (DFT) and Wannier analysis. Crucially, we experimentally demonstrate that this momentum-independent flat band exhibits remarkable robustness, surviving from the bulk crystal down to the few-layer limit at room temperature. Our theoretical analysis traces its origin to the hybridization between Nb-dz2 orbital chains and the Lieb-like dx2-y2 sublattice, which is further reinforced by Peierls dimerization. Our findings not only establish transition-metal oxychlorides as a robust and tunable platform for flat-band-driven correlated phases under ambient conditions, but also uncover a new orbital-selective design principle for realizing flat bands in quantum materials.
Authors: Zihao Huo, Wenxuan Wang, Jian Xie, Yves H. Kwan, Jonah Herzog-Arbeitman, Zaizhe Zhang, Qiu Yang, Min Wu, Kenji Watanabe, Takashi Taniguchi, Kaihui Liu, Nicolas Regnault, B. Andrei Bernevig, Xiaobo Lu
Rhombohedral multilayer graphene has emerged as a powerful platform for investigating flat-band-driven correlated phenomena, yet most aspects remain not understood. In this work, we systematically study the moire-dependent band topology in rhombohedral hexalayer graphene. For the first time we demonstrate that the moire twist angle plays a crucial role in the formation of the moire Chern insulators in rhombohedral hexalayer graphene/hexagonal boron nitride (RHG/hBN) moire superlattices. In the moire-distant regime at filling factor v = 1, only systems with a twist angle {\theta} < 1.1° exhibit an integer moire Chern insulator, while the fractional Chern insulator at v = 2/3 requires smaller twist angle to be stabilized. Our theoretical modelling, which includes quantum fluctuations and exact diagonalization results, suggests that mean-field theory, which has been widely adopted, does not explain the twist-angle dependence of the v = 1 phase diagram, and that correlation effects are crucial. Moreover, we realize two distinct stacking configurations ( /Xi=0 and /Xi=1) between graphene and hBN, and find that both cases can yield a Chern insulator at v = 1. Our experimental work upends the current mean-field paradigm, illuminates how quantum fluctuations and moiré effects shape the RHG/hBN phase diagram, and paves the way for future understanding and engineering of topological correlated states in rhombohedral graphene moire systems.
Authors: Makoto Shimizu, Youichi Yanase
Pressure-induced changes in the magnetic and superconducting properties of a spin-triplet superconductor candidate UTe2 have attracted considerable interest, underscoring the need for microscopic theoretical insight. In this paper, we investigate magnetic fluctuations and their anisotropy at ambient pressure and under pressure using density functional theory (DFT) combined with the random phase approximation (RPA). For each pressure, we perform DFT+U calculations for several values of the Coulomb interaction U, construct a 72-orbital periodic Anderson model, and calculate magnetic susceptibilities with use of the RPA. For U = 2 eV, the Fermi surfaces have a quasi-two-dimensional shape, antiferromagnetic fluctuations develop with the wave vector along the a* axis, and the magnetic anisotropy follows $\chi^b > \chi^a > \chi^c$. The antiferromagnetic fluctuations are suppressed under pressure because of a reduced density of states at the Fermi level, while the magnetic anisotropy is weakened. In contrast, for U = 1 eV, where Fermi surfaces are more three-dimensional, antiferromagnetic fluctuations with Q2 = 0.22 b* appear, accompanied by anisotropy $\chi^a > \chi^c > \chi^b$, consistent with experiments. Under pressure, antiferromagnetic fluctuations around Q2 are enhanced, the magnetic wave vector tilts slightly toward the a* direction due to Fermi-surface distortion, and the magnetic anisotropy is suppressed. These results demonstrate that the pressure evolution of magnetism in UTe2 is governed by the momentum-space distribution of U-5f states and the density of states at the Fermi level, providing a microscopic basis for understanding the magnetic and superconducting properties of UTe2.
Authors: Xuance Jiang, Sayed Ali Akbar Ghorashi, Deyu Lu, Jennifer Cano
We propose a new pathway to the quantized anomalous Hall effect (QAHE) by coupling an altermagnet to a topological crystalline insulator (TCI). The former gaps the topological surface states of the TCI, thereby realizing the QAHE in a robust and switchable platform with near- vanishing magnetization. We demonstrate the feasibility of this approach by studying a slab of the TCI SnTe coupled to an altermagnetic RuO2 layer. Our first-principles calculations reveal that the d-wave altermagnetism in RuO2 induces a 7 meV gap to the Dirac surface states on the (110) surface of SnTe, producing a finite anomalous Hall effect. Our approach generalizes to broader classes of altermagnetic materials and TCIs, thereby providing a family of topological altermagnetic heterostructures with small or vanishing magnetization that support nontrivial Chern numbers. Our results highlight a promising new topological platform with great tunability and applications to spintronics.
Authors: Mateusz Kędziora, Andrzej Opala, Maciej Zaremba, Helgi Sigurðsson, Barbara Piętka
Controlling the spin degree of freedom of light at the microscale is crucial for advancing photonic information processing. Spin polarized light propagation, combined with strong optical nonlinearities, unlocks new functionalities in compact photonic circuits and active spin optronic devices. Lead halide perovskite exciton polaritons uniquely combine room temperature operation, pronounced nonlinearities, and versatile microstructuring, making them a powerful platform for spin based photonic technologies. Here, we demonstrate polarized edge emission from polariton condensates in perovskite single crystals predesigned into a microwire, forming natural, DBR free cavity. Above threshold, we observe a distinct waveguiding optical spin Hall effect pattern in both real- and reciprocal-space emission, accompanied by pseudospin phase locking arising from coherence between opposite edges. Beyond static polarization textures, we achieve spin-resolved polariton edge lasing with chirality exceeding 80\% and spin-polarized signal propagation over tens of micrometres. These results establish CsPbBr3 waveguides as a promising easy to fabricate platform for on chip spin coded information transport and nonlinear spin optoelectronics.
Authors: Sayan Mondal, Pei-Hao Fu, Jorge Cayao
Superconductor-semiconductor hybrids are useful for realizing the Josephson diode effect, where nonreciprocity in the supercurrents occurs due to the interplay of the Josephson effect and applied magnetic fields. These junctions can host Andreev and Majorana states with the same ingredients, though their interplay with the Josephson diode effect is unclear. In this work, we consider short Josephson junctions based on superconductor-semiconductor systems under homogeneous Zeeman fields and investigate the Josephson diode effect in the presence of Andreev and Majorana states. Under generic conditions, the Zeeman field component parallel to the spin-orbit axis promotes an asymmetric low-energy spectrum as a function of the superconducting phase, which persists in the trivial and topological phases hosting Andreev and Majorana bound states, respectively. Interestingly, this asymmetry creates supercurrents that are not odd functions of the phase difference, leading to a nonreciprocal behaviour and the Josephson diode effect. We show that the Josephson diode effect is particularly promoted under the presence of both zero-energy Andreev and Majorana bound states, revealing that Josephson diodes can be realized in the trivial and topological phases of superconductor-semiconductor hybrids. We then demonstrate that the Zeeman field evolution of the diode's efficiencies can map the topological phase transition and the formation of Majorana bound states via an oscillatory behavior that becomes more visible in long superconductors. While Josephson diodes generally exist in the trivial and topological phases of Josephson junctions, we discover that in the tunneling regime only a Josephson diode effect in the topological phase remains due to the finite contribution of Majorana bound states. Our findings clarify the Josephson diode effect and aid in realizing Majorana-only Josephson diodes.
Authors: Saikat Nandi, Monika Jawale, Sanjay Bachhar, Rahul Kumar, Marlis Schuller, Rabindranath Bag, J. Wilkinson, Jörg Sichelschmidt, A. Sundaresan, Sara Haravifard, N. Büttgen, A.V. Mahajan
Spin-1/2 Heisenberg antiferromagnetic frustrated spin chain systems display exotic ground states with unconventional excitations and distinct quantum phase transitions as the ratio of next-nearest-neighbor to nearest-neighbor coupling is tuned. We present a comprehensive investigation of the structural, magnetic, and thermodynamics properties of the spin-1/2 compound, Cu(Ampy)ClBr (Ampy= C$_6$H$_8$N$_2$ = 2-(Aminomethyl)pyridine) via x-ray diffraction, magnetization, specific heat, $^1$H nuclear magnetic resonance (NMR), electron spin resonance (ESR), and muon spin relaxation ($\mu$SR) techniques. The crystal structure features an anisotropic triangular chain lattice of magnetic Cu$^{2+}$ ions. Our bulk and local probe experiments detect neither long-range magnetic ordering nor spin freezing down to 0.06 K despite the presence of moderate antiferromagnetic interaction between Cu$^{2+}$ spins as reflected by a Curie-Weiss temperature of about $-9$ K from the bulk susceptibility data. A broad maximum is observed at about 9 K in magnetic susceptibility and specific heat data, indicating the onset of short-range spin correlations. At low temperatures, the zero-field magnetic specific heat and the $^1$H NMR spin-lattice relaxation rate follow an exponential temperature dependence, indicating the presence of gapped magnetic excitations. Furthermore, persistent spin dynamics down to 0.088 K observed by zero-field $\mu$SR evidences lack of any static magnetism.
Authors: Xi-Han Zhou, Xiyin Ye, Tao Yu
We report a non-contact mechanism for directional injection of magnons in magnetic films when driven by a spin accumulation $\pmb{\mu}_s$ of electrons of a nearby metallic layer, governed by the long-range dipolar coupling between magnons and electron spins, which spontaneously generates a magnon current ${\bf J}_m$ flowing in the film plane. Crucially, in such near-field radiative spin transfer, the magnon flow ${\bf J}_m$ is always perpendicular to the spin accumulation $\pmb{\mu}_s$, showing a universal chiral locking relation. The spin injection is efficient even when $\pmb{\mu}_s$ is parallel to the magnetization, a feature breaking the limitation of the spin transfer by contact exchange interaction. Our findings reveal the critical role of dipolar chirality in driving the magnon thermal current and paving the way for the functional design of magnonic devices based on near-field radiative spin transfer.
Authors: David M T Kuo
In this study, we investigate the electronic structures of 13-11-13 and 15-13-15 armchair graphene nanoribbon (AGNR) superlattices (SLs) using a tight-binding model. We demonstrate that the conduction and valence subbands of 15-13-15 AGNR SLs can be accurately described by the Su-Schrieffer-Heeger model, with topologically protected interface states emerging at the junctions between 15-AGNR and 13-AGNR segments. These interface states enable the formation of quantum dot arrays with energy levels well separated from bulk states, making them promising candidates for high-temperature solid-state quantum processors. For 15-13-15 AGNRH segments, we observe both localized zigzag edge states and topologically protected interface states under longitudinal electric fields, with the latter providing efficient tunneling channels in contrast to the less conductive edge states. We further explore nonlinear charge transport through these interface states under Pauli spin blockade, showing that tunneling current spectra reveal charge stability diagrams and Coulomb blockade oscillations, consistent with experimental findings in other serial double quantum dot systems. Additionally, we examine the impact of orbital offsets on tunneling current rectification and demonstrate that significant current rectification is achieved over a wide temperature range when level broadening is optimized. These results highlight the potential of 15-13-15 AGNRHs for robust spin-current conversion and applications in quantum devices, offering advantages over other proposed structures due to precise tunability of key parameters via bottom-up synthesis techniques and the ease of two-gate electrode integration.
Authors: Grace M. Lu, Dallas R. Trinkle (Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA)
Explainable machine learning can help to discover new physical relationships for material properties. To understand the material properties that govern the activation energy for oxygen diffusion in perovskites and pyrochlores, we build a database of experimental activation energies and apply a grouping algorithm to the material property features. These features are then used to fit seven different machine learning models. An ensemble consensus determines that the most important features for predicting the activation energy are the ionicity of the A-site bond and the partial pressure of oxygen for perovskites. For pyrochlores, the two most important features are the A-site $s$ valence electron count and the B-site electronegativity. The most important features are all constructed using the weighted averages of elemental metal properties, despite weighted averages of the constituent binary oxides being included in our feature set. This is surprising because the material properties of the constituent oxides are more similar to the experimentally measured properties of perovskites and pyrochlores than the features of the metals that are chosen. The easy-to-measure features identified in this work enable rapid screening for new materials with fast oxide-ion diffusivity.
Authors: Ling-Feng Zhang, Wing Chi Yu
We study the quantum entanglement and quantum phase transition of the non-Hermitian anisotropic spin-$\frac{1}{2}$ XY model and XXZ model with the staggered imaginary field by analytical methods and numerical exact diagonalization, respectively. Various entanglement measures, including concurrence, negativity, mutual information, and quantum coherence, and both biorthogonal and self-normal quantities are investigated. Both the biorthogonal and self-normal entanglement quantities, except the biorthogonal concurrence, are found to be capable of detecting the first-order and $\mathcal{PT}$ transitions in the XXZ model, as well as the Ising and $\mathcal{RT}$ transitions in the XY model. In addition, we introduce the unconstrained concurrence and demonstrate its effectiveness in detecting these transitions. On the other hand, the Berezinskii-Kosterlitz-Thouless (BKT) transition in the XXZ model is revealed through concurrence and negativity at small non-Hermiticity strengths. Notably, the critical points observed in the Hermitian limit evolve into exceptional points as the strength of the non-Hermiticity increases. Furthermore, we find that the first-order transition survives up to a higher non-Hermiticity strength compared to the BKT transition within the $\mathcal{PT}$-symmetric regime of the XXZ model.
Authors: Xueqing Wan, Zhenlong Zhang, Charles Paillard, Jinyang Ni, Lei Zhang, Zhijun Jiang, Laurent Bellaiche
Sliding ferroelectrics, which exhibit out-of-plane polarization arising from specific stacking rather than conventional ionic displacements, are new types of ferroelectrics whose underdeveloped physics needs to be explored. Here, we investigate the electro-optic (EO) response of these materials using first-principles calculations, focusing on ZrI$_{2}$ as a prototype. We reveal that, contrary to conventional ferroelectrics, the EO effect in ZrI$_{2}$ is dominated by its electronic contribution rather than the ionic one, which promises faster EO responses. Furthermore, both biaxial and uniaxial strains significantly enhance this response, and a universal-like linear relationship between the band gap and such response is discovered. We also report a large elasto-optic coefficient that is independent of biaxial strain. Similar large linear EO coefficients and properties are found in other sliding ferroelectrics, including different zirconium dihalides, as well as BN and BP bilayers. These findings highlight sliding ferroelectrics as highly promising candidates for ultrafast nonlinear optical devices and reveal unusual mechanisms.
Authors: Amir Khan, Shalini Sharma, Tiago de Oliveira Schneider, Markus Meinert
Planar current-induced magnetization switching (CIMS) driven by spin-orbit torque (SOT) requires an in-plane uniaxial magnetic anisotropy (UMA), which can be induced by oblique-angle sputter deposition of the heavy-metal underlayer in heavy-metal/ferromagnet heterostructures. To enhance the SOT efficiency, we employ trilayer heterostructures of (Ta or W)/CoFeB/Pt, where the CoFeB layer exhibits a UMA of 50 mT at 2 nm thickness of Ta or W. The magnetization reversal in Hall-bar devices is detected through unidirectional spin Hall magnetoresistance (USMR) for the type Y geometry (easy-axis transverse to current) and planar Hall measurements for the type X geometry (easy-axis parallel to current). Both configurations exhibit CIMS with sub-microsecond current pulses, reaching switching current densities as low as $2 \times 10^{11}$ A/m$^2$ for a W (4 nm)/CoFeB (1.4 nm)/Pt (2 nm) stack with a UMA of 146 mT. Macrospin simulations reproduce the type Y switching as coherent magnetization rotation, whereas the type X devices switch at much lower currents than predicted, indicating that nucleation and domain-wall propagation dominate reversal in this geometry. Our results show that combining oblique-angle deposition with easy-axis engineering enables deterministic, field-free switching, paving the way for future low-power spintronic devices.
Authors: Xin Li, Mohamed Al Begaowe, Shu Zhang, Benedetta Flebus
The non-Hermitian skin effect (NHSE) has emerged as a hallmark of non-Hermitian physics, with far-reaching implications for transport, topology, and sensing. While recent works have uncovered the NHSE in magnetic systems, these analyses rely on effective non-Hermitian Hamiltonians, thereby leaving open critical questions regarding their applicability and predictive power in experimentally feasible platforms. Here, we address this gap by exploring both the non-Hermitian and Liouvillian dynamics of a spin chain coupled to a shared bosonic reservoir. We identify the parameter regime in which these frameworks yield congruent predictions, while showing that the non-Hermitian approach fails to capture essential dynamical features -- such as relevant timescales and conditions for experimental observability. Our analysis also reveals that the NHSE stems from the interplay between chiral spin couplings and reciprocal nonlocal dissipation -- two interactions that can naturally occur in magnetic crystals and be easily engineered in magnetic heterostructures. Focusing on a concrete example of such heterostructures, we establish an explicit connection between their Landau-Lifshitz-Gilbert (LLG) dynamics and our microscopic model, providing a tangible route toward realizing the NHSE in an experimentally relevant spintronics setup.
Authors: Deqian Kong, Shi Feng, Jianwen Xie, Ying Nian Wu
We introduce a Markov Chain Monte Carlo (MCMC) algorithm that dramatically accelerates the simulation of quantum many-body systems, a grand challenge in computational science. State-of-the-art methods for these problems are severely limited by $O(N^3)$ computational complexity. Our method avoids this bottleneck, achieving near-linear $O(N \log N)$ scaling per sweep. Our approach samples a joint probability measure over two coupled variable sets: (1) particle trajectories of the fundamental fermions, and (2) auxiliary variables that decouple fermion interactions. The key innovation is a novel transition kernel for particle trajectories formulated in the Fourier domain, revealing the transition probability as a convolution that enables massive acceleration via the Fast Fourier Transform (FFT). The auxiliary variables admit closed-form, factorized conditional distributions, enabling efficient exact Gibbs sampling update. We validate our algorithm on benchmark quantum physics problems, accurately reproducing known theoretical results and matching traditional $O(N^3)$ algorithms on $32\times 32$ lattice simulations at a fraction of the wall-clock time, empirically demonstrating $N \log N$ scaling. By reformulating a long-standing physics simulation problem in machine learning language, our work provides a powerful tool for large-scale probabilistic inference and opens avenues for physics-inspired generative models.
Authors: G. Krizman, A. Kazakov, C.-W. Cho, V. V. Volobuev, A. Majou, E. Ben Achour, T. Wojtowicz, G. Bauer, Y. Guldner, B. A. Piot, Th. Jolicoeur, G. Springholz, L.-A. de Vaulchier
Two-dimensional quantum materials can host original electronic phases that arise from the interplay of electronic correlations, symmetry and topology. In particular, the spontaneous breaking of internal symmetry that acts simultaneously on the pseudospin and the spatial degree of freedom realizes a nematic ordering. We report evidence of a quantum Hall valley nematic phase with an underlying SU(3) order parameter space obtained by a spontaneous polarization between the threefold degenerate valley pseudospins in Pb1-xSnxSe quantum wells. In the presence of a Zeeman field, we demonstrate a further control of the nematic ordering with an explicit symmetry breaking. Evidence of both spontaneous and explicit SU(3) symmetry breaking, reminiscent of the quark flavor paradigm, is of fundamental interest to shape the many body physics in a SU(3) system.
Authors: Marek Maciaszek, Bartłomiej Baur
Optically active defects in hexagonal boron nitride (hBN) are promising candidates for active components in emerging quantum technologies, such as single-photon emitters and spin centers. However, further progress in hBN-based quantum technologies requires a deeper understanding of the physics and chemistry of hBN defects. In this work, we employ ab initio calculations to investigate the thermodynamic stability and optical properties of defect complexes involving carbon, boron vacancies, and hydrogen. We demonstrate that the formation of CBVB-nH complexes (n from 0 to 3) is energetically favorable under nitrogen-rich conditions in the presence of carbon and hydrogen. The low formation energies and high binding energies of these complexes arise from the strong electrostatic attraction between the positively charged carbon substitutional defect (CB) and the negatively charged hydrogen-passivated boron vacancies (VB-nH). These complexes are particularly likely to form in metal-organic vapor-phase epitaxy (MOVPE)-grown samples, where growth occurs in the presence of carbon and hydrogen and is accompanied by a high density of boron vacancies. The optical properties of CBVB-nH complexes are analyzed and compared to recent photoluminescence measurements on MOVPE-grown hBN samples. In particular, we investigate the origin of the emission peaks at 1.90 eV and 2.24 eV and demonstrate that both the energies and lineshapes are consistent with hole capture by negatively charged CBVB and CBVB-H complexes.
Authors: Xiaoxi Huang, Qi Song, Gautam Gurung, Daniel A. Pharis, Thow Min Jerald Cham, Yulan Chen, Rakshit Jain, Maciej Olszewski, Yufan Feng, Amal El-Ghazaly, Evgeny Y. Tsymbal, Darrell G. Schlom, Daniel C. Ralph
We report measurements of the current-induced spin torque produced by the delafossite antiferromagnet PdCrO2 and acting on an adjacent ferromagnetic permalloy layer. The spin torque increases strongly as the temperature is reduced through the Neel temperature, when the PdCrO2 transitions from a paramagnetic phase to a noncollinear antiferromagnetic state. This result is qualitatively consistent with density functional theory calculations regarding how spin-current generation changes upon antiferromagnetic ordering in PdCrO2.
Authors: Konrad Koenigsmann, Peter Schauss, Gia-Wei Chern
The interplay between topological phenomena and nonequilibrium dynamics in open quantum systems represents a rapidly developing frontier in condensed matter physics. In this work, we investigate the nonequilibrium steady states of the Haldane model driven by a continuous-wave laser and coupled to a thermal reservoir. Dissipation is modeled within the Lindblad formalism adapted for quadratic fermionic systems, enabling us to study both the relaxation dynamics and the emergence of quasi-steady states. While conventional topological invariants and the bulk-boundary correspondence do not directly apply to such nonequilibrium settings, we introduce an occupation-weighted Chern number that captures the residual topological character of this quasi-steady state. We additionally examine the charge transport of this system under simultaneous driving and damping, showing that inversion symmetry breaking via a staggered sublattice potential generates a finite DC current. The magnitude and direction of this DC current are sensitive to the driving strength, highlighting the intricate interplay between topology, symmetry, and dissipation in open quantum systems.
Authors: Xinyu Yang, Shan-Shan Wang, Shuai Dong
The development of altermagnets is fundamentally important for advancing spintronic device technology, but remains unpractical for the weak spin splitting in most cases, especially in two-dimensional materials. Based on spin group symmetry analysis and first-principles calculations, a novel hydroxyl rotation strategy in collinear antiferromagnets has been proposed to design altermagnets. This approach achieves a large chirality-reversible spin splitting exceeding $1130$ meV in $\alpha_{60}$-Mn$_2$B$_2$(OH)$_2$ monolayer. The system also exhibits intrinsic features of a node-line semimetal in the absence of spin-orbit coupling. Besides, the angles of hydroxyl groups serve as the primary order parameter, which can switch on/off the altermagnetism coupled with the ferroelastic mechanism. The corresponding magnetocrystalline anisotropy have also been modulated. Moreover, an interesting spin-related transport property with the spin-polarized conductivity of 10$^{19}$ $\Omega^{-1}m^{-1}s^{-1}$ also emerges. These findings uncover the hydroxyl rotation strategy as a versatile tool for designing altermagnetic node-line semimetals and opening new avenues for achieving exotic chemical and physical characteristics associated with large spin splitting.
Authors: Jinpeng Xiao, Qianglin Hu, Zuodong Yu, Weipeng Chen, Xiaobing Luo
Higher-order topological superconductivity typically depends on spin-orbit interaction, and often necessitates well designed sample structures, nodal superconducting pairings or complex magnetic order. In this work, we propose a model that incorporates a Zeeman field, antiferromagnetic order, and $s$-wave superconducting pairing, all without the need for spin-orbit interaction. In a two-dimensional system, we realize a second-order topological superconductor by utilizing a staggered flux, provided that the Zeeman field is oriented perpendicular to the magnetic order moments. In three-dimensional systems, we achieve second- and third-order topological superconductors in theory, through stacking the two-dimensional second-order topological superconductor.
Authors: Ryuji Hakuno, Youichi Yanase
Superconductivity in UTe$_{2}$ has garnered significant attention, as it is widely recognized as a promising candidate for a spin-triplet superconductor. However, the symmetry of superconductivity and the microscopic origin of spin-triplet pairing remain subjects of debate. Nevertheless, various experiments imply an intimate coupling between magnetism and superconductivity. In this paper, we analyze a multi-sublattice periodic Anderson model that incorporates a spin-orbit coupling allowed in locally noncentrosymmetric crystals to discuss magnetic fluctuations and superconductivity in UTe$_2$. Due to the sublattice-dependent spin-orbit coupling, magnetic fluctuations become anisotropic, and the spin degeneracy of superconducting states is lifted. Our calculations reveal anisotropic antiferromagnetic fluctuations along the $b$- and $c$-axes, anisotropic ferromagnetic fluctuations along the $a$-axis, and their coexistence. These can be tuned by the $f$-electron's level. Superconductivity in the $A_u$ representation is predominant for a wide range of parameters, whereas the $B_{2u}$ representation is almost degenerate and can be stabilized. The direction of the $d$-vector changes as we increase the spin-orbit coupling. We discuss the consistency between our results and several experiments.
Authors: Dao-He Ma, Jin An
Topological nodal superconductors (SCs) have attracted considerable interest due to their gapless bulk excitations and exotic surface states. In this paper, by establishing a general framework of the effective theory for multi-orbital SCs, we realize a class of three-dimensional (3D) time-reversal (T )-invariant Dirac SCs, with their topologically protected gapless Dirac nodes being located at general positions in the Brillouin zone. By introducing T -breaking pairing perturbations, we demonstrate the existence of Majorana hinge modes in these Dirac SCs as evidence of their realization of higher-order topology. We also propose a new kind of T -breaking Dirac SCs, whose Dirac nodes possess nonzero even chiralities and so are characterized by surface Majorana arcs.
Authors: Harold J.W. Zandvliet, Pantelis Bampoulis, Cristiane Morais Smith, Lumen Eek
A twisted honeycomb bilayer exhibits a moiré superstructure that is composed of a hexagonal arrangement of AB and BA stacked domains separated by domain boundaries. In the case of twisted bilayer graphene, the application of an electric field normal to the bilayer leads to the opening of inverted band gaps in the AB and BA stacked domains. The inverted band gaps result in the formation of a two-dimensional triangular network of counterpropagating valley protected helical domain boundary states, also referred to as the quantum valley Hall effect. Owing to spin-orbit coupling and buckling, the quantum valley Hall effect in twisted bilayer silicene and germanene is more complex than in twisted bilayer graphene. We found that there is a range of electric fields for which the spin degree of freedom is locked to the valley degree of freedom of the electrons in the quantum valley Hall states, resulting in a stronger topological protection. For electric fields smaller than the aforementioned range the twisted bilayer does not exhibit the quantum valley Hall effect, whereas for larger electric fields the spin-valley locking is lifted and the emergent quantum valley Hall states are only valley-protected.
Authors: Mohammad Shafiei, Farhad Fazileh, Milorad V. Milošević
Floquet engineering with high-frequency light offers dynamic control over topological phases in quantum materials. While in 3D Dirac systems circularly polarized light is known to induce topological phase transitions via gap opening, linearly polarized light (LPL) has generally been considered ineffective. Here we show that in quasi-2D Dirac materials the second-order momentum term arising from the intersurface coupling can induce a topological phase transition under LPL, leading to chiral edge channels. Considering an ultrathin Bi$_2$Se$_3$ film as a representative system, we show that this transition occurs at experimentally accessible light intensities. Our results thus promote quasi-2D materials as viable platforms for light-controlled topological phases, expanding the potential of Floquet topological engineering.
Authors: Yuri Fukaya, Bo Lu, Keiji Yada, Yukio Tanaka, Jorge Cayao
Superconducting altermagnets have proven to be a promising ground for emergent phenomena but their study has involved two dimensional systems. In this work, we investigate three-dimensional $d$- and $g$-wave altermagnets with chiral $d$-wave superconductivity and show the formation of crossed surface flat bands due to the underlying symmetries. We find that these crossed flat bands appear at zero energy in the surface along $z$ due to the superconducting nodal lines in the $xy$-plane, while the number of corners is determined by the crystal symmetry of altermagnets. We also show that the superconducting nodal lines give rise to Bogoliubov-Fermi surfaces, which then affect the appearance of zero-energy arcs in the surface along $x$. Moreover, we demonstrate that the crossed surface flat bands, surface arcs, and Bogoliubov-Fermi surfaces give rise to distinct signals in charge conductance, hence offering a solid way for their detection and paving the way for realizing higher dimensional topological phases using altermagnets.
Authors: Quintin N. Meier, Alberto Carta, Claude Ederer, Andres Cano
Altermagnets are collinear antiferromagnets with spin-split electronic states. We introduce Ruddlesden-Popper chromates Sr$_{n+1}$Cr$_n$O$_{3n+1}$ (including SrCrO$_3$) as candidate materials in which altermagnetism can emerge from spontaneous orbital ordering rather than crystal symmetry. First-principles calculations reveal a layer-dependent spin splitting: if the spin and orbital orders align in adjacent layers, the system exhibits non-relativistic spin splitting, and thus altermagnetism. In contrast, if either the spin or the orbital order is reversed in adjacent layers, we observe a layerwise uncompensated spin splitting, that is compensated in the adjacent layer, giving rise to the concept of anti-altermagnetism. In the RP series, odd $n$ members support coexistence of altermagnetism and anti-altermagnetism, whereas even $n$ and the perovskite limit are strictly anti-altermagnetic. In both cases, larger $n$ favors metallicity, and in odd $n$ compounds strain can further stabilize altermagnetism.
Authors: Naïmo Davier, Flavia A. Gómez Albarracín, H. Diego Rosales, Pierre Pujol, Ludovic D. C. Jaubert
Spin liquids form fluctuating magnetic textures which have to obey certain rules imposed by frustration. These rules can often be written in the form of a Gauss law, indicating the local conservation of an emergent electric field. In reciprocal space, these emergent Gauss laws appear as singularities known as pinch points, that are accessible to neutron-scattering measurements. But more exotic forms of electromagnetism have been stabilized in spin liquids, and in a few rare instances, these zero-dimensional singularities have been extended into one-dimensional pinch lines. Here we propose a simple framework for the design of pinch-line spin liquids in a layered structure of two-dimensional algebraic spin liquids. A plethora of models can be build within this framework, as exemplified by several concrete examples where our theory is confirmed by simulations, and where the rank of the tensorial gauge field is continuously varied along the pinch line, opening new avenues in fractonic matter. Then we use our framework to understand how the evolution of the singularity pinch point along the pinch line can be understood as the interference pattern of two emergent electric fields. Finally, we apply our intuition on these emergent electric fields in real space to generic pinch line models beyond our layered framework, and revisit the recently proposed pinch line model on the octochlore lattice.
Authors: Jiayu David Cao, Konstantin S. Denisov, Igor Zutic
Excitonic states of tightly-bound electron-hole pairs dominate the optical response in a growing class of two-dimensional (2D) materials and their van der Waals (vdW) heterostructures. In transition metal dichalcogenides (TMDs) a useful guidance for the excitonic spectrum is the analogy with the states in the 2D hydrogen atom. From our symmetry analysis and solving the Bethe-Salpeter equations we find a much richer picture for excitons and predict their tunable resonant s-p mixing. The resonance is attained when the subband splitting matches the energy difference between the 1s and 2p+ (or 2p-) excitons, resulting in the anticrossing of the spectral lines in the absorption as a function of the subband splitting. By focusing on TMDs modified by magnetic proximity, and gated 3R-stacked bilayer TMD, we corroborate the feasibility of such tunable spin splitting. The resulting tunable and bright s-p excitons provide unexplored opportunities for their manipulation and enable optical detection of Rashba or interlayer coupling in vdW heterostructures.
Authors: Juan Sánchez-Baena
We characterize a system of tilted dipoles in a quasi two-dimensional (flattened) geometry and in the thermodynamic limit. We consider a finite trapping in the z-axis achievable in current experiments. We compute the phase diagram of the system at its equilibrium density for high tilting angles, where it becomes self-bound, and a striped liquid state emerges. To characterize the system, we perform a variational calculation, which is benchmarked with the solution of the extended Gross-Pitaevskii equation. We connect the phenomenology in the thermodynamic limit to the physics of the finite-size system, provide parameters for the realization of potentially supersolid striped states and study the critical number for dipolar droplet formation. Our results are helpful to guide potential experiments in the study of dipolar atoms in quasi two-dimensional geometries in the dipole-dominated regime.
Authors: Priyadarshini Kapri
We investigate equilibrium (background), linear, and nonlinear spin currents in two-dimensional Rashba spin-orbit coupled altermagnet systems, using a modified spin current operator that includes anomalous velocity from non-zero Berry curvature. The background spin current, stemming from spin-orbit coupling and modulated by the altermagnet term ($t_j$), exhibits in-plane polarization, increases linearly with Fermi energy ($\epsilon_F$), and is enhanced by both the altermagnet ($t_j$) and the Rashba parameter ($\lambda$). Linear spin current is always transverse with out-of-plane polarization and can be viewed as Spin Hall current, primarily driven by band velocity, with $t_j$ enabling a band-induced contribution (previously absent in simple Rashba systems ($t_j=0$)). This highlights altermagnet system as a promising source of spin Hall current generation. For linear spin Hall current, its band contribution's magnitude increases linearly with $\epsilon_F$, while the magnitude of anomalous component saturates at higher $\epsilon_F$. Further, the magnitude of spin Hall current is enhanced by $t_j$ but reduced by $\lambda$. Nonlinear spin currents feature both longitudinal and transverse components with in-plane polarization. Both the nonlinear longitudinal spin current from band velocity and the nonlinear transverse spin current from anomalous velocity initially decrease with $\epsilon_F$ before saturating at higher $\epsilon_F$. Importantly, $t_j$ reduces these currents while $\lambda$ enhances them. Meanwhile, the nonlinear transverse current from band velocity increases and then saturates with $\epsilon_F$, enhanced by $\lambda$ and showing non-monotonic variation with $t_j$. These findings highlight the tunability of spin current behavior through Rashba and altermagnet parameters, offering insights for spintronic applications.
Authors: Nadav Shaibe, Jared M. Erb, Steven M. Anlage
Vortex singularities in speckle patterns formed from random superpositions of waves are an inevitable consequence of destructive interference and are consequently generic and ubiquitous. Singularities are topologically stable, meaning they persist under small perturbations and can only be removed via pairwise annihilation. They have applications including sensing, imaging and energy transfer in multiple fields such as optics, acoustics, and elastic or fluid waves. We generalize the concept of speckle patterns to arbitrary parameter spaces and any complex scalar function that describes wave phenomena involving complicated scattering. In scattering systems specifically, we are often concerned with singularities associated with complex zeros of various functions of the scattering matrix S, such as Coherent Perfect Absorption, Reflectionless Scattering Modes, Transmissionless Scattering Modes, and Exceptional Points. Experimentally, we find that all singularities share a universal statistical property: any quantity that diverges as a simple pole at a singularity has a probability distribution function with a -3 power law tail. The tail of the distribution provides an estimate for the likelihood of finding a given singularity in a generic system. We use these universal statistical results to determine that homogeneous system loss is the most important parameter determining singularity density in a given parameter space of an absorptive scattering system. Finally, we discuss events where distinct singularities coincide in parameter space, which result in higher order singularities that are not topologically protected, and we do not find universal statistical properties for them. We support our empirical results from microwave experiments with Random Matrix Theory simulations and conclude that the statistical results presented hold for all generic non-Hermitian scattering systems.
Authors: Michael J. Desrochers, Dominic Marchand, P.C.E. Stamp
At low temperature T we expect vacuum tunneling processes to occur in superfluid $^{4}$ He films. We distinguish between extrinsic processes, in which single vortices nucleate by tunneling off boundaries in the system, and intrinsic processes, in which vortex/anti-vortex pairs nucleate far from boundaries. It is crucial to incorporate the varying effective mass of the vortex in tunneling calculations. The intrinsic processes are the superfluid analogue of the Schwinger mechanism in quantum field theory; here they appear as a quantum phase transition at T = 0, driven by an external supercurrent. We calculate the tunneling rate for these processes, and describe a means of testing the predictions using a specific vortex counting experiment.
Authors: Michelangelo Tagliavini, Fabian Wenzel, Maurits W. Haverkort
Resonant Inelastic X-Ray Scattering (RIXS) is a well-established tool for probing excitations in a wide range of materials. The measured spectra strongly depend on the scattering geometry, via its influence on the polarization of the incoming and outgoing light. By employing a tensor representation of the 4-point response function that governs the RIXS intensity, we disentangle the experimental geometry from the intrinsic material properties. In dipole-dipole RIXS processes and low-symmetry crystals, up to 81 linearly independent fundamental spectra can be measured as a function of light polarization. However, for crystals or molecules with symmetry, the number of independent fundamental spectra that define the RIXS tensor is significantly reduced. This work presents a systematic framework for determining the number of fundamental spectra and expressing the RIXS tensor in terms of these fundamental components. Given a specific experimental geometry, the measured spectrum can be represented as a linear combination of these fundamental spectra. To validate our approach, we performed calculations for different point group symmetries, both with and without an applied magnetic field. Within the same framework, we derived expressions for powder spectra in momentum-independent processes and spectra obtained using Bragg spectrometers. This formalism provides a valuable toolkit for optimizing experiment planning, data interpretation, and RIXS simulation.
Authors: Samin Tajik, Michael. j. Desrochers, Philip C.E. Stamp
We review work in areas ranging from condensed matter physics to quantum gravity, with the following interconnected questions in mind: (i) what is the nature of the vacuum in condensed matter systems, in quantum field theory, and in classical and quantum gravity; (ii) how do analogies between these systems work, how well do they work, and how useful are they; (iii) what modifications can we make to quantum mechanics to deal with quantum gravity, and (iv) how and why low-energy theories of quantum gravity are, in our view, the right way to make progress in this field. We use many different examples to illustrate our arguments.
Authors: Egor I. Kiselev
We show how crystalline inversion symmetry can be dynamically broken by optical phonons with generic, hardening Kerr-like non-linearities. The symmetry-broken state is reached through a parametric instability that can be accessed by driving close to half the phonon resonance. After the onset of the instability, the system settles to a steady state with inversion-symmetry breaking phonon trajectories and strong second harmonic generation. The time averaged positions of the atoms are displaced relative to equilibrium in the steady state, resulting in a rectification of the driving signal.
Authors: Jorge Cardenas-Gamboa, Martin Gutierrez-Amigo, Aritz Leonardo, Gregory A. Fiete, Juan L. Mañes, Jeroen van den Brink, Claudia Felser, Maia G. Vergniory
Chiral crystals offer an unique platform for controlling structural handedness through external stimuli. However, the ability to select between structural enantiomers remains challenging, both theoretically and experimentally. In this work, we demonstrate a two-step pathway for enantiomer selectivity in layered chiral NbOX$_2$ (X = Cl, Br, I) crystals based on photostriction-driven phase transitions. Ab-initio simulations reveal that optical excitation is capable of inducing a structural phase transition in NbOX$_2$ from the monoclinic ($C2$) ground state to the higher-symmetry ($C2/m$) structure. In the resulting transient high-symmetry state, an applied electric field breaks the residual inversion-symmetry degeneracy, selectively stabilizing one enantiomeric final state configuration over the other. Our results establish a combined optical-electrical control scheme for chiral materials, enabling reversible and non-contact enantiomer selection with potential applications in ultrafast switching, optoelectronics, and chiral information storage.
Authors: Archi Banerjee, Meng Zeng
Using bulk gapless topological superconductors in both 1d and 2d as free fermion model examples, we demonstrate the power of subsystem correlation spectrum (the spectrum of correlation matrix), or equivalently the entanglement spectrum for the case of free fermions, in characterizing the topology of the non-trivial ground state. For the systems considered, we show that signatures of the lowenergy spectrum, including both the edge modes and the bulk modes, appear in the correlation spectrum, albeit with different behaviors. This work generalizes the 2d Li-Haldane entanglement spectrum characterization of topological edge states to 2d topological systems with gapless bulk.
Authors: Colby Schimelfenig, Federico Serrano, Corey Halverson, Annesh Mukhopadhyay, Qingze Guan, Peter Engels
Self-trapping is a hallmark phenomenon of nonlinear dynamics. It has significant applications in modern physics, including band structure engineering, phase transition dynamics, quantum metrology, and more. Dilute-gas Bose-Einstein condensates (BECs), in which self-trapping can arise from interatomic interactions, are a prime testbed for probing nonlinear dynamics. In this Letter, we report the observation of self-trapping in a spin-orbit coupled BEC subjected to a stationary optical lattice. We employ Raman-induced spin-orbit coupling, complemented by a matching optical lattice that facilitates coupling between momentum eigenstates of the spin-orbit coupled system. By ramping the Raman detuning, we probe atomic current flow between these eigenstates and identify a clear distinction between a delocalized mixed state and a self-trapped regime. Following a quench of the Raman detuning, the time-averaged atomic current exhibits non-analytic behavior across the transition between these two regimes in certain parameter ranges, signaling a dynamical phase transition in the system.
Authors: Wei-qi Xia, Xiao-ting Zheng, Xiao-wei Chen, Gui-hua Chen
Quantum droplets, stabilized by beyond-mean-field effects, represent a novel state of matter in quantum many-body systems. While previous studies have focused primarily on dipolar and contact-interacting systems, quadrupolar condensates remain relatively unexplored. In this work, we explore the formation, structural properties, and dynamical behaviors of quantum droplets in a two-component quadrupolar Bose-Einstein condensate confined to a quasi-two-dimensional geometry. Analytical results obtained via the Thomas-Fermi approximation predict flat-topped density profiles and linear scaling between effective area and particle number. These predictions are corroborated by numerical simulations, which also reveal the saturation of peak density and chemical potential at large norm. Furthermore, vortex quantum droplets exhibit anisotropic elliptical morphologies due to the directional nature of QQIs, with their aspect ratios significantly tunable by varying the particle number and quadrupolar interaction strength. Collision dynamics demonstrate rich behavior modulated by velocity and topology: ground-state droplets transition from inelastic merging to quasi-elastic scattering and quantum penetration, while vortex droplets exhibit phase-induced repulsion, fragmentation, and topologically protected tunneling. These findings offer a comprehensive understanding of how higher-order interactions and quantum fluctuations govern the formation and stability of quadrupolar droplets. This work lays a theoretical foundation for experimental realization and opens new directions for exploring anisotropic quantum fluids, topological excitations, and applications in quantum sensing and simulation.
Authors: Hideo Aoki
There is a recent upsurge of interests in flat bands in condensed-matter systems and the consequences for magnetism and superconductivity. This article highlights the physics, where peculiar quantum-mechanical mechanisms for the physical properties such as flatband ferromagnetism and flatband superconductivity that arise when the band is not trivially flat but has a strange Hilbert space with non-orthogonalisable Wannier states, which goes far beyond just the diverging density of states. Peculiar wavefunctions come from a quantum-mechanical interference and entanglement. Interesting phenomena become even remarkable when many-body interactions are introduced, culminating in flatband superconductivity as well as flatband ferromagnetism. Flatband physics harbours a very wide range physics indeed, extending to non-equilibrium physics in laser illumination, where Floquet states for topologcial superconductivity is promoted in flatbands. While these are theoretically curious, possible candidates for the flatband materials are beginning to emerge, which is also described. These provide a wide and promising outlook.
Authors: Zheng Wang, Beichen Ruan, Zhuoheng Li, Shu-Shen Lyu, Kaixuan Chen
The quest for robust, intrinsically magnetic topological materials exhibiting the quantum anomalous Hall (QAH) effect is a central challenge in condensed matter physics and the application of revolutionary electronics. However, progress has been hampered by the limited number of candidate materials, which often suffer from poor stability and complex synthesis. Here, we introduce a new paradigm by exploring the emergent magnetism and nontrivial band topology in the largely overlooked family of two-dimensional (2D) pentagonal MN$_8$ monolayers. Employing first-principles calculations, we reveal that these systems host out-of-plane ferromagnetic ground states, a key feature that unlocks nontrivial topological properties driven by the localized $d$-orbitals of the embedded transition metals. Remarkably, we identify TiN$_8$ as a QAH insulator characterized by a Chern number of $C=-1$. Even more strikingly, MoN$_8$ is predicted to be a rare high-Chern-number QAH insulator, boasting a Chern number of $C=2$. Our findings establish the penta-MN$_8$ family as a fertile and versatile platform for realizing exotic topological quantum states. This work not only significantly expands the material landscape for magnetic topological insulators but also provides a solid theoretical foundation for designing next-generation spintronic and quantum computing devices.
Authors: Hong Jian Zhao, Laurent Bellaiche, Yanming Ma
Polar distortion, the collective off-center displacements of atoms, is a fingerprint of a ferroelectric that governs its properties and functionalities. Since the 1970s, the concepts of proper, improper and triggered ferroelectrics have been established to shed light on a diversity of polar distortion mechanisms. Such concepts assign a single nature to polar distortion and are helpful to interpret how polar distortions occur in conventional ferroelectrics such as barium titanate. However, applying these concepts to complex ferroelectrics (e.g., polar orthorhombic hafnia) is notoriously challenging and can yield highly controversial arguments. Here we resolve this issue by developing a tailor-made graph theory for clarifying the nature of polar distortions in complex ferroelectrics, which emphasizes that polar distortions in such ferroelectrics usually exhibit multiple natures among proper, improper and triggered characteristics. We demonstrate the robustness of our theory by working with perovsktie superlattices and polar orthorhombic hafnia (i.e., two representative cases). We successfully identify the mixed proper-improper nature in perovsktite superlattices and reconcile the controversy on polar orthorhombic hafnia by confirming its mixed trigger-improper nature. Our work will definitely lead to a revisitation of concepts in ferroelectric physics and provide opportunities for discovering novel ferroelectrics and related phenomena.
Authors: Albert Suceava, Sankalpa Hazra, Aiden Ross, Ian Reed Philippi, Dylan Sotir, Brynn Brower, Lei Ding, Yingxin Zhu, Zhiyu Zhang, Himirkanti Sarkar, Saugata Sarker, Yang Yang, Suchismita Sarker, Vladimir A. Stoica, Darrell G. Schlom, Long-Qing Chen, Venkatraman Gopalan
The search for thin film electro-optic (EO) materials that can retain superior performance under cryogenic conditions has become critical for quantum computing. Barium titanate thin films show large linear EO coefficients in the tetragonal phase at room temperature, which is severely degraded down to ~200 pm V$^{-1}$ in the rhombohedral phase at cryogenic temperatures. There is immense interest in manipulating these phase transformations and retaining superior EO properties down to liquid helium temperature. Utilizing the thermodynamic theory of optical properties, a large low-temperature EO response is designed by engineering the energetic competition between different ferroelectric phases, leading to a low-symmetry monoclinic phase with a massive EO response. The existence of this phase is demonstrated in a strain-tuned BaTiO$_{3}$ thin film that exhibits a linear EO coefficient of 2516 +/- 100 pm V$^{-1}$ at 5 K, which is an order of magnitude higher than the best reported performance thus far. Importantly, the EO coefficient increases by 100x during cooling, unlike the conventional films, where it degrades. Further, at the lowest temperature, significant higher order EO responses also emerge. These results represent a new framework for designing materials with property enhancements by stabilizing highly tunable metastable phases with strain. Copyright 2025 The Author(s). Advanced Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. (A. Suceava, S. Hazra, A. Ross, et al. "Colossal Cryogenic Electro-Optic Response Through Metastability in Strained BaTiO3 Thin Films." Adv. Mater. (2025): e07564. this https URL)
Authors: Volker Karle, Oriana K. Diessel, Vasil Rokaj, Ceren B. Dağ
Recent advances in chiral cavities that can couple coherently to two-dimensional materials have opened a powerful route to reshape electronic topology without an external drive. Here we establish the bulk-boundary correspondence for graphene embedded in a circularly polarized cavity. By combining exact diagonalization (ED) of zigzag ribbons, a semi-analytic T-matrix for half-infinite lattices, and analytical insights from a Dirac-Jaynes-Cummings model, we show that (i) every light-matter interaction-induced gap hosts pairs of unidirectional light-matter edge currents depending on the Chern number of the band while some of them are even bright; (ii) these chiral states persist throughout the entire photon ladder; and (iii) their dispersion, localization length and photon distribution exhibit a universal scaling controlled by the light-matter interaction. Time-evolution simulations further demonstrate that a dark electronic edge excitation can be converted into a bright and unidirectionally propagating current, that remains coherent over long time scales. Our results predict an experimental signature of the hybrid band topology and a blueprint for reconfigurable chiral channels in next-generation quantum-optical devices.
Authors: Ruijing Fang, Jie Zhang, Zhichao Zhou, Xiao Li
Valley Hall effect is fundamental to valleytronics and provides a promising avenue for advancing information technology. While conventional valley Hall effect requires the inversion symmetry breaking, the recently proposed nonlinear valley Hall (NVH) effect removes the symmetry constraint, and broaden material choices. However, existing studies are limited to nonmagnetic materials without spin involvement and rely on external strain to break rotational symmetry. Here, to address these limitations, we design a magnetically controllable NVH effect in centrosymmetric ferromagnets, by the tight-binding model and first-principles calculations. The model calculations demonstrate nonvanishing NVH conductivities can emerge in pristine hexagonal lattice without external strain, with the magnitude, sign, and spin polarization of the conductivities being all dependent on the magnetization orientation. The effect thus generates various spin-polarized valley Hall currents, characterized by distinct combinations of current direction and spin polarization. First-principle results on a ferromagnetic VSi$_2$N$_4$ bilayer confirm considerable NVH conductivities and their dependence on the magnetization. The magnetically controllable NVH effect unlocks the potential of centrosymmetric magnets for valleytronics, and offer opportunities for novel spintronic and valleytronic devices.
Authors: Jannes van Poppelen, Annica M. Black-Schaffer
Magic-angle twisted bilayer graphene (TBG) with its flat bands provides a rich platform for exploring emergent electronic orders. Similarly, periodically buckled monolayer graphene has been proposed as a tunable alternative for realizing flat bands. Here, we investigate the combined effect of buckling and twisting in bilayer graphene. We find that periodic buckling in large-angle TBG initially enhances band flattening compared to monolayer graphene, but for sufficiently strong buckling, it instead increases the band dispersion. This occurs both because of the presence of interlayer coupling, which reduces the in-plane kinetic energy, and due to the opening of a gap at the Dirac point resulting from inversion-symmetry breaking. Additionally, we find that buckling-induced band flattening competes with twist-induced band flattening. While the former breaks sublattice symmetry, generating a sublattice polarization, the latter prefers to preserve it. This prevents buckling from generating even flatter bands at the magic angle. Nevertheless, we find that buckled TBG can exhibit flatter bands than pristine TBG over a wide range of twist angles, with a flatness similar to that of pristine magic-angle TBG.
Authors: S. K. Mahatha, A. Kar, J. Corral-Sertal, Josu Diego, A. Korshunov, C.-Y. Lim, F. K. Diekmann, D. Subires, J. Phillips, T. Kim, D. Ishikawa, G. Marini, I. Vobornik, Ion Errea, S. Rohlf, M. Kalläne, V. Bellini, A. Q. R. Baron, Adolfo O. Fumega, A. Bosak, V. Pardo, K. Rossnagel, S. Blanco-Canosa
First-order phase transitions, characterized by a discontinuous change in the order parameter, are intriguing phenomena in condensed matter physics. However, the underlying, material-specific, microscopic mechanisms often remain unclear. Here, we unveil a high-temperature incommensurate charge-order precursor with the wave vector $\mathbf{q}^* = (0, \frac{1}{4}+\delta, \frac{1}{2})$ in the 1T' phase of TaTe$_2$, which competes with fluctuating high-temperature Ta trimer bonding states at $\mathbf{q}_\mathrm{CO} =(0, \frac{1}{3}, 0)$. The precursor state follows the temperature dependence of the hidden incommensurability of the $\textit{quasi}$-1D nested Fermi surface. In contrast, the low-temperature commensurate charge order at $\mathbf{q}_\mathrm{CO}$, characterized by a charge disproportionation of the inequivalent Ta sites, appears to be driven by local chemical bonding. Dynamical lattice calculations identify an imaginary optical mode at $\mathbf{q}^*$, involving an in-plane vibration of the Ta atoms forming a chain-like structure that renormalizes below $T_\mathrm{CO}$. Our experimental and theoretical observations suggest that the controversial first-order phase transition, as captured by phenomenological Ginzburg-Landau theory, results from the competition between two order parameters: one involving Fermi surface nesting and the other involving local chemical bonding.
Authors: M. M. Piva, T. Helm, J. C. Souza, K. R. Pakuszewski, C. Adriano, P. G. Pagliuso, M. Nicklas
The Weyl semimetal CeAlSi crystallises in the noncentrosymmetric tetragonal space group $I4_1md$ and exhibits ferromagnetic order below 8 K, thereby breaking both spatial inversion and time-reversal symmetries. This unique combination of properties establishes CeAlSi as a model system for studying the interplay between non-trivial topological states and strong electron correlations. In this work, we report observations of Shubnikov-de Haas oscillations in the electrical resistivity under magnetic fields up to 68 T applied parallel to the [001] crystallographic axis. Our measurements reveal an abrupt change in the oscillation frequencies near 14 T, which is indicative of a field-induced Lifshitz transition. Additionally, our results are consistent with the ferromagnetic order bringing the Weyl nodes closer to the Fermi level in CeAlSi. Furthermore, they suggest that the RKKY interaction plays an important role.
Authors: Benjamin Z. Gregory, Neha Wadehra, Shuyuan Zhang, Yi Wu, Samuel Poage, Jörg Strempfer, Asish K. Kundu, Anil Rajapitamahuni, Elio Vescovo, Anita Verma, Betül Pamuk, Jacob Ruf, Hari Nair, Nathaniel J. Schreiber, Kaveh Ahadi, Kyle M. Shen, Darrell G. Schlom, Andrej Singer
Excitement about the magnetic and electronic properties of RuO$_2$ is growing, fueled by reports of antiferromagnetism, strain-induced superconductivity, and its recent classification as a member of a newly proposed magnetic class, altermagnets, with RuO$_2$ widely regarded as the paradigmatic example. Nevertheless, the magnetic ground state of RuO$_2$ remains contentious, as several recent experiments report no evidence of magnetic order. To address this discrepancy, we performed resonant elastic scattering measurements on a series of epitaxial RuO$_2$ thin films grown on the (100)-plane of TiO$_2$ substrates across a range of strain states. Leveraging full polarization control and azimuthal scans of the structurally forbidden 100 Bragg reflection, we systematically tested for signatures of colinear antiferromagnetic order. We found that the resonant elastic scattering signal in RuO$_2$ thin films likely originates from anisotropic charge scattering, not long-range antiferromagnetic order. Using angle-resolved photoemission spectroscopy we uncover a band structure without altermagnetic band splitting that is consistent with a nonmagnetic phase. Similarly, anisotropic magnetoresistance results show no evidence of magnetism. The combination of three independent measurements suggests the absence of altermagnetism in RuO$_2$.
Authors: B. D. MacNeil, J. S. R. McCoombs, D. Kalliecharan, J. Myra, M. Pula, J. F. Britten, G. B. G. Stenning, K. Gupta, G. M. Luke, T. L. Monchesky
We report on a novel method to grow B20 MnGe thin films which employs an ultrathin CrSi template layer on Si(111). This layer is expected to be non-magnetic, in contrast to MnSi and FeGe buffer layers that have been used previously, allowing an investigation of the intrinsic properties the MnGe in the ultrathin film limit without the influence of a neighboring magnetic layer. Single-phase MnGe(111) films were grown with thicknesses between 2 and 40 nm, which exhibited low interfacial roughnesses on the order of 0.6 nm. The films crystallized in a B20 structure with a small rhombohedral distortion. Magnetometry measurements in out-of-plane fields are consistent with a conical state. However, an unexpected remanent moment develops below 35 K, concomitant with features in the field dependence of the transport data. This provides indirect evidence for the presence of a low-temperature phase which has been identified by others as either a triple-Q topological spin-hedgehog lattice, or a multi-domain single-Q conical state.
Authors: P. Zhou, X. N. Peng, Y. Z. Hu, B. R. Pan, S. M. Liu, Pengbo Lyu, L. Z. Sun
Considering the similarity of the real-space configurations for the opposite spin sublattices in both antiferromagnets (AFM) and altermagnets (AM), the relationship between them should be profound. In this work, we demonstrate that AFM and AM can be connected with spin groups and their subgroups. Consequently, the breaking of the combined inversion or translation operation with time-reversal symmetry (PT or tT) in AFM will induce transition from AFM to AM. We systematically list all collinear spin point groups and space groups that can realize the transition for the three types of AFMs: PT-type, tT-type and PT-tT-type. Moreover, we propose that Floquet engineering using circularly polarized light and surface cutting engineering are effective approaches to break PT and tT symmetries of AFM, respectively, achieving the transition. Interestingly, the features and magnitude of altermagnetic spin splitting can be tuned by adjusting various parameters of Floquet engineering. Our work not only establishes a theoretical framework for the transition from AFM to AM, but also provides practical approaches utilizing the achievements in AFM for a hundred years to obtain AM, significantly expanding the scope of altermagnetic materials for both theoretical studies and future practical applications.
Authors: Lulu Xiong, Jin Cao, Fan Yang, Xiaoxin Yang, Shen Lai, Xian-Lei Sheng, Cong Xiao, Shengyuan A. Yang
Few-layer CrPS$_{4}$ is a two-dimensional (2D) magnetic material with excellent stability in ambient environment, which attracted significant interest in recent research. Here, via first-principles calculations, we show that 2D CrPS$_{4}$ hosts a variety of anomalous Hall transport phenomena, owing to its layer-dependent magnetism and symmetry character. Monolayer CrPS$_{4}$ can display a sizable linear anomalous Hall effect, while its nonlinear anomalous Hall response is forbidden. In contrast, bilayer CrPS$_{4}$ can produce pronounced intrinsic nonlinear anomalous Hall response from Berry-connection polarizability, in the absence of linear anomalous Hall effect. We clarify that the large peaks in these responses originate from gapped Dirac points in the band structure. Furthermore, we show that linear anomalous Hall effect can be induced and controlled in bilayer CrPS$_{4}$ by gate electric field or in-plane magnetic field, which break the spacetime inversion symmetry. Our findings unveil the interesting layer-dependent Hall transport physics in 2D CrPS$_{4}$ magnets, suggesting its potential in electronic and spintronic device applications.
Authors: Qiong Qin, Congjun Wu
Motivated by the recent experimental discovery of superconductivity in rhombohedral tetralayer graphene, we investigate the pairing mechanism arising from the density-density interactions within the random-phase approximation. This approach successfully highlights the dominance of the chiral $p$-wave pairing between electrons with the same spin and valley index at low densities, while also predicting the superconducting range in agreement with experimental findings. Furthermore, we examine the characteristics of distinct superconducting regions: SC1 and SC2 exhibit chiral finite-momentum superconductivity with pronounced phase fluctuations, whereas SC4 displays zero-momentum superconductivity, with its transition temperature constrained by the pairing strength.
Authors: Elena Agliari, Andrea Alessandrelli, Adriano Barra, Martino Salomone Centonze, Federico Ricci-Tersenghi
The common thread behind the recent Nobel Prize in Physics to John Hopfield and those conferred to Giorgio Parisi in 2021 and Philip Anderson in 1977 is disorder. Quoting Philip Anderson: "more is different". This principle has been extensively demonstrated in magnetic systems and spin glasses, and, in this work, we test its validity on Hopfield neural networks to show how an assembly of these models displays emergent capabilities that are not present at a single network level. Such an assembly is designed as a layered associative Hebbian network that, beyond accomplishing standard pattern recognition, spontaneously performs also pattern disentanglement. Namely, when inputted with a composite signal -- e.g., a musical chord -- it can return the single constituting elements -- e.g., the notes making up the chord. Here, restricting to notes coded as Rademacher vectors and chords that are their mixtures (i.e., spurious states), we use tools borrowed from statistical mechanics of disordered systems to investigate this task, obtaining the conditions over the model control-parameters such that pattern disentanglement is successfully executed.
Authors: Khoa B. Le, Ali Esquembre-Kucukalic, Hsiao-Yi Chen, Ivan Maliyov, Yao Luo, Jin-Jian Zhou, Davide Sangalli, Alejandro Molina-Sanchez, Marco Bernardi
Modeling spin-wave (magnon) dynamics in novel materials is important to advance spintronics and spin-based quantum technologies. The interactions between magnons and lattice vibrations (phonons) limit the length scale for magnon transport. However, quantifying these interactions remains challenging. Here we show many-body calculations of magnon-phonon (mag-ph) coupling based on the ab initio Bethe-Salpeter equation. We derive expressions for mag-ph coupling matrices and compute them in 2D ferromagnets, focusing on hydrogenated graphene and monolayer CrI3. Our analysis shows that electron-phonon (e-ph) and mag-ph interactions differ significantly, where modes with weak e-ph coupling can exhibit strong mag-ph coupling (and vice versa), and reveals which phonon modes couple more strongly with magnons. In both materials studied here, the inelastic magnon relaxation time is found to decrease abruptly above the threshold for emission of strongly coupled phonons, thereby defining a low-energy window for efficient magnon transport. By averaging in this window, we compute the temperature-dependent magnon mean-free path, a key figure of merit for spintronics, entirely from first principles. The theory and computational tools shown in this work enable studies of magnon interactions, scattering, and dynamics in generic materials, advancing the design of magnetic systems and magnon- and spin-based devices.
Authors: Olivier Bleu, Brendan C. Mulkerin, Cesar R. Cabrera, Jesper Levinsen, Meera M. Parish
We investigate the possibility of using a Rabi drive to tune the interactions in an atomic Fermi gas. Specifically, we consider the scenario where two fermion species (spins) are Rabi coupled and interacting with a third uncoupled species. Using an exact calculation within a minimal low-energy model, we derive analytical expressions for the effective scattering length and effective range that characterize the collisions between a Rabi-dressed atom and an atom from the third species. In particular, we find that new scattering resonances emerge in the Rabi-coupled system, which we demonstrate are linked to the existence of hybrid two-body bound states. Furthermore, we show via a generalized Thouless criterion that the scattering properties have a direct impact on the superfluid transitions in the Rabi-coupled Fermi gas. The presence of Rabi-induced resonances thus has implications for the investigation of many-body physics with driven atomic gases.
Authors: Brendan C. Mulkerin, Olivier Bleu, Cesar R. Cabrera, Meera M. Parish, Jesper Levinsen
We explore the paired superfluid phases of a Fermi gas in the presence of a continuous Rabi drive. We focus on the case where two components are strongly coupled by the drive, forming hybrid superpositions, and interacting with an uncoupled third component. Using a generalized Bardeen- Cooper-Schrieffer (BCS) ansatz, we show that there are two coupled superfluid order parameters, and we obtain the associated free energy and quasiparticle excitation spectrum. We find that we can drive BCS-BCS, BCS-Bose-Einstein condensate (BEC) and BEC-BEC crossovers purely by varying the detuning of the Rabi drive from the bare transition, with the precise crossover depending on the sign of the underlying interactions between the coupled and uncoupled components. We furthermore identify an exotic excited branch which features both normal to BCS superfluid transitions, as well as a BCS-BEC-BCS crossover. Introducing a generalized Thouless criterion, we show that this behavior is reflected in the critical temperature for superfluidity. Our Rabi-coupled scenario also gives possesses additional thermodynamic properties related to the pseudospin of the coupled components, which provide novel signatures of the state of the many-body system. The Rabi-driven Fermi gas thus emerges as a unique platform for engineering and probing a rich array of multi-band superfluid phases.
Authors: Junkai Dong, Ophelia Evelyn Sommer, Tomohiro Soejima, Daniel E. Parker, Ashvin Vishwanath
Recent advances in 2D materials featuring nonzero Berry curvature have inspired extensions of the Wigner crystallization paradigm. This paper derives a low-energy effective theory for such quantum crystals, including the anomalous Hall crystal (AHC) with nonzero Chern number. First we show that the low frequency dispersion of phonons in AHC, despite the presence of Berry curvature, resembles that of the zero field (rather than finite magnetic field) Wigner crystal due to the commutation of translation generators. We explain how key parameters of the phonon theory such as elastic constants and effective mass can be extracted from microscopic models, and apply them to two families of models: the recently introduced $\lambda$-jellium model and a model of rhombohedral multilayer graphene (RMG). In the $\lambda$-jellium model, we explore the energy landscape as crystal geometry shifts, revealing that AHC can become `soft' under certain conditions. This causes transitions in lattice geometry, although the quantized Hall response remains unchanged. Surprisingly, the Berry curvature seems to enhance the effective mass, leading to a reduction in phonon speed. For the AHC in RMG, we obtain estimates of phonon speed and shear stiffness. We also identify a previously overlooked `kineo-elastic' term in the phonon effective action that is present in the symmetry setting of RMG, and leads to dramatic differences in phonon speeds in opposite directions. We numerically confirm these predictions of the effective actions by time-dependent Hartree-Fock calculations.
Authors: Yazhuang Miao, Yiming Zhao, Yong Wang, Jie Qiao, Xiaolong Zhao, Xuexi Yi
We investigate a non-Hermitian extension of the Su--Schrieffer--Heeger model that incorporates spin-dependent SU(2) gauge fields, represented by non-Abelian couplings between lattice sites, as well as independent nonreciprocal hopping amplitudes. This framework gives rise to a rich phase structure characterized by complex-energy braiding and tunable non-Hermitian skin effects. By employing the generalized Brillouin zone approach, we analyze the bulk-boundary correspondence and identify topological transitions protected by chiral symmetry. Notably, we demonstrate that non-Abelian gauge fields significantly enhance the dynamical resilience of the system, enabling robust self-healing under a moving scattering potential. These results clarify the role of SU(2) gauge fields in stabilizing non-Hermitian topological phases and indicate that the proposed model can be realized with currently available photonic, atomic, and superconducting experimental platforms.
Authors: Pablo Perez-Bastías, Rodrigo Soto
Active Brownian particles (ABPs) serve as a minimal model of active matter systems. When ABPs are sufficiently persistent, they undergo a liquid-gas phase separation and, in the presence of obstacles, accumulate around them, forming a wetting layer. Here, we perform simulations of ABPs in a quasi-one-dimensional domain in the presence of a wall, studying the dynamics of the polarization field. On the course of time, we observe a transition from a homogeneous (where all particles are aligned) to a heterogeneous (where particles align only at the interface) polarization regime. We propose coarse-grained equations for the density and polarization fields based on microscopic and phenomenological arguments that correctly account for the observed phenomena.
Authors: Yuri Fukaya, Keiji Yada, Yukio Tanaka
A new type of magnet called $p$-wave unconventional magnet is proposed, stimulated by the discovery of altermagnet. We study the tunneling conductance of $p$-wave unconventional magnet/superconductor junctions by adopting the effective Hamiltonian of $p$-wave unconventional magnets with time-reversal symmetry breaking, suggested in Ref [arXiv: 2309.01607 (2024)]. The tunneling conductance shows an asymmetric behavior with respect to bias voltage in the helical $p$-wave superconductor junctions. It is caused by the missing of helical edge states contributing to the charge conductance owing to the momentum-dependent spin-split feature of the Fermi surface in $p$-wave unconventional magnets. In chiral $d$ and $p$-wave superconductor junctions, the resulting spin-resolved tunneling conductance takes a different value for spin sectors due to the time-reversal symmetry breaking in superconductors. Our results qualitatively reproduce the results based on the simplified Hamiltonian in Ref [J.\ Phys.\ Soc.\ Jpn.\ \textbf{93}, 114703 (2024)], where only the odd function of the exchange coupling of $p$-wave unconventional magnets is taken into account, which gives the shift of the Fermi surface and preserves the time-reversal symmetry similar to the spin-orbit coupling.
Authors: Arafat Rahman, Alamgir Kabir, Tareq Mahmud
The quest for materials that simultaneously exhibit superconductivity and nontrivial topology has drawn significant attention in recent years, driven by their potential to host exotic quantum states. Their unique coexistence often leads to rich physics and potential applications in quantum technologies. Here, we predict cubic Nd$_3$In as an exceptional candidate in this class, combining strong-coupling superconductivity with distinctive topological features. Using first-principles calculations, we find that the strong-coupling superconductivity in Nd$_3$In arises primarily due to pronounced Fermi surface nesting, leading to an electron-phonon coupling constant of $\lambda = 1.39$. Our fully anisotropic Migdal--Eliashberg analysis predicts a superconducting transition temperature \( T_c \approx 14\ \mathrm{K} \) at ambient pressure, which is the highest value reported so far among cubic semimetallic superconductors. When subjected to a pressure of 15 GPa, \( T_c \) increases further to 18 K. Beyond superconductivity, Nd$_3$In is found to be a Weyl semimetal, as evidenced by the presence of Fermi arcs and nontrivial $\mathbb{Z}_2$ topological invariants, confirming its topological nature. The combination of strong-coupling superconductivity and nontrivial topological states makes Nd$_3$In a promising candidate for quantum transport and topological quantum computation.
Authors: Andrew D. King, Alberto Nocera, Marek M. Rams, Jacek Dziarmaga, Roeland Wiersema, William Bernoudy, Jack Raymond, Nitin Kaushal, Niclas Heinsdorf, Richard Harris, Kelly Boothby, Fabio Altomare, Mohsen Asad, Andrew J. Berkley, Martin Boschnak, Kevin Chern, Holly Christiani, Samantha Cibere, Jake Connor, Martin H. Dehn, Rahul Deshpande, Sara Ejtemaee, Pau Farré, Kelsey Hamer, Emile Hoskinson, Shuiyuan Huang, Mark W. Johnson, Samuel Kortas, Eric Ladizinsky, Tony Lai, Trevor Lanting, Ryan Li, Allison J.R. MacDonald, Gaelen Marsden, Catherine C. McGeoch, Reza Molavi, Richard Neufeld, Mana Norouzpour, Travis Oh, Joel Pasvolsky, Patrick Poitras, Gabriel Poulin-Lamarre, Thomas Prescott, Mauricio Reis, Chris Rich, Mohammad Samani, Benjamin Sheldan, Anatoly Smirnov, Edward Sterpka, Berta Trullas Clavera, Nicholas Tsai, Mark Volkmann, Alexander Whiticar, Jed D. Whittaker, Warren Wilkinson, Jason Yao, T.J. Yi, Anders W. Sandvik, Gonzalo Alvarez, Roger G. Melko, Juan Carrasquilla, Marcel Franz, Mohammad H. Amin
Quantum computers hold the promise of solving certain problems that lie beyond the reach of conventional computers. However, establishing this capability, especially for impactful and meaningful problems, remains a central challenge. Here, we show that superconducting quantum annealing processors can rapidly generate samples in close agreement with solutions of the Schrödinger equation. We demonstrate area-law scaling of entanglement in the model quench dynamics of two-, three-, and infinite-dimensional spin glasses, supporting the observed stretched-exponential scaling of effort for matrix-product-state approaches. We show that several leading approximate methods based on tensor networks and neural networks cannot achieve the same accuracy as the quantum annealer within a reasonable time frame. Thus, quantum annealers can answer questions of practical importance that may remain out of reach for classical computation.
Authors: Laurens Lootens, Clement Delcamp, Frank Verstraete
The fields of entanglement theory and tensor networks have recently emerged as central tools for characterising quantum phases of matter. In this article, we determine the entanglement structure of ground states of gapped symmetric quantum lattice models, and use this to obtain the most efficient tensor network representation of those ground states. We do this by showing that degeneracies in the entanglement spectrum arise through a duality transformation of the original model to the unique dual model where the entire dual (generalised) symmetry is spontaneously broken and subsequently no degeneracies are present. Physically, this duality transformation amounts to a (twisted) gauging of the unbroken symmetry in the original ground state. This result has strong implications for the complexity of simulating many-body systems using variational tensor network methods. For every phase in the phase diagram, the dual representation of the ground state that completely breaks the symmetry minimises both the entanglement entropy and the required number of variational parameters. We demonstrate the applicability of this idea by developing a generalised density matrix renormalisation group algorithm that works on (dual) constrained Hilbert spaces, and quantify the computational gains obtained over traditional tensor network methods in a perturbed Heisenberg model. Our work testifies to the usefulness of generalised non-invertible symmetries and their formal category theoretic description for the practical simulation of strongly correlated systems.
Authors: Khrystyna O. Levchenko, Kristýna Davídková, Jan Mikkelsen, Andrii V. Chumak
This review explores the development of spin-wave technology, highlighting magnonics as a promising route for radio frequency (RF) communication systems. The rollout of 5G and the upcoming 6G networks intensifies the demand for devices that can operate at higher frequencies while remaining scalable, compact, and energy-efficient - requirements that spin waves are well suited to meet. The first two sections revisit the fundamentals of magnonics, trace major milestones in spin-wave research, and summarize recent advances in materials and device design. The third section reviews RF applications studied over the past 50 years, with emphasis on key passive components, such as filters, limiters, delay lines, phase shifters, and directional couplers. The final section discusses both the advantages and the open challenges of spin-wave devices, including insertion losses, linearity, and power handling, together with the strategies to address them. By linking fundamental insights with technological needs, this review outlines a path toward practical RF platforms. Spin-wave-based devices, with their scalability, versatility, and potential for low-power operation, hold strong promise for future wireless communication, particularly in the 5G and 6G era.
Authors: Imon Mia, Armi Tiihonen, Anna Ernst, Anusha Srivastava, Tonio Buonassisi, William Vandenberghe, Julia W.P. Hsu
Bayesian Optimization (BO) machine learning method is increasingly used to guide experimental optimization tasks in materials science. To emulate the large number of input variables and noise-containing results in experimental materials research, we perform batch BO simulation of six design variables with a range of noise levels. Two test cases relevant for materials science problems are examined: a needle-in-a-haystack case (Ackley function) that may be encountered in, e.g., molecule optimizations, and a smooth landscape with a local optimum in addition to the global optimum (Hartmann function) that may be encountered in, e.g., material composition optimization. We show learning curves, performance metrics, and visualization to effectively track the optimization progression and evaluate how the optimization outcomes are affected by noise, batch-picking method, choice of acquisition function, and exploration hyperparameter values. We find that the effects of noise depend on the problem landscape: noise degrades the optimization results of a needle-in-a-haystack search (Ackley) dramatically more. However, with increasing noise, we observe an increasing probability of landing on the local optimum in Hartmann. Therefore, prior knowledge of the problem domain structure and noise level is essential when designing BO for materials research experiments. Synthetic data studies -- with known ground truth and controlled noise levels -- enable us to isolate and evaluate the impact of different batch BO components, {\it e.g.}, acquisition policy, objective metrics, and hyperparameter values, before transitioning to the inherent uncertainties of real experimental systems. The results and methodology of this study will facilitate a greater utilization of BO in guiding experimental materials research, specifically in settings with a large number of design variables to optimize.
Authors: E. M. Anderson, C. R. Allemang, A. J. Leenheer, S. W. Schmucker, J. A. Ivie, D. M. Campbell, W. Lepkowski, X. Gao, P. Lu, C. Arose, T.-M. Lu, C. Halsey, T. D. England, D. R. Ward, D. A. Scrymgeour, S. Misra
Atomic precision advanced manufacturing (APAM) dopes silicon with enough carriers to change its electronic structure and can be used to create novel devices by defining metallic regions whose boundaries have single-atom abruptness. Incompatibility with the thermal and lithography process requirements for gated silicon transistor manufacturing have inhibited exploration of both how APAM can enhance CMOS performance and how transistor manufacturing steps can accelerate the discovery of new APAM device concepts. In this work, we introduce an APAM process that enables direct integration into the middle of a transistor manufacturing workflow. We show that a process that combines sputtering and annealing with a hardmask preserves a defining characteristic of APAM, a doping density far in excess of the solid solubility limit, while trading another, the atomic precision, for compatibility with manufacturing. The electrical characteristics of a chip combining a transistor with an APAM resistor show that the APAM module has only affected the transistor through the addition of a resistance and not by altering the transistor. This proof-of-concept demonstration also outlines the requirements and limitations of a unified APAM tool, which could be introduced into manufacturing environments, greatly expanding access to this technology and inspiring a new generation of devices with it.
Authors: Jie Liu, Xin Wang
Hamiltonian learning (HL), enabling precise estimation of system parameters and underlying dynamics, plays a critical role in characterizing quantum systems. However, conventional HL methods face challenges in noise robustness and resource efficiency, especially under limited measurements. In this work, we present \textit{Inverse Physics-Informed Neural Networks for Hamiltonian Learning (iPINN-HL)}, an approach that incorporates the Schrödinger equation as a soft constraint via a loss function penalty into the ML procedure. This formulation allows the model to integrate both observational data and known physical laws to infer Hamiltonian parameters with greater accuracy and resource efficiency. We benchmark iPINN-HL against a deep-neural-network-based quantum state tomography method (denoted as DNN-HL) and demonstrate its effectiveness across several different scenarios, including one-dimensional spin chains, cross-resonance gate calibration, crosstalk identification, and real-time compensation to parameter drift. Our results show that iPINN-HL can approach the Heisenberg limit and exhibits robustness to noises, while outperforming DNN-HL in accuracy and resource efficiency. Therefore, iPINN-HL is a powerful and flexible framework for quantum system characterization for practical tasks.
Authors: Atma Anand
Information-processing systems that coordinate multiple agents and objectives face fundamental thermodynamic constraints. We show that solutions with maximum utility to act as coordination focal points have a much higher selection pressure for being findable across agents rather than accuracy. We derive that the information-theoretic minimum description length of coordination protocols to precision $\varepsilon$ scales as $L(P)\geq NK\log_2 K+N^2d^2\log (1/\varepsilon)$ for $N$ agents with $d$ potentially conflicting objectives and internal model complexity $K$. This scaling forces progressive simplification, with coordination dynamics changing the environment itself and shifting optimization across hierarchical levels. Moving from established focal points requires re-coordination, creating persistent metastable states and hysteresis until significant environmental shifts trigger phase transitions through spontaneous symmetry breaking. We operationally define coordination temperature to predict critical phenomena and estimate coordination work costs, identifying measurable signatures across systems from neural networks to restaurant bills to bureaucracies. Extending the topological version of Arrow's theorem on the impossibility of consistent preference aggregation, we find it recursively binds whenever preferences are combined. This potentially explains the indefinite cycling in multi-objective gradient descent and alignment faking in Large Language Models trained with reinforcement learning with human feedback. We term this framework Thermodynamic Coordination Theory (TCT), which demonstrates that coordination requires radical information loss.
Authors: Arezoo Afshar, Andrew Proppe, Noah Lupu-Gladstein, Lilian Childress, Aaron Z. Goldberg, Khabat Heshami
Nitrogen vacancy (NV) centers in diamond are optically addressable and versatile light-matter interfaces with practical application in magnetic field sensing, offering the ability to operate at room temperature and reach sensitivities below pT/$\sqrt{\mathrm{Hz}}.$ We propose an approach to simultaneously probe all of the magnetically sensitive states using a broadband microwave field and demonstrate that it can be used to measure the external DC magnetic field strength with sensitivities below 1~nT/$\sqrt{\mathrm{Hz}}.$ We develop tools for analyzing the temporal signatures in the transmitted broadband microwaves to estimate the magnetic field, comparing maximum likelihood estimation based on minimizing the Kullback-Leibler divergence to various neural network models, and both methods independently reach practical sensitivities. These results are achieved without optimizing parameters such as the bandwidth, power, and shape of the probing microwave field such that, with further improvements, sensitivities down to $\mathrm{pT/\sqrt{Hz}}$ can be envisioned. Our results motivate novel implementations of NV-based magnetic sensors with the potential for vectorial magnetic field detection at 1-10 kHz update rates and improved sensitivities without requiring a bias magnetic field.
Authors: Joachim P. Leibold (1, 5, 6), Lina M. Todenhagen (2, 5, 6), Matthias Althammer (3, 5, 6), Nikhita Khera (4), Elke Neu (4), Martin S. Brandt (2, 5, 6), Hans Huebl (3, 5, 6), Dominik B. Bucher (1, 6) ((1) Department of Chemistry, School of Natural Sciences, Technical University of Munich, Garching, Germany (2) Walter Schottky Institute, Technical University of Munich, Garching, Germany (3) Walther-Meißner-Institute, Bavarian Academy of Sciences and Humanities, Garching, Germany (4) Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern Landau, Kaiserslautern, Germany (5) Department of Physics, School of Natural Sciences, Technical University of Munich, Garching, Germany (6) Munich Center for Quantum Science and Technology (MCQST), Munich, Germany)
Nitrogen-vacancy (NV) centers in diamond are optically addressable spin defects with great potential for nanoscale quantum sensing. A key application of NV centers is the detection of external spins at the diamond surface. Among metals, platinum thin films - widely used in spintronics, catalysis and electrochemistry - provide a particularly interesting system for such studies. However, the interaction between NV centers and metals is known to affect their quantum sensing capabilities. In this work, we study five platinum-covered diamond samples containing shallow NVs created via nitrogen implantation with different energies (2.5-60 keV) and investigate the optical and quantum properties of NV ensembles beneath the metal films. We find a substantial reduction of the photoluminescence lifetime and a pronounced decrease of the NV$^{-}$ population for NV ensembles located near the platinum layer. As a result, optically detected magnetic resonance experiments could only be efficiently performed on diamonds implanted with at least 20 keV, where we observed a strong increase in the T$_{2}$ coherence time beneath the platinum thin films. Our study describes the various processes affecting NV centers near platinum films and provides guidance for the integration of thin metal films with near-surface NV centers.
Authors: Ben T. McDonough, Marius Lemm, Andrew Lucas
Strong disorder often has drastic consequences for quantum dynamics. This is best illustrated by the phenomenon of Anderson localization in non-interacting systems, where destructive quantum wave interference leads to the complete absence of particle and information transport over macroscopic distances. In this work, we investigate the extent to which strong disorder leads to provably slow dynamics in many-body quantum lattice models. We show that in any spatial dimension, strong disorder leads to a non-perturbatively small velocity for ballistic information transport under unitary quantum dynamics, almost surely in the thermodynamic limit, in every many-body state. In these models, we also prove the existence of a "prethermal many-body localized regime", where entanglement spreads logarithmically slowly, up to non-perturbatively long time scales. More generally, these conclusions hold for all models corresponding to quantum perturbations to a classical Hamiltonian obeying a simple non-resonant condition. Deterministic non-resonant models are found, including spin systems in strong incommensurate lattice potentials. Consequently, quantum dynamics in non-resonant potentials is asymptotically easier to simulate on both classical or quantum computers, compared to a generic many-body system.
Authors: Adithya Suresh, Ramon Guerrero-Suarez, Tanmay Maiti, Shuang Liang, Geoffrey Gardner, Claudio Chamon, Michael Manfra
The scaling exponent $g$ of the quasiparticle propagator for incompressible fractional quantum Hall states in the Laughlin sequence is expected to be robust against perturbations that do not close the gap. Here we probe the topological robustness of the chiral Luttinger liquid at the boundary of the $\nu=1/3$ state by measuring the tunneling conductance between counterpropagating edge modes as a function of quantum point contact transmission. We demonstrate that for transmission $t\geq 0.7$ the tunneling conductance is well-described by the first two terms of a perturbative series expansion corresponding to $g=1/3$. We further demonstrate that the measured scaling exponent is robustly pinned to $g=1/3$ across the plateau, only deviating as the bulk state becomes compressible. Finally we examine the impact of weak disorder on the scaling exponent, finding it insensitive. These measurements firmly establish the topological robustness of anyon tunneling at $\nu=1/3$ and substantiate the chiral Luttinger liquid description of the edge mode.
Authors: Omkar Dhungel, Saravanan Sengottuvel, Mariusz Mrozek, Till Lenz, Nir Bar-Gill, Adam M. Wojciechowski, Arne Wickenbrock, Dmitry Budker
Nitrogen-vacancy centers in nanodiamond offer a microwave-free, noninvasive platform for probing superconductors via near zero-field cross-relaxation magnetometry. We demonstrate this by depositing nanodiamonds on YBCO thin films to measure critical parameters: transition temperature and penetration field. This method leverages nanodiamond fluorescence modulation as a result of magnetic field variation with 1mT amplitude to observe the Meissner effect and field scans to measure the penetration field. The approach is minimally invasive and can be applied to superconducting samples with rough surfaces, facilitating the study of flux vortices and critical phenomena in complex geometries.
Authors: Zhengyang Qiu, Junfeng Chen, Dmitrii V. Semenok, Qingyi Zhong, Di Zhou, Jingyuan Li, Peiyue Ma, Xing Huang, Mengwu Huo, Tao Xie, Xiang Chen, Ho-kwang Mao, Viktor Struzhkin, Hualei Sun, Meng Wang
Systematically controlling the superconducting transition temperature ($T_\text{c}$) in the bilayer Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_7$ remains a significant challenge. Here, we address this by synthesizing high-quality polycrystalline La$_{3-x}$Nd$_x$Ni$_2$O$_7$ ($0 \leq x \leq 2.4$) with record-level rare-earth substitution. Nd doping compresses the lattice, particularly along the $c$ axis, enhances the spin density wave transition temperature, and elevates the pressure required for the orthorhombic-to-tetragonal structural transition. Superconductivity is observed across all doping levels under high pressures, with the onset $T_\text{c}$ rising to $\sim$93~K for $x = 2.1$ and $2.4$ from the electronic transport measurement. Using the radio-frequency transmission technique, newly applied to nickelate superconductors, we detect signatures of superconductivity at $98 \pm 2$~K in the $x=2.4$ compound, pushing the $T_\text{c}$ frontier further. We identify a universal linear relationship where $T_\text{c}$ decreases with the $c$-axis lattice parameter at a rate of approximately $-28$~K/Å, demonstrating that enhanced interlayer magnetic exchange coupling is the dominant mechanism for superconducting pairing. Our work establishes the critical role of magnetism and provides a unified structural descriptor for elevating $T_\text{c}$ in bilayer nickelates.
Authors: Ji-Hai Yuan, Ya-Dong Gu, Yun-Qing Shi, Hao-Yu He, Qing-Song Liu, Jun-Kun Yi, Le-Wei Chen, Zheng-Xin Lin, Jia-Sheng Liu, Meng Wang, Zhi-An Ren
The Ge-doped GaNb4Se8 polycrystalline samples were synthesized by solid-state reaction method. Zero resistance transitions were observed in one batch of samples with the highest onset superconducting Tc at 45 K. This discovery may demonstrate a new class of Nb-based high-Tc superconductors arising from doped Mott insulators.
Authors: C. Iorio-Duval, E. Beauchesne-Blanchet, F. Perreault, J. L. Santana González, W. Sun, Y. F. Nie, A. Gourgout, G. Grissonnanche
In many unconventional superconductors, the strange-metal regime is thought to emerge from quantum criticality, yet in cuprates this link is obscured by the enigmatic pseudogap. Superconducting infinite-layer nickelates provide a new arena to test this paradigm but are constrained to thin films, precluding calorimetry. We use the Seebeck coefficient as a low-temperature proxy for entropy per carrier and uncover a clear quantum-critical thermodynamic signature: in La$_{1-x}$Sr$_x$NiO$_2$ at the onset of $T$-linear resistivity ($x=0.20$), $S/T$ diverges logarithmically upon cooling, $S/T \propto \log T$. Boltzmann transport based on ARPES-derived band structure reproduces the high-temperature magnitude and sign of $S/T$ and reveals a threefold mass renormalization at the Fermi level. To identify the terminating phase, we analyze Hall data across Nd$_{1-x}$Sr$_x$NiO$_2$ and show that its temperature evolution is quantitatively captured by a minimal two-band model in which a strongly correlated Ni-$d_{x^2-y^2}$ Fermi surface exhibits Planckian $T$-linear scattering while the rare-earth Nd-$s$ pocket remains Fermi-liquid-like. Inverting the zero-temperature Hall response reveals a collapse of the Ni-$d_{x^2-y^2}$ band carrier density from $1+p$ to $p$ holes across the critical doping, without long-range magnetic order -- mirroring the cuprate pseudogap transition in cuprates. These results establish a quantum critical point at the end of a pseudogap-like phase in infinite-layer nickelates and unify the broader paradigm among correlated superconductors that strange metal behaviour is intimately linked to quantum criticality.
Authors: Guoan Li, Xiaofan Shi, Ruixuan Zhang, Yuxiao Song, Marco Rossi, Ghada Badawy, Zhiyuan Zhang, Anqi Wang, Xingchen Guo, Xiao Deng, Xiao Chen, Liangqian Xu, Bingbing Tong, Peiling Li, Xiaohui Song, Zhaozheng Lyu, Guangtong Liu, Fanming Qu, Michał P. Nowak, Paweł Wójcik, Ziwei Dou, Erik P. A. M. Bakkers, Li Lu, Jie Shen
Hybrid superconductor-semiconductor(SC-SM) nanowires remain one of the foremost platforms for engineering topological superconductivity and Majorana zero modes(MZMs) towards fault-tolerant topological qubits, especially with the rapid development of artificial Kitaev chains. In contrast to the widely used aluminum(Al)-based hybrids, lead(Pb) offers a bulk superconducting gap of ~1.4meV and a critical temperature of ~7.2K, giving rise to a proximity-induced gap that is roughly five times larger than that obtained with Al. Here we present the first three-terminal Pb-hybrid devices and perform nonlocal differential-conductance spectroscopy on this platform. The nonlocal measurement simultaneously resolves a dual-gap feature of the parent Pb gap and the large, hard, gate-tunable induced superconducting gap, distinguished by a switch between electron- and hole-like dissipation processes. Within the induced gap we observe several types of Andreev bound states(ABSs) that undergo singlet-doublet transitions. Moreover, by tuning gate voltages we achieve gate-controlled resonating sign reversals of the nonlocal conductance, identifying three distinct regimes that correspond to different configurations of quantum-dot(QD) resonances(single-resonance, double-resonance, and series-resonance). Finally, the coupling between ABSs and QDs also present and can be modulated from the weak- to strong-coupling limit, indicating the feasibility of realizing the artificial Kitaev chains. Crucially, the robust nonlocal signatures persist up to temperatures(~1K) far above the operating temperature of Al-based devices thanks to the unusually large induced gap, thereby widening the accessible parameter space greatly and underscoring the suitability of Pb-based hybrids for implementing warm temperature artificial Kitaev chains and the topological quantum devices protected by a substantially larger topological gap.
Authors: Yichen Xu, Yiqing Zhou, James P. Sethna, Eun-Ah Kim
The threshold theorem promises a path to fault-tolerant quantum computation by suppressing logical errors, provided the physical error rate is below a critical threshold. While transversal gates offer an efficient method for implementing logical operations, they risk spreading errors and potentially lowering this threshold compared to a static quantum memory. Available threshold estimates for transversal circuits are empirically obtained and limited to specific, sub-optimal decoders. To establish rigorous bounds on the negative impact of error spreading by the transversal gates, we generalize the statistical mechanical (stat-mech) mapping from quantum memories to logical circuits. We establish a mapping for two toric code blocks that undergo a transversal CNOT (tCNOT) gate. Using this mapping, we quantify the impact of two independent error-spreading mechanisms: the spread of physical bit-flip errors and the spread of syndrome errors. In the former case, the stat-mech model is a 2D random Ashkin-Teller model. We use numerical simulation to show that the tCNOT gate reduces the optimal bit-flip error threshold to $p=0.080$, a $26\%$ decrease from the toric code memory threshold $p=0.109$. The case of syndrome error coexisting with bit-flip errors is mapped to a 3D random 4-body Ising model with a plane defect. There, we obtain a conservative estimate error threshold of $p=0.028$, implying an even more modest reduction due to the spread of the syndrome error compared to the memory threshold $p=0.033$. Our work establishes that an arbitrary transversal Clifford logical circuit can be mapped to a stat-mech model, and a rigorous threshold can be obtained correspondingly.
Authors: Benius Dunn, Javier Meza-Arroyo, Armi Tiihonen, Mark Lee, Julia W. P. Hsu
Neuromorphic computing hardware enables edge computing and can be implemented in flexible electronics for novel applications. Metal oxide materials are promising candidates for fabricating flexible neuromorphic electronics, but suffer from processing constraints due to the incompatibilities between oxides and polymer substrates. In this work, we use photonic curing to fabricate flexible metal-insulator-metal capacitors with solution-processible aluminum oxide dielectric tailored for neuromorphic applications. Because photonic curing outcomes depend on many input parameters, identifying an optimal processing condition through a traditional grid-search approach is unfeasible. Here, we apply multi-objective Bayesian optimization (MOBO) to determine photonic curing conditions that optimize the trade-off between desired electrical properties of large capacitance-frequency dispersion and low leakage current. Furthermore, we develop a human-in-the-loop (HITL) framework for incorporating failed experiments into the MOBO machine learning workflow, demonstrating that this framework accelerates optimization by reducing the number of experimental rounds required. Once optimization is concluded, we analyze different Pareto-optimal conditions to tune the dielectrics properties and provide insight into the importance of different inputs through Shapley Additive exPlanations analysis. The demonstrated framework of combining MOBO with HITL feedback can be adapted to a wide range of multi-objective experimental problems that have interconnected inputs and high experimental failure rates to generate usable results for machine learning models.
Authors: José Geraldo Telles Ribeiro, Americo Cunha Jr
Polymer-based plastics exhibit time-dependent deformation under constant stress, known as creep, which can lead to rupture or static fatigue. A common misconception is that materials under tolerable static loads remain unaffected over time. Accurate long-term deformation predictions require experimental creep data, but conventional models based on simple rheological elements like springs and dampers often fall short, lacking the flexibility to capture the power-law behaviour intrinsic to creep processes. The springpot, a fractional calculus-based element, has been used to provide a power-law relationship; however, its fixed-order nature limits its accuracy, particularly when the deformation rate evolves over time. This article introduces a variable-order (VO) springpot model that dynamically adapts to the evolving viscoelastic properties of polymeric materials during creep, capturing changes between glassy, transition and rubbery phases. Model parameters are calibrated using a robust procedure for model identification based on the cross-entropy (CE) method, resulting in physically consistent and accurate predictions. This advanced modelling framework not only overcomes the limitations of the fixed-order models but also establishes a foundation for applying VO mechanics to other viscoelastic materials, providing a valuable tool for predicting long-term material performance in structural applications.
Authors: Nisarga Paul
Variational wavefunctions offer a practical route around the exponential complexity of many-body Hilbert spaces, but their expressive power is often sharply constrained. Matrix product states, for instance, are efficient but limited to area law entangled states. Neural quantum states (NQS) are widely believed to overcome such limitations, yet little is known about their fundamental constraints. Here we prove that feed-forward neural quantum states acting on $n$ spins with $k$ scalar nonlinearities, under certain analyticity assumptions, obey a bound on entanglement entropy for any subregion: $S \leq c k\log n$, for a constant $c$. This establishes an NQS analog of the area law constraint for matrix product states and rules out volume law entanglement for NQS with $O(1)$ nonlinearities. We demonstrate analytically and numerically that the scaling with $n$ is tight for a wide variety of NQS. Our work establishes a fundamental constraint on NQS that applies broadly across different network designs, while reinforcing their substantial expressive power.
Authors: Zhiyuan Wang
We show that a family of secret communication challenge games naturally define a hierarchy of emergent quasiparticle statistics in three-dimensional (3D) topological phases. The winning strategies exploit a special class of the recently proposed $R$-paraparticles to allow nonlocal secret communication between the two participating players. We first give a high-level, axiomatic description of emergent $R$-paraparticles, and show that any physical system hosting such particles admits a winning strategy. We then analyze the games using the categorical description of topological phases (where point-like excitations in 3D are described by symmetric fusion categories), and show that only $R$-paraparticles can win the 3D challenge in a noise-robust way, and the winning strategy is essentially unique. This analysis associates emergent $R$-paraparticles to deconfined gauge theories based on an exotic class of finite groups. Thus, even though this special class of $R$-paraparticles are fermions or bosons under the categorical classification, their exchange statistics can still have nontrivial physical consequences in the presence of appropriate defects, and the $R$-paraparticle language offers a more convenient description of the winning strategies. Finally, while a subclass of non-Abelian anyons can win the game in 2D, we introduce twisted variants that exclude anyons, thereby singling out $R$-paraparticles in 2D as well. Our results establish the secret communication challenge as a versatile diagnostic for both identifying and classifying exotic exchange statistics in topological quantum matter.
Authors: Izzatjon Allayarov, Andrey B. Evlyukhin, Antonio Calà Lesina
Membrane-metasurfaces, formed by periodic arrangements of holes in a dielectric layer, are gaining attention for their easier manufacturing via subtractive techniques, unnecessity of substrates, and access to resonant near-fields. Despite their practical relevance, their theoretical description remains elusive. Here, we present a semi-analytical dipole-quadrupole model for the multipole analysis of numerically-obtained reflection and transmission spectra in metasurfaces excited at arbitrary angles. Dipole models are generally sufficient to study traditional metasurfaces made of solid nanostructures. However, the inclusion of electric and magnetic quadrupoles is necessary to study membrane-metasurfaces, which offer an ideal platform to showcase our method. We demonstrate the importance of choosing the optimal position of a symmetric membrane-metasurface's unit cell to ensure the sufficiency of the dipole-quadrupole approximation. We show that our formalism can explain complex phenomena arising from inter-multipole interference, including lattice anapole and generalized Kerker effects, Fano resonances, and quasi-bound states in the continuum. We also present the applicability of the method to membrane-metasurfaces with non-centrosymmetric unit cells (e.g., conical holes and surface voids). By enabling a deeper insight into the coupling mechanisms leading to the formation of local and collective resonances, our method expands the electromagnetics toolbox to study, understand, and design conventional and membrane-metasurfaces.
Authors: Yankai Zhang, oshitaka Tanimura
We investigate the quantum dynamics of Coulomb potential systems in thermal baths. We study these systems within the framework of open quantum dynamics theory, focusing on preserving the rotational symmetry of the entire system, including the baths. Thus, we employ a three-dimensional rotationally invariant system-bath (3D-RISB) model to derive numerically ``exact'' hierarchical equations of motion for atomic orbitals (AO-HEOM) that enable a non-perturbative and non-Markovian treatment of system-bath interactions at finite temperatures. To assess the formalism, we calculated the linear absorption spectrum of an atomic system under isotropic thermal environment, with systematic variation of system-bath coupling strength and temperature.
Authors: Yonggang Hu, Yiqing Liao, Lufeng Yang, Ke Zhang, Yufan Peng, Shijun Tang, Shengxiang Wang, Meifang Ding, Jiahao Wu, Jianrong Lin, Jinding Liang, Yimin Wei, Yanting Jin, Zhengliang Gong, Anatoliy Senyshyn, Jie Chen, Yong Yang
Non-destructive characterization of lithium-ion batteries provides critical insights for optimizing performance and lifespan while preserving structural integrity. Optimizing electrolyte design in commercial LIBs requires consideration of composition, electrolyte-to-capacity ratio, spatial distribution, and associated degradation pathways. However, existing non-destructive methods for studying electrolyte infiltration, distribution, and degradation in LIBs lack the spatiotemporal resolution required for precise observation and quantification of the electrolyte. In this study, we employ neutron imaging with sufficient spatial resolution ~150 um and large field of view 20x20 cm2 to quantitatively resolve the electrolyte inventory and distribution within LiFePO4/graphite pouch cells under high-temperature accelerated aging. Quantitative standard curves based on neutron transmission attenuation reveal a clear electrolyte dry-out threshold at 3.18 g Ah-1 and the two stages evolutions of EI during cell aging were quantified. By integrating non-destructive electrochemical diagnostics, accelerated graphite material loss and liquid phase Li+ diffusion degradation is observed during pore-drying. Further analysis, including operando cyclic aging, reveals that the neutron transmission below the saturation reference is due to the enrichment of hydrogen nuclei within the solid-electrolyte interphase. Assumed pore-drying does not occur, the SEI signal of the electrodes can be quantitatively decoupled during ageing. Combined analyses with NI, TOF-SIMS, and SEM reveal that high EI cells exhibit uniform SEI growth and reduced degradation, while low EI cells show uneven SEI formation, accelerating capacity loss. This study unveils a dynamic electrolyte infiltration-consumption-dry-out process in LIBs, offering non-destructive and quantitative insights to guide sustainable and durable battery development.
Authors: Lijie Ding, Jan-Michael Carrillo, Changwoo Do
We introduce ToPolyAgent, a multi-agent AI framework for performing coarse-grained molecular dynamics (MD) simulations of topological polymers through natural language instructions. By integrating large language models (LLMs) with domain-specific computational tools, ToPolyAgent supports both interactive and autonomous simulation workflows across diverse polymer architectures, including linear, ring, brush, and star polymers, as well as dendrimers. The system consists of four LLM-powered agents: a Config Agent for generating initial polymer-solvent configurations, a Simulation Agent for executing LAMMPS-based MD simulations and conformational analyses, a Report Agent for compiling markdown reports, and a Workflow Agent for streamlined autonomous operations. Interactive mode incorporates user feedback loops for iterative refinements, while autonomous mode enables end-to-end task execution from detailed prompts. We demonstrate ToPolyAgent's versatility through case studies involving diverse polymer architectures under varying solvent condition, thermostats, and simulation lengths. Furthermore, we highlight its potential as a research assistant by directing it to investigate the effect of interaction parameters on the linear polymer conformation, and the influence of grafting density on the persistence length of the brush polymer. By coupling natural language interfaces with rigorous simulation tools, ToPolyAgent lowers barriers to complex computational workflows and advances AI-driven materials discovery in polymer science. It lays the foundation for autonomous and extensible multi-agent scientific research ecosystems.
Authors: Masahiro Negishi, Hyunsoo Park, Kinga O. Mastej, Aron Walsh
To address pressing scientific challenges such as climate change, increasingly sophisticated generative artificial intelligence models are being developed that can efficiently sample the large chemical space of possible functional materials. These models can quickly sample new chemical compositions paired with crystal structures. They are typically evaluated using uniqueness and novelty metrics, which depend on a chosen crystal distance function. However, the most prevalent distance function has four limitations: it fails to quantify the degree of similarity between compounds, cannot distinguish compositional difference and structural difference, lacks Lipschitz continuity against shifts in atomic coordinates, and results in a uniqueness metric that is not invariant against the permutation of generated samples. In this work, we propose using two continuous distance functions to evaluate uniqueness and novelty, which theoretically overcome these limitations. Our experiments show that these distances reveal insights missed by traditional distance functions, providing a more reliable basis for evaluating and comparing generative models for inorganic crystals.
Authors: Aakash Anand, A. Bhattacharyay
Understanding surface-driven transport is of paramount importance from the perspective of biological applications and the synthesis of microfluidic devices. In this work, we develop an analysis of a local inversion symmetry broken fluid flow model through an undulating microchannel. Surface undulations of a few tens of Hertz in a soft microchannel keep the fluid flow in a low Reynolds number regime, allowing the advantage of a perturbation analysis of fluid flow. Using this, we develop a detailed analysis of the relationship between the fluid velocity and surface undulations, which is crucial for the subsequent numerical analysis of tracer motion. We used this information to study the dynamics of a tracer particle in the velocity field of an undulating microchannel. We show that the tracer particle can undergo ratcheting (which we call the hydrodynamics ratchet effect) in very specific, physically meaningful circumstances. We observe a ratcheting velocity of $\sim 0.15 \;\mu$m/sec for a micrometre-sized particle at room temperature in water when the undulations wavelength is of the order of 1 $\mu$m.
Authors: Yaoqi Ye, Chengkai Lin, Xiao Wang
We derive semiclassical analytical solutions for both the diagonal and off-diagonal functions in the eigenstate thermalization hypothesis (ETH) in a quarter-stadium quantum billiard. For a representative observable, we obtain an explicit expression and an asymptotic closed-form solution that naturally separate into a local contribution and a phase-space correlation term. These analytical results predict the band structure of the observable matrix, including its bandwidth and scaling behavior. We further demonstrate that our analytical formula is equivalent to the prediction of Berry's conjecture. Supported by numerical evidence, we show that Berry's conjecture captures the energetic long-wavelength behavior in the space of eigenstates, while our analytical solution describes the asymptotic behavior of the f function in the semiclassical limit. Finally, by revealing the connection between the bandwidth scaling and the underlying classical dynamics, our results suggest that the ETH carries important physical implications in single-particle and few-body systems, where "thermalization" manifests as the loss of information about initial conditions.
Authors: Domenico Lippolis
In the realm of spatiotemporal chaos, unstable periodic orbits play a major role in understanding the dynamics. Their stability changes and bifurcations in general are thus of central interest. Here, coupled map lattice discretizations of nonlinear partial differential equations, exhibiting a variety of behaviors depending on the coupling strength, are considered. In particular, the linear stability analysis of synchronized states is performed by evaluating the Bravais lattice orbit Jacobian in its reciprocal space first Brillouin zone, with space and time treated on equal grounds. The eigenvalues of the orbit Jacobian operator, computed as functions of the coupling strength, tell us about the stability of the periodic orbit under a perturbation of a certain time- and space frequency. Moreover, the stability under aperiodic, that is, incoherent perturbations, is revealed by integrating the sum of the stability exponents over all space-time frequencies.
Authors: Chandrodoy Chattopadhyay, Josh Ott, Thomas Schaefer, Vladimir V. Skokov
We study heat conduction and momentum transport in the context of stochastic fluid dynamics. We consider a fluid described by model H in the classification of Hohenberg and Halperin. We study both non-critical and critical fluids, and we investigate transport properties in two as well as three dimensions. Our results are based on numerical simulations of model H using a Metropolis algorithm, and we employ Kubo relations to extract transport coefficients. We observe the expected logarithmic divergence of the shear viscosity in a two-dimensional non-critical fluid. At a critical point, we find that the transport coefficients exhibit power-law scaling with the system size $L$. The strongest divergence is seen for the thermal conductivity $\kappa$ in two dimensions. We find $\kappa\sim L^{x_\kappa}$ with $x_\kappa=1.6\pm 0.1$. The divergence is weaker in three dimensions, $x_\kappa=1.25 \pm 0.3$, and the scaling exponent for the shear viscosity, $x_\eta$, is significantly smaller than $x_\kappa$ in both two and three dimensions.
Authors: Eric Alejandro Rozan, Mario Ignacio Simoy, Sebastian Bouzat, Marcelo Nestor Kuperman
Accurate epidemic forecasting requires models that account for the layered and heterogeneous nature of real social interactions. The basic reproduction number $\mathcal R_0$ calculated from models that assume homogeneous mixing or single-layer contact structures have limited applicability to complex social systems. Here, we propose an expression of $\mathcal R_0$ in the context of multiplex networks, enabling the analysis of disease transmission across multiple social layers. We adapt the Degree-Based Mean-Field (DBMF) SIR model for single-layered complex networks to the multiplex setting, where each layer has its own degree distribution and infection rate. Using the Next Generation Matrix method, we derive an analytical expression for the basic reproduction number $\mathcal R_0$. Numerical integration of the multiplex DBMF equations shows that $\mathcal R_0 = 1$ marks the epidemic threshold and governs the functional dependence of key outbreak indicators. In addition to the exact result for the $\mathcal R_0$, we provide an approximation denoted as $\tau$, which is easier to compute and more straightforward to interpret in terms of the parameters of the system, and shares most of the expected properties of the basic reproduction number. Stochastic agent-based simulations confirm these results, demonstrating a direct correspondence between $\tau$ and the average number of secondary infections in the early epidemic phase, in line with the interpretation of $\mathcal R_0$. This research provides a robust generalization of $\mathcal R_0$ for layered contact structures, offering a more realistic basis for epidemic forecasting and the design of intervention strategies.
Authors: Pasquale Filice, Marco Schirò, Giacomo Mazza
We introduce time-dependent variational principles to study the non-unitary dynamics of open quantum many-body systems, including dynamics described by the full Lindblad master equation, the non-Hermitian dynamics corresponding to the no-click limit of the fully post-selected quantum trajectories, and the dynamics described by a hybrid Lindbladian with a control parameter $\alpha$ which interpolates between the full post-selection and averaging over all quantum trajectories. As an application we study the non-unitary dynamics of a lossy or driven-dissipative BCS superconductors, evolving in presence of two-body losses and two-body pumps. We show that the non-Hermitian limit acts as a singular limit of the hybrid dissipative dynamics, leading to a sharp modification of the universal approach to the driven-dissipative steady-states. By considering the dissipative dynamics with pair losses, we show that, as the non-Hermitian limit is approached, the density dynamics sharply evolves from a universal power-law to exponential decay that converges towards a quasi-steady plateau characterized by the freezing of the particle depletion due to pair losses. The reached quasi-stationary density increases as a function of the dissipation rate highlighting the emergence of a non-Hermitian Zeno effect in the lossy dynamics. For the driven-dissipative case, we show that, in the non-Hermitian limit, the system gets trapped into an effective negative temperature state, thus skipping the infinite temperature steady-state reached in the presence of finite contribution of the quantum jumps. We rationalize these findings in terms of the conservation of the length of the pseudospins which, in the non-Hermitian limit, suppresses the effective single-particle losses and pumps acting on the non-condensed particles.
Authors: Himanshu Badhani, Dhanuja G S, Siddhartha Das
We explore the thermodynamics of quantum processes (quantum channels) by axiomatically introducing the free energy for channels, defined via the quantum relative entropy with an absolutely thermal channel whose fixed output is in equilibrium with a thermal reservoir. This definition finds strong support through its operational interpretations in designated quantum information and thermodynamic tasks. We construct a resource theory of athermality for quantum processes, where free operations are Gibbs preserving superchannels and golden units are unitary channels with respect to absolutely thermal channel having fully degenerate output Hamiltonian. We exactly characterize the one-shot distillation and formation of quantum channels using hypothesis-testing and max-relative entropy with respect to the absolutely thermal channel. These rates converge asymptotically to the channel free energy (up to a multiplicative factor of half the inverse temperature), establishing its operational meaning and proving the asymptotic reversibility of the athermality. We show the direct relation between the resource theory of athermality and quantum information tasks such as private randomness and purity distillation and thermodynamic tasks of erasure and work extraction. Our work connects the core thermodynamic concepts of free energy, energy, entropy, and maximal extractable work of quantum processes to their information processing capabilities.
Authors: Lukas Homeier, Andrea Pizzi, Hongzheng Zhao, Jad C. Halimeh, Fabian Grusdt, Ana Maria Rey
Universal aspects of thermalization in interacting many-body systems are typically challenging to derive microscopically, yet provide a powerful framework for understanding emergent phenomena. Here, we numerically study the mean-field dynamics of a $(2+1)$D spin system with thousands of spins and show that experimentally-feasible two-body Ising interactions can stabilize a prethermal $\mathbb{Z}_2$ lattice gauge structure with dynamical matter, manifested by a gauge-invariant plateau with exponentially long lifetime. Eventually, the metastable prethermal $\mathbb{Z}_2$ gauge structure breaks down via a proliferation of Gauss' law defects, similar to bubble formation in false vacuum decay. In this regime, we discover spatio-temporal correlations described by a non-linear surface growth consistent with the $(1+1)$D Kardar-Parisi-Zhang (KPZ) universality class. We benchmark our results in small systems against semi-classical discrete time Wigner approximation (DTWA) and exact diagonalization (ED), where the breakdown of DTWA signals the emergence of an extensive number of local symmetries that strongly influence the thermalization pathway. Our model provides a testbed for quantum simulators and is directly implementable in large-scale arrays of Rydberg atoms.
Authors: Giacomo Mazza, Costantino Budroni
We investigate entanglement detection in quantum materials through criteria based on the simultaneous suppression of collective matter excitations. Unlike other detection schemes, these criteria can be applied to continuous and unbounded variables. By considering a system of interacting dipoles on a lattice, we show the detection of collective entanglement arising from two different physical mechanisms, namely, the ferroelectric ordering and the dressing of matter degrees of freedom by light. In the latter case, the detection shows the formation of a collective entangled phase not directly related to spontaneous symmetry breaking. These results open a new perspective for the entanglement characterization of competing orders in quantum materials, and have direct application to quantum paraelectrics with large polariton splittings.
Authors: Eric Nilsson, Ulf Gran, Johannes Hofmann
Pauli blocking in Fermi liquids imposes strong phase-space constraints on quasiparticle lifetimes, leading to a well-known quadratic-in-temperature decay rate of quasiparticle modes at low temperatures. In two-dimensional systems, however, even longer-lived modes are predicted (dubbed ``odd-parity'' modes) that involve a collective deformation of the Fermi distribution. Here, we present an efficient method to evaluate the full spectrum of relaxational eigenmodes of a Fermi liquid within kinetic theory. We employ this method to study the experimentally relevant case of a Fermi liquid with screened Coulomb interactions and map out the decay rates of quasiparticle modes beyond the asymptotic low-temperature limit up to the Fermi temperature, thus covering the entire temperature range of typical experiments. We confirm the existence of anomalously long-lived odd-parity modes and provide a comprehensive classification and detailed analysis of the relaxation spectrum. In particular, we find that (i) the odd-parity effect in the decay rates extends to temperatures as large as $T=0.15T_F$, (ii) there is only a small number of long-lived odd-parity modes, with an infinite number of remaining modes that show standard Fermi-liquid scaling, and (iii) the ratio between the odd- and even-parity lifetimes is tunable with the Coulomb interaction strength, in addition to temperature, which reflects a difference in the microscopic relaxation mechanism of the modes. Our findings provide a comprehensive description of the nonequilibrium relaxation behavior of two-dimensional electron gases and bridge a significant gap in our understanding of these systems.
Authors: Andres Robles-Navarro, Shaun Cooper, Andreas W. Hauser, Fabian Zehetmair, Odile Smits, Peter Schwerdtfeger
The diffusionless Burgers-Bain phase transition from a hcp arrangement to a cuboidal lattice (fcc and bcc) is analysed in great detail for Lennard-Jones solids. From the lattice vectors of an underlying bi-lattice smoothly connecting these phases, we are able to express the corresponding lattice sums for inverse power potentials in terms of fast converging Bessel function expansions resulting in an efficient evaluation to computer accuracy for cohesive energies. From the kissing hard-sphere limit we derive exact analytical expressions for the lattice parameters varying along the minimum energy path of the phase transition. This simple model suggests that for the Burgers-Bain transformation of a LJ solid requires a minimum of four lattice parameters, $(a,\alpha,\beta,\gamma=c/a)$, describing the change in the base lattice lengths $a$ and $c$, the shear force acting on the hexagonal base plane ($\alpha$), the sliding force of the middle layer of the original hexagonal packing arrangement($\beta$), and the cuboidal transformation ($\gamma=c/a$). This choice results in a two-step process: hcp$\to$fcc$\to$bcc. However, a further extension of the parameter space including an additional slide parameter for the middle layer, one suddenly observes a distinct symmetry-breaking effect along the hcp$\rightarrow$fcc transition path with a bifurcation point appearing joining the original Burgers with the Bain path of the bcc$\rightarrow$fcc cuboidal transition. Furthermore, for soft LJ potentials the bcc phase appears as a local minimum along the Burgers hcp$\rightarrow$fcc path with two transition states to either the hcp or fcc phase. The underlying topology of the Burgers-Bain phase transition also incorporates the rhombohedral distortion of the bcc phase, which is analyzed in detail.
Authors: Karl J Friston, Maxwell J D Ramstead, Dalton A R Sakthivadivel
We discuss an approach to mathematically modelling systems made of objects that are coupled together, using generative models of the dependence relationships between states (or trajectories) of the things comprising such systems. This broad class includes open or non-equilibrium systems and is especially relevant to self-organising systems. The ensuing variational free energy principle (FEP) has certain advantages over using random dynamical systems explicitly, notably, by being more tractable and offering a parsimonious explanation of why the joint system evolves in the way that it does, based on the properties of the coupling between system components. The FEP is a method whose use allows us to build a model of the dynamics of an object as if it were a process of variational inference, because variational free energy (or surprisal) is a Lyapunov function for its dynamics. In short, we argue that using generative models to represent and track relations amongst subsystems leads us to a particular statistical theory of interacting systems. Conversely, this theory enables us to construct nested models that respect the known relations amongst subsystems. We point out that the fact that a physical object conforms to the FEP does not necessarily imply that this object performs inference in the literal sense; rather, it is a useful explanatory fiction which replaces the `explicit' dynamics of the object with an `implicit' flow on free energy gradients -- a fiction that may or may not be entertained by the object itself.
Authors: David M. Long, Dominic V. Else
Many-body localization (MBL) lends remarkable robustness to nonequilibrium phases of matter. Such phases can show topological and symmetry breaking order in their ground and excited states, but they may also belong to an anomalous localized topological phase (ALT phase). All eigenstates in an ALT phase are trivial, in that they can be deformed to product states, but the entire Hamiltonian cannot be deformed to a trivial localized model without going through a delocalization transition. Using a correspondence between MBL phases with short-ranged entanglement and locality preserving unitaries - called quantum cellular automata (QCA) - we reduce the classification of ALT phases to that of QCA. This method extends to periodically (Floquet) and quasiperiodically driven ALT phases, and captures anomalous Floquet phases within the same framework as static phases. We considerably develop the study of the topology of QCA, allowing us to classify static and driven ALT phases in low dimensions. The QCA framework further generalizes to include symmetry-enriched ALT phases (SALT phases) - which we also classify in low dimensions - and provides a large class of soluble models suitable for realization in quantum simulators. In systematizing the study of ALT phases, we both greatly extend the classification of interacting nonequilibrium systems and clarify a confusion in the literature which implicitly equates nontrivial Hamiltonians with nontrivial ground states.
Authors: Olivia Vincent, Aparna Sreekumari, Manoj Gopalakrishnan, Vishwas V Vasisht, Bibhu Ranjan Sarangi
We investigate the positional behavior of a single bacterium confined within a vesicle by measuring the probability of locating the bacterium at a certain distance from the vesicle boundary. We observe that the distribution is bi-exponential in nature. Near the boundary, the distribution exhibits rapid exponential decay, transitioning to a slower exponential decay, and eventually becoming uniform further away from the boundary. The length scales associated with the decay are found to depend on the confinement radius. We interpret these observations using molecular simulations and analytical calculations based on the Fokker-Planck equation for an Active Brownian Particle model. Our findings reveal that the small length scale is strongly influenced by the translational diffusion coefficient, while the larger length scale is governed by rotational diffusivity and self-propulsion. These results are explained in terms of two dimensionless parameters that explicitly include the confinement radius. The scaling behavior predicted analytically for the observed length scales is confirmed through simulations.
Authors: Hongyu Chen, Guijing Duan, Changle Liu, Yi Cui, Weiqiang Yu, Z. Y. Xie, Rong Yu
Frustrated quantum magnets can host a variety of exotic spin excitations, including fractionalized spin excitations coupled to emergent gauge fields at deconfined quantum critical points (DQCPs) and chiral magnons in altermagnets. Here, we investigate the spin excitation spectra of the highly frustrated $S=1/2$ antiferromagnetic (AFM) Shastry-Sutherland model, focusing on the evolution of low-energy collective modes from the Néel AFM phase to the plaquette valence bond solid (PVBS). We demonstrate that the AFM state exhibits altermagnetic behavior, characterized by a non-relativistic splitting between two chiral magnon bands. Furthermore, we identify two additional low-energy excitations: a Higgs mode in the longitudinal excitation channel and an $S=0$ excitation with vanishing spectral weight. As the system approaches the AFM-to-PVBS transition, both these modes soften along with the lowest-energy triplet and singlet modes in the PVBS state. The closing gap of the Higgs mode, combined with the nearly degenerate velocities of $S=1$ and $S=0$ excitations, provides spectral evidence that the AFM-to-PVBS transition is proximate to a DQCP with emergent $O(4)$ symmetry. Our results help clarify the spectral signature of a broad class of symmetry enhanced quantum phase transitions including deconfined quantum criticality.
Authors: J. Galen Wang, Umesh Dhumal, Monica E. A. Zakhari, Roseanna N. Zia
We examine why simulations replicating monodisperse purely-repulsive hard sphere (MPRHS) theory fail to produce explicit, spontaneous, equilibrium coexistence of fluid and crystal domains. MPRHS fluid-to-solid phase transitions are well established, as is prediction of the coexistence region via thermodynamic theory. Consensus holds that the MPRHS coexistence region is metastable, where nucleation governs crystallization. Our review explores the abundant physics and rheology literature for MPRHS, revealing two related observations: We find clear mechanistic explanation for crystallization of MPRHS, and that producing spontaneous MPRHS coexistence in simulations is notoriously difficult. Frenkel's mechanism-that vibrational entropy gains offset configurational entropy losses to drive MPRHS phase transition-suggests system size is the fundamental simulation issue. Alder and Wainwright recognized this constraint and emphasized the merit of direct observation in simulations, of explicitly following an isotherm through the coexistence region. But with 1M particles, estimated nucleation time is 317M years. Recent large-scale simulations reinforce this, showing phase transition, but not reporting explicit phase separation. The ideal condition is a tractably-large system and minimal perturbation to exit metastability. Instead, brute force is often used to trigger nucleation and phase separation via seeding, pre-construction, or gravity. Some simulations do show brief spontaneous coexistence but a metastable crystal or fluid subsequently overtakes the system. Putatively-hard WCA potentials allow extra free volume, lowering osmotic pressure and the energy barrier, and avoiding the strict short/long-range entropy challenge. Overall, rheological and computational demonstration of Frenkel's mechanism for MPRHS remains elusive, awaiting sufficiently large systems of sufficiently hard MPRHS.
Authors: Shaoyong Zhang, Zhaoyu Fei, Xiaoguang Wang
Temperature of a finite-sized system fluctuates due to the thermal fluctuations. However, a systematic mathematical framework for measuring or estimating the temperature is still underdeveloped. Here, we incorporate the estimation theory in statistical inference to estimate the temperature of a finite-sized system and propose optimal estimation based on the uniform minimum variance unbiased estimation. Treating the finite-sized system as a thermometer measuring the temperature of a heat reservoir, we demonstrate that different optimal estimation of parameters yield different formulas of entropy, e.g., optimal estimation of inverse temperature (or temperature) aligns with the Boltzmann entropy (or Gibbs entropy). The optimal estimation leads to a achievable energy-temperature uncertainty relation and exhibits sample-size dependence, coinciding with their counterparts in nanothermodynamics. The achievable bound and the non-Gaussian distribution of temperature enable experimental testing in finite-sized systems.
Authors: Shan-Zhong Li, Yi-Cai Zhang, Yucheng Wang, Shanchao Zhang, Shi-Liang Zhu, Zhi Li
Anderson localization describes disorder-induced phase transitions, distinguishing between localized and extended states. In quasiperiodic systems, a third multifractal state emerges, characterized by unique energy and wave functions. However, the corresponding multifractal-enriched mobility edges and three-state-coexisting quantum phases have yet to be experimentally detected. In this work, we propose exactly-solvable one-dimensional quasiperiodic lattice models that simultaneously host three-state-coexisting quantum phases, with their phase boundaries analytically derived via Avila's global theorem. Furthermore, we propose experimental protocols via Rydberg atom arrays to realize these states. Notably, we demonstrate a spectroscopic technique capable of measuring inverse participation ratios across real-space and dual-space domains, enabling simultaneous characterization of localized, extended, and multifractal quantum phases in systems with up to tens of qubits. Our work opens new avenues for the experimental exploration of Anderson localization and multifractal states in artificial quantum systems.
Authors: Weiguang Cao, Yuan Miao, Masahito Yamazaki
Non-invertible dualities/symmetries have become an important tool in the study of quantum field theories and quantum lattice models in recent years. One of the most studied examples is non-invertible dualities obtained by gauging a discrete group. When the physical system has more global symmetries than the gauged symmetry, it has not been thoroughly investigated how those global symmetries transform under non-invertible duality. In this paper, we study the change of global symmetries under non-invertible duality of gauging a discrete group $G$ in the context of (1+1)-dimensional quantum lattice models. We obtain the global symmetries of the dual model by focusing on different Hilbert space sectors determined by the $\mathrm{Rep}(G)$ symmetry. We provide general conjectures of global symmetries of the dual model forming an algebraic ring of the double cosets. We present concrete examples of the XXZ models and the duals, providing strong evidence for the conjectures.
Authors: Meghdad Yazdani-Hamid, Mehdi Biderang, Alireza Akbari
Motivated by the sensitivity of Sr$_2$RuO$_4$ to Fermi surface reconstructions under strain, we investigate how Fermi surface geometry and Van Hove singularities influence the optical Hall response and polar Kerr effect. Within a three-orbital model, we explore the impact of chemical potential and interlayer hopping on superconducting pairing and response functions. We find that $d_{x^2-y^2}$ and $d_{x^2-y^2}+ig$ symmetries are the leading candidates for the quasi-2D orbital, while a chiral $p$-wave state in the quasi-1D orbitals is essential for generating an accessible Kerr angle. The Lifshitz transition is shown to affect coherence factors and density-of-states peaks, producing sharp signatures in $T_c$ and optical transport. Inter-orbital charge transfer further enhances these effects by modifying the balance between quasi-1D and quasi-2D contributions. These results provide a framework for interpreting Kerr effect experiments in multi-orbital superconductors.
Authors: Mathieu Lizée, Mohammadmehdi Torkzadeh, François Debontridder, Marie Hervé, Christophe Brun, Igor Burmistrov, Tristan Cren
Anderson localization is predicted to enhance the critical temperature of disordered superconductors. Despite a huge body of theoretical work based on non-linear sigma models, experiments are lacking to understand correlated electrons in disordered potentials. In this study, we investigate a tin monolayer on silicon, a material known for its likely antiferromagnetic Mott-correlated groundstate. We analyze the statistical properties of tunneling conductance maps of increasingly localized states as we approach the edge of the valence band. Using multifractal analysis, we show that the system follows an exact symmetry relation based on the algebraic structure of nonlinear sigma-models (NLsMs). We anticipate that this symmetry may be broken in specific - e.g. chiral electronic phases. Finally, we point out that multifractal analysis can equally be applied to universal conductance fluctuations in magneto-transport experiments, thus providing a powerful tool to probe the underlying symmetries of disordered electronic phases.
Authors: Johanna Richter, Somnath Jana, Robert Behrends, Carl S. Davies, Dieter W. Engel, Martin Hennecke, Daniel Schick, Clemens von Korff Schmising, Stefan Eisebitt
The development of spectroscopic techniques in the extreme ultraviolet (XUV) spectral range has significantly advanced the understanding of ultrafast interactions in magnetic systems triggered by optical excitation. In this work, we introduce a previously missing geometry that facilitates the observation of the ultrafast magnetization dynamics of magnetic systems with an out-of-plane magnetization grown on XUV opaque substrates. This approach to probing ultrafast magnetization dynamics combines the magneto-optical Kerr effect with the strong dependence of a sample's reflectance near its Brewster angle. It therefore works with linearly polarized light and does not require any additional polarizing optics. We provide a comprehensive analysis of the technique by presenting both simulations and experimental data as a function of the energy and the polarization of the XUV probe radiation as well as of the delay time after optical excitation.
Authors: Jesse Liebman, Svetlana Torunova, John A. Schlueter, Elena Zhilyaeva, Natalia Drichko
In condensed matter physics, experimental control of the properties of materials realizes the aspiration to physically govern the properties of materials and demonstrates an understanding of their underlying physics. In recent years, meaningful progress has been made towards a description of the physics of correlated electron systems, but examples of control of these systems remain rare. In this work, we confirm a phase diagram theoretically proposed for organic Mott insulators. We use $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$X (X=Br,Cl) (BEDT-TTF = bis(ethylenedithio)tetrathiafuvalene) materials as experimental realization of the proposed model and demonstrate the ability to tune them both ways across a phase border between a Mott insulator with a uniformly distributed charge and a charge ordered state through the application of uniaxial strain. We induce charge order at 33 K in the quantum dipole liquid material $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Br through the application of tensile strain of 0.4% along the c-axis. We suppress charge order down to 10 K in $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl by applying a tensile strain of 1.6% along the b-axis. We use Raman scattering spectroscopy to probe both the charge state and a soft mode of collective dipole fluctuations close to the phase border.
Authors: Shiva Heidari, Shervin Parsi, Pouyan Ghaemi
We study the effects of strain on exciton dynamics in transition metal dichalcogenide (TMD) nanoribbons. Using the Bethe-Salpeter formalism, we derive the exciton dispersion relation in strained TMDs and demonstrate that strain-induced pseudo-gauge fields significantly influence exciton transport and interactions. Our results show that low-energy excitons occur at finite center-of-mass momentum, leading to modified diffusion properties. Furthermore, the exciton dipole moment depends on center-of-mass momentum, which enhances exciton-exciton interactions. These findings highlight the potential of strain engineering as a powerful tool for controlling exciton transport and interactions in nanoribbon-based TMD optoelectronic and quantum devices.
Authors: Shashwat Sharan, Judith Gonzalez Sorribes, Patrick Sprenger, Mark A. Hoefer, P. Engels, Boaz Ilan, M. E. Mossman
An experimental and theoretical study of sonic horizons emerging from the dam-break problem in a Bose-Einstein condensate confined in an anisotropic harmonic trap is presented. Measurements, analysis, and numerics reveal the formation of a sonic horizon that undergoes acceleration due to harmonic confinement. The superfluid is characterized using a robust measurement technique to determine Riemann invariants. Experimental observations agree with an analytical solution of the Gross-Pitaevskii equation and computations. The collision and annihilation between two sonic horizons at long times is predicted.
Authors: Maciej Matys, Atsushi Yamada, Toshihiro Ohki, Kouji Tsunoda
The AlGaN/GaN quantum-well heterostructures typically exhibit a positive photoconductivity (PPC) during the light illumination. Surprisingly, we found that introducing the GaN/AlN superlattice (SL) back barrier into N-polar AlGaN/GaN quantum-well heterostructures induces a transition in these heterostructures from PPC to negativie photoconductivity (NPC) as the SL period number increased at room temperature. This transition occurred under an infrared light illumination and can be well explained in terms of the excitation of hot electrons from the two-dimensional electron gas and subsequent trapping them in a SL structure. The NPC effect observed in N-polar AlGaN/GaN heterostructures with SL back barrier exhibits photoconductivity yield exceeding 85 % and thus is the largest ones reported so far for semiconductors. In addition, NPC signal remains relatively stable at high temperatures up to 400 K. The obtained results can be interesting for the development of NPC related devices such as photoelectric logic gates, photoelectronic memory and infrared photodetectors.
Authors: Jewel Kumar Ghosh, Francisco Peña-Benítez, Patricio Salgado-Rebolledo
We study the hydrostatic equilibrium of multi-Weyl semimetals, a class of systems with Weyl-like quasi-particles but anisotropic dispersion relation $\omega^2 \sim k_\parallel^2 + k_\perp^{2n}$, with $n$ a possitive integer. A characteristic feature of multi-Weyl systems is the lack of Lorentz invariance, instead, they possess the reduced spacetime symmetry $(SO(1,1)\times SO(2))\ltimes \mathbb R^4$. In this work we propose a covariant formulation for the low energy theory, allowing for a minimal coupling of the fermion field to external geometric background and $U(1)$ gauge field. The non-Lorentzian structure of the field theory demands introducing an Aristotelian spacetime analogous to the so-called stringy Newton-Cartan geometry \cite{Andringa:2012uz}. Our proposal allows for a systematic study of the hydrostatic properties via the derivation of the partition function of the system. In addition to multi-Weyl models, our formulation can be applied to systems with similar spacetime symmetry groups, such as Bjorken flow.
Authors: Aamir A. Makki, Mytraya Gattu, J. K. Jain
The recent discovery of fractional quantum anomalous Hall (FQAH) states - fractional quantum Hall (FQH) states realized without an external magnetic field - in twisted transition-metal dichalcogenide (TMD) bilayers represents a significant development in condensed matter physics. Notably, these states were first observed via photoluminescence (PL) spectroscopy. Surprisingly, a general theoretical understanding of PL is not available even for the standard FQH states. For an ideal two-dimensional system, the energy of the emitted photon is predicted to be independent of the correlations, but we show that the PL intensity contains valuable information. Specifically, we predict that at finite temperatures, the PL intensity peaks at the Jain fillings \nu = n/(2n \pm 1), and away from these fillings, the binding energies of the composite-fermion excitons and trions can be deduced from the temperature dependence of the intensity. We discuss implications for PL experiments in semiconductor quantum wells and twisted TMD bilayers.
Authors: Jacky Even, Simon Thebaud, Aseem Rajan Kshirsagar, Zeli Xu, Laurent Pedesseau, Marios Zacharias, Claudine Katan
Short abstract: The paper reviews the physics of Fröhlich excitonic polarons from the viewpoint of empirical approaches with some original developments. Models for excitonic polarons in ionic semiconductors in the spirit of the Lee Low and Pines (LLP) model for free polarons were initiated by Toyozawa and Hermanson and extended by Pollman and Buttner (PB). The dominant electron-hole interaction with the lattice introduced by Frohlich is represented by a long-range effective interaction with a single longitudinal optical polar mode. The properties of the excitonic polarons are characterized by various physical quantities such as effective dielectric constants, effective masses, virtual phonon populations, carrier self-energies and binding energies, and effective electron-hole interactions mediated by the lattice. In 3D perovskites, the excitonic polarons deviate from the simplified picture of weakly interacting (almost free) polarons, with sizeable effects of electron-hole correlations on all the physical properties.
Authors: Martin Rodriguez-Vega, Terry A. Loring, Alexander Cerjan
The topological properties of a material depend on its symmetries, parameters, and spatial dimension. Changes in these properties due to parameter and symmetry variations can be understood by computing the corresponding topological invariant. Since topological invariants are typically defined for a fixed spatial dimension, there is no existing framework to understand the effects of changing spatial dimensions via invariants. Here, we introduce a framework to study topological phase transitions as a system's dimensionality is altered using real-space topological markers. Specifically, we consider Shiba lattices, which are class D materials formed by magnetic atoms on the surface of a conventional superconductor, and characterize the evolution of their topology when an initial circular island is deformed into a chain. We also provide a measure of the corresponding protection against disorder. Our framework is generalizable to any symmetry class and spatial dimension, potentially guiding the design of materials by identifying, for example, the minimum thickness of a slab required to maintain three-dimensional topological properties.
Authors: Daniela Moreno-Chaparro, Florencio Balboa Usabiaga, Nicolas Moreno, Marco Ellero
Fluid-structure interactions are commonly modeled using no-slip boundary conditions. However, small deviations from these conditions can significantly alter the dynamics of suspensions and particles, especially at the micro and nano scales. This work presents a robust implicit solvent method for simulating non-colloidal suspensions with non-homogeneous Navier slip boundary conditions. Our approach is based on a regularized boundary integral formulation, enabling accurate and efficient computation of hydrodynamic interactions. This makes the method well-suited for large-scale simulations. We validate the method by comparing computed drag forces on homogeneous and Janus particles with analytical results. Additionally, we consider the effective viscosity of suspensions with varying slip lengths, benchmarking against available analytical no-slip and partial-slip theories.
Authors: Yan Zhao, Kaiyue Jiang, Peng-Yi Liu, Jie Li, Ruoning Li, Xin Li, Xinchen Fang, Anjing Zhao, Yutong Zhu, Hongxiang Xu, Ting Chen, Dong Wang, Xiaodong Zhuang, Shimin Hou, Kai Wu, Song Gao, Qing-Feng Sun, Yajie Zhang, Yongfeng Wang
Quantum manipulation of molecular radical spins provides a crucial platform for exploring emergent phenomena in many-body systems. Here, we combine surface-confined synthesis with scanning tunneling microscopy(STM)tip-induced dehydrogenation to achieve atom-precise engineering of quasi-one-dimensional porphyrin-based Kondo chains (1-7 units) on Au(111). High-resolution STS measurements and low-energy effective modeling collectively demonstrate that {\pi}-radicals at each fused-porphyrin unit form Kondo singlets screened by conduction electrons. Adjacent singlets develop direct coherent coupling via quantum-state-overlap-enabled electron tunneling. Crucially, chiral symmetry in the effective model governs zero-mode distribution-present in odd-length chains yet absent in even-length chains-which dictates pronounced odd-even quantum effects in STS spectra of finite chains. Furthermore, the number of parallel porphyrin chains non-monotonically tunes the competition between the Kondo effect and spin exchange, showing opposing trends in strength and demonstrating that both wave-function overlap and the SOMO-LUMO gap collectively govern these interactions. This work simultaneously resolves the dimensional dependence of many-body correlations in confined quantum systems and pioneers approaches for quantum-critical manipulation in molecular spin architectures.
Authors: Jae-Mo Lihm, Samuel Poncé
We present a self-consistent many-body framework for computing phonon-limited electronic transport from first principles, incorporating both beyond-quasiparticle effects and vertex corrections. Using the recently developed first-principles scGD0 method, we calculate spectral functions with nonperturbative effects such as broadening, satellites, and energy-dependent renormalization. We show that the scGD0 spectral functions outperform one-shot G0D0 and cumulant approximations in model Hamiltonians and real materials, eliminating unphysical spectral kinks and correctly predicting the phonon emission continuum. Building on this, we introduce the self-consistent ladder formalism for transport, which captures vertex corrections due to electron-phonon interactions. This approach unifies and improves upon the two state-of-the-art approaches for first-principles phonon-limited transport: the bubble approximation and the Boltzmann transport equation. Moreover, as a charge-conserving approximation, it enables consistent calculations of the optical conductivity and dielectric function. We validate the developed method against numerically exact results for model Hamiltonians in the dilute polaronic limit and apply it to real materials. Our results show quantitative agreement with the experimental dc conductivities in intrinsic semiconductors Si and ZnO and the SrVO3 metal, as well as excellent agreement with the experimental THz optical and dielectric properties of Si and ZnO. This work unifies first-principles and many-body approaches for studying transport, opening new directions for applying many-body theory to materials with strong electron-phonon interactions.
Authors: Satoshi Nishimoto
We systematically investigate the stability of the symmetry-protected topological (SPT) Haldane phase in spin-1/2 Heisenberg and half-filled Hubbard ladders coupled by ferromagnetic Hund's interactions. Using density-matrix renormalization group (DMRG) method, we analyze key signatures of the Haldane phase: long-range string order, finite spin gap, and characteristic entanglement spectrum degeneracies. In spin-only Heisenberg ladders, we find immediate onset and continuous strengthening of the Haldane phase with increasing Hund's coupling. In contrast, the inclusion of charge fluctuations in Hubbard ladders leads to a nontrivial stability regime, revealing a robust yet bounded region where SPT order persists despite significant charge fluctuations. We identify distinct boundaries separating a trivial insulating phase from the Haldane SPT phase, governed by both Coulomb repulsion and Hund's coupling. Our results highlight the subtle interplay of spin and charge degrees of freedom in correlated itinerant systems and establish essential criteria for observing Haldane physics experimentally in fermionic ladder materials.
Authors: Vivek Pandey, Snehasish Nandy, Pankaj Bhalla
Polarizability plays an essential role in characterizing key phenomena, such as the screening effects, collective excitations, and dielectric functions present in the system. In three-dimensional materials, it typically comprises an intraband contribution, dependent on the chemical potential, and an interband contribution, largely independent of it. In this study, within the random phase approximation framework, we uncover a novel interband contribution that, unlike the conventional case, exhibits an explicit dependence on the chemical potential, which has no counterpart in two dimensions. In the long-wavelength limit, this term introduces a resonance feature with cubic wave-vector dependence when the chemical potential approaches the band edge, in contrast to the quadratic behavior characteristic of standard intraband and interband processes. Focusing on three-dimensional Dirac nodal line semimetals, we show that the polarizability is intraband-dominated at low frequencies, while interband processes prevail at intermediate and high frequencies, with the overall response being tunable via the chemical potential. Material-specific estimates for Ca$_3$P$_2$ and ZrSiS reveal a strong tunability of both contributions. These findings open new directions for probing frequency-dependent dielectric properties and hold promise for applications in tunable plasmonic and optoelectronic devices.
Authors: Eugene B. Kolomeisky, Mia Kyler, Ishaan U. Patel
Abrikosov vortices play a central role in the disruption of superconductivity in type-II superconductors. It is commonly accepted that as one moves away from the vortex's axis of an $s$-wave superconductor, the density of superconductive electrons gradually increases from zero to its bulk value. However, we demonstrate that this behavior is qualitatively altered in the zero-temperature limit provided that the Cooper pairs comprising the superconductive liquid are sufficiently tightly bound. Specifically, outside the vortex core, the density of superconductive electrons reaches a maximum surpassing its bulk value. This phenomenon has electrostatic origins: since normal electrons are absent and there exists a charged ionic background, the spatial variation of the charge density of superconductive electrons violates local neutrality, leading to the generation of an electric field. This electric field shrinks the vortex core and turns the density profile into that with a maximum, ensuring global neutrality. The effect is most pronounced in the limit of strong electrostatic screening, where the field configurations describing the vortex attain a universal form, with the electric field screened over a length scale determined by the London penetration depth.
Authors: Shaokang Li, Livio Gibelli, Yonghao Zhang
Enskog-Vlasov equation is currently the most sophisticated kinetic model for describing non-equilibrium evaporative flows. While it enables more efficient simulations than the molecular dynamics (MD) methods, its accuracy in reproducing the flow properties of real fluids is limited by both the assumptions underlying the Vlasov forcing term and the approximation introduced by the Enskog collision term for short-range molecular interactions. To address this limitation, this work proposes a molecular kinetic model specifically designed for real fluids, with the Lennard-Jones fluids as an example. The model is first applied to evaluate the equilibrium characteristics of a liquid-vapour system, including the liquid-vapour coexistence curve, transport coefficients, vapour pressure, and surface tension coefficient. The results show excellent agreement with the MD simulation and experimental data. Furthermore, the model is used to investigate non-equilibrium evaporation, with a particular focus on the velocity distribution function adjacent to the liquid-vapour interface. The results confirm that deviations from the Maxwellian distribution persist in the vapour region, indicating limitations of the classical Hertz-Knudsen relation under pronounced non-equilibrium conditions. This work represents a critical step towards the development of an accurate and efficient computational framework for modelling non-equilibrium liquid-vapour flows for real fluids, with direct relevance to practical applications such as flow cooling.
Authors: Wei Lv, Zihao Nie, Heng Wang, Haoliang Huang, Guangdi Zhou, Qikun Xue, Zhuoyu Chen
The discovery of ambient-pressure nickelate high-temperature superconductivity provides a new platform for probing the underlying superconducting mechanisms. However, the thermodynamic metastability of Ruddlesden-Popper nickelates Lnn+1NinO3n+1 (Ln = lanthanide) presents significant challenges in achieving precise control over their structure and oxygen stoichiometry. This study establishes a systematic approach for growing phase-pure, high-quality Ln3Ni2O7 thin films on LaAlO3 and SrLaAlO4 substrates using gigantic-oxidative atomic-layer-by-layer epitaxy. The films grown under an ultrastrong oxidizing ozone atmosphere are superconducting without further post annealing. Specifically, the optimal Ln3Ni2O7/SrLaAlO4 superconducting film exhibits an onset transition temperature (Tc,onset) of 50 K. Four critical factors governing the crystalline quality and superconducting properties of Ln3Ni2O7 films are identified: 1) precise cation stoichiometric control suppresses secondary phase formation; 2) complete atomic layer-by-layer coverage coupled with 3) optimized interface reconstruction minimizes stacking faults; 4) accurate oxygen content regulation is essential for achieving a single superconducting transition and high Tc,onset. These findings provide valuable insights for the layer-by-layer epitaxy growth of diverse oxide high-temperature superconducting films.
Authors: Constantin Hilbrunner, Tobias Meyer, Joerg Malindretos, Angela Rizzi
2H-TaS$_2$ few layers have been grown epitaxially onto GaN(0001). A high substrate growth temperature of 825$^{\circ}$C induces best structural properties of the overlayer, as revealed by in-situ electron diffraction (RHEED and LEED). The 2D-overlayer grows unstrained right after deposition of a monolayer. However, evidence of pits at the interface is provided by scanning transmission electron microscopy, most probably due to GaN thermal decomposition at the high growth temperature. In-situ x-ray photoemission spectroscopy shows core level shifts that are consistently related to electron transfer from the n-GaN(0001) to the 2H-TaS$_2$ epitaxial layer as well as the formation of a high concentration of nitrogen vacancies close to the interface. Further, no chemical reaction at the interface between the substrate and the grown TaS$_2$ overlayer is deduced from XPS, which corroborates the possibility of integration of 2D 2H-TaS$_2$ with an important 3D semiconducting material like GaN.
Authors: Minyoung You
It has been suggested that non-invertible symmetry protected topological phases (SPT), due to the lack of a stacking structure, do not have symmetric entanglers (globally symmetric finite-depth quantum circuits) connecting them. Using topological holography, we argue that a symmetric entangler should in fact exist for $1+1$d systems whenever the non-invertible symmetry has SPT phases connected by fixed-charge dualities (FCD). Moreover, we construct an explicit example of a symmetric entangler for the two SPT phases with $\mathrm{Rep}(A_4)$-symmetry, as a matrix product unitary (MPU).
Authors: Yoshikazu Suzumura, Takao Tsumuraya, Masao Ogata
Seebeck coefficient, $S=L_{12}/(TL_{11})$, which is proportional to a ratio of the thermoelectric conductivity $L_{12}$ to the electric conductivity $L_{11}$ with $T$ being temperature is examined for two-dimensional Dirac electrons in a three-quarter filled organic conductor, $\alpha$-(BETS)$_2$I$_3$, [BETS = BEDT-TSeF = bis(ethylenedithio)tetraselenafulvalene] at ambient this http URL a tight-binding (TB) model obtained by first-principles relativistic density-functi onal theory method [Eur. Phys. J. B 94, 17 (2021)], we calculate $S$ in the presence of the impurity and electron--phonon (e--p) scatterings. It is shown that $S_x < 0$ and $S_y >0$ at high temperatures, where $S_x$ ($S_y$) denotes $S$ perpendicular (parallel) to the molecular stacking axis. There is a sign change of $S_y$ with increasing $T$. It is found that, at low temperatures the absolute value of $S$ is enhanced by the spin-orbit coupling. The Seebeck coefficient is examined by dividing into components of the conduction and valence bands to find that the electron and hole contributions compete each other. Such $T$ dependence of $S$ is clarified using the spectral conductivity, which determines $L_{12}$ and $L_{11}$.
Authors: Vikki Anand Varma, Alberto Scacchi
Partitioning of (bio)materials in polymeric mixtures is a key phenomenon both in cellular environments, as well as in industrial applications. In cells, several macromolecules are suspended within different biomolecular phases. On the other hand, the coexistence of polymeric aqueous phases has been exploited for the extraction and purification of (bio)materials suspended in water. Despite its relevance, key physical and chemical properties controlling the phase behavior of these complex systems are still lacking. Here, we have developed a classical density functional theory approach for describing the phase coexistence and partitioning of an arbitrary number of polymers and suspended materials. As a case example, we focus on a binary mixture of phase separating polymers in which a third material is dispersed. We explore the effect of size ratios and affinities between the different materials and address their distribution and coexisting densities, and find optimal conditions for partitioning.
Authors: Bernd Rosenow, Bertrand I. Halperin
Anyon colliders -- quantum Hall devices where dilute quasiparticle beams collide at a quantum point contact -- provide an interferometer-free probe of anyonic exchange phases through current cross correlations. Within a non-equilibrium bosonization framework, the normalized cross-correlations take a universal form depending only on the exchange phase and the dynamical exponent, enabling experimental demonstration of anyonic statistics. This result can be interpreted as time-domain interference -- braiding in time rather than spatial exclusion or real-space interferometry. Extension to hierarchical states shows that the semiclassical step-function description of quasiparticles fails at large statistical angles. Introducing a finite soliton width resolves this issue and enables quantitative modeling of charge-$e/5$ quasiparticle collisions.
Authors: Max T. Birch, Sebastian Wintz, Yuhan Sun, Akiko Kikkawa, Markus Weigand, Takahisa Arima, Yoshinori Tokura
Novel antiferromagnets with broken time reversal symmetry (TRS) have launched a new direction in spintronics research, combining the advantageous dynamical properties of conventional antiferromagnets with the controllability typically associated with ferromagnets. However, antiferromagnetic domains are notoriously challenging to image in real-space. X-ray magnetic circular dichroism (XMCD) offers a route to overcome this difficulty: XMCD contrast may be finite in TRS-breaking antiferromagnets with an appropriate magnetic space group. Here, we exploit this to image the octupole domains in a focused ion beam-fabricated device of the non-collinear antiferromagnet Mn$_3$Sn. Using scanning transmission x-ray microscopy, we spatially resolve the weak pre-edge XMCD contrast (of 0.2%) that is sensitive to $T_z$, achieving a contrast resolution better than 0.02%. We observe hysteretic switching of the octupole order through both the XMCD contrast and the corresponding anomalous Hall effect within the same device. These results confirm the bulk nature of this contrast, and establish XMCD-based microscopy as a powerful real space imaging method for TRS-breaking antiferromagnets, including altermagnets, enabling future studies of their dynamics, switching, and symmetry-tunable phenomena.
Authors: Eric Chatterjee, Daniel Soh, Matt Eichenfield
We provide a quantum mechanical description of phonon amplification in a heterostructure consisting of a two-dimensional electron gas (2DEG) stacked on top of a piezoelectric material. An applied drift voltage effectively creates a population inversion in the momentum states of the 2DEG electrons, giving rise to spontaneous emission of phonons. Once an acoustic wave is launched, the pumped electrons release phonons via stimulated emission, returning to depleted ground states before being pumped back to the excited states. We show that whereas efficient amplification using a 1D electron gas requires the acoustic wavelength to roughly equal the average electron-electron spacing, a 2DEG enables efficient amplification for any wavelength greater than the average electron-electron spacing. We derive the imaginary and real parts of the 2DEG first-order acoustic susceptibility as functions of electronic drift velocity in specific limits and derive the gain per unit length for the signal and the quantum noise, with the gain matching the classical result in the short-electronic-lifetime (low-mobility) regime. Moreover, we analyze the gain clamping due to pump depletion and calculate the maximum achievable intensity. Our results provide a framework for designing novel acoustic devices including a quantum phononic laser and phase-insensitive quantum phononic amplifiers.
Authors: Tyafur Rahman Pathan, Daryoosh Vashaee
The coherence and fidelity of quantum dot (QD) spin qubits are fundamentally limited by charge noise arising from electrically active trap states at oxide interfaces, heterostructure boundaries, and within the bulk semiconductor. These traps introduce electrostatic fluctuations that couple to the qubit via spin-orbit interactions or charge-sensitive confinement potentials, leading to dephasing and gate errors. In this work, we present a general trap characterization framework for identifying and quantifying the spectral signatures of these trap states using AC impedance spectroscopy, deep-level transient spectroscopy (DLTS), and conventional capacitance-voltage (C-V) analysis. While our case study focuses on strained Ge/SiGe quantum well heterostructures, the approach is broadly applicable to other material systems and qubit types. We demonstrate that each class of traps (oxide interface, quantum well interface, and bulk) exhibits distinct fingerprints across frequency- and time-domain measurements. Oxide traps dominate the low-frequency conductance peaks and appear strongly in Nyquist and transient spectra. QW interface traps, despite being nearly invisible at low densities in conventional C-V and AC impedance analysis, are clearly resolved through multi-exponential decay signatures in time-domain response. Bulk traps contribute to high-frequency admittance and steady-state leakage currents. By correlating each trap type to its characteristic time constant, spatial location, and spectral impact, we provide a diagnostic toolset for disentangling noise sources that degrade qubit performance. This unified methodology bridges traditional defect metrology with emerging qubit noise analysis and enables material- and process-level strategies for coherence optimization in scalable quantum devices.
Authors: Chi-Fang Chen, Michael J. Kastoryano, András Gilyén
Preparing thermal and ground states is an essential quantum algorithmic task for quantum simulation. In this work, we construct the first efficiently implementable and exactly detailed-balanced Lindbladian for Gibbs states of arbitrary noncommutative Hamiltonians. Our construction can also be regarded as a continuous-time quantum analog of the Metropolis-Hastings algorithm. To prepare the quantum Gibbs state, our algorithm invokes Hamiltonian simulation for a time proportional to the mixing time and the inverse temperature $\beta$, up to polylogarithmic factors. Moreover, the gate complexity reduces significantly for lattice Hamiltonians as the corresponding Lindblad operators are (quasi-) local (with radius $\sim\beta$) and only depend on local Hamiltonian patches. Meanwhile, purifying our Lindbladians yields a temperature-dependent family of frustration-free "parent Hamiltonians", prescribing an adiabatic path for the canonical purified Gibbs state (i.e., the Thermal Field Double state). These favorable features suggest that our construction serves as a quantum algorithmic counterpart to classical Markov chain Monte Carlo sampling.
Authors: Ye Wu, Qing Zhang, Yishi Wang, Yu Hu, Zehui Li, Zining Li, Chang Gao, Xun Liu, Haijun Huang, Yingwei Fei
Davemaoite, as the third most abundant mineral in the lower mantle, constitutes significant amounts in pyrolite and mid-ocean ridge basalts. Due to its unquenchable nature, measurements by static compression techniques on physical properties of davemaoite at lower mantle conditions are rare and technically challenging, and those are essential to constrain compositions and properties of mineralogical models in the lower mantle. Here, we present Hugoniot equation of state and sound velocity of CaSiO3 glass under shock compression. The CaSiO3 glass transforms into the crystalline phase above 34 GPa and completely transforms into davemaoite above 120 GPa. Thermal equation of state and Hugoniot temperature of davemaoite have been derived from the shock wave data. The CaSiO3 glass under shcok compression has very high shock temperature. Shock wave experiments for sound velocity of CaSiO3 glass indicate that no melting is observed at Hugoniot pressure up to 117.6 GPa. We propose that the melting temperature of davemaoite should be higher than those reported theoretically by now.
Authors: Zixia Wei, Yasushi Yoneta
Understanding the mechanisms by which complex correlations emerge through the dynamics of quantum many-body systems remains a fundamental challenge in modern physics. To address this, quench dynamics starting from nonthermal states have been extensively studied, leading to significant progress. In this paper, we propose a novel quench protocol, termed the "crosscap quench", to investigate how highly structured thermal pure states relax into typical ones. We begin by analyzing conformal field theories (CFTs) and derive universal features in the time evolution of the entanglement entropy. Furthermore, leveraging the AdS/CFT correspondence, we study holographic CFTs, providing an analytically tractable example in chaotic CFTs. Finally, we validate these findings through numerical simulations in both nonintegrable and integrable quantum spin systems.
Authors: Keerthi Kumaran, Faisal Alam, Norhan Eassa, Kaelyn Ferris, Xiao Xiao, Lukasz Cincio, Nicholas Bronn, Arnab Banerjee
Qutrit-based quantum circuits could help reduce the overall circuit depths, and hence the effect of noise, when the system of interest has a local dimension of three. Accessing second excited states in superconducting transmons provides a straightforward hardware realization of qutrits useful for such ternary encoding. In this work, we successfully calibrate microwave pulse gates to a low error rate to operate transmon qutrits. We use these qutrits to simulate one-dimensional spin-1 AKLT states (Affleck, Kennedy, Lieb, and Tasaki), which exhibit a multitude of interesting phenomena, such as topologically protected ground states, string order, and the existence of a robust Berry phase. We demonstrate the efficacy of qutrit-based simulation by preparing high-fidelity ground states of the AKLT Hamiltonian with open boundaries for various chain lengths. We then use ground state preparations of the perturbed AKLT Hamiltonian with periodic boundaries to calculate the Berry phase and illustrate non-trivial ground state topology. To establish the advantage of qutrits over qubits in the presence of noise, we present scalable methods for preparing the AKLT state and computing its Berry phase using tensor network simulations. Our work provides a pathway toward more general spin-1 physics simulations using transmon qutrits, with applications in chemistry, magnetism, and topological phases of matter.
Authors: Chetan S. Madasu, Chirantan Mitra, Lucas Gabardos, Ketan D. Rathod, Thomas Zanon-Willette, Christian Miniatura, Frederic Chevy, Chi Kwong, David Wilkowski
Spin-orbit interaction couples the spin of a particle to its motion and leads to spin-induced transport phenomena such as spin-Hall effects and Chern insulators. In this work, we extend the concept of internal-external state coupling to higher internal symmetry, exploring features beyond the established spin-orbit regime. We couple suitable resonant laser beams to a gas of ultracold atoms, thereby inducing artificial SU(3) non-Abelian gauge fields that act on a degenerate ground state manifold comprised of three dark states. We demonstrate the inherent all-state connectivity of SU(3) systems by performing targeted geometric transformations. Then, we investigate color-orbit coupling, an extension of SU(2) spin-orbit coupling to SU(3) systems. We reveal a rich dynamical interplay between three distinct oscillation frequencies, which possesses interesting analogies with neutrino oscillations and quark mixing mechanisms. In the future, the system should provide a testbed for exploring topological properties of SU(3) systems.
Authors: Abdelrahman Hussein
This document summarizes the main concepts of the finite element (FE) theory and constitutive relations as implemented in the open-source code phase-field multiphysics materials simulator PHIMATS this https URL. PHIMATS is written in C++ and uses Python for pre- and post-processing. It provides tools for discretizing the weak form of partial differential equations (PDE), interfacing with PETSc data structures (Vec/Mat) and solvers (KSP/SNES). The framework supports both single-physics and coupled multiphysics problems primarily using staggered coupling schemes. Hands-on examples can be found in the CaseStudies directory on GitHub repository. Rather than detailing the derivations of specific models, this document focuses on the key mathematical formulations and numerical strategies used within the implementation. For in-depth theoretical discussions, the reader is encouraged to consult the references. For citing this document, please use: [Abdelrahman Hussein. Finite Element Theory for PHIMATS. 2025. doi: https://doi.org/10.48550/ARXIV.2502.16283].
Authors: Yutao Hu, Chao Yang, Yucheng Wang
Flat bands (FBs) play a crucial role in condensed matter physics, offering an ideal platform to study strong correlation effects and enabling applications in diffraction-free photonics and quantum devices. However, the study and application of FB properties are susceptible to interference from dispersive bands. Here, we explore the impact of bond dissipation on systems hosting both flat and dispersive bands by calculating the steady-state density matrix. We demonstrate that bond dissipation can drive particles from dispersive bands into FBs and establish the general conditions for this phenomenon to occur. Our results demonstrate that dissipation can facilitate FB preparation, property measurement, and utilization. This opens a new avenue for exploring FB physics in open quantum systems, with potential implications for strongly correlated physics.
Authors: Lucas Tsunaki, Anmol Singh, Sergei Trofimov, Boris Naydenov
The nitrogen-vacancy (NV) center in diamond is a crucial platform for quantum technologies, where its precise numerical modeling is indispensable for the continued advancement of the field. We present here a Python library for simulating the NV spin dynamics under general experimental conditions, i.e. a digital twin. Our library accounts for electromagnetic pulses and other environmental inputs, which are used to solve the system's time evolution, resulting in a physical output in the form of a quantum observable given by fluorescence. The simulation framework is based on a non-perturbative time-dependent Hamiltonian model, where the states initialization and readout are postulated from the interaction with optical fields. By eliminating oversimplifications such as the adoption of rotating frames for the microwave and radio frequency fields, our simulations reveal subtle dynamics emerging from realistic pulse constraints. The software is illustrated with three examples and validated by comparing the simulations with experimental reports, relevant to the fields of quantum computing (conditional logic gates), sensing (dynamical decoupling sequences with coupled spins) and networks (state teleportation). Overall, this digital twin delivers a robust numerical modeling of the NV spin dynamics, with simple and accessible usability, which can be used for a wide range of applications.
Authors: Jason Hindes, George Stantchev, Klimka Szwaykowska Kasraie, Ira B. Schwartz
An important goal for swarming research is to create methods for predicting, controlling and designing swarms, which produce collective dynamics that solve a problem through emergent and stable pattern formation, without the need for constant intervention, and with a minimal number of parameters and controls. One such problem involves a swarm collectively producing a desired (target) density through local sensing, motion, and interactions in a domain. Here, we take a statistical physics perspective and develop and analyze a model wherein agents move in a stochastic walk over a networked domain, so as to reduce the error between the swarm density and the target, based on local, random, and uncertain measurements of the current density by the swarming agents. Using a combination of mean-field, small-fluctuation, and finite-number analysis, we are able to quantify how close and how fast a swarm comes to producing a target as a function of sensing uncertainty, stochastic collision rates, numbers of agents, and spatial variation of the target.
Authors: Nuno Crokidakis, Lucas Sigaud
In social contexts where individuals consume varying amounts, such as shared meals or bar gatherings, splitting the total bill equally often yields surprisingly fair outcomes. In this work, we develop a statistical physics framework to explain this emergent fairness by modeling individual consumption as stochastic variables drawn from a realistic distribution, specifically the gamma distribution. Introducing a Boltzmann-like weighting factor, we derive exact analytical expressions for the partition function, average consumption, variance, and entropy under economic or social penalization constraints. Numerical simulations, performed using the Marsaglia-Tsang algorithm, confirm the analytical results with high precision. Drawing a direct parallel between individual consumption and ideal gas particle energy in the canonical ensemble, we show how the law of large numbers, mutual compensation, and the effective ordering induced by penalization combine to make equal cost-sharing statistically robust and predictable. These findings reveal that what appears to be an informal social convention is, in fact, grounded in the same fundamental principles that govern the collective behavior of particles in thermodynamic systems, highlighting the interdisciplinary power of statistical physics.
Authors: Lucas Bourgoin (IRMA)
We derive the asymptotic expansion of the partition function of a Coulomb gas system in the determinantal case on compact Riemann surfaces of any genus g. Our main tool is the bosonization formula relating the analytic torsion and geometric quantities including the Green functions appearing in the definition of this partition function. As a result, we prove the geometric version of the Zabrodin-Wiegmann conjecture in the determinantal case.
Authors: Oskar Leinonen, Jonas B. Flaten, Stian D. Bilek, Øyvind S. Schøyen, Morten Hjorth-Jensen, Niyaz R. Beysengulov, Zachary J. Stewart, Jared D. Weidman, Angela K. Wilson
Systems of individual electrons electrostatically trapped on condensed noble gas surfaces have recently attracted considerable interest as potential platforms for quantum computing. The electrons form the qubits of the system, and the purity of the noble gas surface protects the relevant quantum properties of each electron. Previous work has indicated that manipulation of a confining double-well potential for electrons on superfluid helium can generate entanglement suitable for two-qubit gate operations. In this work, we incorporate a time-dependent tuning of the potential shape to further explore operation of two-qubit gates with the superfluid helium system. Through numerical time evolution, we show that fast, high-fidelity two-qubit gates can be achieved. In particular, we simulate operation of the $\sqrt{i\mathrm{SWAP}}$ and CZ gates and obtain fidelities of 0.999 and 0.996 with execution times of 2.9 ns and 9.4 ns, respectively. Furthermore, we examine the stability of these gate fidelities under non-ideal execution conditions, which reveals new properties to consider in the device design. With the insights gained from this work, we believe that an experimental realization of two-qubit gates using electrons on helium is feasible.
Authors: Cameron Hahn, Nishan Ranabhat, Fabio Anza
Building on the geometric formulation of quantum mechanics, we develop a coherence theory for ensembles that exploits the probability-phase structure of the quantum state space. Standard coherence measures quantify superposition within density matrices but cannot distinguish ensembles that produce the same mixed state through different distributions of pure states. First, we introduce the probability-phase mutual information $I(P;\Phi)$, which measures statistical correlations between measurement-accessible probabilities and measurement-inaccessible phases across an ensemble. Then, we prove this satisfies the axioms of a coherence monotone, establishing it as a bona-fide measure of ensemble-level coherence. Eventually, through the definition of the \emph{coherence surplus} $\delta_{\mathcal{C}} \geq 0$, we show how ensemble coherence relates to, but exceeds, density-matrix coherence, thus quantifying structure lost in statistical averaging.
Authors: Tomoya Hayata, Kazuhiro Seki, Seiji Yunoki
Simulating nonequilibrium dynamics of quantum many-body systems is one of the most promising applications of quantum computers. However, a faithful digital quantum simulation of the Hamiltonian evolution is very challenging in the present noisy quantum devices. Instead, nonequilibrium dynamics under the Floquet evolution realized by the Trotter decomposition of the Hamiltonian evolution with a large Trotter step size is considered to be a suitable problem for simulating in the present or near-term quantum devices. In this work, we propose simulating the many-body localization crossover as such a nonequilibrium problem in the disordered Floquet many-body systems. As a demonstration, we simulate the many-body localization crossover in a disordered kicked Ising model on a heavy-hex lattice using $60$ qubits from $156$ qubits available in the IBM Heron r2 superconducting qubit device named ibm\_fez. We compute out-of-time-ordered correlators as an indicator of the many-body localization crossover. From the late-time behavior of out-of-time-ordered correlators, we locate the quantum chaotic and many-body localized regimes as a function of the disorder strength. The validity of the results is confirmed by comparing two independent error mitigation methods, that is, the operator renormalization method and zero-noise extrapolation.
Authors: Anubhav Ganguly
We study the scaling properties of avalanche activity in the two-dimensional Abelian sandpile model. Instead of the conventional avalanche size distribution, we analyze the site activity distribution, which measures how often a site participates in avalanches when grains are added across the lattice. Using numerical simulations for system sizes up to \(L = 160\), averaged over \(10^4\) configurations, we determine the probability distribution \(P(A, L)\) of site activities. The results show that \(P(A, L)\) follows a finite-size scaling form \[ P(A, L) \sim L^{-2} F\Big(\frac{A}{L^2}\Big). \] For small values \(A \ll L^2\) the scaling function behaves as \[ F(u) \sim u^{-1/2}, \quad \text{corresponding to} \quad P(A) \sim \frac{1}{L}, \] while for large activities \(A \sim O(L^2)\) the distribution decays as \[ F(u) \sim \exp\big(-c_3 u - c_4 u^2\big). \] The crossover between these two regimes occurs at \[ A^* \sim 0.1 \, L^2, \] marking the threshold between typical and highly excitable sites. This characterization of local avalanche activity provides complementary information to the usual avalanche size statistics, highlighting how local regions serve as frequent conduits for critical dynamics. These results may help connect sandpile models to real-world self-organized critical systems where only partial local activity can be observed.
Authors: Arjun Dey, Loic Herviou, Christopher Mudry, Andreas Martin Läuchli
We present a model for strongly interacting fermions with internal O(3) symmetry on the fuzzy-sphere that (i) preserves the rotational symmetry of the fuzzy sphere and (ii) undergoes a quantum phase transition in the (2+1)-dimensional O(3) Wilson-Fisher universality class. Using exact diagonalization (ED) and density matrix renormalization group (DMRG), we locate the quantum critical point via conformal perturbation theory and obtain scaling dimensions from finite-size spectra. We identify 24 primary operators and determine some of their operator product expansion coefficients through first-order conformal perturbation theory. The results are benchmarked against conformal bootstrap and large quantum-number expansions and reveal a weakly irrelevant operator that plays a role in dimerized antiferromagnets. Our work establishes the fuzzy sphere as a general framework for quantitatively accessing conformal data in non-Abelian conformal field theories (CFTs).
Authors: Tycho J. Blom, Matthijs Rog, Marieke Altena, Andrea Capa Salinas, Stephen D. Wilson, Chuan Li, Kaveh Lahabi
Materials with a Kagome lattice are intensely studied because they host novel, exotic states that combine strong correlations and electronic topology. The AV3Sb5 (A = K, Rb, Cs) group, in particular, is of major interest due to its combination of charge density waves, unconventional superconductivity, and indications of time-reversal symmetry breaking and electronic nematicity. Recently, critical current oscillations in an external magnetic field were observed in an unstructured flake of CsV3Sb5 at low current densities. In this work, we unequivocally show that the origin of these oscillations is a network of Josephson junctions intrinsic to the flake that emerges below its critical temperature. Under radio-frequency radiation, we observe perfectly quantized, integer Shapiro steps. The sensitivity of the step height to the contact placement indicates a rich and complex network of junctions. By performing interference studies along multiple field directions, we demonstrate that the observed interference effects are a result of geometrically small junctions and filamentary supercurrent flow. Upon microstructuring the flake, prominent features of the interference pattern are fully preserved, illustrating the localized nature of these flakes and their stability to thermal cycles. These results pave the way for determining the exact nature of superconductivity in the AV3Sb5 family.
Authors: M.P. Telenkov, Yu.A. Mityagin
Electron-electron scattering processes involving Landau levels of two subband are considered. A matrix of electron-electron scattering rates containing all tipes of transitions between Landau levels is calculated/ This matrix is analized, and the relative rates of transitions of different types are determined. The effect of the quantizing magnetic field orientation on electron-electron scattering processes is ectablished.
Authors: Jordan T. McCourt, John Chiles, Chun-Chia Chen, Kenji Watanabe, Takashi Tanaguchi, Francois Amet, Gleb Finkelstein
The interfaces of quantum Hall insulators with superconductors have emerged as a promising platform to realise interesting physics that may be relevant for topologically protected quantum computing. However, these interfaces can host other effects which obscure the detection of the desired excitations. Here we present measurements of the thermoelectric effect at the quantum Hall-superconductor interface. We explain the heat transport by considering the formation of a hotspot at the interface, which results in a non-equilibrium distribution of electrons that can propagate across the superconductor through vortex cores. The observed thermoelectric effect results in a voltage which changes sign on quantum Hall plateaus and responds to the rearrangement of vortices in the wire. These observations highlight the complex interplay of thermal and charge phenomena at the quantum Hall -- superconductor interfaces and should be considered when interpreting transport measurements in similar systems.
Authors: Xin-Feng Zhang, Huan-Bo Luo, Josep Batle, Bin Liu, Yongyao Li
The present contribution explores phase transitions that occur in the ground state (GS) of spin-1 Bose-Einstein condensates (BECs) with spin-orbit coupling (SOC) under the action of gradient magnetic fields. By solving the corresponding linearized system in an exact fashion, we identify the conditions under which the GS phase transitions occur, thus transforming excited states into GS. The study of the full nonlinear system, including both density-density and spin-spin interactions, is numerically analyzed. For the case of repulsive spin-spin interactions, the results resemble the linear case, while attractive spin-spin interactions lead to the formation of mixed-states near the GS phase-transition points. Additionally, higher-order vortex solitons are found to be stable even in the nonlinear regime. These findings demonstrate that arbitrary winding numbers can be achieved as corresponding to stable GS and thus contributing to the understanding of topological properties in SOC BECs.
Authors: Johnathan Kowalski, Liangbo Liang
Monolayer transition metal dichalcogenides (TMDs) are a key class of two-dimensional (2D) materials with broad technological potential. Their Janus counterparts exhibit unique properties due to broken out-of-plane symmetry and further enrich the functionalities of TMDs. However, experimental synthesis and identification of Janus TMDs remain challenging. It is thus highly desirable to have a rapid, simple, and in situ characterization technique to monitor, in real time, the conversion process from the parent to Janus structure. Raman spectroscopy stands out for such a task as it is a powerful, non-destructive, and very commonly used tool to characterize 2D materials both in situ and ex situ. To realize the full potential of Raman spectroscopy on rapid characterization of Janus TMDs, we present a computational "Raman digital twin" library for various monolayer Janus TMDs in both 2H and Td phases. We focus on group-6 TMDs: MoS$_2$, WS$_2$, MoSe$_2$, WSe$_2$, MoTe$_2$, WTe$_2$ and their Janus variants: MoSSe, MoSTe, MoSeTe, WSSe, WSTe, and WSeTe. Using first-principles density functional theory (DFT), we calculate their vibrational properties and predict distinct Raman fingerprints. These phonon and Raman signatures reflect each material's structural symmetry and atomic composition, enabling clear identification via Raman spectroscopy. Our theoretical work supports experimental efforts by providing benchmarks for material identification, structural analysis, and quality control. The computational library expedites the discovery and development of Janus 2D materials, facilitating tighter integration between theoretical predictions and experimental validation.
Authors: Soma Nagahama, Yuki Sato, Minoru Kawamura, Ilya Belopolski, Ryutaro Yoshimi, Atsushi Tsukazaki, Naoya Kanazawa, Kei S Takahashi, Masashi Kawasaki, Yoshinori Tokura
The superconducting diode effect (SDE) is characterized by the nonreciprocity of Cooper-pair motion with respect to current direction. In three-dimensional (3D) materials, SDE results in a critical current that varies with direction, making the effect distinctly observable: the material exhibits superconductivity in one direction while behaving as a resistive metal in the opposite direction. However, in genuinely two-dimensional (2D) materials, the critical current density is theoretically zero, leaving the manifestation of SDE in the 2D limit an intriguing challenge. Here, we present the observation of SDE in a heterostructure composed of the topological insulator Bi$_2$Te$_3$ and the iron based superconductor Fe(Se,Te) $-$a candidate for topological superconductor$-$ where superconductivity is confined to the 2D limit. The observed I-V characteristics reveal nonreciprocity in the vortex-creep regime, where finite voltages arise due to the two-dimensional nature of superconductivity. Furthermore, our 2D film demonstrates abrupt voltage jumps, influenced by both the current flow direction and the transverse magnetic field direction. This behavior resembles that of 3D materials but, in this case, is driven by the vortex-flow instability, as illustrated by voltage controlled S-shaped I-V curves. These results underscore the pivotal role of vortex dynamics in SDE and provide new insights into the interplay between symmetry breaking and two-dimensionality in topological insulator/superconductor systems.
Authors: Takeshi Takahashi, Hiroki Saito
Bose-Einstein condensates (BECs) of $^{87}\textrm{Rb}$ atoms with a hyperfine spin of 2 are open quantum systems, where the atoms are lost through two-body inelastic collisions. In this dissipation process, a collision channel with total spin of 4 is forbidden by angular momentum conservation, which results in magnetization of the atoms remaining in the condensate. Here, we investigate the quantum many-body properties of spin-2 bosons that undergo two-body atomic loss. We show that the system finally reaches a steady state, which is a mixture of the states with maximum total spins. In addition, we find that a non-classical steady state can be obtained by quenching the quadratic Zeeman coefficient.
Authors: Daniel Schroller, Daniel Sitter, Thomas Koch, Viktor Adam, Noah Glaeser, Clement Godfrin, Stefan Kubicek, Julien Jussot, Roger Loo, Yosuke Shimura, Danny Wan, Yaorong Chen, Mario Ruben, Kristiaan De Greve, Wolfgang Wernsdorfer
Molecular spin qudits offer an attractive platform for quantum memory, combining long coherence times with rich multi-level spin structures. Terbium bis(phthalocyaninato) (TbPc$_2$) exemplifies such systems, with demonstrated quantum control and chemical reproducibility. In hybrid quantum architectures, TbPc$_2$ can act as the primary memory element, with semiconductor qubits providing scalable readout and coupling. Here we present a step toward such a hybrid system: using an industrially manufactured silicon metal-oxide-semiconductor (SiMOS) spin qubit to detect electronic spin transitions of an ensemble of TbPc$_2$ molecules. The readout is based on a compact and robust protocol that applies a microwave pulse while all gate voltages defining the qubit are held at a fixed operating point. This protocol, which combines simultaneous Rapid adiabatic Passage and Spin- Selective tunneling (RPSS), enables high-contrast resonance detection and avoids repeated $\pi$-pulse recalibration common in decoupling schemes. By demonstrating ensemble detection, we establish a foundation for integrating molecular quantum memories with industrial qubit platforms and mark an important step toward single-molecule hybrid quantum technologies.
Authors: Xiaohui Yao, Jiahui Ji, Xuanchi Zhou
The metal-insulator transition (MIT) in correlated oxide systems opens up a new paradigm to trigger the abruption in multiple physical functionalities, enabling the possibility in unlocking exotic quantum states beyond conventional phase diagram. Nevertheless, the critical challenge for practical device implementation lies in achieving the precise control over the MIT behavior of correlated system across a broad temperature range, ensuring the operational adaptability in diverse environments. Herein, correlated vanadium dioxide (VO2) serves as a model system to demonstrate effective modulations on the MIT functionality through bandwidth and band-filling control. Leveraging the lattice mismatching between RuO2 buffer layer and TiO2 substrate, the in-plane tensile strain states in VO2 films can be continuously adjusted by simply altering the thickness of buffer layer, leading to a tunable MIT property over a wide range exceeding 20 K. Beyond that, proton evolution is unveiled to drive the structural transformation of VO2, with a pronounced strain dependence, which is accompanied by hydrogenation-triggered collective carrier delocalization through hydrogen-related band filling in t2g band. The present work establishes an enticing platform for tailoring the MIT properties in correlated electron systems, paving the way for the rational design in exotic electronic phases and physical phenomena.
Authors: Andrey V. Sadakov, Vladimir A. Vlasenko, A.Yu. Levakhova, I.V. Zhuvagin, E.M. Fomina, V.A. Prudkoglyad, A.Y. Tsvetkov, A.S. Usoltsev, N. D. Zhigadlo
We present a comprehensive investigation of the field-dependent critical current density and pinning force, combined with a detailed analysis of the nanostructural defect landscape in single crystal of underdoped PrFeAs(O,F) superconductor. Our study demonstrates that for both in-plane and out-of-plane magnetic field orientations critical current density exhibits a strong pinning regime in intermediate fields across the entire temperature range. The dominant contribution to pinning originates from oxygen-to-fluorine substitutional defects, oxygen vacancies, which all act as point defects via a quasiparticle mean free path fluctuation mechanism. Scanning transmission electron microscope studies did not reveal any volume or surface defect types within the lattice.
Authors: Riju Pal, Kakan Deb, Nitesh Kumar, Bernd Büchner, Alexey Alfonsov, Vladislav Kataev
MgMn$_6$Sn$_6$ is the itinerant ferromagnet on the kagome lattice with high ordering temperature featuring complex electronic properties due to the nontrivial topological electronic band structure, where the spin-orbit coupling (SOC) plays a crucial role. Here, we report a detailed ferromagnetic resonance (FMR) spectroscopic study of MgMn$_6$Sn$_6$ aimed to elucidate and quantify the intrinsic magnetocrystalline anisotropy that is responsible for the alignment of the Mn magnetic moments in the kagome plane. By analyzing the frequency, magnetic field, and temperature dependences of the FMR modes, we have quantified the magnetocrystalline anisotropy energy density that reaches the value of approximately $ 3.5\cdot 10^6$ erg/cm$^3$ at $T = 3$ K and reduces to about $1\cdot 10^6$ erg/cm$^3$ at $T = 300$ K. The revealed significantly strong magnetic anisotropy suggests a sizable contribution of the orbital magnetic moment to the spin magnetic moment of Mn, supporting the scenario of the essential role of SOC for the nontrivial electronic properties of MgMn$_6$Sn$_6$.
Authors: Heng Wu, Houssam el Mrabet Haje, Michiel Dubbelman, Brenden R. Ortiz, Stephen D. Wilson, Mazhar N. Ali, Yaojia Wang
Superconductivity represents a macroscopic quantum state notable for its rich manifestations of electronic coherence and collective behavior. Kagome materials AV3Sb5 (A= K, Cs, Rb) possess cascade intertwined quantum phases including superconductivity, symmetry-breaking charge orders, nematic orders and topological states, making them attractive materials for exploring exotic superconducting states. However, the superconducting properties and the Cooper pairing behaviors have not been fully explored and understood. In this work, by studying both the magnetoresistance and critical current behaviors in KV3Sb5 ring and pristine flakes, we reveal the charge 2e paring in KV3Sb5 although anomalous oscillations with smaller periodicity were observed, and report the intrinsic superconducting phase coherence in KV3Sb5 flakes. The former is demonstrated by the careful verification of the Little-Parks oscillations in differential resistance colormaps, and the latter indicates the existence of superconducting domains in KV3Sb5. Moreover, we observed a special phenomenon: the transfer of supercurrent interference patterns between the superconducting ring and the superconducting flake, which demonstrates the global critical current effect of the superconducting phase coherence. These findings provide new insights into the Cooper pairing behaviors in KV3Sb5 and highlight the importance of global effect of superconducting phase coherence in the understanding of the superconducting behaviors.
Authors: Jixiang Yang, Omid Sharifi Sedeh, Chiho Yoon, Shenyong Ye, Henok Weldeyesus, Armel Cotten, Tonghang Han, Zhengguang Lu, Zach Hadjri, Junseok Seo, Lihan Shi, Emily Aitken, Prayoga P Liong, Zhenghan Wu, Mingchi Xu, Christian Scheller, Mingyang Zheng, Rasul Gazizulin, Kenji Watanabe, Takashi Taniguchi, Dominique Laroque, Mingda Li, Fan Zhang, Dominik M. Zumbühl, Long Ju
Spin-polarized superconductors offer a rare platform for studying electronic correlations, but few candidate systems have been experimentally confirmed to date. Here, we report the observation of a spin-polarized superconducting state, denoted SC5, in WSe2-proximitized rhombohedral trilayer graphene. At in-plane magnetic field B|| = 0 T, SC5 has a critical temperature of 68 mK and an out-of-plane critical magnetic field of only 12 mT. Surprisingly, these values are significantly enhanced as B|| increases, and the superconductivity persists to B|| = 8.8 T. This value corresponds to a record-high Pauli-limit violation ratio of at least 80 among all superconductors, while the true critical field is beyond the limit of our instrument. We conclude that SC5 experiences a canting crossover from Ising-type to spin-polarized superconductor with increased B||.
Authors: Xiao-Yu Yan, Guowei Liu, Hanbin Deng, Xitong Xu, Haiyang Ma, Hailang Qin, Jun-Yi Zhang, Yuanyuan Zhao, Haitian Zhao, Zhe Qu, Yigui Zhong, Kozo Okazaki, Xiquan Zheng, Yingying Peng, Zurab Guguchia, X. X. Wu, Qianghua Wang, X-H Fan, Wei Song, M-W Gao, Hendrik Hohmann, Matteo Durrnagel, Ronny Thomale, Jia-Xin Yin
The pair-density-wave (PDW) exhibits periodic amplitude and sign modulations of the superconducting order parameter. Such a pairing state has been proposed to be sensitive to nonmagnetic scattering. In this work, we observe the nonmagnetic PDW-breaking effect in a kagome superconductor, using scanning tunneling microscopy. We observe 2x2 PDW induced by the coupling between charge order and superconductivity. The global PDW is substantially suppressed upon doping the kagome lattice with dilute isovalent nonmagnetic impurities, whereas the charge order and uniform superconductivity remain robust. Spatial correlation analysis further confirms that PDW is distinctly suppressed near dopants. We attribute the PDW suppression to a nonmagnetic PDW breaking effect, arising from phase sign modulation of PDW in the kagome d-orbital hosting Bogoliubov Fermi states.
Authors: H. Sakai, C. Tabata, K. Kaneko, Y. Tokiwa, T. Kitazawa, S. Kambe, Y. Tokunaga, Y. Haga
alpha-UTe3, a van der Waals (vdW) actinide compound with a monoclinic ZrSe3-type structure, is a narrow-gap semiconductor with 5f moments. 125Te NMR reveals strongly anisotropic, layer-confined spin fluctuations below about 20 K, with the a-axis component enhanced, and a signal wipeout at the antiferromagnetic (AFM) transition at TN = 5 K. Single-crystal neutron diffraction finds q approx. (0.17, 0.5, 0) and a longitudinal sinusoidal modulation of a-axis moments (amplitude about 0.8 muB) with AFM stacking along b. A CEF singlet-singlet induced-moment framework accounts for the easy-axis anisotropy, the small heat-capacity anomaly at TN, the reduced ordered moment, and the exchange-driven selection of q in this localized 5f vdW magnet, establishing a constrained exchange geometry stabilizing this in-plane incommensurate state.
Authors: Chi Zhang, Quan Shen, Mengmeng Zhang, Zhiming Deng, Taishen Wu, Xuying Zhong, Gang Ouyang, Dongsheng Tang, Qi Zheng, Jiansheng Dong, Weichang Zhou
The limited quantum yield of strained monolayer transition metal dichalcogenides grown by vapor-phase methods and during transfer-based stacking poses a fundamental challenge for their optoelectronic applications. Here, we introduce the concept of "entropy engineering" as a transformative strategy to selectively enhance light-matter interactions through controlled electron-phonon coupling. We unveil how tailored entropy introduced via precise selenium doping or interfacial van der Waals proximity can significantly amplify radiative recombination from momentum-dark excitons in WS2 monolayers. Notably, we discover that slight selenium doping drastically enhances the photoluminescence (PL) of WS2 under strain. While both undoped and heavily doped WS2 suffer from strong PL quenching owing to the direct-to-indirect bandgap transition, lightly Se-doped samples exhibit an order-of-magnitude increase in emission intensity. This counterintuitive boost is traced to doping-induced structural disorder, which intensifies electron-phonon interactions and unlocks efficient phonon-assisted emission from otherwise non-radiative indirect excitons. Moreover, we demonstrate that van der Waals coupling to adjacent Se-doped layers can impart interfacial entropy and further augment PL via proximity effects. Our work highlights entropy engineering via controlled doping as a powerful strategy for activating high-efficiency light emission in atomically thin semiconductors.
Authors: Chi Zhang, Shihao Zhang, Mengmeng Zhang, Lin He, Qi Zheng
Insulating, atomically flat transition metal dichalcogenides (TMDs) like WSe2 are ideal substrates for probing intrinsic graphene properties. Conventionally, their influence on graphene's band structure is assumed negligible, particularly when small moire patterns form. Combining scanning tunneling microscopy/spectroscopy and theoretical analysis, we reveal that the atomic registry in graphene/WSe2 heterostructures profoundly modulates the electronic structure of magic-angle twisted bilayer graphene (MATBG). At special graphene/WSe2 twist angles, an incommensurate moire superlattice hosts three distinct atomic stacking configurations (A, B, X types). These induce position-dependent potentials that asymmetrically shift MATBG's flat bands, transforming them from hole-side to electron-side asymmetric within a single AA-stacked region. This symmetry breaking enables the unprecedented coexistence of orthogonal stripe charge orders in the correlated regime-a phenomenon previously considered mutually exclusive due to Coulomb repulsion. This band modulation arises from the synergistic effects of the graphene/WSe2 interfacial atomic registry and heterostrain within the MATBG, exhibiting multi-field tunability. Our work establishes interfacial atomic registry as a critical, previously overlooked tuning parameter for flat-band physics, opening avenues to engineer correlated quantum states in van der Waals heterostructures.
Authors: Masafumi Udagawa, Roderich Moessner
Fractional excitations provide a key to identifying sought-after topological quantum spin liquid states in realistic materials. Their single-particle dynamics already presents a challenging many-body problem on account of the coupling to their emergent gauge field. Here, we study the spinon excitations of kagome ice, realized at the $2/3$ magnetization plateau of spin ice, by combining up-to-$63$-site exact diagonalization with an analytical state graph mapping. We find a macroscopically degenerate mode in the spinon spectrum. It originates from the destructive interference due to the interaction with surrounding gauge fields, a form of many-body caging. We explicitly construct, and count, the concomitant many-body wave functions. Finally, we discuss the possible role of these flat modes in the magnetization process of kagome antiferromagnets, in particular with regard to the asymmetric termination of the kagome ice magnetisation plateau.
Authors: A. A. Kamashev, N. N. Garif'yanov, A. A. Validov, A. S. Osin, Ya. V. Fominov, I. A. Garifullin
The structures of the superconducting spin valve (SSV) Fe/\allowbreak Si$_3$N$_4$/\allowbreak Pb/\allowbreak Si$_3$N$_4$/\allowbreak Fe (where Si$_3$N$_4$ is a dielectric insulating layer of controlled thickness) were investigated. The dependence of the magnitude of the SSV effect on the thicknesses of the superconducting (S) and insulating (I) layers was studied. Optimization of the S and I layer thicknesses enabled a complete switching between the normal and superconducting states when the mutual orientation of the magnetizations of the ferromagnetic (F) layers changed from antiparallel to parallel. A maximal SSV effect value of 0.36\,K was achieved in an external magnetic field of 1\,kOe. These results demonstrate that SSV structures with tunable S/F interface transparency controlled by insulating interlayers are promising for achieving a significant magnitude of the effect. This opens new avenues for the development of such systems and their potential applications in spintronic devices.
Authors: Ramanand Singh Yadav, Ralf Metzler, Rajarshi Chakrabarti
Using computer simulations in two dimensions we investigate the dynamics and structure of passive polymeric tracer with different topologies immersed in a low-density active particle bath. One of the key observations is that polymer exhibit faster dynamics compared to passive colloidal particles at high activity, for the same particle density, in both linear and star polymer topologies. This enhanced motion is attributed to the accumulation of active particles, which induces prolonged and persistent movement of the polymer. Further analysis reveals that star polymers exhibit more complex and intriguing behavior than their linear counterparts. Notably, the accumulation of active particles promotes the pairing of arms in star polymers. For instance, a three-armed star polymer adopts a conformation similar to a linear polymer with two-arms due to this pairing as a result, at high activity, the dynamics of both the polymers converge. Finally, we explore the dynamics of a linear polymer with the same total number of beads as the star polymer. Interestingly, at high activity -- where arm pairing in the star polymer is significant -- the star polymer demonstrates faster dynamics than the linear polymer, despite having the identical number of beads. These findings contribute to a broader understanding of the interactions between active and passive components of varying topologies in dilute systems and highlight their potential for innovative applications ranging from materials science to biomedicine.
Authors: Max Tymczyszyn, Edward McCann
We present example four-band Hermitian tight-binding Bogoliubov-de-Gennes (BdG) Hamiltonians and Kramer's degenerate Hamiltonians in one dimension. Starting from a generalized Rice-Mele model, we incorporate superconducting terms to obtain a four-band BdG Hamiltonian with intrinsic charge-conjugation symmetry, and constrain it using symmorphic or nonsymmorphic time-reversal symmetries. In position space we find that each form of time-reversal symmetry, when applied to random BdG matrices, results in a unique block diagonalization of the Hamiltonian when translational symmetry is also enforced. We provide representative models in all relevant symmorphic symmetry classes, including the non-superconducting CII class. For nonsymmorphic time-reversal symmetry, we identify a $\mathbb{Z}_4$ topological index with two phases supporting Majorana zero modes and two without, and study disorder effects in the presence of topological solitons. We further generalize a winding-number method, previously applied only to $\mathbb{Z}_2$ invariants without Kramer's degeneracy, to compute indices for both the $\mathbb{Z}_4$ model and a non-superconducting AII model with nonsymmorphic chiral symmetry and Kramer's degeneracy. We propose topolectric circuit implementations of the charge-density-wave and $\mathbb{Z}_4$ models which agree with the topological calculations. Finally, we show that, in one dimension, nonsymmorphic unitary symmetries do not produce new topological classifications beyond $\mathbb{Z}$ or $\mathbb{Z}_2$ indices.
Authors: Á. A. Carrasco Álvarez, M. Giantomassi, J. Lihm, G. E. Allemand, M. Mignolet, M. Verstraete, S. Poncé
Magnetic materials are crucial for manipulating electron spin and magnetic fields, enabling applications in data storage, spintronics, charge transport, and energy conversion, while also providing insight into fundamental quantum phenomena. In numerous applications, the interaction between electrons and lattice vibrations, known as electron-phonon coupling, can be of significant importance. In that regard, we extend the EPW package to be able to interpolate the electron-phonon matrix elements combining perturbation theory and maximally localized Wannier functions. This allows to use dense momentum grids at a reasonable computational cost when computing electron-phonon-related quantities and physical properties. We validate our implementation considering ferromagnetic iron and nickel, where we explore the absence of phonon-driven superconductivity, finding that superconductivity is intrinsically suppressed. Furthermore, we evaluate the carrier resistivity at finite temperatures for both systems, considering the role of the magnetic phase in carrier transport. Our findings indicate that in the case of Fe, the primary contributor to resistivity is electron-phonon scattering. In contrast, for Ni, electron-phonon scattering constitutes less than one-third of the resistivity, underscoring a fundamental difference in the transport properties of the two systems.
Authors: Tim Kokkeler, Tero T. Heikkilä, F. Sebastian Bergeret
We study the nonequilibrium spin-splitter effect in superconducting altermagnets and superconductor altermagnet hybrids by computing the alternating spin current and edge the spin density in the presence of an alternating electric field. We show that while in the normal state the effect is not sensitive to the field frequency, in the superconducting state, there is a strong effect for frequencies on the scale of $\Delta_0$ or lower. We contrast the effect to the spin accumulation induced by the spin-Hall effect, by showing that for the altermagnet spin-splitter effect the out-of-phase spin density does not diverge in the adiabatic limit. This difference is attributed to the absence of any equilibrium spin-splitter effect in altermagnets. In fact, the out-of-phase component vanishes below the gap excitation frequency $2\Delta_0$, because below this frequency the absence of dissipation and the behavior of the system under time-reversal directly determine the relative phase between the charge current, spin current, and spin accumulation. The nonequilibrium effect can be tuned by external parameters like temperature. In fact, it has a nonmonotonic temperature dependence, taking its largest value for temperatures around $0.8T_{c}$. The value at this temperature can be significantly larger than the normal state spin density or the low temperature spin density. Thus, besides using the nonequilibrium spin-splitter effect to identify altermagnets, its tunability makes it also suitable for applications.
Authors: Martin Haller, Julia Hewelt, V. Y. M. Rajesh Chirala, Loi Vinh Tran, Ankur Bhide, Muriel Wegner, Stefan Förster, Wolf Widdra
Dodecagonal oxide quasicrystals (OQCs) have so far been limited to a few elemental systems, with no general formation mechanism established. Here, we demonstrate a versatile approach to OQC formation via a host-atom-induced transformation of a metal-oxide honeycomb (HC) network. Adsorption of Ba, Sr, or Eu onto the HC layer triggers its reorganization into a dodecagonal tiling, as revealed by low-energy electron diffraction and scanning tunneling microscopy. Full conversion occurs when 73% of the honeycomb rings are occupied. Kelvin probe and UV photoelectron spectroscopy show a linear decrease in work function with increasing host coverage, followed by a sharp increase upon quasicrystal formation due to reduced host dipoles. This transformation mechanism enables the fabrication of structurally precise OQCs, including a new Eu-Ti-O phase that extends the field to lanthanide quasicrystals, forming a 2D grid of localized magnetic moments. The method offers a general route to explore lattice-matched substrates for epitaxial growth and may be adapted to other 2D honeycomb materials - such as graphene, hexagonal ice, and silica - paving the way for engineered aperiodic systems beyond transition metal oxides.
Authors: Liang Fu
Representing fermionic wavefunctions efficiently is a central problem in quantum physics, chemistry and materials science. In this work, we introduce a universal and exact representation of continuous antisymmetric functions by lifting them to continuous symmetric functions defined on an enlarged space. Building on this lifting, we obtain a \emph{parity-graded representation} of fermionic wavefunctions, expressed in terms of symmetric feature variables that encode particle configuration and antisymmetric feature variables that encode exchange statistics. This representation is both exact and minimal: the number of required features scales as $D\sim N^d$ ($d$ is spatial dimension) or $D\sim N$ depending on the symmetric feature maps employed. Our results provide a rigorous mathematical foundation for efficient representations of fermionic wavefunctions and enable scalable and systematically improvable neural network solvers for many-electron systems.
Authors: Partha Sarathi Banerjee, Rahul Marathe, Sankalpa Ghosh
A transfer-matrix-based theoretical framework is developed to study transport in superconductor-quantum Hall-Superconductor (SQHS) Josephson junctions modulated by local potential barriers in the quantum-Hall regime. The method allows one to evaluate the change in the conductivity of such SQHS Josephson junctions contributed by the intermediate chiral edge states (ICES) induced by these local potential barriers at their electrostatic boundaries at specific electron filling-fractions. It is particularly demonstrated how these ICES created at different Landau levels (LL) overlap with each other through intra- and inter-LL ICES mixing with the change in strength and width of the potential barriers. This results in different mechanisms for forming Landau bands when an array of such potential barriers are present. It is also demonstrated that our theoretical framework can be extended to study the lattice effect in a bounded domain in such SQHS Josephson junctions by simultaneously submitting the normal region to a transverse magnetic field and periodic potential.
Authors: David Soldner, Igor Lesanovsky, Gabriele Perfetto
Stochastic resetting generates nonequilibrium steady states by interspersing unitary quantum dynamics with resets at random times. When the state to which the system is reset is chosen conditionally on the outcome of a global and spatially resolved measurement, the steady state can feature collective behavior similar to what is typically observed at phase transitions. Here we investigate such conditional reset protocol in a system of noninteracting spins, where the reset state is chosen as a magnetization eigenstate, that is selected (conditioned) on the outcome of a previous magnetization measurement. The stationary states that emerge from this protocol are characterized by the density of spins in a given magnetization eigenstate, which is the analogue of the order parameter. The resulting stationary phase diagram features multiple nonanalytic points. They are of first-order type for half-integer spin, while multicritical behavior, signalled by both first and second-order discontinuities, is found for integer spin. We also show that the associated dynamics is nonergodic, i.e., which stationary state the system ultimately assumes is determined be the initial state. Interestingly, the mechanism underlying these phenomena does not rely on interactions, but the emergent nonlinear behavior is solely a consequence of correlations induced by the measurement.
Authors: Zhijie Sun, Zhenyu Li, Chu Guo
The Anderson impurity model (AIM) is of fundamental importance in condensed matter physics to study strongly correlated effects. However, accurately solving its long-time dynamics still remains a great numerical challenge. An emergent and rapidly developing numerical strategy to solve the AIM is to represent the Feynman-Vernon influence functional (IF), which encodes all the bath effects on the impurity dynamics, as a matrix product state (MPS) in the temporal domain. The computational cost of this strategy is basically determined by the bond dimension $\chi$ of the temporal MPS. In this work, we propose an efficient and accurate method which, when the hybridization function in the IF can be approximated as the summation of $n$ exponential functions, can systematically build the IF as a MPS by multiplying $O(n)$ small MPSs, each with bond dimension $2$. Our method gives a worst case scaling of $\chi$ as $2^{8n}$ and $2^{2n}$ for real- and imaginary-time evolution respectively. We demonstrate the performance of our method for two commonly used bath spectral functions, where we show that the actually required $\chi$s are much smaller than the worst case.
Authors: Om Prakash, Sharmistha Dey, Mayur Khan, Abhijith T, Udai Bhan Singh, Ambuj Tripathi, Santanu Ghosh
We illustrate ion-beam engineering of MoO3 Ag Au multilayer plasmonic substrates to improve SERS performance, We illustrate ion-beam engineering of MoO3-Ag-Au multilayer plasmonic substrates to improve SERS performance. Orthorhombic {\alpha}-MoO3 microflakes were produced via chemical vapour deposition (CVD) on Si-SiO2 substrates. Thin films of Ag (5 nm) and Au (5 nm) were thermally evaporated onto the MoO3 flakes, and the samples were subjected to 100 MeV Ag8+ swift heavy ion irradiation at fluences of 3e11 and 3e12 ions cm-2. Irradiation causes dewetting of metal films, prompting structural and morphological changes that result in the formation of dispersed Ag-Au nanoparticles, enhanced surface roughness, and defect generation within the MoO3 lattice. X-ray diffraction (XRD) verifies the {\alpha}-MoO3 phase; field emission scanning electron microscopy (FESEM) elucidates nanoparticle formation and surface reorganisation; Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) disclose vibrational alterations and binding-energy shifts in Mo 3d, indicative of oxygen vacancies (V_O) and partial reduction of Mo. SERS measurements of molecular probes demonstrate significantly increased Raman intensities following ion irradiation.
Authors: Peter Mlkvik, Lena Geistlich, Nicola A. Spaldin, Claude Ederer
We present a systematic density-functional theory study of the effects of strain on the structural and electronic properties in vanadium dioxide (VO$_2$), with particular emphasis on its effect on the relative stability of the metallic rutile and the insulating monoclinic M1 phases. We consider various strain conditions that can be related to epitaxial strain present in VO$_2$ films grown on different lattice planes. Our calculations confirm the dominant role of $c$ axis strain, i.e., along the direction of the V-V dimerization in the M1 phase. Our analysis suggests that this effect stems primarily from the weakening of the lattice stiffness, with the hopping along the $c$ axis playing a minor role. We also confirm that, in strain scenarios that deform the basal plane, the $c$ axis strain still has a dominant effect on the phase stability.
Authors: Ying Chen, Guijing Duan, Yuejiu Zhao, Ning Xi, Bingying Pan, Xiaoyu Xu, Zhanlong Wu, Kefan Du, Shuo Li, Ze Hu, Rui Bian, Xiaoqun Wang, Wei Li, Long Zhang, Yi Cui, Shiyan Li, Rong Yu, Weiqiang Yu
The $S=1/2$ antiferromagnetic Heisenberg chain is a paradigmatic quantum system hosting exotic excitations such as spinons and solitons, and forming random singlet state in the presence of quenched disorder. Realizing and distinguishing these excitations in a single material remains a significant challenge. Using nuclear magnetic resonance (NMR) on a high-quality single crystal of copper benzoate, we identify and characterize all three excitation types by tuning the magnetic field at ultra-low temperatures. At a low field of 0.2 T, a temperature-independent spin-lattice relaxation rate ($1/T_1$) over more than a decade confirms the presence of spinons. Below 0.4 K, an additional relaxation channel emerges, characterized by $1/T_1 \propto T$ and a spectral weight growing as $-\ln(T/T_0)$, signaling a random-singlet ground state induced by weak quenched disorder. At fields above 0.5 T, a field-induced spin gap $\Delta \propto H^{2/3}$ observed in both $1/T_1$ and the Knight shift signifies soliton excitations. Our results establish copper benzoate as a unique experimental platform for studying one-dimensional quantum integrability and the interplay of disorder and correlations.
Authors: Navdeep Rana, Ramin Golestanian
We extensively study the phenomenology of one dimensional Nonreciprocal Cahn Hilliard model for varying nonreciprocity $(\alpha)$ and different boundary conditions. At small $\alpha$, a perturbed uniform state evolves to a defect laden configuration that lacks global polar order. Defects are the sources and sinks of travelling waves and nonreciprocity selects defects with a unique wave number that increases monotonically with $\alpha_c$. A critical threshold $\alpha_c$ marks the onset of a transition to states with finite global polar order. For periodic boundaries, above $\alpha_c$, the system shows travelling waves that are completely ordered. In contrast, travelling waves are incompatible with Dirichlet and Neumann boundaries. Instead, for $\alpha \gtrsim \alpha_c$, we find fluctuating domains that show intermittent polar order and at large $\alpha$, the system partitions into two domains with opposite polar order.
Authors: Souvik Kundu, Kedar Damle
Motivated by recent work that mapped the low-temperature properties of a class of frustrated spin $S=1$ kagome antiferromagnets with competing exchange and single-ion anisotropies to the fully-packed limit (with each vertex touched by exactly one dimer or nontrivial loop) of a system of dimers and nontrivial (length $s > 2$) loops on the honeycomb lattice, we study this fully-packed dimer-loop model on the three-dimensional bipartite cubic and diamond lattices as a function of $w$, the relative fugacity of dimers. We find that the $w \rightarrow 0$ O($1$) loop-model limit is separated from the $w \rightarrow \infty$ dimer limit by a geometric phase transition at a nonzero finite critical fugacity $w_c$: The $w>w_c$ phase has short loops with an exponentially decaying loop-size distribution, while the $w
Authors: Piotr Tatarczak, Tomasz Fąs, Jan Pawłowski, Aleksandra Krystyna Dąbrowska, Jan Suffczyński, Piotr Wróbel, Andrzej Wysmołek, Johannes Binder
Single-photon emitters (SPEs) in two-dimensional materials are highly promising candidates for quantum technologies. SPEs in hexagonal boron nitride (hBN) have been widely investigated, but mostly in exfoliated or powder samples that require an activation process, making it difficult to compare studies and reproduce results. Here, we address this problem and propose a platform based on large-area metaloraganic vapour phase epitaxy (MOVPE)-grown hBN, which combines reproducibility and scalability with the ability to readily host SPEs without activation. Through the creation of bubbles via electron-beam irradiation, we achieve additional functionalities, including an interference-mediated enhancement of emission by approximately 100-200\%, dedicated structures that allow the relocation of individual emitters across different systems, and the opportunity to investigate strain-induced effects. Moreover, in contrast to other gas-filled bubbles that deflate at low temperatures, our bubbles remain stable under cryogenic conditions, allowing studies as a function of temperature. To improve the control over the shape and position of bubbles, we demonstrate a~mask-based method that enables deterministic control over bubble formation. The presented hBN bubbles constitute a versatile platform for reproducible studies of hBN-based emitters, providing a reliable insight into their nature and properties.
Authors: Y. Sun, Y. Ahn, D. Sapkota, H. S. Arachchige, R. Xue, S. Mozaffari, D. G. Mandrus, L. Zhao, J. Orenstein, V. Sunko
Multiferroic materials, in which electric polarization and magnetic order coexist and couple, offer rich opportunities for both fundamental discovery and technology. However, multiferroicity remains rare due to conflicting electronic requirements for ferroelectricity and magnetism. One route to circumvent this challenge is to exploit the noncollinear ordering of spin cycloids, whose symmetry permits the emergence of polar order. In this work, we introduce another pathway to multiferroic order in which strain generates polarization in materials that host nonpolar spin spirals. To demonstrate this phenomenon, we chose the spin spiral in the well-studied helimagnet Cr1/3NbS2. To detect the induced polarization, we introduce the technique of magnetoelectric birefringence (MEB), an optical probe that enables spatially-resolved and unambiguous detection of polar order. By combining MEB imaging with strain engineering, we confirm the onset of a polar vector at the magnetic transition, establishing strained Cr1/3NbS2 as a type-II multiferroic.
Authors: Sunilkumar V, Rajat, Sandeep Gautam, Arko Roy
We investigate the ferromagnetic-paramagnetic phase transition in coherently (Rabi) coupled Bose-Einstein condensates at zero and finite temperatures, exploring different routes to the transition by tuning the Rabi coupling or increasing the temperature at a fixed coupling. Using the Hartree-Fock-Bogoliubov theory within the Popov approximation, we map out the finite-temperature phase diagram of a three-dimensional homogeneous condensate and identify the critical line through the softening of the spin gap. Magnetization and the spin dispersion branch reveal the progressive suppression of the ferromagnetic order with increasing temperature. In quasi-one-dimensional harmonic traps, the transition, driven by Rabi coupling, is inferred through the softening of the spin breathing mode with its minimum shifting to lower coupling values with increasing temperature. Notably, the thermally driven transition causes monotonic hardening of all the spin modes. For both coupling and temperature-driven transition, the hybridized density modes in the ferromagnetic phase acquire more density character while approaching the critical point.
Authors: Hiroto Takahashi, Jack Murphy, Mitikorn Wood-Thanan, Pascal Puphal, Miguel Angel Sanchez-Martinez, Fabian Jerzembeck, Chun-Chih Hsu, Jonathan Ward, Masahiko Isobe, Yosuke Matsumoto, Hidenori Takagi, Stephen J. Blundell, Michael R. Norman, Felix Flicker, J. C. Séamus Davis
The kagome lattice of spin-1/2 Cu atoms in herbertsmithite (ZnCu3(OH)6Cl2) may sustain a quantum spin liquid (QSL) state with spinon quasiparticles. Each kagome plane is separated from its homologues by a layer of spinless Zn atoms. Providentially, however, some spin-1/2 Cu atoms substitute randomly onto these inter-kagome Zn sites. We reconceptualize these 'impurity' atoms as quantum 'witness-spins', an exceptional new interrogative of the conjectured Z2-gauge-symmetric QSL state. Thus we introduce spin-noise spectroscopy to explore herbertsmithite witness-spin dynamics for QSL studies. It reveals the existence, slowing and intensification of spin noise, prefatory to a sharp transition at T* {\approx} 260 mK. Below T* the spin-noise power spectral density S_M({\omega},T) {\propto} {\omega}^{-{\alpha}(T)} stabilizes at {\alpha} {\approx} 1; the spin noise variance {\sigma}_M^2(T) diminishes precipitously; the ultra-low-field magnetic susceptibility {\chi}(T) undergoes a sharp transition into a phase exhibiting an Edwards-Anderson order-parameter and ultra-slow spin-state relaxation. A Z2 QSL theory of spinon-mediated witness-spin interactions corresponds best to all these experimental observations, predicting slowing and intensification of witness-spin fluctuations and noise spectrum S_M({\omega},T) with cooling, with a transition into a unique spinon-mediated phase signified by rapidly diminishing spin noise, with S_M({\omega},T) {\propto} {\omega}^{-1}, a sharp cusp in the DC magnetic susceptibility {\chi}(T), and the appearance of an Edwards-Anderson order-parameter. We rule out numerous other mechanisms for these effects, so that only spinon-mediation by either a Z2 or U(1) QSL is consistent with all present herbertsmithite empirics, with the former model providing a closer match to data.
Authors: Ruiqi Xu, Arnab Seth, Itamar Kimchi
We study the honeycomb lattice with a single magnetic impurity modeled by adding imaginary next-nearest-neighbor hopping ih on a single hexagon. This Haldane defect gives a topological mass term to the gapless Dirac cones and generates chirality. For a small density of defects Neehus et al [arXiv:2405.19289] found that the system's chirality reverses at a critical hc ~ 0.95 associated with an unexpected tri-critical point of Dirac fermions at zero defect density. We investigate this zero-density limit by analyzing a single defect and computing two experimentally relevant measures of chirality: (1) orbital magnetization via local Chern marker, a bulk probe of all occupied states; and (2) electronic currents of low-energy states. Both probes show a chirality reversal at a critical hc ~ 0.9--1. Motivated by this consistency we propose a defect-scale toy model whose low energy states reverse their chirality at hc' ~ 0.87. Remarkably, the same pair of zero energy bound states also generate the critical point hc in the full impurity projected T-matrix. Our results show how the chirality reversal produced by an impurity can be observed either in local probes or in the global topology and suggest a possible role of the microscopic defect structure at the critical point.
Authors: Louis Sharma, Ahmedeo Shokry, Rajah Nutakki, Olivier Simard, Michel Ferrero, Filippo Vicentini
Accurate simulations of the Hubbard model are crucial to understanding strongly correlated phenomena, where small energy differences between competing orders demand high numerical precision. In this work, Neural Quantum States are used to probe the strongly coupled and underdoped regime of the square-lattice Hubbard model. We systematically compare the Hidden Fermion Determinant State and the Jastrow-Backflow ansatz, parametrized by a Vision Transformer, finding that in practice, their accuracy is similar. We also test different symmetrization strategies, finding that output averaging yields the lowest energies, though it becomes costly for larger system sizes. On cylindrical systems, we consistently observe filled stripes. On the torus, our calculations display features consistent with a doped Mott insulator, including antiferromagnetic correlations and suppressed density fluctuations. Our results demonstrate both the promise and current challenges of neural quantum states for correlated fermions.
Authors: Glen McHale (1), Sara Janahi (1), Hernán Barrio-Zhang (1), Yaofeng Wang (1), Jinju Chen (2), Gary G. Wells (1), Rodrigo Ledesma-Aguilar (1) ((1) Institute for Multiscale Thermofluids, School of Engineering, The University of Edinburgh, Edinburgh, UK, (2) Department of Materials, Loughborough University, Loughborough, UK)
Kinetic frictional forces resisting droplet motion often appear to be separate to surface wettability and adhesive forces. Here we show that such friction arises from a simple combination of the contact angle hysteresis and adhesive force. We show theoretically, and confirm using tilt angle experiments of droplets on liquid-like surfaces, the dependence of the coefficient of droplet-on-solid kinetic friction on system parameters. We also show that a molecular kinetic-type model can describe the observed non-linear velocity-force relationship. Our findings provide a fundamental understanding of the relationship between droplet-on-solid friction, and wettability and liquid adhesion.
Authors: Ali Jaberi (3), Amin Sadeghi (2), Runze Zhang (1), Zhaoyang Zhao (1), Qiuyu Shi (1), Robert Black (3), Zoya Sadighi (3), Jason Hattrick-Simpers (1) ((1) Department of Material Science and Engineering, University of Toronto, Toronto, Ontario, Canada, (2) Canmet MATERIALS, Natural Resources Canada, Hamilton, ON, Canada, (3) Clean Energy Innovation Research Center, National Research Council Canada, Mississauga, Ontario, Canada)
Electrochemical impedance spectroscopy (EIS) data is typically modeled using an equivalent circuit model (ECM), with parameters obtained by minimizing a loss function via nonlinear least squares fitting. This paper introduces two new loss functions, log-B and log-BW, derived from the Bode representation of EIS. Using a large dataset of generated EIS data, the performance of proposed loss functions was evaluated alongside existing ones in terms of R2 scores, chi-squared, computational efficiency, and the mean absolute percentage error (MAPE) between the predicted component values and the original values. Statistical comparisons revealed that the choice of loss function impacts convergence, computational efficiency, quality of fit, and MAPE. Our analysis showed that X2 loss function (squared sum of residuals with proportional weighting) achieved the highest performance across multiple quality of fit metrics, making it the preferred choice when the quality of fit is the primary goal. On the other hand, log-B offered a slightly lower quality of fit while being approximately 1.4 times faster and producing lower MAPE for most circuit components, making log-B as a strong alternative. This is a critical factor for large-scale least squares fitting in data-driven applications, such as training machine learning models on extensive datasets or iterations.
Authors: Xinlun Cheng, Bingzhe Chen, Joseph Choi, Yen T. Nguyen, Pradeep Seshadri, Mayank Verma, H. S. Udaykumar, Stephen Baek
Modeling shock-to-detonation phenomena in energetic materials (EMs) requires capturing complex physical processes such as strong shocks, rapid changes in microstructural morphology, and nonlinear dynamics of chemical reaction fronts. These processes participate in energy localization at hotspots, which initiate chemical energy release leading to detonation. This study addresses the formation of hotspots in crystalline EMs subjected to weak-to-moderate shock loading, which, despite its critical relevance to the safe storage and handling of EMs, remains underexplored compared to the well-studied strong shock conditions. To overcome the computational challenges associated with direct numerical simulations, we advance the Physics-Aware Recurrent Convolutional Neural Network (PARCv2), which has been shown to be capable of predicting strong shock responses in EMs. We improved the architecture of PARCv2 to rapidly predict shear localizations and plastic heating, which play important roles in the weak-to-moderate shock regime. PARCv2 is benchmarked against two widely used physics-informed models, namely, Fourier neural operator and neural ordinary differential equation; we demonstrate its superior performance in capturing the spatiotemporal dynamics of shear band formation. While all models exhibit certain failure modes, our findings underscore the importance of domain-specific considerations in developing robust AI-accelerated simulation tools for reactive materials.
Authors: Jeffrey Z. Song, Gilad Kishony, Erez Berg, Mark S. Rudner
We introduce a variational approach for preparing low energy states of arbitrary target Hamiltonians. The protocol is defined in terms of a repeated cycle consisting of p layers of unitary gates applied to the system and ancilla "bath" qubits, followed by reset of the bath qubits. The gate parameters within each cycle are optimized such that the steady state achieved after many cycles has a low energy expectation value with respect to the target Hamiltonian, and that the energy converges toward the steady state value in as few cycles as possible. We illustrate the protocol for the transverse field Ising model, and study its systematic behaviors with respect to system size, model parameters, and noise using tensor network based classical simulations. We then experimentally demonstrate its operation on IBM's ibm_kingston quantum processor for up to 28 system qubits coupled to 14 bath sites. Classical training on small system sizes and with few unitary layers per cycle gives robust results that transfer well to larger system sizes and to noisy hardware.
Authors: Richard John, Yunrui Qiu, Lukas Herron, Pratyush Tiwary
Generative modeling becomes increasingly data-intensive in high-dimensional spaces. In molecular science, where data collection is expensive and important events are rare, compression to lower-dimensional manifolds is especially important for various downstream tasks, including generation. We combine a time-lagged information bottleneck designed to characterize molecular important representations and a diffusion model in one joint training objective. The resulting protocol, which we term Diffusive State Predictive Information Bottleneck (D-SPIB), enables the balancing of representation learning and generation aims in one flexible architecture. Additionally, the model is capable of combining temperature information from different molecular simulation trajectories to learn a coherent and useful internal representation of thermodynamics. We benchmark D-SPIB on multiple molecular tasks and showcase its potential for exploring physical conditions outside the training set.
Authors: Nathan London, Mohammad R. Momeni
Feynman path integrals (PIs) have found many uses in approximate quantum dynamics methods that are able to efficiently calculate real-time quantum correlation functions. The PIs typically take the form of discrete imaginary time slices over a closed path, where the slices form the ``beads'' of a ring polymer (RP) necklace. Some methods, such as centroid molecular dynamics (CMD), use the RP to generate an effective potential for the dynamics, while others, like RP molecular dynamics (RPMD), directly utilize the RP in real-time dynamics in order to incorporate quantum effects. The standard, discretized bead forms of CMD and RPMD can require a large number of RP beads to provide accurate results for systems where quantum effects are strong, such as at low temperatures. In Paper I, we introduced the bead-Fourier (BF) CMD method, where we utilized the inclusion of a Fourier sine series to reduce the number of beads needed to converge the CMD effective potential up to eightfold. In this work, we extend RPMD to incorporate BF-PIs in the form of BF-RPMD. We study a number of different implementations of the method through the calculation of correlation functions for both linear and non-linear operators. The effectiveness of the BF-RPMD method is sensitive to both the system and form of the operators being studied, but we show that this method is able to produce results on par with standard RPMD, with at worst twofold and up to eightfold reduction in the number of beads by including two to three Fourier components.
Authors: Yiran Bai, Feng Xiong, Xueheng Kuang
Classical computation of electronic properties in large-scale materials remains challenging. Quantum computation has the potential to offer advantages in memory footprint and computational scaling. However, general and practical quantum algorithms for simulating large-scale materials are still lacking. We propose and implement random-state quantum algorithms to calculate electronic-structure properties of real materials. Using a random state circuit with only a few qubits, we employ real-time evolution with first-order Trotter decomposition and Hadamard test to obtain electronic density of states, and we develop a modified quantum phase estimation algorithm to calculate real-space local density of states via direct quantum measurements. Furthermore, we validate these algorithms by numerically computing the density of states and spatial distributions of electronic states in graphene, twisted bilayer graphene quasicrystals, and fractal lattices, covering system sizes from hundreds to thousands of atoms. Our results manifest that the random-state quantum algorithms provide a general and qubit-efficient route to simulating electronic properties of large-scale periodic and aperiodic materials on quantum computers.
Authors: Pascal Isenring, Zaher Salman
The use of a Si pixel-based particle tracking scheme in muSR will, among others, allow measurements using a ten-fold increased stopped muons rate and samples ten times smaller than currently possible. Here we present simulation results to assess the effects of magnetic fields on two spectrometer configurations using a two-layered tracking scheme for the incoming and outgoing particles. At a low magnetic field of up to ~50 mT, the tracking and reconstruction accuracy is only minimally influenced. Beyond a magnetic field of ~80 mT the tracking capabilities diminish significantly. Operating a two-layered scheme using small magnetic fields hence does not require adaptations. Only at large magnetic fields, a tracking scheme that makes use of an accurate field map or the use of at least three layers must be employed to achieve reliable particle tracking.
Authors: Sunita Khod, Vinay Kamma, Ravi Kumar Verma, Mayank Goswami
This study proposes an Artificial Intelligence (AI) driven methodology for predicting a combination of brazed ceramic-metal composite materials. Multiple machine learning (ML) algorithms are compared with the deep learning (DL) model. The developed models are tested using k-fold validation. Nine different input-output feature configurations are evaluated to assess the model performance. The input-output feature comprises material properties, namely, the coefficient of thermal expansion (CTE) and molecular mass of brazed ceramic-metal composite materials obtained from literature and the strength parameter (average Von Mises Stress (VMS)) estimated from Finite Element Method (FEM) simulation for joint assembly structure. A multi-output model, Autoencoder (AE), has also been developed and tested to predict various features. The ML model, namely the polynomial regression (PR), outperforms the other ML/DL models with a Mean square Error (MSE) of 0.01 for the test data. The autoencoder model with a 32-16-32 structure outperforms LR, PR, RF, and ANN with an MSE of 0.04% for the prediction of unseen data. The developed multi-output model accurately predicts all the features (single and multiple), while PR fails to accurately predict multi-output features of low importance. The developed AE model predicts the different material properties with an average error of ~0.16-3.78% with literature-reported values.
Authors: Pranay Jaiswal, Ivar S. Haugerud, Hidde D. Vuijk, Christoph A. Weber
Life relies on a sophisticated metabolic molecular machinery that turns over high-energy molecules to evolve complex macromolecules and assemblies. At the molecular origin of life, such machinery was absent, implying the need for simple yet robust physical mechanisms to harvest energy from the environment and perform chemical work or produce chemical power. However, the mechanisms involved in harvesting energy from a macroscopic cyclic environment to drive chemical processes on the molecular scale remain elusive. In this work, we propose a theory that describes the kinetics of chemical reactions in a system subject to a cyclic reservoir with varying properties. We compare cycles of solvent (wet-dry cycles), with cycles of a component participating in a chemical reaction (reactant cycle). We find that for both wet-dry and reactant cycles, resonance frequencies exist at which the chemical power is maximal. We identify which cycle type is more beneficial in harvesting chemical power for different molecular interactions. Our findings of harvest efficiencies around ten percent suggest that the cyclic environment could have played a key role in catalyzing the metabolic molecular machinery at the molecular origin of life.
Authors: Elijah Pelofske
This study numerically investigates the thermal sampling properties of QAOA, the Quantum Alternating Operator Ansatz which was generalized from the original Quantum Approximate Optimization Algorithm. Specifically, the ability of QAOA to sample from the Gibbs distribution, equivalently the Boltzmann distribution, defined by a classical Ising model, specifically a fully connected disordered spin glass (Sherrington-Kirkpatrick) model. We focus on two different QAOA mixers; the standard transverse field X mixer, and the Grover mixer. At a QAOA depth of one we examine, for a single full QAOA parameter search space period, the energy landscape, the Shannon entropy landscape of the QAOA probability distribution, and the tradeoff between Boltzmann distribution sampling temperature and error rate (how close to the true Boltzmann distribution is the QAOA distribution). We find that at very high temperatures one-round Grover mixer QAOA can sample from the Boltzmann distribution more accurately than the standard X mixer QAOA at one round. Both X mixer and Grover mixer depth one QAOA can serve as approximate Boltzmann distribution samplers, and how good this approximation is depends heavily on the QAOA angle choice.
Authors: Marcus Lin, Peng Zhang, Aaron D. Ratschow, Oscar Li, Sankara Arunachalam, Dan Daniel
Charged water drops are more widespread than commonly acknowledged. For example, raindrops typically carry charges of order Q ~ 1 pC, while routine pipetting in the laboratory produces drops with Q ~ 50 pC. Here, we show that such modest charging can spontaneously generate periodic Coulomb fissions for evaporating water drops on lubricated surfaces, with more than 60 successive cycles observed over 30 min. Interestingly, the underlying instability can be quantitatively predicted by two fissility thresholds: one marking the onset of drop elongation and another triggering fission. Each fission culminates with a fine liquid jet that disintegrates into 40-50 microdroplets, expelled within microseconds. The phenomenon spans an extraordinary range of length scales (from millimetres to microns) and time scales (hour to microseconds), with broad potential applications ranging from nanoscale fabrication to electrospray ionization.
Authors: Harshit Joshi, Samriddhi Sankar Ray
The significance of small-scale forcing of particles on the carrier two-dimensional turbulent flow has been shown [Pandey, Perlekar, and Mitra, Phys. Rev. E, 100, 013114 (2019)] to influence the spectral scaling properties of the carrier fluid. We investigate possible consequences of such two-way coupling in a turbulent suspension of inertial particles in one and two-point Eulerian and Lagrangian statistics. In particular, we find signatures of a possibly enhanced intermittency in the vorticity distributions. We characterize the changes in the (small-scale) geometry of the flow via the Okubo-Weiss parameter. Finally, we examine the scaling properties of the second-order (vorticity) structure functions and find a non-trivial form of scale-invariance at finite mass-loading. This suggests that a dual-scale forcing mechanism on the two-dimensional Navier-Stokes equation may be an effective model to mimic the role of particle feedback in turbulence.
Authors: Naoki Maruyama, Masayuki Ohzeki, Kazuyuki Tanaka
Quantum annealing (QA) with a transverse field often fails to sample degenerate ground states fairly, limiting applicability to problems requiring diverse optimal solutions. Although Quantum Monte Carlo (QMC) is widely used to simulate QA, its ability to reproduce such unfair ground-state sampling remains unclear because stochastic and coherent quantum dynamics differ fundamentally. We quantitatively evaluate how accurately QMC reproduces the sampling bias in QA by comparing the final ground-state distributions from the QMC master equation and the Schrödinger equation. We find QMC tends to produce uniform ground-state probabilities, unlike QA's biased distribution, and that this uniformity bias strengthens as annealing proceeds. Our analysis reveals that this bias originates from replica alignment -- the dominance of configurations in which all Trotter replicas coincide -- caused by the energetic suppression and entropic reduction of kink configurations (replica mismatches). These findings clarify a fundamental limitation of discrete-time QMC in faithfully simulating QA dynamics, highlighting the importance of replica correlations and transition rules in achieving realistic ground-state sampling.
Authors: Zhao-Fan Cai, Tao Liu
The well-established non-Bloch band theory predicts exponential localization of skin-mode eigenstates in one-dimensional (1D) non-Hermitian systems. Recent studies, however, have uncovered anomalous algebraic localization in higher dimensions. Here, we extend these ideas to Hermitian bosonic quadratic Hamiltonians incorporating quantum squeezing, offering a genuine quantum framework to explore non-Hermitian phenomena without external reservoirs. We construct a two-dimensional (2D) bosonic lattice model with two-mode squeezing and study its spectral properties of bosonic excitation within the Bogoliubov-de Gennes (BdG) formalism. We demonstrate an algebraic non-Hermitian skin effect (NHSE), characterized by quasi-long-range power-law localization of complex eigenstates. The system shows ultra spectral sensitivity to double infinitesimal on-site and long-range hopping impurities, while remaining insensitive to single impurities. Analytical treatment via the Green's function reveals that this sensitivity originates from the divergence of the nonlocal Green's function associated with the formation of nonlocal bound states between impurities. Our study establishes a framework for realizing novel higher-dimensional non-Hermitian physics in Hermitian bosonic platforms such as superconducting circuits, photonic lattices, and optomechanical arrays, with the demonstrated ultraspectral sensitivity enabling quantum sensing and amplification via bosonic squeezing.
Authors: Hussein Nassar
Holding a shell in their hands, one can apply six loads: three by pulling and shearing, and three by bending and twisting. Here, it is shown that the shell will resist exactly three load cases and comply with the other three, provided the shell is simply connected, meaning it has no holes and no handles.
Authors: Yuma Ichikawa, Shuhei Kashiwamura, Ayaka Sakata
Quantized neural network training optimizes a discrete, non-differentiable objective. The straight-through estimator (STE) enables backpropagation through surrogate gradients and is widely used. While previous studies have primarily focused on the properties of surrogate gradients and their convergence, the influence of quantization hyperparameters, such as bit width and quantization range, on learning dynamics remains largely unexplored. We theoretically show that in the high-dimensional limit, STE dynamics converge to a deterministic ordinary differential equation. This reveals that STE training exhibits a plateau followed by a sharp drop in generalization error, with plateau length depending on the quantization range. A fixed-point analysis quantifies the asymptotic deviation from the unquantized linear model. We also extend analytical techniques for stochastic gradient descent to nonlinear transformations of weights and inputs.
Authors: Boutros Pierre Embaid
Recently a new meteoritic mineral, Zolenskyite (Fe0.99Mn0.04Ca0.01Cr1.99S3.98), was discovered from the Indarch meteorite. Zolenskyite was structurally indexed as the monoclinic C2/m CrNb2Se4 - Cr3S4 type structure of synthetic FeCr2S4, with unit cell parameters a = 12.84(1) Å, b = 3.44(1) Å, c = 5.94(1) Å and \b{eta} = 117(1)°. Zolenskyite was reported as high-pressure phase formed from Daubréelite at high pressures and temperatures in highly shocked regions of the EH parent asteroid. Although this discovery provides valuable information about the origin of meteoritic mineral assemblages, the results and conclusions raise controversies with those reported in previous articles where the synthetic FeCr2S4 was described. In this review, an alternative analysis of the supplementary X-ray data from Zolenskyite was made and yields to the monoclinic I2/m Cr3S4 type structure of synthetic FeCr2S4, with unit cell parameters a = 5.940 Å, b = 3.440 Å, c = 11.441 Å and \b{eta} = 90.55°, in agreement with previous results in the literature and differ from those reported above. Regarding the genesis of Zolenskyite and according to solid-state laboratory synthesis, the transformation of cubic FeCr2S4 phase (ideal composition of Daubréelite) to monoclinic FeCr2S4 (ideal composition of Zolenskyite) requires a process whose replication in Shock metamorphism stages is not well established and remains an open issue to address, together with another open issue related to the real composition of meteoritic minerals, with minor and trace metals, which is often overlooked when compared with synthetic ideal compositions. Whatever the results to be obtained by addressing the above open issues, they will shed more light on the genesis of Zolenskyite. In this context, it is worth to promote an open debate about the hypothesis of artificial origin.
Authors: Benjamin Anwasia, Diogo Arsénio
We consider the description of a Fermi gas of free electrons given by the Boltzmann--Fermi--Dirac equation, and aim at providing a precise mathematical understanding of the Fermi ground state and its first-order approximation of excited states on the Fermi sphere. In order to achieve that, using the framework of hydrodynamic limits in collisional kinetic theory, we identify the low-temperature regimes in which charge-density fluctuations concentrate on the Fermi sphere. In three spatial dimensions or higher, we also characterize the thermodynamic equilibra and energy spectra of fluctuations. This allows us to derive the macroscopic hydrodynamic equations describing how charge densities flow and propagate in metals, thereby providing a precise description of plasma oscillations in conductors. The two-dimensional case is fundamentally different and is handled in a companion article. Remarkably, our results establish that excited electrons and their energy can be distributed on the Fermi sphere anisotropically, which deviates from the common intuitive assumption that electrons and their energy should be distributed uniformly in all directions. The hydrodynamic regimes featured in this work are akin to the acoustic limit of the classical Boltzmann equation. However, we emphasize that our derivation holds for arbitrarily fast rates of convergence of the Knudsen number, which significantly extends the applicability of the known proofs of the classical acoustic limit. This suggest that low-temperature limits of Fermi gases provide a promising avenue of research toward a complete understanding of the compressible Euler limit.
Authors: Wenbing Jiang, Xuankai Xu, Jiazhen Pan, Hancong Sun, Yu Guo, Huabing Wang, Libing Zhou, Tao Wu
Lamb wave resonators (LWRs) operating at ultralow temperatures serve as promising acoustic platforms for implementing microwave-optical transduction and radio frequency (RF) front-ends in aerospace communications because of the exceptional electromechanical coupling (k^2) and frequency scalability. However, the properties of LWRs at cryogenic temperatures have not been well understood yet. Herein, we experimentally investigate the temperature dependence of the quality factor and resonant frequency in higher order antisymmetric LWRs down to millikelvin temperatures. The high-frequency A1 and A3 mode resonators with spurious-free responses are comprehensively designed, fabricated, and characterized. The quality factors of A1 modes gradually increase upon cryogenic cooling and shows 4 times higher than the room temperature value, while A3 mode resonators exhibit a non-monotonic temperature dependence. Our findings provide new insights into loss mechanisms of cryogenic LWRs, paving the way to strong-coupling quantum acoustodynamics and next-generation satellite wireless communications.
Authors: Thomas K. Bracht, Rachel N. Clark, Petros Androvitsaneas, Matthew Jordan, Samuel G. Bishop, Harry E. Dyte, Moritz Cygorek, Ian A. Farrer, Doris E. Reiter, Anthony J. Bennett
Mixing the fields generated by different light sources has emerged as a powerful approach for engineering non-Gaussian quantum states. Understanding and controlling the resulting photon statistics is useful for emerging quantum technologies that are underpinned by interference. In this work, we investigate intensity correlation functions arising from the interference of resonance fluorescence from a quantum emitter with a coherent laser field. We show that the observed bunching behavior results from a subtle interplay between quantum interference and the normalization of the correlation functions. We show that by adjusting the mixing ratio and phase one can achieve full tunability of the second-order correlation, ranging from anti-bunching to bunching. We further extend our analysis to third-order correlation functions, both experimentally and theoretically, to provide new insights into the interpretation of higher-order correlations and offer practical tools for shaping quantum optical fields.
Authors: Yuxuan Chen, Ruotong Yang, Zhengyang Zhang, Mehreen Ahmed, Yanming Wang
Microscopic characterizations, such as Scanning Electron Microscopy (SEM), are widely used in scientific research for visualizing and analyzing microstructures. Determining the scale bars is an important first step of accurate SEM analysis; however, currently, it mainly relies on manual operations, which is both time-consuming and prone to errors. To address this issue, we propose a multi-modal and automated scale bar detection and extraction framework that provides concurrent object detection, text detection and text recognition with a Large Language Model (LLM) agent. The proposed framework operates in four phases; i) Automatic Dataset Generation (Auto-DG) model to synthesize a diverse dataset of SEM images ensuring robust training and high generalizability of the model, ii) scale bar object detection, iii) information extraction using a hybrid Optical Character Recognition (OCR) system with DenseNet and Convolutional Recurrent Neural Network (CRNN) based algorithms, iv) an LLM agent to analyze and verify accuracy of the results. The proposed model demonstrates a strong performance in object detection and accurate localization with a precision of 100%, recall of 95.8%, and a mean Average Precision (mAP) of 99.2% at IoU=0.5 and 69.1% at IoU=0.5:0.95. The hybrid OCR system achieved 89% precision, 65% recall, and a 75% F1 score on the Auto-DG dataset, significantly outperforming several mainstream standalone engines, highlighting its reliability for scientific image analysis. The LLM is introduced as a reasoning engine as well as an intelligent assistant that suggests follow-up steps and verifies the results. This automated method powered by an LLM agent significantly enhances the efficiency and accuracy of scale bar detection and extraction in SEM images, providing a valuable tool for microscopic analysis and advancing the field of scientific imaging.
Authors: Pablo Tieben, Jan Rhensius, Takuya F. Segawa, Risei Abe, Konosuke Shimazaki, Shigeki Takeuchi, Andeas W. Schell, Hideaki Takashima
Diamonds containing color centers have recently gathered significant attention for photonic quantum technologies, including quantum sensing, photonic quantum computers, and quantum networks. Among the various color centers, tin-vacancy (SnV) centers are particularly promising due to the high emission efficiency from the zero-phonon line and due to their long spin coherence times. However, the extraction of photons from diamond remains a key challenge. Here we demonstrate high photon extraction from a single SnV center incorporated in a diamond nanopillar with tapered sidewalls and a multi-cone structure. A sharp emission peak with a full width at half maximum (FWHM) of $6\,$nm was observed at a wavelength of $619\,$nm. Furthermore, the second-order correlation function exhibited an antibunching dip well below $g^{(2)}(0) = 0.5$, indicating single-photon emission. Remarkably, the emitter achieved a high saturation count rate of approximately $9\,$Mcps. These results establish our nanopillar platform as a promising candidate for bright and stable quantum sources and sensors based on SnV centers in diamond.
Authors: Thomas W. Gries, Davide Regaldo, Yanyan Duan, Florian Scheler, Maxim Simmonds, Valerio Stacchini, Annamaria Petrozza, Eva Unger, Antonio Abate, Jean-Paul Kleider, Artem Musiienko
Photoluminescence (PL) is a ubiquitous proxy for material quality in optoelectronic devices, widely used for high-throughput materials discovery. However, we demonstrate that in the presence of charge-selective contacts, PL loses its predictive reliability and can exhibit strong quenching even in highly efficient photovoltaic devices under open-circuit conditions. By combining steady-state and transient PL with contactless transient surface photovoltage measurements we disentangle the intertwined processes of extraction and recombination, clarifying the physical origin of this phenomenon. This joint approach reveals extraction dynamics not captured by PL alone. A digital replica of the interface shows that Coulomb attraction and interfacial recombination are the fundamental mechanisms driving quenching after charge extraction. Based on these insights, we present a decision tree for heterojunction classification and PL interpretation applicable across diverse optoelectronic systems, including photovoltaics, photodetectors, and LEDs. Our approach supports systematic screening and optimization of half-devices, bridging the gap between accelerated materials discovery and accelerated device discovery.
Authors: Hubert J. Naguszewski, Christopher D. Woodgate, David Quigley
Flat histogram methods, such as Wang-Landau sampling, provide a means for high throughput calculation of phase diagrams of atomistic/lattice model systems. Many parallelisation schemes with varying degrees of complexity have been proposed to accelerate such sampling simulations. In this study, several widely used schemes are benchmarked - both in isolation and in combination - to establish best practice. The schemes studied include energy domain decomposition with both static sizing of energy sub-domains, as well as a dynamic sub-domain sizing scheme which we propose. We also assess the benefits both of replica exchange and of including multiple random walkers per sub-domain, to determine which factors have the largest impact on parallel efficiency. Additionally, the influence of the choice of size of energy sub-domain overlap regions is discussed. As an illustrative test case, we implement and apply the aforementioned strategies to a lattice-based model describing the internal energies of the AlTiCrMo refractory high-entropy superalloy, which is understood to crystallographically order into a B2 (CsCl) structure with decreasing temperature. We find that - while all of the proposed strategies confer a non-negligible speedup - parallelisation across energy domains which are non-uniform in size offers the most appreciable performance improvements. This work offers concrete recommendations for which parallelisation strategies should be prioritised to optimally accelerate flat-histogram Monte Carlo simulations.
Authors: Yi J. Zhao, Joel E. Moore, Juzar Thingna, Christopher W. Wächtler
Synchronization in quantum systems has been recently studied through persistent oscillations of local observables, which stem from undamped modes of the dissipative dynamics. However, the existence of such modes requires fine-tuning the system to satisfy specific symmetry constraints. We investigate the response of spin systems that possess such oscillating modes to generic, weak perturbations. We show that even when these perturbations break the symmetry and lead to a single steady state, the phase correlations in the resulting state exhibit signatures of synchronization. Our results therefore connect the persistent oscillation notion (dynamical) and the notion based on phase correlations (steady-state) of synchronization, which so far have been regarded as distinct phenomena. Furthermore, we demonstrate that steady-state synchronization in these systems can exhibit features that are absent in the dynamical synchronization. Our work suggests robustness of synchronization and points toward a potential unifying framework of quantum synchronization.
Authors: Daniel K. Mark, Federica M. Surace, Thomas Schuster, Adam L. Shaw, Wenjie Gong, Soonwon Choi, Manuel Endres
Gauge theories describe the fundamental forces of nature. However, high-energy dynamics, such as the formation of quark-gluon plasmas, is notoriously difficult to model with classical methods. Quantum simulation offers a promising alternative in this regime, yet experiments have mainly probed low energies. Here, we observe the formation of a ballistic plasma and long-time memory effects in high-energy gauge theory dynamics on a high-precision quantum simulator. Both observations are unexpected, as the initial state - fully filled with particle-antiparticle pairs - was thought to rapidly thermalize. Instead, we find correlations spreading ballistically to long distances and a memory of charge clusters. Our observations cannot be explained by many-body scars, but are captured by a new theory of plasma oscillations between electric field and current operators, persisting all the way to the continuum limit of the (1+1)D Schwinger model, of which we simulate a lattice version. Adapting techniques from quantum optics, we visualize plasma oscillations as rotations of Wigner distributions, leading to a novel set of predictions which we test in experiment and numerics. The new framework encompasses both our scenario and scars, which show up as coherent states of the plasma. The experimental surprises we observe in the high-energy dynamics of a simple gauge theory point to the potential of high-precision quantum simulations of gauge theories for general scientific discovery.
Authors: Lukas Ebner, Berndt Müller, Andreas Schäfer, Leonhard Schmotzer, Clemens Seidl, Xiaojun Yao
We investigate the time dependence of anti-flatness in the entanglement spectrum, a measure for non-stabilizerness and lower bound for non-local quantum magic, on a subsystem of a linear SU(2) plaquette chain during thermalization. Tracing the time evolution of a large number of initial states, we find that the anti-flatness exhibits a barrier-like maximum during the time period when the entanglement entropy of the subsystem grows rapidly from the initial value to the microcanonical entropy. The location of the peak is strongly correlated with the time when the entanglement exhibits the strongest growth. This behavior is found for generic highly excited initial computational basis states and persists for coupling constants across the ergodic regime, revealing a universal structure of the entanglement spectrum during thermalization. We conclude that quantitative simulations of thermalization for nonabelian gauge theories require quantum computing. We speculate that this property generalizes to other quantum chaotic systems.
Authors: Chunsheng Gong, Shangjie Tian, Zhijun Tu, Qiangwei Yin, Yang Fu, Ruitao Luo, Hechang Lei
We report the detailed physical properties of YRu3Si2 with the Ru kagome lattice at normal and superconducting states. The results of resistivity and magnetization show that YRu3Si2 is a type-II bulk superconductor with Tc ~ 3.0 K. The specific heat measurement further suggests that this superconductivity could originate from the weak or moderate electron-phonon coupling. On the other hand, both large Kadawaki-Woods ratio and Wilson ratio indicate that there is a strong electron correlation effect in this system, which may have a connection with the featured flat band of kagome lattice.
Authors: V.R. Shaginyan, A.Z. Msezane, G.S. Japaridze
We demonstrate that an absolutely flat band retains the superconducting state at $T_c\to 0$. When $T_c>0$ the flat band disappears, since it must be modified by the superconducting state. Thus, a number of the results on ultra-strong coupling superconductivity in flat band considered in the article ("Evidence for Dirac flat band superconductivity enabled by quantum geometry", Nature 614, 440 (2023)) were predicted and explained many years ago. One has to take into account that at $T_c>0$ the flat band distorts, becoming tilted. As a result, the charge carriers' velocity $v_F\propto T_c$ becomes finite, rather than being extremely slow, as it is stated in the article. Thus, the statement "the charge carriers' group velocity $v_ F$ is extremely slow" is incorrect and leads the authors to the conceptional misunderstanding, confusing the reader.
Authors: Maurizio Monti, Khalid M. Siddiqui, Daniel Perez-Salinas, Naman Agarwal, Martin Bremholm, Xiang Li, Dharmalingam Prabhakaran, Xin Liu, Danylo Babich, Mathias Sander, Yunpei Deng, Henrik T. Lemke, Roman Mankowsky, Xuerong Liu, Simon E. Wall
Understanding how light modifies long-range order in quantum materials is key to improving our ability to control functionality. However, this is challenging if the response is heterogeneous. Here we address the most common form of light-induced heterogeneity, surface melting, and measure the dynamics of orbital order in the layered manganite, La0.5Sr1.5MnO4. We isolate the surface dynamics from the bulk by measuring the orbital truncation rod as well as orbital Bragg peak. After photoexcitation, the orbital Bragg peak shows an unusual narrowing, which suggests an increase in the correlation length in the probed volume. In contrast, the correlation length at the surface decreases. These differences can be reconciled if the material is heterogeneous, and light melts a less ordered surface. By isolating the surface response, we determine that the loss of long-range order is an incoherent process, which is likely accompanied by the formation of local polarons.
Authors: Giulia Del Pace, Diego Hernández-Rajkov, Vijay Pal Singh, Nicola Grani, Marcia Frómeta Fernández, Giulio Nesti, Jorge Amin Seman, Massimo Inguscio, Luigi Amico, Giacomo Roati
We report the observation of Shapiro steps in a periodically driven Josephson junction between strongly-interacting Fermi superfluids of ultracold atoms. We observe quantized plateaus in the current-potential characteristics, the height and width of which mirror the external drive frequency and the junction nonlinear response. Direct measurements of the current-phase relationship showcase how Shapiro steps arise from the synchronization between the relative phase of the two reservoirs and the external drive. Such mechanism is further supported by the detection of periodic phase-slippage processes, in the form of vortex-antivortex pairs. Our results are corroborated by a circuital model and numerical simulations, overall providing a clear understanding of Shapiro dynamics in atomic Fermi superfluids. Our work demonstrates phase-coherent and synchronization effects in driven strongly-interacting superfluids, opening prospects for studying emergent non-equilibrium dynamics in quantum many-body systems under external drives.
Authors: Yuhao Ma, Jinchao Zhao, Edwin W. Huang, Dhruv Kush, Barry Bradlyn, Philip W. Phillips
We study in depth the charge susceptibility for the band Hatsugai-Kohmoto (HK) and orbital (OHK) models. As either of these models describes a Mott insulator, the charge susceptibility takes on the form of a modified density response function with lower and upper Hubbard bands, thereby giving rise to a multi-pole structure. The particle-hole continuum consists of hot spots along the $\omega$ vs $q$ axis arising from inter-band transitions. Such transitions, which are strongly suppressed in non-interacting systems, obtain here because of the non-rigidity of the Hubbard bands. This modified density response function gives rise to a plasmon dispersion that is inversely dependent on the momentum, resulting in an additional contribution to the conventional f-sum rule. This extra contribution originates from a long-range diamagnetic contribution to the current. This results in a non-commutativity of the long-wavelength ($q\rightarrow 0$) and thermodynamic ($L\rightarrow\infty$) limits. When the correct limits are taken, we find that the Kubo response computed with either open or periodic boundary conditions yields identical results that are consistent with the continuity equation contrary to recent claims. We also show that the long wavelength pathology of the current noted previously also plagues the Anderson impurity model interpretation of dynamical mean-field theory (DMFT).
Authors: Pankaj Sharma, Narayan Mohanta
Planar Josephson junctions are theoretically predicted to harbor zero-energy Majorana bound states (MBS) in a tunable two-dimensional geometry, at the two ends of the middle metallic channel. Here we show that three distinct topological superconducting regimes, governing the localization of the near-zero-energy MBS, appear in these planar Josephson junctions. The topologically-protected MBS appear near the narrow edges of the junction -- not only in the middle metallic channel but also in the superconducting leads which have widths similar to the values used in recent experiments. We incorporate random fluctuation in the chemical potential to investigate the influence of non-magnetic disorder on the localization of the MBS in different topological regimes and find that the MBS are quite robust against disorder because of the two-dimensional geometry. Interestingly, moderate amount of disorder reduces the splitting between the MBS pairs, possibly by minimizing the wave function overlap of the MBS. We also discuss the changes in the topological superconducting phases when the superconducting lead width is varied. Our results reveal a rich structure of the localization of topologically protected multiple MBS in experimentally-accessible planar Josephson junctions, and call for their experimental confirmation.
Authors: Ji Zou, Stefano Bosco, Jelena Klinovaja, Daniel Loss
Quantum spintronics is an emerging field focused on developing novel applications by utilizing the quantum coherence of magnetic systems. A key challenge in this context is achieving scalable long-range quantum information transmission in magnetic systems. Here, we propose a novel transmission scheme based on topological spin textures in a hybrid architecture combining a magnetic racetrack and localized spin qubits. We demonstrate this principle by employing the domain wall (DW), the most fundamental texture, to transport quantum signal between distant qubits. We introduce a measurement-free protocol that utilizes DW mobility to enable high-fidelity and tunable entanglement generation. Furthermore, we demonstrate that spin qubits can function as quantum stations on the racetrack, enabling flexible state transfer among fast-moving DWs on a single track. Finally, we discuss concrete material platforms to implement the proposed scheme. Our work introduces a new hybrid quantum platform that merges topological spin textures with solid-state qubits, offering a scalable architecture for quantum information processing and opening promising directions for quantum spintronics.
Authors: Valentin Goblot, Kexin Wu, Enrico Di Lucente, Yuchun Zhu, Elena Losero, Quentin Jobert, Claudio Jaramillo Concha, Niels Quack, Nicola Marzari, Michele Simoncelli, Christophe Galland
Among all materials, mono-crystalline diamond has one of the highest measured thermal conductivities, with values above 2000 W/m/K at room temperature. This stems from momentum-conserving `normal' phonon-phonon scattering processes dominating over momentum-dissipating `Umklapp' processes, a feature that also suggests diamond as an ideal platform to experimentally investigate phonon heat transport phenomena that violate Fourier's law. Here, we introduce dilute nitrogen-vacancy color centers as in-situ, highly precise spin defect thermometers to image temperature inhomogeneities in single-crystal diamond microstructures heated from ambient conditions. We analyze cantilevers with cross-sections in the range from about 0.2 to 2.6 $\mu$m$^2$, observing a strong reduction of the cantilevers' conductivity as the width decreases. We use first-principles simulations based on the linearized phonon Boltzmann transport equation and viscous heat equations to quantitatively predict the cantilevers' thermal transport properties, rationalizing how the interplay between intrinsic and extrinsic phonon scattering mechanisms determines the observed non-diffusive behavior. Our temperature-imaging method paves the way for the exploration of unconventional, non-diffusive heat transport phenomena in devices and nanostructures of arbitrary geometries.
Authors: Wei Yue, Xiaohu Zheng, Chongli Yang, Kun Peng, Katsumi Tanigaki, Rui-Rui Du
The Mott insulator a-RuCl3, featuring the intertwined interplay of spin-orbit coupling (SOC) and Kitaev spin correlations, provides an unparalleled platform for probing quantum many-body physics. Using scanning tunneling microscopy/spectroscopy (STM/STS), we compare temperature-dependent dI/dV spectra between in-situ grown monolayers and exfoliated bulk samples. Both systems exhibit pronounced Mott gap softening near 110 K, manifested by spectral weight transfer from Hubbard bands toward the Fermi level, resulting in low-energy correlated charge delocalization. Although this gap softening coincides with Kitaev paramagnetic and structural phase transitions in bulk crystals, monolayer studies provide compelling insights. By eliminating structural phase transition in monolayer sample, we suggest that spin correlations, rather than Coulomb interactions alone, may govern charge dynamics within the Mott-Hubbard framework, challenging conventional Mott-Hubbard paradigms. These results resolve a long-standing controversy regarding the Mott gap magnitude in a-RuCl3 and experimentally confirm the critical role of spin correlations in Mott physics.
Authors: Frank Lechermann, Steffen Bötzel, Ilya M. Eremin
Superconductivity in nickelates apparently takes place in two different Ni oxidation regimes, namely either for infinite-layer-type compounds close to Ni$^{+}$, or for Ruddlesden-Popper materials close to Ni$^{2+}$. The reduced La$_3$Ni$_2$O$_6$ bilayer with a nominal Ni$^{1.5+}$ oxidation state may therefore serve as a normal-state mediator between the two known families of $3d^8$-like and $3d^9$-like superconducting nickelates. Using first-principles many-body theory, we explain its experimental 50\,meV charge gap as originating from a new type of correlated (quasi-)insulator. Flat-band electrons of Ni-$d_{z^2}$ character become localized from scattering with orbital-selective Mott-localized Ni-$d_{x^2-y^2}$ electrons, by trading in residual hopping energy for a gain in local exchange energy in a ferromagnetic Kondo-lattice scenario. Most importantly, the flat-band electrons offer another route to unconventional superconductivity in nickelates at ambient pressure.
Authors: Pritha Dolai, Arghya Das
We discuss analytical results for a run-and-tumble particle (RTP) in one dimension in presence of boundary reservoirs. It exhibits `kinetic boundary layers', nonmonotonous distribution, current without density gradient, diffusion facilitated current reversal and optimisation on tuning dynamical parameters, and a new transport effect in the steady state. The spatial and internal degrees of freedom together possess a symmetry, using which we find the eigenspectrum for large systems. The eigenvalues are arranged in two bands which can mix in certain conditions resulting in a crossover in the relaxation. The late time distribution for large systems is obtained analytically; it retains a strong and often dominant `active' contribution in the bulk rendering an effective passive-like description inadequate. A nontrivial `Milne length' also emerges in the dynamics. Finally, a novel universality is proposed in the absorbing boundary problem for dynamics with short-range colored noise. Active processes driven by active reservoirs may thus provide a common physical ground for diverse and new nonequilibrium phenomena.
Authors: Ahsan Javed, Sajid Ali
Understanding excitonic effects in two-dimensional (2D) materials is critical for advancing their potential in next-generation electronic and photonic devices. In this study, we introduce a machine learning (ML)-based framework to predict exciton binding energies in 2D materials, offering a computationally efficient alternative to traditional methods such as many-body perturbation theory (GW) and the Bethe-Salpeter equation. Leveraging data from the Computational 2D Materials Database (C2DB), our ML models establish connections between cheaply available material descriptors and complex excitonic properties, significantly accelerating the screening process for materials with pronounced excitonic effects. Additionally, Bayesian optimization with Gaussian process regression was employed to efficiently filter materials with largest exciton binding energies, further enhancing the discovery process. Although developed for 2D systems, this approach is versatile and can be extended to three-dimensional materials, broadening its applicability in materials discovery.
Authors: Moksh Bhateja, Nicolas Dupuis, Adam Rançon
The two-body contact is a fundamental quantity of a dilute Bose gas that relates the thermodynamics to the short-distance two-body correlations. For a Bose gas in an optical lattice, near the superfluid--Mott-insulator transition, we show that a ``universal'' contact $C_{\rm univ}$ can be defined from the singular part $P-P_{\rm MI}$ of the pressure ($P_{\rm MI}$ is the pressure of the Mott insulator). Its expression $C_{\rm univ}=C_{\rm DBG}(|n-n^{\rm MI}|,a^*)$ coincides with that of a dilute Bose gas provided we consider the effective ``scattering length'' $a^*$ of the quasi-particles at the quantum critical point (QCP) rather than the scattering length in vacuum, and the excess density $|n-n^{\rm MI}|$ of particles (or holes) with respect to the Mott insulator. Close to the transition, we find that the singular part $n^{\rm sing}_{\bf k} = n_{\bf k} - n^{\rm MI}_{\bf k}$ of the momentum distribution exhibits a high-momentum tail of the form $Z_{\rm QP} C_{\rm univ}/|{\bf k}|^4$ over a broad region of the Brillouin zone, where $Z_{\rm QP}$ is the quasi-particle weight of the elementary excitations at the QCP. Our results demonstrate that the notion of contact extends to strongly correlated lattice bosons, and we argue that the contact $C_{\rm univ}$ can be measured in state-of-the-art experiments on Bose gases in optical lattices and magnetic insulators.
Authors: Nicolas Dupuis, Moksh Bhateja, Adam Rançon
We present a strong-coupling expansion of the Bose-Hubbard model based on a mean-field treatment of the hopping term, while onsite fluctuations are taken into account exactly. This random phase approximation (RPA) describes the universal features of the generic Mott-insulator--superfluid transition (induced by a density change) and the superfluid state near the phase transition. The critical quasi-particles at the quantum critical point have a quadratic dispersion with an effective mass $m^*$ and their mutual interaction is described by an effective $s$-wave scattering length $a^*$. The singular part of the pressure takes the same form as in a dilute Bose gas, provided we replace the boson mass $m$ and the scattering length in vacuum $a$ by $m^*$ and $a^*$, and the density $n$ by the excess density $|n-n_{\rm MI}|$ of particles (or holes) with respect to the Mott insulator. We define a ``universal'' two-body contact $C_{\rm univ}$ that controls the high-momentum tail $\sim 1/|{\bf k}|^4$ of the singular part $n^{\rm sing}_{\bf k}$ of the momentum distribution. We also apply the strong-coupling RPA to a lattice model of hard-core bosons and find that the high-momentum distribution is controlled by a universal contact, in complete agreement with the Bose-Hubbard model. Finally, we discuss a continuum model of bosons in an optical lattice and define two additional two-body contacts: a short-distance ``universal'' contact $C_{\rm univ}^{\rm sd}$ which controls the high-momentum tail of $n^{\rm sing}_{\bf k}$ at scales larger than the inverse lattice spacing, and a ``full'' contact $C$ which controls the high-momentum tail of the full momentum distribution $n_{\bf k}$.
Authors: Kamalesh Bera, Pritam Chatterjee, Priyanka Mohan, Arijit Saha
We theoretically investigate the thermoelectric properties (electronic contribution) of a normal-superconductor (NS) hybrid junction, where the normal region consists of magic-angle twisted bilayer graphene (MATBG). The superconducting region is characterized by a common $s$-wave superconductor closely proximitized to the MATBG. We compute various thermoelectric coefficients, including thermal conductance, thermopower, and the figure of merit ($zT$), using the scattering matrix formalism. These results are further supported by calculations based on a lattice-regularized version of the effective Hamiltonian. Additionally, we explore the impact of trigonal warping and valley polarization on the thermoelectric coefficients. Notably, we find a significant variation in $zT$ as a function of these parameters, reaching values as high as 2.5. Interestingly, we observe a violation of the Wiedemann-Franz law near the charge neutrality point with the superconducting correlation, indicating that MATBG electrons behave as slow Dirac fermions in this regime. This observation is further confirmed by the damped oscillatory behavior of the thermal conductance as a function of the barrier strength when an insulating barrier is modelled at the interface of the NS junction. Beyond theoretical insights, our findings suggest new possibilities for thermoelectric applications using MATBG based NS junctions.
Authors: Felix Weber, Maxime Vassaux, Lukas Laubert, Sebastian Pfaller
Molecular dynamics (MD) simulations are widely used to provide insights into fracture mechanisms while maintaining chemical specificity. However, particle-based techniques such as MD are limited in terms of accessible length scales and applicable boundary conditions, which restricts the investigation of fracture phenomena in typical engineering settings. In an attempt to overcome these limitations, we apply the partitioned-domain Capriccio method to couple atomistic MD samples representing silica glass with the finite element (FE) method. With this approach, we perform mode I (rectangular panel under tension, three-, and four-point bending), mode II as well as mode III (rectangular panel under in-plane or out-of-plane shear) simulations. Thereby, we investigate multiple criteria to identify the onset of crack propagation based on the virial stress, the number of pair interactions, the kinetic energy/temperature, the crack velocity, and the crack opening displacement. The approach presented provides quantitatively plausible results for the critical stress intensity factors KIc, KIIc, and KIIIc. This contribution shows that the Capriccio method is a flexible means of performing fracture simulations that take into account boundary conditions typical of experimental test setups with atomistic specificity near the crack tip. While also pointing out the current limitations of the Capriccio method, we demonstrate its potential to integrate atomistic insights into FE models with significantly larger overall dimensions.
Authors: Prakash Pandey, Sudhir K. Pandey
The search of multiple topological phases (TPs) and their transitions by tuning different parameters through chemical substitutions, electric field, magnetic field, strain and Floquet engineering, etc has garnered a widespread attention in recent time. In spite of great effort, the observations of multiple TPs in a single material and multiple TP transitions in the presence of one parameter remain elusive. Here we demonstrate the presence of multiple TPs and their transitions with uniaxial compressive strain (UCS) in orthorhombic Cu$_2$SnS$_3$ by using $state$-$of$-$the$-$art$ $ab$-$initio$ calculations. In the absence of spin-orbit coupling (SOC), the Cu$_2$SnS$_3$ exhibits a single (type-II) nodal-ring and in the presence of SOC, it hosts Weyl phase with seven Weyl points (three at $\Gamma$ and four at general positions) along with nodal arcs. On the application of UCS, it remains type-II nodal-ring $<5.5$\%, which further evolves into type-III nodal-ring for $5.5\% \leq$ UCS $<5.6$\%. Interestingly, at 5.6\% of UCS, it shows Weyl phase with four Weyl nodes even in the absence of SOC. All the above-mentioned seven Weyl points persist below $5$\% of UCS. For 5\% $\leq$ UCS $<5.6$\%, four Weyl points (at general positions) disappear and nodal-arcs remain intact in all the studied range of UCS. The TPs observed in the absence of SOC appears to arise due to the presence of strain driven topological flat band, which is typically reported to be seen in kagome and Lieb lattices.
Authors: M. Schuyler Moss, Roeland Wiersema, Mohamed Hibat-Allah, Juan Carrasquilla, Roger G. Melko
Machine-learning-based variational Monte Carlo simulations are a promising approach for targeting quantum many-body ground states, especially in two dimensions and in cases where the ground state is known to have a non-trivial sign structure. While many state-of-the-art variational energies have been reached with these methods for finite-size systems, little work has been done to use these results to extract information about the target state in the thermodynamic limit. In this work, we employ recurrent neural networks (RNNs) as a variational ansätze, and leverage their recurrent nature to simulate the ground states of progressively larger systems through iterative retraining. This transfer learning technique allows us to simulate spin-$\frac{1}{2}$ systems on lattices with more than 1,000 spins without beginning optimization from scratch for each system size, thus reducing the demands for computational resources. In this study, we focus on the square-lattice antiferromagnetic Heisenberg model, where it is possible to carefully benchmark our results. We show that we are able to systematically improve the accuracy of the results from our simulations by increasing the training time, and obtain results for finite-sized lattices that are in good agreement with the literature values. Furthermore, we use these results to extract accurate estimates of the ground-state properties in the thermodynamic limit. This work demonstrates that RNN wavefunctions are able to extract accurate information about quantum many-body systems in the thermodynamic limit.
Authors: Miguel Antonio Sulangi
Scanning tunneling spectroscopy experiments on a number of cuprate superconductors have revealed that these materials are highly inhomogeneous. However, even though this inhomogeneity is well-characterized experimentally, a theoretical understanding of the effect of an inhomogeneous superconducting $d$-wave order parameter on various observables is still not complete. Here, we focus on the particular role played by the length scale of superconducting order-parameter inhomogeneity. We make use of a model involving square patches tiling the system, with each patch hosting a broadly distributed random value of the $d$-wave parameter. By using large-scale simulations, we are able to study how the size of the patches affects the correspondence between various measures of the superconducting gap and the underlying order parameter. If the length scale of the inhomogeneity is smaller than the average superconducting coherence length, the resulting $d$-wave superconductor is homogeneous. However, when the order parameter varies on the scale of the coherence length, we find the emergence of a striking low-/high-energy dichotomy, in which the low-energy regime is homogeneous while the high-energy states are strongly inhomogeneous. Kinks in the local spectra are found at the energy demarcating the homogeneous-inhomogeneous transition. We also observe that the gap extracted from the low-energy slope of the LDOS is extremely uniform. We find in both of these regimes that the distribution of the spectral gap is narrower than that of the order parameter; these start to match only when the size of the patches becomes parametrically larger than the coherence length. We comment on the applicability of these results to the cuprates, discuss the limitations of the inhomogeneous $d$-wave model, and point out where beyond-mean-field correlation effects are likely to be present in addition to inhomogeneity.
Authors: Pierre Le Doussal
We study the probability distribution function $P(\lambda)$ of the largest eigenvalue $\lambda_{\rm max}$ of $N \times N$ random matrices of the form $H + V$, where $H$ belongs to the GOE/GUE ensemble and $V$ is a full rank deterministic diagonal perturbation. This model is related to spherical spin glasses and semi-discrete directed polymers. In the large $N$ limit, using the replica method introduced in Ref. \cite{TrivializationUs2014}, we obtain the rate function ${\cal L}(\lambda)$ which describes the upper large deviation tail $P(\lambda) \sim e^{- \beta N {\cal L}(\lambda) }$. We also obtain the moment generating function $\langle e^{N s {\lambda}_{\max} } \rangle \sim e^{N \phi(s)}$ and the overlap of the optimal eigenvector with the perturbation $V$. For suitable $V$, a transition generically occurs in the rate functions. For the GUE it has a direct interpretation as a localisation transition for tilted directed polymers with competing columnar and point disorder. Although in a different form, our results are consistent with those obtained recently by Mc Kenna in \cite{McKenna2021}. Finally, we consider briefly the quadratic optimisation problem in presence of an additional random field and obtain its large deviation rate function, although only within the replica symmetric phase.
Authors: Van Tuan Vo, Andreas Dechant, Keiji Saito
Nonequilibrium current fluctuations represent one of the central topics in nonequilibrium physics. The thermodynamic uncertainty relation (TUR) is widely acclaimed for rigorously establishing a lower bound on current fluctuations, expressed in terms of the entropy production rate and the average current. In this study, we focus on an upper bound for the fluctuations, referred to as the inverse thermodynamic uncertainty relation (iTUR). We derive a universal iTUR expression in terms of the entropy production rate for continuous-variable systems governed by overdamped Langevin equations, as well as for discrete-variable systems described by Markov jump processes. The iTUR establishes a no-go theorem prohibiting perpetual superdiffusion in systems with a finite entropy production rate and a finite spectral gap. The divergence of the variance of any current becomes possible only when the spectral gap of the symmetrized time-evolution operator closes or the entropy production rate diverges. As a relevant experimental scenario, we apply the iTUR to the phenomenon of giant diffusion, emphasizing the pivotal roles of the spectral gap and entropy production.
Authors: Jong E. Han
Numerical renormalization group (NRG) is formulated for nonequilibrium steady-state by converting finite-lattice many-body eigenstates into scattering states. Extension of the full-density-matrix NRG for a biased Anderson impurity model, simplified by formulating with the original orbital basis as the Hamiltonian, enables detailed studies of the sub-Kondo spectral evolution in the zero-temperature limit, confirming the double-resonance structure at bias of the Kondo energy scale $T_K$. The distribution shows distinct multi-scale spectral features at energy $\omega$ below the Kondo scale ($\omega\lesssim T_K$) and near the bias ($\omega\gtrsim V$), leading to the nonequilibrium temperature $T_{\rm loc}$ local to the Kondo dot scaling as $k_BT_{\rm loc}\approx V$ for $V\gg T_K$. The current-voltage relation in the low-temperature limit ($T\ll T_K$) deviates from the unitary limit as the bias exceeds the Kondo scale ($V/2\gtrsim T_K$) and reaches the current saturation regime.
Authors: Shunki Yamamoto, Masahiro Sato, Satoshi Fujimoto, Takeshi Mizushima
Optical vortex beams are a type of topological light characterized by their inherent orbital angular momentum, leading to the propagation of a spiral-shaped wavefront. In this study, we focus on two-dimensional electrons with Rashba and Dresselhaus spin-orbit interactions and examine how they respond to pulsed vortex beams in the terahertz frequency band. Spin-orbital interactions play a vital role in transferring the orbital angular momentum of light to electron systems and generating spatiotemporal spin textures. We show that the spatiotemporal spin polarization of electrons reflects orbital angular momentum carried by optical vortex pulses. These findings demonstrate how optical vortices facilitate ultrafast spin manipulation in spin-orbit-coupled electrons. Our results can be straightforwardly extended to the case of higher-frequency vortex beams for other two-dimensional metals with a larger Fermi energy.
Authors: Brenna C. Bierman, Gillian Nolan, Hongrui Ma, Ying Wang, Pinshane Huang, Daniel A. Rhodes
Using Sn-intercalated TaSe$_2$ as a model system, we demonstrate the presence of structural heterogeneity captured by single-crystal X-ray diffraction (SCXRD) and scanning transmission electron microscopy (STEM) that eludes the routine characterization techniques of powder X-ray diffraction, Raman spectroscopy, and electronic transport measurements. From a single growth composition (1:1:2 Sn:Ta:Se), we obtained crystals diverse in stoichiometry and structure, with near-continuous intercalation for Sn$_x$TaSe$_2$ from $0\lesssim{x}\lesssim1$. Using SCXRD, we found global structural diversity, identifying three new structure types: Sn$_{0.18}$TaSe$_{2.0}$/Sn$_{0.08}$TaSe$_{1.96}$ ($R3m$), Sn$_{0.16}$TaSe$_{2.0}$ ($P6_3/mmc$), and Sn$_{1.2}$TaSe$_{1.9}$ ($Fmm2$). Using STEM, we observed local structural diversity, manifested as regions of highly variable stacking within a single crystal. In contrast, powder X-ray diffraction did not resolve all observed global structures. Raman spectroscopy was unable to distinguish between different structures or compositions in the standard measurement range. Electronic transport measurements showed consistent superconductivity and charge density wave behavior irrespective of Sn-intercalation amount. Our results indicate that routine approaches to characterization of intercalated transition metal dichalcogenides may be inadequate for capturing the diversity of this family of materials, highlighting the need for high-resolution structural characterization when examining the properties of van der Waals-layered compounds.
Authors: Ryan C. Spieler
We use various topological operations to systematically study phase transitions between theories with $\mathbb{Z}_2$ and time reversal symmetry in two spacetime dimensions. The phases (and accompanying CFTs) we consider come in two types - bosonic phases that are defined on unorientable manifolds and fermionic phases that are sensitive to a $\text{Pin}^-$ structure. In both cases, our analysis leads to eight phase diagrams, with the two sets of eight connected by fermionization/bosonization. Starting from a seed CFT, we obtain the CFT that governs each transition. Many of these exhibit symmetry enriched criticality. In addition to showing many symmetry enriched CFTs in their natural habitats, our work discusses the fermionic analogs of the $\mathbb{Z}_2$ bosonic operations, which we have not seen discussed in the literature.
Authors: Kamalesh Bera, Debasish Mondal, Arijit Saha, Debashree Chowdhury
Utilizing the established Bistritzer-MacDonald model for twisted bilayer graphene (tBLG), we theoretically investigate the non-Hermitian (NH) topological properties of this in the presence of non-reciprocal (NR) hopping on both layers and hexagonal boron nitride (hBN) induced mass term incorporated only on the top layer of the tBLG system. It is well known that the hBN mass term breaks the \(C_{2}\) symmetry of tBLG and gaps out the Dirac cones inducing a valley Hall insulating phase. However, when NR hopping is introduced, this system transits into a NH valley Hall insulator (NH-VHI). Our analysis reveals that, in the chiral limit, the bandwidth of the system vanishes under NH effects for a wide range of twist angles. Such range can be visibly expanded as we enhance the degree of non-Hermiticity (\(\beta\)). At the magic angle, we observe that enhancement of \(\beta\) inflates the robustness of the gapless Dirac points, requiring a progressively larger mass term to induce a gap in the NH tBLG system. Additionally, for a fixed NH parameter, we identify a range of twist angles where gap formation is significantly obstructed. To explore the topological aspects of the NH tBLG, we analyze the direct band gap in the Moiré Brillouin zone (mBZ) and compute the Chern number for the NH system. We find that the corresponding topological phase transitions are associated with corresponding direct band gap closings in the mBZ.
Authors: Yongtai Li, Gour Jana, Chinedu E. Ekuma
We present an extension of the dynamical cluster approximation (DCA) that incorporates Rashba spin-orbit coupling (SOC) to investigate the interplay between disorder, spin-orbit interaction, and nonlocal spatial correlations in disordered two-dimensional systems. By analyzing the average density of states, momentum-resolved self-energy, and return probability, we demonstrate how Rashba SOC and nonlocal correlations jointly modify single-particle properties and spin-dependent interference. The method captures key features of the symplectic universality class, including SOC-induced delocalization signatures at finite times. We benchmark the DCA results against those obtained from the numerically exact kernel polynomial method, finding good agreement. This validates the computationally efficient, mean-field-based DCA framework as a robust tool for exploring disorder, spin-orbit coupling, and nonlocal correlation effects in low-dimensional systems, and paves the way for simulating multiorbital and strongly correlated systems that were previously inaccessible due to computational limitations.
Authors: Silpa Mariya, Jeremy J. Barr, P. Sunthar, J. Ravi Prakash
We investigate the static and dynamic properties of dendrimers diffusing through a network of linear associative polymers using coarse-grained Brownian dynamics simulations. Both dendrimers and network chains are modelled as bead-spring chain polymers, with hydrodynamic interactions incorporated for the accurate prediction of dynamic properties. Linear chains form a network via the associating groups distributed along their backbones, and the dendrimers interact attractively or repulsively with the network, enabling a direct comparison of sticky and non-sticky behaviour of dendrimers. Structural analysis reveals that while non-sticky dendrimers shrink with increasing network concentration, similar to linear polymer behaviour, sticky dendrimers exhibit stretching at low concentrations due to binding interactions. Dendrimer dynamics are largely insensitive to network architecture but are strongly influenced by the strength of dendrimer-network interactions. Increasing attraction to the network leads to subdiffusive motion and non-Gaussian displacement statistics, even when dendrimers are smaller than the average mesh size. The long-time diffusivity aligns with theoretical predictions for nanoparticle transport in polymer networks. Additionally, dendrimers deform the network locally, altering the mesh size distribution depending on their stickiness. These findings offer insight into the interplay between macromolecular architecture, binding interactions, and transport in polymeric environments.
Authors: M.P. Telenkov, Yu.A. Mityagin
Electron-electron scattering processes in a quantum well in a quantizing magnetic field are considered. A matrix of electron-electron scattering rates containing all types of transitions between Landau levels within a single subband is calculated. This matrix is analyzed, and the relative magnitude of transition rates of different types is determined.
Authors: Gaia Stella Bolognini, Zeyang Xue, Michael Alexander Eichenberger, Nick Sauerwein, Francesca Orsi, Ekaterina Fedotova, Rohit Prasad Bhatt, Jean-Philippe Brantut
We present the design and assembly of a cavity microscope for quantum simulations with ultracold atoms. The system integrates a high-finesse optical cavity with a pair of high-numerical aperture lenses sharing a common optical axis, enabling simultaneous operation with light close-to-atomic resonance. The system keeps the advantages of a rigid, single-block structure holding the lenses and cavity together, and improves over existing designs by using most of the solid angle left free by the cavity mode for imaging and atomic manipulation purposes. The cavity has a length of \SI{19.786}{\milli\meter}, a finesse of \SI{2.35}{\times 10^4} and operates \SI{214}{\micro\meter} away from the concentric limit, deep in the strong coupling regime. The two lenses offer a numerical aperture of $0.52$ each and maximal optical access in all directions transverse to the cavity axis, compatible with applications in quantum-gas microscopes, micro-tweezer arrays or few-fermions systems, as well as future cavity-assisted quantum simulation protocols demanding sub-cavity-mode control of the atom-cavity coupling.
Authors: Pok Man Tam, Hao Chen, Biao Lian
Quantum Hall edge states in proximity to a superconductor (SC) usually acquire a non-quantized electron-to-hole conversion probability in transport, due to non-universal SC couplings and disorders. With counter-propagating modes, we show that the situation can be the opposite in the $\nu=2/3$ fractional quantum Hall (FQH) edge states with SC proximity, where disordered SC-couplings can reconstruct the edge states into an infinite set of stable phases with quantized electron-to-hole conversion probability along a long edge. Each phase is dominated by a disordered SC-coupling that tunnels $\pm |q_N|$ Cooper pairs, which can take values $|q_N|=1, 4, 15$, etc. We predict that this gives rise to a quantized downstream resistance $R_d = h/(2q^2_Ne^2)$ in an FQH-SC junction, serving as a quantized electrical transport signature beyond the Hall conductance. Higher-order nonlinear transport due to irrelevant Cooper pair tunneling or vortex dissipation is further studied, which becomes dominant when the edge is in a normal phase. Our results apply to both the single-layer state (as a particle-hole conjugate of $\nu=1/3$) and the bilayer Halperin-(112) state, revealing a rich landscape of disorder-stabilized phases in FQH edge states with SC proximity, and may as well apply to fractional Chern insulators recently observed at the same filling.
Authors: M. Schuyler Moss, Roeland Wiersema, Mohamed Hibat-Allah, Juan Carrasquilla, Roger G. Melko
Variational Monte Carlo simulations have been crucial for understanding quantum many-body systems, especially when the Hamiltonian is frustrated and the ground-state wavefunction has a non-trivial sign structure. In this paper, we use recurrent neural network (RNN) wavefunction ansätze to study the triangular-lattice antiferromagnetic Heisenberg model (TLAHM) for lattice sizes up to $30\times30$. In a recent study [M. S. Moss et al. arXiv:2502.17144], the authors demonstrated how RNN wavefunctions can be iteratively retrained in order to obtain variational results for multiple lattice sizes with a reasonable amount of compute. That study, which looked at the sign-free, square-lattice antiferromagnetic Heisenberg model, showed favorable scaling properties, allowing accurate finite-size extrapolations to the thermodynamic limit. In contrast, our present results illustrate in detail the relative difficulty in simulating the sign-problematic TLAHM. We find that the accuracy of our simulations can be significantly improved by transforming the Hamiltonian with a judicious choice of basis rotation. We also show that a similar benefit can be achieved by using variational neural annealing, an alternative optimization technique that minimizes a pseudo free energy. Ultimately, we are able to obtain estimates of the ground-state properties of the TLAHM in the thermodynamic limit that are in close agreement with values in the literature, showing that RNN wavefunctions provide a powerful toolbox for performing finite-size scaling studies for frustrated quantum many-body systems.
Authors: Andrew Urilyon, Leonardo Biagetti, Jitendra Kethepalli, Jacopo De Nardis
One-dimensional integrable and quasi-integrable systems display, on macroscopic scales, a universal form of transport known as Generalized Hydrodynamics (GHD). In its standard Euler-scale formulation, GHD mirrors the equations of a two-dimensional compressible fluid but ignores fluctuations and becomes numerically unwieldy as soon as integrability-breaking perturbations are introduced. We show that GHD can be efficiently simulated as a gas of semiclassical wave packets - a natural generalisation of hard-rod particles - whose trajectories are efficiently mapped onto those of point particles. This representation (i) provides a transparent route to incorporate integrability-breaking terms, and (ii) automatically embeds the exact fluctuating-hydrodynamics extension of GHD. The resulting framework enables fast, large-scale simulations of quasi-integrable systems even in the presence of complicated integrability-breaking perturbations. It also manifest the pivotal role of two-point correlations in systems confined by external potentials: we demonstrate that situations where local one-point observables appear thermalised can nevertheless sustain long-lived, far-from-equilibrium long-range correlations for arbitrarily long times, signaling that, differently from what previously stated, true thermalisation is not reached at diffusive time-scales.
Authors: Marco Benedetti, Andrej Bogdanov, Enrico M. Malatesta, Marc Mézard, Gianmarco Perrupato, Alon Rosen, Nikolaj I. Schwartzbach, Riccardo Zecchina
Square Wave Perceptrons (SWPs) form a class of neural network models with oscillating activation function that exhibit intriguing ``hardness'' properties in the high-dimensional limit at a fixed constraint density $\alpha = O(1)$. In this work, we examine two key aspects of these models. The first is related to the so-called \emph{overlap-gap property}, that is a disconnectivity feature of the geometry of the solution space of combinatorial optimization problems proven to cause the failure of a large family of solvers, and conjectured to be a symptom of algorithmic hardness. We identify, both in the storage and in the teacher-student settings, the emergence of an overlap gap at a threshold $\alpha_{\mathrm{OGP}}(\delta)$, which can be made arbitrarily small by suitably increasing the frequency of oscillations $1/\delta$ of the activation. This suggests that in this small-$\delta$ regime, typical instances of the problem are hard to solve even for small values of $\alpha$. Second, in the teacher-student setup, we show that the recovery threshold of the planted signal for message-passing algorithms can be made arbitrarily large by reducing $\delta$. These properties make SWPs both a challenging benchmark for algorithms and an interesting candidate for cryptographic applications.
Authors: Andriy Goychuk
Phase separation into domains with distinct composition and properties has widespread implications, ranging from alloys and emulsions to biomolecular condensates in cells. In living and nonliving matter, the organization of these domains can be controlled by nonequilibrium chemical reactions, external fields, or mechanical stresses. In this context, stationary states can emerge from long-range monopolar interactions analogous to electrostatics. More generally, as discussed here, because fluxes induce dipolar force fields, externally controlled boundary motion effectively polarizes the domain even for microscopically nonpolarizable matter. The dipole-dipole interactions resulting from this translation-induced polarization cause directed coalescence of domains. This coarsening mechanism complements Ostwald ripening and coalescence due to Brownian motion or Marangoni flows, and has implications for controlling domains by electric fields or concentration gradients. Interestingly, the chemical potential gradients around a domain that nucleates material are exactly opposite to the hydrodynamic pressure gradients around an impermeable colloid that pushes the fluid, suggesting a competition between phase separation and hydrodynamics. In addition to chemical control, the motion of domains can also be driven by mechanical stresses. An example is the cell interior, where mechanical stresses are actively generated by molecular motors and opposed by passive viscoelastic stresses in the cytoplasm and nucleoplasm. The resulting fluid flows lead to Brownian motion with a suppressed or enhanced size scaling which modifies collision-coalescence. For active stresses with a long correlation time, the domains show superdiffusion on intermediate time scales. Together, these findings shed new light on the dynamics of domains in viscoelastic media and conserved order parameters in general.
Authors: Bowy M. La Rivière, Rik Mulder, Natalia Chepiga
We report the emergence of exact zero modes in junctions of two, three and four short interacting Majorana wires, equivalent to a chain with an impurity bond, Y- and X- junctions respectively. These exact zero modes are due to incommensurate short-range correlations induced by the interacting Majorana fermions, and they appear as unavoided level crossings between in-gap states upon continuously tuning the interaction. In a junction of only two chains we report exact zero modes and parity switching as soon as the coupling between the chains across a junction is positive. Remarkably, for junctions with multiple chains the in-gap states group up into sets of parity pairs -- pairs of states with opposite parity and similar energies. We demonstrate that the formation of these parity pairs are always due to the interaction of the outer edges of the junction. The behavior within each pair can be efficiently described by two coupled chains. In the Y-junction, we detect four in-gap states (two parity pairs) that show exact zero modes not only within each pair but also between them. This is attributed to an additional Majorana fermion localized at the center of junction that is protected by symmetry. Therefore, coupling between the Majorana fermions at the outer edges of the junction is mediated by that in the center. We argue that this is a generic feature of junctions with an odd number of arms. In the X-junction we detect eight in-gap states (four parity pairs) that are the result of two Majorana degrees of freedom localized at the center of the junction. However, we demonstrate that, by contrast to the Y-junction, the appearance of Majorana fermions at the center of the X-junction is not protected and the interaction across the junction can be tuned to the point where there are only Majorana fermions localized at the four outer edges of the junction, forming four in-gap states.
Authors: Kevin G. S. Xie, Colin J. Dale, Kiera Pond Grehan, Maggie Fen Wang, Tilman Enss, Paul S. Julienne, Zhenhua Yu, Joseph H. Thywissen
Understanding the dynamics of short-range correlations is a central challenge in strongly interacting Fermi gases. In ultracold gases, these correlations are quantified by the contact parameter, yet measurements to date have been limited to equilibrium systems or relatively slow, global dynamics. Here, we introduce a rapid spectroscopic technique based on projection of the interacting state onto an alternate scattering channel with a low-lying dimer state. We demonstrate contact measurements on the microsecond timescale -- faster than the inverse Fermi energy. Using $^{40}$K near a broad $s$-wave Feshbach resonance, we show that the strength of the dimer-projection feature scales proportionally with the contact parameter extracted from the high-frequency tail of radio-frequency spectroscopy, in agreement with coupled-channels calculations. Analysis of the spectra further reveals that the dimer feature provides the dominant contribution to the clock shift of the unitary Fermi gas, allowing the first experimental bound on this quantity. The observed deviations from universal predictions highlight the importance of multichannel effects. Our results open new avenues for studying contact correlators, hydrodynamic attractors, and quantum critical behavior.
Authors: Xia-Ze Xu, Tong-Yu Lin, Guang-Ming Zhang
Variational tensor network optimization has become a powerful tool for studying classical statistical models in two dimensions. However, its application to three-dimensional systems remains limited, primarily due to the high computational cost associated with evaluating the free energy density and its gradient. This process requires contracting a triple-layer tensor network composed of a projected entangled pair operator and projected entangled pair states. In this paper, we employ a split corner-transfer renormalization group scheme tailored for the contraction of such a triple-layer network, which reduces the computational complexity while keeping high accuracy. Through numerical benchmarks on the three-dimensional classical Ising model, we demonstrate that the proposed scheme achieves numerical results comparable to the most recent Monte Carlo simulations, providing a substantial speedup over previous variational tensor network approaches. This makes this method well-suited for efficient gradient-based optimization in three-dimensional tensor network simulations.
Authors: Bokai Liang, Wei Qin, Zhenyu Zhang
We propose a programmable platform for engineering topological flat minibands by imposing a tunable electrostatic superlattice potential on a Rashba spin-orbit-coupled thin film subject to a Zeeman field. The interplay between the superlattice potential and Zeeman coupling produces an isolated flat miniband with Chern number $\mathcal{C}=1$. Using many-body exact diagonalization, we show that this miniband supports fractional Chern insulators at filling factors $n = 1/3$ and $2/3$, both of which remain robust over broad parameter ranges. We further identify realistic material candidates and the corresponding device conditions that enable experimental realization. These results establish a versatile and experimentally accessible platform for engineering topological flat minibands and exploring correlated topological phases.
Authors: Cesare Malosso, Edward Danquah Donkor, Stefano Baroni, Ali Hassanali
A growing body of theoretical and experimental evidence strongly supports the existence of a second liquid-liquid critical point (LLCP) in deeply supercooled water leading to the co-existence of two phases: a high-and low-density liquid (HDL and LDL). While the thermodynamics associated with this putative LLCP has been well characterised through numerical simulations, the dynamical properties of these two phases close to the critical point remain much less understood. In this work, we investigate their dynamical and spectroscopic features using machine-learning interatomic potentials (MLIPs). Dynamical analyses using the van-Hove correlation function, reveal that LDL exhibits very sluggish and heterogeneous molecular mobility, in contrast to the faster and more homogeneous dynamics of HDL. Infrared absorption (IR) spectra further show clear vibrational distinctions between LDL and HDL, in particular in the far IR region between 400 - 1000 cm-1. Together, these findings provide new dynamical fingerprints that clarify the microscopic behavior of supercooled water and offer valuable guidance for experimental efforts aimed at detecting the long-sought liquid-liquid transition.
Authors: Nianrui Fu, Siyuan Wang, Yu Zhao, Yidun Wan
Symmetry-enriched topological (SET) phases combine intrinsic topological order with global symmetries, giving rise to novel symmetry phenomena. While SET phases with Abelian anyons are relatively well understood, those involving nonabelian anyons remain elusive. This obscurity stems from the multidimensional internal gauge spaces intrinsic to nonabelian anyons -- a feature first made explicit in [1,2] and further explored and formalized in our recent works [3-8]. These internal spaces can transform in highly nontrivial ways under global symmetries. In this work, we employ an exactly solvable model -- the multifusion Hu-Geer-Wu string-net model introduced in a companion paper [9] -- to reveal how the internal gauge spaces of nonabelian anyons transform under symmetries. We uncover a universal mechanism, global symmetry fragmentation (GSF), whereby symmetry-invariant anyons exhibit internal Hilbert space decompositions into eigensubspaces labeled by generally fractional symmetry charges. Meanwhile, symmetry-permuted anyons hybridize and fragment their internal spaces in accordance with their symmetry behavior. These fragmented structures realize genuinely nonlinear symmetry representations -- to be termed coherent representations -- that transcend conventional linear and projective classifications, reflecting the categorical nature of symmetries in topological phases. Our results identify nonlinear fragmentation as a hallmark of nonabelian SETs and suggest new routes for symmetry-enabled control in topological quantum computation.
Authors: Y. Li, Z. H. Tao, Y. M. Xiao, W. Xu, Q. N. Li, F. M. Peeters, D. Neilson, M. V. Milosevic
Rashba spin-orbit coupling (RSOC) induces strong momentum-dependent spin splitting and plays a crucial role in fields like spintronics and topological photonics. We here theoretically investigate the collective excitations in monolayer transition metal dichalcogenides (ML-TMDs) hosting RSOC, and conceive an approach to precisely quantify the strength of RSOC using plasmons. We determine the electron energy loss function (EELF) and plasmon dispersions for n-type ML-TMD from the dynamic dielectric function in the framework of the standard random phase approximation (RPA). In this system, both optical and acoustic plasmon modes are observed in the EELF and plasmon dispersions. Moreover, the plasmonic and spectral properties are tunable by electron density and dependent on RSOC. Crucially, we identify a minimum energy gap between the two plasmon modes to serve as a direct spectral signature of the RSOC strength. These results establish plasmons as a non-invasive, precise, and broadly tunable technique for determining RSOC in TMD van der Waals heterostructures and devices.
Authors: Jacob Morgan (1), Simon Cox (1) ((1) Department of Mathematics, Aberystwyth University, UK)
Aqueous foams are subject to coarsening, whereby gas from the bubbles diffuses through the liquid phase. Gas is preferentially transported from small to large bubbles, resulting in a gradual decrease of the number of bubbles and an increase in the average bubble size. Coarsening foams are expected to approach a scaling state at late times in which their statistical properties are invariant. However, a model predicting the experimentally observed bubble-size distribution in the scaling state of foams with moderate liquid content, as a function of the liquid fraction $\phi$, has not yet been developed. To this end, we propose a three-dimensional mean-field bubble growth law for foams without inter-bubble adhesion, validated against bubble-scale simulations, and use it to derive a prediction of the scaling-state bubble-size distribution for any $\phi$ from zero up to the unjamming transition $\phi_\text{c} \approx 36\%$. We verify that the derived scaling state is approached from a variety of initial conditions using mean-field simulations implementing the proposed growth law. Comparing our predicted bubble-size distribution with previous simulations and experimental results, we likewise find a large population of small bubbles when $\phi > 0$, but there are qualitative differences from prior results which we attribute to the absence of rattlers, i.e. bubbles not pressed into contact with their neighbours, in our model.
Authors: Pok Man Chiu
We study the degree of band flatness and anisotropic quantum geometry in magic-angle twisted bilayer graphene by varying the twist angle and the lattice relaxation through optical conductivity. We show that the degree of band flatness and its quantum geometry can be revealed through optical absorption and its resulting optical bounds, which are based on the trace condition in quantum geometry. More specifically, the narrow and isolated peak of optical absorption in the low-energy region provides information about the bandwidth between two flat bands. When this value is smaller than the electron interaction, it serves as a critical condition for the emergence of flat band superconductivity. Furthermore, optical absorption also provides the gap value between the flat band and the dispersive band, and when this gap is larger than the electron interaction, it facilitates the realization of fractional Chern insulating phases. We show that the narrow and isolated peak of optical bound near zero energy decreases as lattice relaxation increases. Meanwhile, we demonstrate that the imaginary part of generalized optical Hall conductivity reveals the vanishing of the negative part of Berry curvature, which is enforced by the refined trace-determinant inequality. Accordingly, we show that the total amount of the negative part and component of the Berry curvature approaches zero in the single ideal flat-band case. In contrast, when considering all occupied bands, the total amount of the negative component is slightly different from zero. Finally, we demonstrate that the condition of vanishing of flat band velocities and the emergent chiral symmetry are sufficient for the saturation of the trace condition, which pertains to the isotropic case.
Authors: Daichi Kagamihara, Hironori Kazuta, Yewei Wu, N. J. Fitch, Ippei Danshita
Recent development of cloud-based experiment platforms has enabled physicists to examine theoretical concepts with unprecedented accessibility. Oqtant is a cloud-accessible platform for trapped Bose-Einstein Condensates (BECs) of neutral atomic gases, providing an invaluable experimental tool for studying the dynamics of BECs. An intriguing theoretical prediction of a characteristic phenomenon of BECs is anomalous tunneling, whereby low-energy phonon excitations of BECs easily transmit through a barrier potential. We utilize Oqtant to observe the effects of anomalous tunneling on collective excitations of BECs. For this purpose, we theoretically show that anomalous tunneling affects the frequencies of the collective excitations in the low-energy regime, and experimentally measure these frequencies using Oqtant. Our results reveal that low-energy collective modes are less affected by a potential barrier, which indicates the presence of anomalous tunneling. Our work would contribute to fundamental understandings of BECs, as well as highlight the potential of cloud-based experiments in quantum-body physics.
Authors: Zhiyu Fan, Wei Ku
We present a rigorous proof that under a number-conserving Hamiltonian, one-body quasi-particles generally possess quantized charge and inertial mass identical to the bare particles. It follows that, Bogoliubov zero modes in the vortex (or on the edge) of superconductors $\textit{cannot}$ be their own anti-particles capable of braiding quantum information. As such, the heavily pursued Majorana zero mode-based route for quantum computation requires a serious re-consideration. This study further reveals the conceptual challenge in preparing and manipulating braid-able quantum states via physical thermalization or slow external fields. These profound results should reignite the long-standing quest for a number-conserving theory of superconductivity and superfluidity without fictitiously breaking global U(1) symmetry.
Authors: Anton Talkachov, Egor Babaev
We study conditions of the appearance of $U(1)\times \mathbb{Z}_2$ superconducting states that spontaneously break time-reversal symmetry (BTRS) on a square lattice as a function of applied stress. Calculations show that if critical temperatures coincide at zero stress, they exhibit a linear kink and no kink otherwise for uniaxial and isotropic strain. Linear kink is absent for shear strain. We find that in general, the microscopic calculations show a complex phase diagram, for example, non-monotonic behavior of BTRS transition. Another beyond-Ginzburg-Landau theory result is that $U(1)$ critical temperature can decrease under compressional [100] uniaxial strain for small Poisson ratio materials. In the second part of the paper, we consider the effects of boundaries and finiteness of the sample on the strain-induced splitting of $T_c^{U(1)}$ and $T_c^{\mathbb{Z}_2}$ transitions. A finite sample has BTRS boundary states with persistent superconducting currents over a wide range of band filling. Overall, the BTRS dome occupies a larger band filling--temperature phase space region for a mesoscopic sample with [110] surface compared to an infinite system. Hence, the presence of boundaries helps to stabilize the BTRS phase.
Authors: Ethan Lake, Sunghan Ro
We introduce families of classical stochastic dynamics in two and higher dimensions which stabilize order in the absence of any symmetry. Our dynamics are qualitatively distinct from Toom's rule, and have the unusual feature of being fluctuation-stabilized: their order becomes increasingly fragile in larger dimensions. One of our models maintains an ordered phase only in two dimensions. The phase transitions that occur as the order is lost realize new dynamical universality classes which are fundamentally non-equilibrium in character.
Authors: A.C. Maggs
We consider a multi-walker generalization of the true self-avoiding walk: the bricklayer model. We perform stochastic simulations, and solve the partial differential equations that describe the collective motion of $N$ bricklayers/walkers coupled to the contour of an expanding wall. In the large-$N$ limit, the results from simulation agree with the solution of the partial differential equations.
Authors: Mohid Farooqi, Ingmar Bösing, Conrard G. Tetsassi Feugmo
Physics-informed neural networks (PINNs) offer a novel AI-driven framework for integrating physical laws directly into neural network models, facilitating the solution of complex multiphysics problems in materials engineering. This study systematically explores the application of PINNs to simulate oxide film layer growth in halide-free solutions using the point defect model (PDM). We identify and analyze four key failure modes in this context: imbalanced loss components across different physical processes, numerical instabilities due to variable scale disparities, challenges in enforcing boundary conditions within multiphysics systems, and convergence to mathematically valid but physically meaningless solutions. To overcome these challenges, we implement and validate established techniques including nondimensionalization for training stabilization, Neural Tangent Kernel-based adaptive loss balancing, robust enforcement of boundary conditions and hybrid training with sparse data. Our results demonstrate the effectiveness of these strategies in enhancing the reliability and physical fidelity of PINNs, achieving sub $1\%$ relative error as compared to Finite Element Benchmarks with the hybrid model. Thereby showing that PINNs can be used for high fidelity electrochemical simulations with minimal data requirements and highlight necesary factors for fully autonomous PINN simulations.
Authors: Paul Leask
The interactions of anyonic quasi-particles (vortices) in the Chern--Simons extension of the Ginzburg--Landau model is investigated and we show that it manifestly realizes a hybridization of type I/II superconductivity. Through Gauss' law, each vortex simultaneously carries a flux quantum and a proportional Noether charge, thereby realizing an anyonic excitation. The Chern--Simons coupling also modifies the screening structure of the gauge fields, producing complex-conjugate masses that yield a common penetration depth with an oscillatory phase. This altered asymptotic behavior breaks the conventional type-I/type-II dichotomy of the Ginzburg--Landau model. As a result, vortex anyons experience short-range repulsion and long-range attraction, enabling the formation of separated multi-vortex bound states with non-monotonic interaction energy.
Authors: Ethan Huecker, Yuxuan Wang
We analyze the leading vestigial instability due to the melting of a bidirectional pair-density-wave state in two dimensions. In a previous work by one of the authors, it was found that the interplay between pair-density-wave fluctuations with ordering momenta along the $x$ and $y$ directions can provide a strong attractive interaction for charge-$4e$ superconductivity in the $d$-wave channel. In this work, we go beyond the artificial large-$M$ mean-field theory previously adopted and compute the phase diagram by incorporating phase fluctuations of the pair-density-wave order parameters. By investigating the relevance of various topological defects, we show that the interaction in the $d$-wave channel, together with the strong anisotropy of phase fluctuations around the pair-density-wave ordering momenta, favors a vestigial charge-$4e$ superconducting order at intermediate temperatures. By contrast, a competing charge-density-wave vestigial order does not develop, due to the suppression of its stiffness.
Authors: Xun-Jiang Luo, Jin-Xin Hu, K. T. Law
Inspired by the discovery of altermagnets, which exhibit even-parity nonrelativistic spin splitting, odd-parity magnets (OPMs) have been proposed and emerged as a novel research frontier. In this study, we perform a comprehensive spin group symmetry analysis to establish symmetry criteria for the emergence of OPMs. We identify eight distinct symmetry-driven cases that support OPMs, enabling their realization in collinear, coplanar, and noncoplanar magnetic orders. These OPMs are categorized into three types based on their spin textures for Bloch states: collinear (type-I), coplanar (type-II), and noncoplanar (type-III). For type-I OPMs, we further delineate additional symmetry requirements for $p$-wave and $f$-wave spin splitting. We identify 48 candidate materials in the Magndata database that satisfy these symmetry criteria. Additionally, we construct two theoretical models to validate the effectiveness of the established symmetry criteria. Finally, we show that OPMs can exhibit an intrinsic $\mathbb{Z}_2$ topology and construct a theoretical model to realize this phase.
Authors: Yingchen Peng, Yanan Ge, Zihan Wang, Kang Wang, Kezhao Du, Xingzhi Wang, Ye Yang
Layered van der Waals (vdW) magnetic semiconductors open a new avenue for exploring intertwined excitonic and magnetic phenomena. Here, we investigate this interplay in the vdW MnPS3 antiferromagnet, uncovering an exceptionally long exciton lifetime (~100 {\mu}s) below the Néel temperature (T_N). We demonstrate that the exciton lifetime is governed by phonon-mediated nonradiative recombination and thus exhibits a strong temperature dependence. On the contrary, the radiative recombination rate shows a distinct temperature dependence, which is dominated by magnon-assisted emission mechanism below T_N and by short-range spin correlations and phonons above T_N. These findings not only establish MnPS3 as a compelling candidate for excitonic devices due to its long-lifetime and correlation with magnetic orders but also provide crucial insights into the interplay between excitons, spins, and lattice in vdW magnetic semiconductors.
Authors: Yan Meng, Kainan Chang, Yanyan Qian, Luxia Wang, Jin Luo Cheng
Black phosphorene (BP) has emerged as a promising platform for tunable nonlinear photonics due to its layer-dependent bandgap, high carrier mobility, and remarkable in-plane anisotropy. This study investigates the second-harmonic generation (SHG) of monolayer and bilayer BP under an external static electric field, with describing the electronic states by a tight-binding model and the dynamics by semiconductor Bloch equations. Our results reveal that BP exhibits large second-order nonlinear optical response along the armchair direction, with significant resonant enhancement when the incident photon energy approaches half of its bandgap. Under an applied electric field of $10^7$ V/m, the effective second-order nonlinear susceptibility of BP can be as large as $10^3$ pm/V, surpassing that of the conventional nonlinear crystal AgGaSe$_2$ by more than an order of magnitude. With respect to the static electric field induced by gate voltage, we discuss the relation between the electric-field-induced second harmonic (EFISH) generation and conventional SHG -- under lower gate voltage, the EFISH approach agrees well with the SHG solutions, whereas the former is no longer applicable under higher gate voltage. Specifically, as the increasing gate voltage, monolayer BP exhibits the bandgap expansion and the corresponding blue-shift in the SHG resonant peak. In contrast, bilayer BP undergoes a semiconductor-to-semimetal transition, forming Dirac cone and generating divergent SHG spectra as photon energy goes to zero. Additionally, the chemical potential allows for precise control over interband and intraband nonlinear responses. This work provides important theoretical foundations for the development of BP-based tunable nonlinear photonic devices and expands the application potential of anisotropic two-dimensional materials in nonlinear optics.
Authors: Riek H. Rüstemeier, H. P. Ojeda Collado, Ludwig Mathey
The field of coherent electronics aims to advance electronic functionalities by utilizing quantum coherence. Here, we demonstrate a viable and versatile methodology for controlling electron dynamics optically in graphene nanoribbons. In particular, we propose to flatten the band structure of armchair graphene nanoribbons via control electrodes, arranged periodically along the extended direction of the nanoribbon. This addresses a key mechanism for dephasing in solids, which derives from the momentum dependence of the energy gap between the valence and the conduction band. We design an optimal driving field pulse to produce collective Rabi oscillations between these bands, in their flattened configuration. As an example for coherent control, we show that these optimized pulses can be used to invert the entire electronic band population by a $\pi$ pulse in a reversible fashion, and to create a superposition state via a $\pi/2$ pulse, which generates an alternating photocurrent. Our proposal consists of a platform and methodological approach to optically control the electron dynamics of graphene nanoribbons, paving the way toward novel coherent electronic and quantum information processing devices in solid-state materials.
Authors: Abhay Srivastav, Vivek Pandey, Brij Mohan, Arun Kumar Pati
Traditional quantum speed limits formulated in density matrix space are generally unattainable for a wide class of dynamics and it is difficult to characterize the fastest possible dynamics. To address this, we present two distinct quantum speed limits in Liouville space for Completely Positive and Trace-Preserving (CPTP) dynamics. The first bound saturates for time-optimal CPTP dynamics, while the second bound is exact for all states and all CPTP dynamics. Our bounds have a clear physical and geometric interpretation arising from the uncertainty relations for operators acting on Liouville space, and the geometry of quantum evolution in Liouville space. We also obtain the form of the Liouvillian, which generates the time-optimal CPTP dynamics that connect the given initial and target states. To illustrate our findings, we show that the speed of evolution in Liouville space bounds the growth of the spectral form factor and Krylov complexity of states, which are crucial for studying information scrambling and quantum chaos. In another important application, we show that our results can help us understand the counter-intuitive phenomenon of the Mpemba effect in non-equilibrium open quantum dynamics, as the minimal relaxation time scale obtained by speed limits is dictated by the eigenmodes of the Liouvillian.
Authors: András Grabarits, Federico Balducci, Adolfo del Campo
We investigate the efficiency of approximate counterdiabatic driving (CD) in accelerating adiabatic passage through exponentially small gaps. First, we analyze a minimal spin-glass bottleneck model that is analytically tractable and exhibits both an exponentially small gap at the transition point and a change in the ground state that involves a macroscopic rearrangement of spins. Using the variational Floquet-Krylov expansion to construct CD terms, we find that while the formation of excitations is significantly suppressed, achieving a fully adiabatic evolution remains challenging. Extending our investigation to realistic NP-hard spin-glass problems -- specifically, the $3$-regular \textsc{Max Cut} and $3$-\textsc{XORSAT} -- we find again that local CD expansions lead to negligible improvements in the final ground state fidelity. These results highlight the limited impact of local CD methods in overcoming the bottlenecks associated with first-order quantum phase transitions. To address this limitation, we propose an alternative method, termed quantum brachistochrone counterdiabatic driving (QBCD), which employs the approximate full CD connecting the ground state and the first excited state at a single parameter value close to the critical point. In the minimal spin-glass model, QBCD enables exponentially faster adiabatic evolution than the local strategies. To alleviate the challenges of its experimental and classical implementation for realistic \textsc{NP}-hard problems, we exponentially reduce the non-locality of the QBCD Hamiltonian by sparsifying its matrix elements to the density of the local expansions. Despite this drastic simplification, sparsified QBCD maintains finite ground-state fidelity at driving times exponentially shorter than in local strategies and counterdiabatic optimized local driving (COLD).
Authors: Antoine Maillard
Given a sequence of $d \times d$ symmetric matrices $\{\mathbf{W}_i\}_{i=1}^n$, and a margin $\Delta > 0$, we investigate whether it is possible to find signs $(\epsilon_1, \dots, \epsilon_n) \in \{\pm 1\}^n$ such that the operator norm of the signed sum satisfies $\|\sum_{i=1}^n \epsilon_i \mathbf{W}_i\|_{\rm op} \leq \Delta$. Kunisky and Zhang (2023) recently introduced a random version of this problem, where the matrices $\{\mathbf{W}_i\}_{i=1}^n$ are drawn from the Gaussian orthogonal ensemble. This model can be seen as a random variant of the celebrated Matrix Spencer conjecture and as a matrix-valued analog of the symmetric binary perceptron in statistical physics. In this work, we establish a satisfiability transition in this problem as $n, d \to \infty$ with $n / d^2 \to \tau > 0$. First, we prove that the expected number of solutions with margin $\Delta=\kappa \sqrt{n}$ has a sharp threshold at a critical $\tau_1(\kappa)$: for $\tau < \tau_1(\kappa)$ the problem is typically unsatisfiable, while for $\tau > \tau_1(\kappa)$ the average number of solutions is exponentially large. Second, combining a second-moment method with recent results from Altschuler (2023) on margin concentration in perceptron-type problems, we identify a second threshold $\tau_2(\kappa)$, such that for $\tau>\tau_2(\kappa)$ the problem admits solutions with high probability. In particular, we establish that a system of $n = \Theta(d^2)$ Gaussian random matrices can be balanced so that the spectrum of the resulting matrix macroscopically shrinks compared to the semicircle law. Finally, under a technical assumption, we show that there exists values of $(\tau,\kappa)$ for which the number of solutions has large variance, implying the failure of the second moment method. Our proofs rely on establishing concentration and large deviation properties of correlated Gaussian matrices under spectral norm constraints.
Authors: Yoshihiko Hasegawa
Enhancing the precision of a thermodynamic process inevitably necessitates a thermodynamic cost. This notion was recently formulated as the thermodynamic uncertainty relation, which states that the lower bound on the relative variance of thermodynamic currents decreases as entropy production increases. From another viewpoint, the thermodynamic uncertainty relation implies that if entropy production were allowed to become infinitely large, the lower bound on the relative variance could approach zero. However, it is evident that realizing infinitely large entropy production is infeasible in reality. This indicates that physical constraints impose precision limits on the system, independent of its dynamics. In this study, we derive fundamental precision limits, dynamics-independent bounds on the relative variance and the expectations of observables for open quantum thermal machines operating within a finite-dimensional system and environment. These bounds are set by quantities such as dimensions and energy bandwidth, which depend only on the initial configuration and are independent of the dynamics. Using a quantum battery model, the fundamental precision limits show that there is a trade-off between the amount of energy storage and the charging precision. Additionally, we investigate how quantum coherence affects these fundamental limits, demonstrating that the presence of coherence can improve the precision limits. Our findings provide insights into fundamental limits on the precision of quantum thermal machines.
Authors: Zhian Jia
We introduce weak Hopf symmetry as a tool to explore (1+1)-dimensional topological phases with non-invertible symmetries. Drawing inspiration from Symmetry Topological Field Theory (SymTFT), we construct a lattice model featuring two boundary conditions: one that encodes topological symmetry and another that governs non-topological dynamics. This cluster ladder model generalizes the well-known cluster state model. We demonstrate that the model exhibits weak Hopf symmetry, incorporating both the weak Hopf algebra and its dual. On a closed manifold, the symmetry reduces to cocommutative subalgebras of the weak Hopf algebra. Additionally, we introduce weak Hopf tensor network states to provide an exact solution for the model. As every fusion category corresponds to the representation category of some weak Hopf algebra, fusion category symmetry naturally corresponds to a subalgebra of the dual weak Hopf algebra. Consequently,the cluster ladder model offers a lattice realization of arbitrary fusion category symmetries.
Authors: S. Günzler, J. Beck, D. Rieger, N. Gosling, N. Zapata, M. Field, S. Geisert, A. Bacher, J. K. Hohmann, M. Spiecker, W. Wernsdorfer, I. M. Pop
Superconducting qubits equipped with quantum non-demolition readout and active feedback can be used as information engines to probe and manipulate microscopic degrees of freedom, whether intentionally designed or naturally occurring in their environment. In the case of spin systems, the required magnetic field bias presents a challenge for superconductors and Josephson junctions. Here we demonstrate a granular aluminum nanojunction fluxonium qubit (gralmonium) with spectrum and coherence resilient to fields beyond one Tesla. Sweeping the field reveals a paramagnetic spin-1/2 ensemble, which is the dominant gralmonium loss mechanism when the electron spin resonance matches the qubit. We also observe a suppression of MHz range fast flux noise in magnetic field, suggesting the freezing of surface spins. Using an active state stabilization sequence, the qubit hyperpolarizes long-lived two-level systems (TLSs) in its environment, previously speculated to be spins. Surprisingly, the coupling to these TLSs is unaffected by magnetic fields, leaving the question of their origin open. The robust operation of gralmoniums in Tesla fields offers new opportunities to explore unresolved questions in spin environment dynamics and facilitates hybrid architectures linking superconducting qubits with spin systems.
Authors: Emma C. King, Moritz Linnebacher, Peter P. Orth, Matteo Rizzi, Giovanna Morigi
A quantum walk on a lattice is a paradigm of a quantum search in a database. The database qubit strings are the lattice sites, qubit rotations are tunneling events, and the target site is tagged by an energy shift. For quantum walks on a continuous time, the walker diffuses across the lattice and the search ends when it localizes at the target site. The search time $T$ can exhibit Grover's optimal scaling with the lattice size $N$, namely, $T\sim \sqrt{N}$, on an all-connected, complete lattice. For finite-range tunneling between sites, instead, Grover's optimal scaling is warranted when the lattice is a hypercube of $d>4$ dimensions. Here, we show that Grover's optimum can be reached in lower dimensions on lattices of long-range interacting particles, when the interaction strength scales algebraically with the distance $r$ as $1/r^{\alpha}$ and $0<\alpha<3d/2$. For $\alpha
Authors: Devanshu Shekhar, Pragya Shukla
We analyze the effect of varying system conditions on the single-particle entanglement entropy for an arbitrary eigenstate of a complex system that can be described by a multiparametric Gaussian ensemble. Our theoretical analysis leads to the identification of a single functional of the system parameters that governs the entropy dynamics. This reveals a sensitivity of the entropy to collective information content, characterized by the functional, instead of the individual system details. The functional can further be used to identify the universality classes as well as a deep web of connection underlying different quantum states.
Authors: Keisuke Okamura
Understanding the statistical laws governing citation dynamics remains a fundamental challenge in network theory and the science of science. Citation networks typically exhibit in-degree distributions well approximated by log-normal distributions yet also display power-law behaviour in the high-citation regime -- an apparent contradiction lacking a unified explanation. Here we identify a previously unrecognised phenomenon: the variance of the logarithm of citation counts per unit time follows a power law with respect to time ($t$) since publication, scaling as $t^{H}$, with $H$ constant. This discovery introduces a new challenge while simultaneously offering a crucial clue to resolving this discrepancy. We develop a stochastic model in which latent attention to publications evolves through a memory-driven process with cumulative advantage, modelled as fractional Brownian motion with Hurst parameter $H$ and volatility. We show that antipersistent fluctuations in attention ($H < 1/2$) yield log-normal citation distributions, whereas persistent attention dynamics ($H > 1/2$) favour heavy-tailed power laws, thus resolving the log-normal--power-law contradiction. Numerical simulations confirm both the $t^{H}$ law and the transition between regimes. Empirical analysis of arXiv e-prints indicates that the latent attention process is intrinsically antipersistent ($H \approx 0.13$). By linking memory effects and stochastic fluctuations in attention to broader network dynamics, our findings provide a unifying framework for understanding the evolution of collective attention in science and other attention-driven processes.
Authors: Yuanzhu Huang, Yang Zhou
We present a method to compute the symmetry-resolved entanglement entropy of spherical regions in higher-dimensional conformal field theories. By employing Casini-Huerta-Myers mapping, we transform the entanglement problem into thermodynamic calculations in hyperbolic space. This method is demonstrated through computations in both free field theories and holographic field theories. For large hyperbolic space volume, our results reveal a universal expansion structure of symmetry-resolved entanglement entropy, with the equipartition property holding up to the constant order. Using asymptotic analysis techniques, we prove this expansion structure and the equipartition property in arbitrary dimensions.
Authors: Pawel Szczypkowski, Adrian Makowski, Wojciech Zwoliński, Katarzyna Prorok, Piotr Wasylczyk, Artur Bednarkiewicz, Radek Lapkiewicz
While scattered light conveys most of the information we perceive, scattering may also distort that information before it reaches our detectors. The problem is acute in many applications, such as in high-resolution microscopy of biological tissue, where scattering degrades both resolution and signal-to-noise ratio. Here, for the first time, we demonstrate that uniting two intrinsic properties of scattered light: speckle statistics and the angular memory effect, with highly non-linear optical response yields, rather surprisingly, super-resolution, low-background, non-invasive imaging of objects completely hidden behind a strongly scattering, opaque layer. Crucially, our technique of non-invasive imaging through scatterers does not resort to wavefront shaping, adaptive optics, complicated optical setups, or iterative image reconstruction algorithms. Because the strategy relies solely on the properties of scattered light and high-order nonlinear response of the fluorophores, it can be applied to any speckle-forming propagation, from biological tissue to multicore fibres, combined with any type of phenomenon that exhibits a sufficiently high order nonlinearity.
Authors: Jeffrey Giansiracusa, David Lanners, Tin Sulejmanpasic
We numerically study $\mathbb{Z}_N$ lattice gauge theories in 4D as prototypical models of systems with $\mathbb{Z}_N$ 1-$\textit{form symmetry}$. For $N \geq 3$, we provide evidence that such systems exhibit not only the expected phases with spontaneously broken/restored symmetry but also a third photon phase. When present, the 1-form symmetry provides a precise notion of confinement, and it is commonly believed that confinement ensues due to the proliferation of extended, string-like objects known as $\textit{center vortices}$, which carry a $\mathbb{Z}_N$ flux. However, this picture is challenged by the three-phase scenario investigated here. We show that both the confined and the photon phases are associated with the proliferation of center vortices and that the key difference between them lies in whether or not vortex-junctions - the $\textit{monopoles}$ - proliferate.
Authors: Akke Mats Houben
Evolution equations of the amplitudes of heterogeneous states (associative memories) stored in the connectivity of distributed systems with non-local interactions are derived. The resulting system of coupled amplitude equations describes the spatio-temporal dynamics of memory recall. It is shown that these types of distributed systems perform pattern completion and selection, and that short-range connections afford spatio-temporal memory pattern dynamics taking the form of patterning fronts.
Authors: Madhumita Rano, Henrik R. Larsson
To understand the dynamics of quantum many-body systems, it is essential to study excited eigenstates. While tensor network states have become a standard tool for computing ground states in computational many-body physics, obtaining accurate excited eigenstates remains a significant challenge. In this work, we develop an approach that combines the inexact Lanczos method, which is designed for efficient computations of excited states, with tree tensor network states (TTNSs). We demonstrate our approach by computing excited vibrational states for three challenging problems: (1) 122 states in two different energy intervals of acetonitrile (12-dimensional), (2) Fermi resonance states of the fluxional Zundel ion (15-dimensional),and (3) selected excited states of the fluxional and very correlated Eigen ion (33-dimensional). The proposed TTNS inexact Lanczos method is directly applicable to other quantum many-body systems.
Authors: Matthew D Butler, Benjamin J Walker, Thomas Montenegro-Johnson, Panayiota Katsamba
Active deformable filaments exhibit a large range of qualitatively different three-dimensional dynamics, depending on their flexibility, the strength and nature of the active forcing, and the surrounding environment. We investigate the dynamic behaviour of elastic, chemically propelled phoretic filaments, combining two existing models; a local version of slender phoretic theory, which determines the resulting slip flows for chemically propelled filaments with a given shape and chemical patterning, is paired with a computationally efficient method for capturing the elastohydrodynamics of a deformable filament in viscous flow to study the chemoelastohydrodynamics of filaments. As the activity increases, or equivalently the filament stiffness decreases, these filaments undergo buckling instabilities that alter their behaviour from rigid rods. We follow their behaviour well beyond the buckling threshold to find a rich array of dynamics. Through two illustrative examples, we conduct initial-value simulations that show that, as the stiffness of the filament is decreased, the dynamic behaviour moves from rigid motion to planar buckling, through an out-of-plane transition, eventually reaching diffusive-like behaviours for very deformable filaments.
Authors: Abbas K. Rizi
The term emergence is increasingly used across scientific disciplines to describe phenomena that arise from interactions among a system's components but cannot be readily inferred by examining those components in isolation. While often invoked to explain higher-level behaviors, such as flocking, synchronization, or collective intelligence, the term is frequently used without precision, sometimes giving rise to ambiguity or even mystique. In this perspective paper, we clarify the scientific meaning of emergence as a measurable and physically grounded phenomenon. Through concrete examples, such as temperature, magnetism, and herd immunity in social networks, we review how collective behavior can arise from local interactions that are constrained by global boundaries. By refining the concept of emergence, we gain a clearer and more grounded understanding of complex systems. Our goal is to show that emergence, when properly framed, offers not mysticism but insight.
Authors: Matheus S. Mariano, José F. Fontanari
The dynamics of casual group formation has long been a subject of interest in social sciences. While early stochastic models offered foundational insights into group size distributions, they often simplified individual behaviors and lacked mechanisms for heterogeneous social appeal. Here, we re-examine the attractiveness-driven interaction model, an agent-based framework where point-like agents move randomly in a 2D arena and exhibit varied social appeal, leading them to pause near highly attractive celebrity peers. We compare this model to a null model where the agents are continuously in movement, which resembles a Random Geometric Graph. Our extensive simulations reveal significant structural and dynamic differences: unlike the null model, the attractiveness-driven model's average degree increases linearly with system size for fixed density, resulting in more compact groups and the suppression of a percolation transition. Crucially, while the null model's group size distribution is either exponentially decaying or bimodal, the attractiveness-driven model robustly exhibits a power-law distribution, $P(n) \propto n^{-2.5}$, with an exponent independent of density. These findings, obtained through computationally intensive simulations due to long equilibration times, offer a thorough quantitative characterization of this model, highlighting the critical role of individual attractiveness in shaping social aggregation in physical space.
Authors: Neil Dowling, Jacopo De Nardis, Markus Heinrich, Xhek Turkeshi, Silvia Pappalardi
Unitary randomness underpins both fundamental tasks in quantum information and the modern theory of quantum chaos. On one side, a central concept is that of approximate unitary designs: circuits that look random according to small moments and for forward-in-time protocols. In a distinct setting, out-of-time-ordered correlators (OTOCs), intensely studied as a measure of information scrambling, have recently been shown to probe freeness between Heisenberg operators, the noncommutative generalization of statistical independence. Bridging these two concepts, we study the emergence of freeness in a random matrix product unitary ensemble. We prove that, with only polynomial bond dimension, these unitaries reproduce Haar values of higher-order OTOCs for local, finite-trace observables, while traceless observables instead require exponential resources. Indeed, local observables are precisely those predicted to thermalize in chaotic many-body systems according to the eigenstate thermalization hypothesis. Moreover, adding to previous literature, we show how random matrix product unitaries constitute approximate designs: we exactly compute the frame potential of the ensemble, showing convergence to the Haar value with polynomial deviations and so indicating that global observables are freely independent on-average. Our results highlight the need to refine previous notions of unitary design in the context of operator dynamics, guiding us towards protocols for quantum advantage and shedding light on the emergent complexity of chaotic many-body systems.
Authors: Yoshiki Fukusumi, Shinichiro Yahagi
We introduce a general method for realizing simple current extensions of the conformal field theories. We systematically obtain the $Z_{N}$ symmetry extended fusion ring of bulk and chiral theories and the corresponding modular partition functions with nonanomalous subgroup $Z_{n}(\subset Z_{N})$. The bulk (or nonchiral) fusion ring provides fundamental algebraic data for conformal bootstrap, and the chiral fusion ring provides fundamental data for the graded symmetry topological field theories. The latter also provides algebraic data of smeared boundary conformal field theories describing zero modes of the extended models. For more general multicomponent or coupled systems, we also obtain a new series of extended theories. By applying the folding trick to the resultant coupled theories, their partition functions correspond to charged or gapped domain walls or massless renormalization group flows preserving quotient group structures. This work opens new research directions in studying the classification of conformal field theories and the corresponding topological quantum field theories (or topological orders) by establishing the traditional methods in abstract algebra and modular form.
Authors: Anatoly Efimov, Chun-Chieh Chang, Simo Pajovic, Wilton J.M. Kort-Kamp, Dongsung Kim, Hou-Tong Chen, Diego A. R. Dalvit, Abul K. Azad
Kirchhoff's law of thermal radiation, which dictates that the emissivity of a surface equals its absorptivity under thermal equilibrium, which dictates that the emissivity of a surface equals its absorptivity under thermal equilibrium, fundamentally limits the efficiency of photonic systems by enforcing reciprocal energy exchange between source and detector. Breaking this reciprocity is particularly important for advancing photonic devices for energy conversion, radiative cooling, and mid-infrared sensing and imaging. Driven by the growing need for photonic platforms to overcome reciprocity constraints, we present the first demonstration of spatiotemporally modulated nonreciprocal metasurfaces operating at mid-infrared frequencies suitable for the violation of the Kirchhoff's law at room temperature. We fabricate a graphene-based integrated photonic structure and experimentally demonstrate nonreciprocal reflection from a metasurface modulated at gigahertz frequencies. We develop a theoretical framework to relate nonreciprocal scattering under spatiotemporal modulation with unequal absorptivity and emissivity for violation of the spectral directional Kirchhoff's law. Our experiment and theory imply effective decoupling of absorption and emission channels by breaking time-reversal symmetry at thermal wavelengths.
Authors: Diyath Pannipitiya, Roland Roeder
Let $Z_n(z,t)$ denote the partition function of the $q$-state Potts Model on the rooted binary Cayley tree of depth~$n$. Here, $z = {\rm e}^{-h/T}$ and $t = {\rm e}^{-J/T}$ with $h$ denoting an externally applied magnetic field, $T$ the temperature, and $J$ a coupling constant. One can interpret $z$ as a ``magnetic field-like'' variable and $t$ as a ``temperature-like'' variable. Physical values $h \in \mathbb{R}$, $T > 0$, and $J \in \mathbb{R}$ correspond to $t \in (0,\infty)$ and $z \in (0,\infty)$. For any fixed $t_0 \in (0,\infty)$ and fixed $n \in \mathbb{N}$ we consider the complex zeros of $Z_n(z,t_0)$ and how they accumulate on the ray $(0,\infty)$ of physical values for $z$ as $n \rightarrow \infty$. In the ferromagnetic case ($J > 0$ or equivalently $t \in (0,1)$) these Lee-Yang zeros accumulate to at most one point on $(0,\infty)$ which we describe using explicit formulae. In the antiferromagnetic case $(J < 0$ or equivalently $t \in (1,\infty)$) these Lee-Yang zeros accumulate to finitely many points of $(0,\infty)$, which we again describe with explicit formulae. The same results hold for the unrooted Cayley tree of branching number two. These results are proved by adapting a renormalization procedure that was previously used in the case of the Ising model on the Cayley Tree by Müller-Hartmann and Zittartz (1974 and 1977), Barata and Marchetti (1997), and Barata and Goldbaum (2001). We then use methods from complex dynamics and, more specifically, the active/passive dichotomy for iteration of a marked point, along with detailed analysis of the renormalization mappings, to prove the main results.
Authors: Nathan Benjamin, Suzanne Bintanja, Yu-Jui Chen, Michael Gutperle, Conghuan Luo, Dikshant Rathore
We construct generalized symmetries in two-dimensional symmetric product orbifold CFTs $\text{Sym}^N(\mathcal{T}),$ for a generic seed CFT $\mathcal{T}$. These symmetries are more general than the universal and maximally symmetric ones previously constructed. We show that, up to one fine-tuned example when the number of copies $N$ equals four, the only symmetries that can be preserved under twisted sector marginal deformations are invertible and maximally symmetric. The results are obtained in two ways. First, using the mathematical machinery of $G$-equivariantization of fusion categories, and second, via the projector construction of topological defect lines. As an application, we classify all preserved symmetries in symmetric product orbifold CFTs with the seed CFT given by any $A$-series $\mathcal{N}=(2,2)$ minimal model. We comment on the implications of our results for holography.
Authors: Philipp Stammer
Lasers provide intense coherent radiation, essential to cool and trap atoms into a Bose-Einstein condensate or can alternatively drive the non-linear dynamics of high-order harmonic generation. Yet, these two fundamental processes remained of independent consideration. Here, we connect matter waves at ultracold temperatures with radiation bursts on the ultrafast attosecond timescale. We do this by exploring high harmonic generation from a Bose-Einstein condensate. We show that the quantum state of the generated harmonics of a driven Bose gas is a classical mixture, while below the critical temperature of Bose-Einstein condensation the emitted harmonic radiation is in a pure quantum state. These states furthermore exhibit squeezing and entanglement across all field modes.
Authors: Atma Anand
Information-processing systems coordinating across multiple agents and objectives face fundamental thermodynamic constraints. We show that solutions with maximum utility to act as coordination focal points have much higher selection pressure for being findable across agents rather than accuracy. We derive that the information-theoretic minimum description length of coordination protocols to precision $\varepsilon$ scales as $L(P)\geq NK\log_2 K+N^2d^2\log (1/\varepsilon)$ for $N$ agents with $d$ potentially conflicting objectives and internal model complexity $K$. This scaling forces progressive simplification, with coordination dynamics changing the environment itself and shifting optimization across hierarchical levels. Moving from established focal points requires re-coordination, creating persistent metastable states and hysteresis until significant environmental shifts trigger phase transitions through spontaneous symmetry breaking. We operationally define coordination temperature to predict critical phenomena and estimate coordination work costs, identifying measurable signatures across systems from neural networks to restaurant bills to bureaucracies. Extending the topological version of Arrow's theorem on the impossibility of consistent preference aggregation, we find it recursively binds whenever preferences are combined. This potentially explains the indefinite cycling in multi-objective gradient descent and alignment faking in Large Language Models trained with reinforcement learning with human feedback. We term this framework Thermodynamic Coordination Theory (TCT), which demonstrates that coordination requires radical information loss.
Authors: Jacquelyn Ho, Yue-Hui Lu, Tai Xiang, Tsai-Chen Lee, Zhenjie Yan, Dan M. Stamper-Kurn
Higher symmetries in interacting many-body systems often give rise to new phases and unexpected dynamical behavior. Here, we theoretically investigate a variant of the Dicke model with higher-order discrete symmetry, resulting from complex-valued coupling coefficients between quantum emitters and a bosonic mode. We propose a driven-dissipative realization of this model focusing on optomechanical response of a driven atom tweezer array comprised of $n$ sub-ensembles and placed within an optical cavity, with the phase of the driving field advancing stepwise between sub-ensembles. Examining stationary points and their dynamical stability, we identify a phase diagram for $n\geq 3$ with three distinctive features: a $\mathbb{Z}_n$ ($\mathbb{Z}_{2n}$) symmetry-breaking superradiant phase for even (odd) $n$, a normal unbroken-symmetry phase that is dynamically unstable due to non-reciprocal forces between emitters, and a first-order phase transition separating these phases. This $n$-phase Dicke model may be equivalently realized in a variety of optomechanical or opto-magnonic settings, where it can serve as a testbed for studying high-order symmetry breaking and non-reciprocal interactions in open systems.
Authors: Ethan Lake
We refine an old idea for performing fault-tolerant error correction in topological codes by simulating confining interactions between excitations. We implement confinement using an array of local classical processors that measure syndromes, broadcast messages to neighboring processors, and move excitations using received messages. The dynamics of the resulting real-time decoder is geometrically local, homogeneous in spacetime, and self-organized, operating without any form of global control. We prove that below a threshold error rate, it achieves a memory lifetime scaling as a stretched exponential in the linear system size $L$, provided that it has access to $O({\rm polylog}(L))$ noiseless classical bits for each noisy qubit. When applied to the surface code subject to depolarizing noise and measurement errors of equal strength, numerics indicate a threshold at $p_c \approx 1.5\%$.
Authors: Riek H. Rüstemeier, H. P. Ojeda Collado, Ludwig Mathey
The field of coherent electronics aims to advance electronic functionalities by utilizing quantum coherence. Here, we demonstrate a viable and versatile methodology for controlling electron dynamics optically in graphene nanoribbons. In particular, we propose to flatten the band structure of armchair graphene nanoribbons via control electrodes, arranged periodically along the extended direction of the nanoribbon. This addresses a key mechanism for dephasing in solids, which derives from the momentum dependence of the energy gap between the valence and the conduction band. We design an optimal driving field pulse to produce collective Rabi oscillations between these bands, in their flattened configuration. As an example for coherent control, we show that these optimized pulses can be used to invert the entire electronic band population by a $\pi$ pulse in a reversible fashion, and to create a superposition state via a $\pi/2$ pulse, which generates an alternating photocurrent. Our proposal consists of a platform and methodological approach to optically control the electron dynamics of graphene nanoribbons, paving the way toward novel coherent electronic and quantum information processing devices in solid-state materials.