Statistical Mechanics · Cross-listed from cs.LG
Capturing non-Markovian dynamics in non-equilibrium stochastic systems using flow matching
Bhargav Sriram Siddani, John B. Bell, Alejandro L. Garcia et al. (+1 more)
Hydrodynamic models of
stochastic particle systems represented by coarse-grained
stochastic partial differential equations (SPDE), such as the regularized Dean-Kawasaki (DK) equation, do not accurately capture the short-time system dynamics that is dominated by non-Markovian effects, and low particle density regimes where the distributions are highly non-Gaussian. We develop a generative flow matching method that directly models the probability distribution of fluxes from particle simulations that explicitly incorporates non-Markovian and non-Gaussian effects. As a demonstration, we use this method to simulate the Kramers first passage time problem for a system of non-interacting Brownian particles. We show the model accurately captures the short-time behavior and provides better predictions of the statistical moments of the number density when compared against the solution of the Markovian baseline, regularized DK equation.
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All authors Bhargav Sriram Siddani, John B. Bell, Alejandro L. Garcia, Ishan Srivastava
Statistical Mechanics · Cross-listed from quant-ph
Higher-order Symmetric Quantum Mpemba Effect in Fragmented Systems
Sreemayee Aditya, Sara Murciano and Xhek Turkeshi
A
quantum system can restore a broken
symmetry faster the more strongly it initially breaks it, an anomaly known as the
quantum Mpemba effect. Whether this effect survives once conservation laws fragment the
Hilbert space into exponentially many disconnected Krylov sectors has remained open. We address this question for
circuits and
Hamiltonians with simultaneous charge and dipole conservation, the paradigmatic setting for strong
Hilbert-space fragmentation. Combining a replica tensor-network formulation for charge and dipole-conserving gates, which reaches the annealed Rényi-2
entanglement asymmetry up to $L=128$, with
Hamiltonian simulations and an exactly solvable dissipative model, we uncover a higher-order symmetric
quantum Mpemba effect: the charge and dipole asymmetries each display Mpemba-like crossings on parametrically distinct timescales. Resolving the state into frozen and active Krylov sectors reveals the mechanism: frozen fragments retain a finite asymmetry that obstructs full restoration, while active fragments host the relaxation responsible for the crossings. Fragmentation thus does not preclude the
quantum Mpemba effect but reshapes it into frozen
memory and active-fragment relaxation, providing a framework for the Mpemba phenomenology of higher-moment
symmetries.
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Superconductivity
Charge density waves and enhanced superconductivity in the electron-hole gas: a plausible, simple, physically intuitive model
Carl A Kukkonen
A neutral degenerate
plasma of equal numbers of electrons and positively charged
fermions (holes) – the electron-hole gas – is studied using a simple, physically motivated two-parameter model (density r_s and mass ratio M/m). Two simplifying assumptions are made but not proven: the electron-hole correlation energy is approximately independent of density and does not affect the pressure or bulk modulus, and the electron-hole contribution to the local field factors is zero, allowing use of the known electron-gas local field factors. With these assumptions the phase diagram, instabilities, and effective interactions can be calculated for all mass ratios and densities using simple formulae, reproducible on a laptop. The key new physics is the additional screening provided by the mobile holes. A single function Delta appears in the denominator of all effective interactions and response functions. Near the zeros of Delta at q = 0 (compressibility instability) and at finite q, three phenomena are simultaneously enhanced: charge density waves (for M/m >= 4.97), a large T^2 electrical resistivity from electron-hole scattering, and an attractive electron-electron interaction that is the purely electronic analog of BCS electron-
phonon coupling. Crudely estimated superconducting transition temperatures approach room temperature, reaching approximately 275 K at M/m = 9. No claim is made that this model applies to any specific material. The aim is to provoke scrutiny of the assumptions, calculation of the unknown local field factors, and investigation of whether this minimal two-carrier framework maps onto real systems.
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Mesoscale and Nanoscale Physics
Non-Hermitian Crystalline Braid Topology from Hermitian Projection: A Zero-Mode Resonance Mechanism
Stefan {\DJ}or{\dj}ević and Vladimir Juričić
Non-Hermitian topological phases are typically engineered through gain and loss, nonreciprocity, or interaction with an environment. Here we show that they can instead emerge purely by projecting a fully Hermitian, topologically trivial parent
lattice onto an embedded subsystem. The mechanism is general: when a zero mode of the eliminated degrees of freedom couples to the retained subsystem, the
embedding self-energy develops a pole, the zero-frequency description becomes singular, and
topology is carried by the finite-frequency projected Green's function. We realize the mechanism exactly in a trivial nearest-neighbor square
lattice with an embedded one-dimensional zig-zag brane. In the periodic transverse geometry, the parity of the eliminated complement selects the outcome: even sectors reduce to a regular Schur complement and yield conventional SSH-type descendants, whereas odd sectors host a sublattice-imbalance zero mode and follow the resonant route. There, the complex bands braid through isolated finite-frequency exceptional points (EPs), while a parity
symmetry inherited from the
embedding, together with $\mathrm{TRS}^{\dagger}$, induces conjugated pseudo-Hermiticity and quantizes the complex Berry phase. The stable bulk invariant of the nondegenerate phases is this quantized complex Berry phase; adjacent sectors are separated by parity-paired exceptional points whose half-integer vorticities encode the local exchange of complex-energy strands.The absence of the non-Hermitian skin effect ensures that the invariant is defined directly on the ordinary Brillouin zone. A topolectrical implementation of the projected response predicts momentum-resolved transmission minima at the exceptional-point transition frequencies together with a characteristic low-frequency resonant admittance, providing an experimentally testable signature of the mechanism.
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Materials Science
Matching Terahertz and Hall Mobilities as a Hallmark of Intrinsic Charge Transport in Metal-Halide Perovskites
Dmitry R. Maslennikov, Ben P. Carwithen, Vladimir V. Bruevich et al. (+9 more)
Charge-carrier transport in soft-
lattice materials, including metal-halide perovskites, is often perceived to be highly heterogeneous across different length scales, and influenced by both the intrinsic (dynamic) thermal electronic disorder and extrinsic (static) disorder due to
crystal defects,
impurities, grain boundaries, and surface states. As a consequence, the reported carrier mobilities obtained by different electrical and optical measurement techniques frequently disagree, raising a critical question: can a truly intrinsic charge transport regime (that is, a regime not dominated by static disorder) extend across macroscopic single
crystals of these materials? Here, we demonstrate such a regime in an exemplary metal-halide perovskite system, epitaxial CsPbBr$_{3}$ single
crystals, where the local mobility obtained via optical pump-terahertz probe (OPTP) spectroscopy quantitatively agrees with the macroscopic transport mobility across a broad range of experimental conditions. Using a dedicated device platform that enables concurrent
Hall-effect and OPTP measurements on the same single-crystalline sample, we obtain consistent room-temperature mobilities of ~ 30 cm$^{2}$V$^{-1}$s$^{-1}$, among the highest reliably reported for CsPbBr$_{3}$. Both techniques reveal band-like temperature dependence of the hole mobility with similar power exponents, confirming that the same intrinsic transport mechanism governs the ultrafast/local and steady-state/macroscopic responses. These results show that defect-free charge transport is achievable in soft-
lattice perovskites on millimetre length scales and establish a robust methodology for benchmarking intrinsic mobility in emerging
semiconductors.
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All authors Dmitry R. Maslennikov, Ben P. Carwithen, Vladimir V. Bruevich, Yichao Cai, Davide Nodari, Navendu Mondal, Xijia Zheng, Beier Hu, Nicola Gasparini, Jarvist M. Frost, Vitaly Podzorov, Artem A. Bakulin
Materials Science
Temperature-Induced Crossover of Coherent Phonon Mechanisms in Chiral 2D Perovskites
Katherine A Koch, Matthew P Hautzinger, Matthew C Beard et al. (+1 more)
The coupling between electronic excitations and
lattice degrees of freedom fundamentally dictates the optoelectronic functionality of hybrid perovskites. While the potential energy surfaces (PESs) of the electronic excited states are typically considered static, albeit modulated by thermal disorder, the exact nature of their structural
evolution with temperature remains elusive. Here, we demonstrate that the excited-state structural reconfiguration in two-dimensional metal-halide perovskites is explicitly temperature-evolving, governed by
lattice compliance. We select a
chiral perovskite framework with an exceptionally large, temperature-dependent bond angle variance to maximize the structural compliance. Through phase-resolved resonant impulsive stimulated Raman scattering, we measure the coherent
phonon dynamics and resolve the real-time structural pathways of
exciton-
lattice dressing. We observe a temperature-induced crossover from field-driven Impulsive Stimulated Raman Scattering (ISRS) to population-driven Displacive Excitation of Coherent
Phonons (DECP). While momentum-driven ISRS pathways dominate at low temperatures, increasing thermal energy softens the
lattice and enhances coordinate-driven displacive pathways, allowing
excitons to sample steeper, highly anharmonic regions of the excited-state PES. Our results show that temperature can actively modulate the excited-state structural coordinates of flexible 2D frameworks, offering a practical strategy to tune
exciton-
lattice interactions in
chiral optoelectronics.
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All authors Katherine A Koch, Matthew P Hautzinger, Matthew C Beard, Ajay Ram Srimath Kandada
Other Condensed Matter · Cross-listed from quant-ph
Sensing ac fields with quantum many-body scars
Matheus Fibger, Andrei Tsypilnikov, Thiago R. de Oliveira et al. (+1 more)
Quantum many-body scars (MBS) exhibit weak ergodicity breaking and long-lived coherent dynamics within an otherwise thermal spectrum. We investigate their metrological properties using the
quantum Fisher information (QFI), focusing on estimating the amplitude of a weak AC field in the PXP model. We show that the approximately uniform energy spacing of the scar tower enables collective resonant processes when the driving frequency matches integer multiples of the scar gap, resulting in a quadratic-in-time growth of the QFI over an extended time window. We analyze how the connectivity induced by different probe operators shapes sensing performance and demonstrate that staggered magnetization leads to a more favorable growth of the QFI with system size than homogeneous magnetization. Through frequency scanning and finite-size analysis, we characterize the scaling of the QFI with the number of particles. Finally, we develop a single-tower approximation under resonant driving, deriving a compact analytical expression that captures the time dependence and system-size scaling of the QFI. Our results establish how to leverage structured non-ergodic dynamics in
quantum sensing protocols.
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All authors Matheus Fibger, Andrei Tsypilnikov, Thiago R. de Oliveira, Fernando Iemini
Strongly Correlated Electrons
Tensor network study of deconfined quantum criticality in a one-dimensional spin-phonon model
Anton Romen, Josef Willsher, David Hofmeier et al. (+2 more)
Deconfined
quantum critical points (DQCPs) describe continuous transitions between ordered phases beyond the Landau paradigm. A simple example is the Néel antiferromagnet (AFM) to valence bond solid (VBS) transition in a 1D
antiferromagnetic $J_1-J_2$ model. In analogy to the
spin-Peierls instability of critical
spin chains, DQCPs are predicted to be unstable towards
lattice distortions below a critical
phonon frequency. In this work, we use tensor network simulations to investigate this instability in the
antiferromagnetic $J_1-J_2$ model coupled to
lattice vibrations. We confirm the stability of DQCP for large
phonon frequencies and demonstrate that the transition turns strongly first-order below a critical frequency. The instability is caused by a reduction of the Luttinger parameter due to
spin-
phonon interactions and we identify the effective theory of the behavior as the double sine-Gordon model. The same effective theory is known to describe the classical Ashkin-Teller model, which enables us to show that the critical endpoint is in the four-state Potts universality class. We argue based on non-linear bosonization that the sign of the double-frequency term is fixed, which provides a microscopic justification for the first-order transition. Furthermore, we provide quantitative numerical scaling results for the
phonon spectral function, offering an experimental signature to probe DQCP-
phonon coupling in low-dimensional materials.
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All authors Anton Romen, Josef Willsher, David Hofmeier, Johannes Knolle, Michael Knap
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Quantum-stabilized patterns in a vector Hopfield network
Richard D. Barney, Sharba Bhattacharjee, Victor Galitski et al. (+2 more)
We introduce the
quantum vector Hopfield network, in which patterns are formed by orientations of
quantum vector
spins;
quantum dynamics arise intrinsically from the non-commutativity of the
spin operators. We derive the equations of state and the phase diagrams for this network as well as its classical counterpart. We find that
quantum fluctuations, surprisingly, stabilize the stored patterns. Both the critical
retrieval temperature and the target pattern overlap are enhanced relative to the classical network. Additionally, we find that this enhancement grows with pattern loading up to network capacity. We interpret this effect as an analog of
quantum order-by-disorder, a mechanism by which
quantum fluctuations promote the formation of ordered phases. These findings offer a new route to
quantum-enhanced associative
memory.
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All authors Richard D. Barney, Sharba Bhattacharjee, Victor Galitski, Kartiek Agarwal, Ivar Martin
Strongly Correlated Electrons
Bootstrap bounds for Quantum Spin Systems using String Operators
Nisarg Chadha, Michael G. Scheer and Eslam Khalaf
Bootstrap is a numerical many-body method that provides rigorous bounds on ground-state observables by imposing a set of necessary constraints on the expectation values of operators. The quality of the resulting bounds is sensitive to the choice of operators entering the constraints. In particular, bounds on ground-state correlations are often loose in spontaneous
symmetry-breaking (SSB) phases, since local operator sets cannot exclude domain-wall excitations. In this work, we introduce non-local, string-like operators into the bootstrap and show that the program can be formulated directly in thermodynamic limit. We then apply our construction to several 1D
spin models. First, we obtain a significant tightening of the bounds in the SSB phase of the 1D transverse-field Ising model. Using the 1D axial next-nearest-neighbor Ising model, we further show that this tightening allows for a quantitative estimate of the locations of phase boundaries. Finally, we generalize the string operators to the 1D $\mathbb{Z}_3$
chiral clock model and track the behavior of the bounds across the phase diagram. Our results broaden the class of constraints available to the bootstrap and open a route toward bootstrapping more general
symmetry-broken and topological phases, where the relevant constraints may involve non-local or extended operators.
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Mesoscale and Nanoscale Physics
Self-organized Floquet band geometry in cavity-driven quantum materials
Christopher Yang, Gil Refael, Mark S. Rudner et al. (+1 more)
Floquet engineering has emerged as a powerful route to dynamically control band structure and
topology in
quantum materials, but most implementations rely on externally imposed
laser fields that are power intensive, difficult to integrate into devices, and weakly coupled to the electronic system. We propose and analyze an alternative paradigm in which a self-generated cavity field Floquet-dresses the electronic bands and produces a
geometric Hall response in an electrically driven cavity material system. We consider a
semiconductor layer embedded in a cavity and coupled to external leads and a bath of acoustic
phonons, where dc pumping leads to the buildup of a coherent intracavity field through light-matter coupling. We determine the resulting nonequilibrium steady state self-consistently and show that, above threshold, the coupled system settles into a stable time-periodic limit cycle with a field amplitude set by the cavity quality factor and dissipation. This emergent periodic field Floquet-dresses the electronic bands and modifies the anomalous
Hall response of a material with broken time-reversal
symmetry. We demonstrate that the resulting
Hall conductivity can be directly probed via in-plane dc transport measurements. Our work establishes a route to self organized Floquet band reconstruction and
geometric transport without external
laser illumination, highlighting cavity driven steady states as a platform for electrically controlled nonequilibrium phases.
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All authors Christopher Yang, Gil Refael, Mark S. Rudner, Iliya Esin
Materials Science
Element-Specific Solute Trapping and Grain Structure Evolution during Laser Powder Bed Fusion of Multicomponent Alloys
Xinxin Yao, James Hanagan, Md Shafiqur Rahman Jame et al. (+5 more)
Under the rapid solidification conditions of
laser powder bed fusion (LPBF), solute trapping manifests in an element-specific manner, altering nonequilibrium partitioning, constitutional undercooling, and grain selection behavior in multicomponent
alloys. Here, we elucidate the mechanisms by which element-specific solute trapping governs nucleation behavior and grain structure
evolution during LPBF demonstrated on a SS316L. This requires quantitative description of nonequilibrium multicomponent thermodynamics and grain
evolution across broad LPBF solidification conditions, which is achieved through a CALPHAD-informed Gaussian Process Regression (GPR)-assisted Phase-Field (PF) approach. The predicted transitions in grain morphology and grain size are validated against EBSD measurements under multiple LPBF processing conditions. Results demonstrate that increasing solidification rate drives a composition-dependent transition from solute
diffusion-controlled nucleation to solute trapping-controlled grain growth, where nonequilibrium solute redistribution intensified by solute trapping suppresses equiaxed grain formation despite high cooling rates. Quantitative decomposition of multicomponent undercooling further reveals distinct element-specific sensitivities to solute trapping, where C, Cr, and Mo remain dominant contributors to the overall undercooling, while the undercooling contribution of low-partitioning elements such as S and P are strongly suppressed relative to their
equilibrium values under rapid solidification conditions. These results reveal how element-specific solute trapping governs grain selection in multicomponent
alloys, providing a mechanistic basis for
alloy design under nonequilibrium solidification conditions.
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All authors Xinxin Yao, James Hanagan, Md Shafiqur Rahman Jame, Mallikharjun Marrey, Mohsen Taheri Andani, Raymundo Arróyave, Veera Sundararaghavan, Lei Chen
Superconductivity · Cross-listed from quant-ph
Amplitude-dependent quantum hydrodynamics from a \(\coth\)-Madelung ansatz
C. Dedes
We investigate a nonlinear extension of the Madelung transformation based on a
hyperbolic phase–amplitude coupling of the form \[ \Psi = R e^{\imath\theta \coth R}, \] where \(R\) is a real amplitude field and \(\theta\) is an auxiliary phase coordinate governed by Schrödinger's equation. In contrast to the conventional polar decomposition, this construction imposes a singular
hyperbolic relation between amplitude and phase, thereby endowing the Bohmian or hydrodynamic description with an intrinsically
geometric structure. We show that the associated velocity field acquires a density-gradient contribution, producing generalized continuity equations and modified
quantum force terms. When interpreted as a complex macroscopic order parameter, this generalized phase structure leads to modified superconducting electrodynamics; in particular, the London equations acquire additional contributions that render the Meissner response sensitive to spatial density gradients. The proposed framework is motivated by broader developments involving complex group velocities, dissipative wave propagation, and amplitude-sensitive transport in
quantum systems.
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Mesoscale and Nanoscale Physics
Coherent room-temperature dipole synchronization in nanocavity sheets
Rakesh Arul, Piper Fowler-Wright, Lille Borresen et al. (+3 more)
Plasmonic nanocavities enable the synchronization of spatially distant emissive dipoles through strong near-field coupling in sub-nm gaps. We report formation of a room-temperature synchronized dipole state in locally-ordered plasmonic nanogap 2D arrays under non-resonant continuous-wave pumping. Unlike
lasers, photonic Bose-Einstein condensates, or
exciton-polariton condensates, this system exhibits spatial coherence across the dipoles, while rapid radiative and non-radiative emission suppresses temporal
photon coherence. A change of behaviour is observed with increasing pumping, marked by the spatial spread of g(1) coherence, but without spectral narrowing or directional emission. This driven-dissipative system exhibits fast temporal coherence decay and complex spatial correlations, offering a new platform for studying synchronization at room temperature. Combining ultralow mode volumes, high Purcell enhancement, and scalable ambient operation, it opens pathways for novel photonic and
quantum technologies.
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All authors Rakesh Arul, Piper Fowler-Wright, Lille Borresen, Brendon W. Lovett, Jonathan Keeling, Jeremy J. Baumberg
Strongly Correlated Electrons
Enhancement of charge correlations and real-space topological marker on an interacting non-Hermitian Su-Schrieffer-Heeger model
Sebastião dos A. Sousa-Júnior, Pedro B. Melo, Rubem Mondaini et al. (+2 more)
We investigate the interacting non-Hermitian Su-Schrieffer-Heeger (SSH) model, focusing on the interplay between
topology and charge ordering. Using a real-space topological marker, charge correlations, and the complex many-body spectrum, we map out the phase diagram under periodic and open boundary conditions. We show that the topological marker remains a robust diagnostic of non-Hermitian topological phases in the presence of interactions and consistently signals their breakdown at the onset of a charge density wave (CDW). We further demonstrate that non-Hermiticity enhances interaction effects: While moderate changes occur under periodic boundary conditions, open boundary conditions lead to a pronounced amplification of staggered charge correlations near exceptional points. This enhancement arises from the accumulation of low-energy states near exceptional points, which promotes electronic instabilities and strengthens CDW tendencies.
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All authors Sebastião dos A. Sousa-Júnior, Pedro B. Melo, Rubem Mondaini, Arnob Kumar Ghosh, Rodrigo Arouca
Mesoscale and Nanoscale Physics
Superconducting triode effect in a quantum-dot Josephson junction with a biased top gate
Yu-Hang Li, Xiaan Du, Hua Jiang et al. (+1 more)
Non-reciprocal supercurrents enable non-dissipative rectification, holding great promise for superconducting electronics. Conventionally, this non-reciprocity, termed the superconducting diode effect, requires the simultaneous breaking of time-reversal and parity
symmetries. Here, we propose a superconducting triode effect in an asymmetric
quantum-dot Josephson junction coupled to an additional metallic top gate, which breaks the parity
symmetry while explicitly preserving time-reversal
symmetry. We demonstrate that the supercurrent across this junction exhibits a strong non-reciprocal effect that can be continuously manipulated via the top gate to achieve an ideal unidirectional supercurrent, thus manifesting a superconducting triode effect. Furthermore, under
radio-frequency radiation, this junction exhibits highly asymmetric Shapiro steps, realizing fully quantized supercurrent rectification. Our work not only provides an alternative physical mechanism for the superconducting diode effect observed in Josephson junctions with explicit time-reversal
symmetry, but also introduces a new tuning knob to manipulate supercurrent non-reciprocity.
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All authors Yu-Hang Li, Xiaan Du, Hua Jiang, X. C. Xie
Quantum Gases · Cross-listed from quant-ph
Energy-Modulated Time-Asymmetric Spontaneous Collapse: Forward-Backward Dynamics from Stochastic Ito Reversal and Bright Solitons
Ikechukwu C. Okoro, Mike O. Osiele and Godfrey E. Akpojotor
We present a rigorous theoretical framework for
symmetry breaking and
quantum irreversibility arising from
stochastic Ito field reversal within a cubic-quintic nonlinear Schrodinger equation (CQ-NLSE) formalism. Starting from three physically motivated considerations, forward and backward nonlinear
stochastic differential equations are derived via the Ito calculus. Kinematic time-reversal is shown to be fundamentally incompatible with the Ito
stochastic structure, yielding the universal asymmetry-coupling parameter of 2/3. An energy-driven collapse operator proportional to the product of noise strength, local probability density, and excitation energy squared is introduced, amplifying the collapse in high-density, high-excitation regions. Exactly bright
soliton solutions are obtained for a quasi-one-dimensional BEC of attractive Li-7 atoms, with forward and backward amplitude ratio of 1.870. Heat map analysis of the parameter planes reveals that the forward collapse operator grows monotonically in time while the backward counterpart decays, achieving a ratio approximately 1030, sharply distinguishing this framework from conventional symmetric collapse models.
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Mesoscale and Nanoscale Physics
1/3 Fractional and Gapless Integer Quantum Anomalous Hall States in Rhombohedral Graphene
Jackson P. Butler, Tonghang Han, Andrew DiFabbio et al. (+6 more)
The fractional
quantum anomalous
Hall (FQAH) effect occurs in moiré superlattices in both twisted
bilayer MoTe$_2$ and rhombohedral $n$-layer
graphene aligned to hexagonal boron nitride (R$n$G/hBN) as a novel
quantum phase driven by intertwined electron correlation and
topology. Although several fractional states in the Jain sequence have been identified, the $1/3$ state, the most robust and fundamental state in conventional fractional
quantum Hall (FQH) systems, was missing in either FQAH system. Determining whether it exists would have a major impact on understanding the mechanism of FQAH, especially in the theoretically still-debated R$n$G/hBN system. Here we report the FQAH effect at moiré filling factor $\nu = 1/3$ in R$5$G/hBN moiré superlattice devices, through a combination of
quantum capacitance and transport measurements. By tuning the displacement field, we observed a topological phase transition from a $1/3$ fractional Chern
insulator (FCI) to a trivial charge density wave state. With the inclusion of the $1/3$ state, the FQAH states in R$5$G/hBN now exhibit a surprising level of particle-hole
symmetry about half-filling, closely resembling the behavior of FQH states in the lowest Landau level. Additionally, we perform compressibility and transport measurements at a filling of one electron per moiré unit
cell, $\nu =1$, and also for $\nu \lesssim 1$, where previous transport measurements displayed the extended
quantum anomalous
Hall (EQAH) effect. While our transport measurements show no change between the integer
quantum anomalous
Hall state (IQAH) and the EQAH region, compressibility measurements reveal a distinct transition from a gapped IQAH state to a gapless and highly compressible EQAH state. Our direct thermodynamic characterization of the rich phase diagram paves the way to engineering of anyon braiding and non-Abelian quasiparticles at zero
magnetic field.
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All authors Jackson P. Butler, Tonghang Han, Andrew DiFabbio, Zach Hadjri, Emily Aitken, Kenji Watanabe, Takashi Taniguchi, Long Ju, Raymond C. Ashoori
Superconductivity
Particle-Hole Ghost Interference in Superconductors
Archisman Panigrahi, Vladislav Poliakov and Leonid Levitov
Mirror-assisted optical interference can improve the fidelity of Young's double-slit interference. Here we discuss an electron analogue: particle-hole interference in
superconductors produced by a single
impurity near a line defect, terrace edge, or phase boundary. Quasiparticle waves scattered directly from the
impurity interfere with waves reflected by the boundary, generating a “ghost” interference pattern that combines conventional $2k_F$ Friedel oscillations with additional
hyperbolic fringes. Compared to the recently studied two-
impurity Young's interference, this effect appears already at first order in the
impurity potential and is therefore parametrically stronger. The resulting spatial modulation extends beyond $\lambda_F/2$ and is directly sensitive to the quasiparticle structure of the paired state, including possible
Fermi-surface anisotropy of the superconducting order parameter. These findings point to boundary-assisted
impurity interference as a robust local probe of superconducting electronic order, with clear signatures accessible to STM/STS measurements.
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Mesoscale and Nanoscale Physics
Quantum Thermal Logic Gates
Shuvadip Ghosh, Arnab Ghosh, Bivas Dutta et al. (+1 more)
We propose a new concept for
quantum thermal logic gates – analogous to classical electronic logic gates – that exploit the heat current in a coupled
quantum-dot system tunnel-coupled to metallic thermal reservoirs for logic operations in
quantum circuits. We obtained a remarkable one-to-one correspondence with the structure of classical electronic logic gate
circuits. An experimental setup is presented that demonstrates a realizable nano-electronic
quantum circuit architecture for implementing such
quantum thermal logic operations.
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All authors Shuvadip Ghosh, Arnab Ghosh, Bivas Dutta, Papiya Maity
Strongly Correlated Electrons
Dynamic nanoscale structural correlations in strontium ruthenate
M. Spaić, R. Spieker, I. Bilonić et al. (+14 more)
Strontium ruthenate (Sr$_2$RuO$_4$, SRO) has been the subject of intense research as a model quasi-two-dimensional metal with strong electronic correlations and potential exotic multi-component
superconductor. Yet the nature of the superconducting state and its emergence remain debated, despite highly detailed knowledge of the normal-state electronic properties. Here we use diffuse
neutron and x-ray scattering to uncover self-organized structural fluctuations on the picosecond timescale in SRO. We show that these nanoscale correlations do not originate from extrinsic disorder but rather involve cooperative displacements of oxygen atoms in the quintessential RuO$_2$ planes. Moreover, the observed displacement pattern is consistent with distortions due to incipient orbital order that we obtain in first-principles calculations, which suggests that orbital effects could play a pivotal role in the physics of SRO. Similar dynamic correlations may play a role in the physical properties of a wide range of prominent
oxides with closely-related lamellar structures, such as the cuprates and nickelates.
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All authors M. Spaić, R. Spieker, I. Bilonić, A. Paul, B. Krohnke Orquera, X. He, E. Topić, A. Minelli, F. Ye, N. Kikugawa, D. Sokolov, M. J. Krogstad, S. Rosenkranz, R. Osborn, T. Birol, M. Greven, D. Pelc
Materials Science
PolyGraphPy: A unified Python framework for atomistic simulation and machine learning-driven polymer design
João G. C. S. Duarte, Shruti Venkatram, Morgan Cencer et al. (+2 more)
Polymers are indispensable materials with daily applications ranging from electronics to medicine, owing to their versatility, which can be tailored by adjusting their chemical composition and architecture. The design space for these compounds is vast and governed by factors such as monomer classes, copolymer configurations (e.g., linear, branched, random, and alternating), chain size, stoichiometry, and material properties (e.g., density, refractive index, solubility, and Poisson's ratio). Thus, its exploration requires efficient computational methodologies for
polymer science. To address this challenge, this paper introduces PolyGraphPy, an open-source, unified Python framework that integrates atomistic simulations with machine learning for accurate property prediction and property-guided
polymer design. The framework automates
quantum mechanics calculations using Density Functional Tight Binding (DFTB+) to efficiently construct structured
datasets for monomers, homopolymers, and alternating copolymers. For property prediction, PolyGraphPy employs
Bayesian Graph Neural Networks (GNNs) utilizing
stochastic graph representations to predict target properties-such as static polarizability, while providing robust uncertainty quantification. Furthermore, the platform incorporates two complementary generative models for the de novo design of targeted molecules: a SELFIES-based Generative Pre-trained
Transformer (GPT) and a Genetic
Algorithm (GA) based on BRICS graph fragmentation. Demonstrated on a
dataset of acrylates, PolyGraphPy provides a highly customizable, end-to-end pipeline that reduces computational costs and accelerates data-driven
polymer informatics.
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All authors João G. C. S. Duarte, Shruti Venkatram, Morgan Cencer, Traian Dumitricǎ, Ketson R. M. dos Santos
Disordered Systems and Neural Networks
Nonreversible Gauge Fields in Fokker–Planck Dynamics: Supersymmetric Hamiltonians and Learned Finite Forces
Masayuki Ohzeki
We formulate stationary-density-preserving nonreversible perturbations of Fokker–Planck dynamics as gauge fields that deform relaxation spectra while leaving the invariant state fixed. When detailed balance holds, a similarity transformation maps the reversible Fokker–Planck operator to a Witten-
Laplacian-type supersymmetric
Hamiltonian; nonreversible gauges then appear as non-Hermitian perturbations that preserve the zero mode but modify the excited spectrum. This operator viewpoint gives a common
language for relaxation gaps, circulating probability currents, hypocoercive acceleration, and finite control costs. We represent admissible gauge currents by antisymmetric tensor fields and identify the detailed-balance-violating Ohzeki–Ichiki force as a constant
symplectic example whose infinite-strength limit is
Hamiltonian dynamics. The continuous-time spectral gap alone does not select a finite gauge strength, so we introduce a finite-time regularized objective and an actor–critic procedure for learning the gauge. An exactly solvable anisotropic Gaussian Ornstein–Uhlenbeck
benchmark separates the spectral transition from the finite-time optimum and shows that the learned gauge recovers the Lyapunov-equation optimum. A double-well
benchmark then illustrates the same constrained selection in a nonconvex metastable landscape.
Stochastic gradient methods enter this framework as physically relevant Fokker–Planck systems: mini-batch noise acts as an effective
diffusion tensor, and adaptive methods such as Adam correspond to metric choices with possible nonequilibrium currents.
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Strongly Correlated Electrons
Revealing quantum geometry effects in magic angle twisted bilayer graphene using the circular photogalvanic effect
Eylon Persky, Leonie Parisot, Minhao He et al. (+7 more)
Magic-angle twisted
bilayer graphene (MATBG) hosts flat bands whose correlated and topological phases depend sensitively on the electronic point-group
symmetry, which is set by the device configuration including twist angle, heterostrain, and substrate and cap-layer coupling. Here we report near-infrared photocurrent measurements of a MATBG device encapsulated by an hBN substrate and a WSe$_2$ cap layer, at a twist angle of 1.05{\deg}. Using spatially resolved photocurrent imaging with polarization analysis, we disentangle the photothermoelectric response from the circular photogalvanic effect (CPGE) across all fillings of the moiré flat bands. A finite CPGE at normal incidence, forbidden in high-
symmetry structures, directly constrains the point-group
symmetry of MATBG and reveals a Berry
curvature dipole intrinsic to the MATBG flat bands, activated by the
symmetry lowering from heterostrain and the asymmetric hBN/WSe$_2$ environment. Our results establish nonlinear photocurrent as an all-optical probe of
symmetry and
quantum geometry in proximity-engineered moiré materials.
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All authors Eylon Persky, Leonie Parisot, Minhao He, Jiaqi Cai, Takashi Taniguchi, Kenji Watanabe, Pierre A. Pantaleon, Francisco Guinea, Xiaodong Xu, Aharon Kapitulnik
Statistical Mechanics
A closed system setting for quantum thermalisation in free fermions
Purvaash Panduranghan-Udhayashankar, Filiberto Ares and Pasquale Calabrese
We study thermalisation and the possible occurrence of the Mpemba effect in a closed
quantum setting that mimics the interaction of a system with thermal reservoirs coupled only at its boundaries. Specifically, we consider a tripartite geometry in which a finite chain, initially prepared at a finite temperature, is suddenly connected on both sides to two semi-infinite chains of the same nature held at a different temperature. These outer chains act as thermal baths, while the full system evolves unitarily under a homogeneous
Hamiltonian. This setup provides a simple
quantum realisation of a temperature quench and closely resembles the original scenario in which the classical Mpemba effect was first observed. We focus on two paradigmatic free-
fermion models, the XX chain and the transverse-field Ising chain, which respectively preserve and break the global $U(1)$ particle-number
symmetry. As a probe of relaxation, we consider the Frobenius distance between the time-evolved reduced density
matrix of the central subsystem and its stationary state, which is the thermal state at the bath temperature. Exploiting the free-fermionic structure of both models, the dynamics remains Gaussian and the Frobenius distance can be expressed exactly in terms of two-point correlation functions. Combining this representation with generalised hydrodynamics, we derive analytical predictions for the Frobenius distance in the hydrodynamic limit, providing a complete characterisation of the thermalisation process. Using these results, we investigate the possible occurrence of the Mpemba effect. We find that, despite the genuine non-
equilibrium dynamics displayed by the system, no Mpemba effect arises in this setting. Our analysis identifies a broad class of boundary-driven thermalisation protocols in which relaxation is fully characterised analytically and exhibits no anomalous acceleration of equilibration.
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Strongly Correlated Electrons
$E_\infty^{1,2}$-type Lieb-Schultz-Mattis anomalies, deconfined quantum critical points, and non-invertible symmetry breaking
Hao-Ran Zhang, Hanlin Lin, Shuo Yang et al. (+1 more)
We study deconfined
quantum critical points (DQCP) associated with Lieb-Schultz-Mattis (LSM) anomalies in one-dimensional
spin chains. Our starting point is a structural characterization of the LSM anomaly in the Lyndon-Hochschild-Serre spectral sequence: $\omega_{\mathrm{LSM}}\in E_\infty^{1,2}= H^1(\mathbb Z_{\mathrm{trans}},H^2(G_{\mathrm{int}},\mathrm{U}(1)))\subseteq H^3(G_{\mathrm{int}}\rtimes_{\rho}\mathbb Z_{\mathrm{trans}},\mathrm{U}(1))$. Physically, this class decorates a translation defect with a projective representation of the internal
symmetry $G_\mathrm{int}$. We show that gauging the internal
symmetry in the presence of an $E_\infty^{1,2}$-type anomaly necessarily produces a non-invertible dual
symmetry. This gives a general mechanism for type-II DQCP: in contrast to type-I examples with $E_\infty^{2,1}$-type anomalies which are dual to ordinary group-like
symmetry breaking, type-II transitions are dual to spontaneous breaking of a non-invertible
symmetry. We illustrate the mechanism using a
spin-$1/2$ chain with an anomalous $D_8$ LSM
symmetry. We construct a dimer-to-ferromagnet DQCP candidate, provide numerical evidence for a critical theory with central charge $c\approx 1$, and show, using both category theory and explicit
lattice constructions, that gauging the internal
symmetry yields the non-invertible $\mathrm{Rep}(H_8)$ dual
symmetry.
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All authors Hao-Ran Zhang, Hanlin Lin, Shuo Yang, Qing-Rui Wang
Statistical Mechanics · Cross-listed from quant-ph
Reliability of asymptotic work extraction
Kaito Watanabe, Bartosz Regula, Marco Tomamichel et al. (+1 more)
Extracting work from
quantum states is a fundamental task in
quantum thermodynamics. Previous studies have primarily focused on determining the best achievable rate of work extraction, and remarkably, this characterization appeared to remain unchanged regardless of the choice of allowed processes: whether one considers the operationally motivated class of energy-conserving thermal operations, or the axiomatic class of Gibbs-preserving operations, the optimal extractable work is given by the Helmholtz free energy. Here, we challenge this perspective, showing that a more refined analysis of the asymptotic performance of work extraction reveals significant differences in the performance for the two different classes of free operations. Precisely, we focus on the trade-off between the extraction rate and its reliability, characterized by the optimal asymptotic speed at which the extraction error can be suppressed. We establish that the reliability of Gibbs-preserving operations and of thermal operations are respectively characterized by the Petz and the sandwiched Rényi relative
entropies, demonstrating that the former in general strictly outperforms the latter, and providing new interpretations of several information-theoretic divergences. Our analysis reveals that operational constraints such as energy conservation impose stronger limitations on the achievable precision of
quantum tasks than can be inferred from their asymptotic rates, thereby questioning the use of Gibbs-preserving operations as a mathematically convenient substitute for the physically realizable thermal processes.
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All authors Kaito Watanabe, Bartosz Regula, Marco Tomamichel, Ryuji Takagi
Mesoscale and Nanoscale Physics
Kauser Zulfiqar, Martin Lang, Samuel J. R. Holt et al. (+3 more)
We investigate the excitation modes of confined synthetic-
antiferromagnetic (SAF) skyrmions using micromagnetic
eigenvalue and ringdown simulations. Starting from a single skyrmion in a
ferromagnetic layer, where the lowest-frequency modes are a gyrotropic and a breathing mode, we study how
antiferromagnetic interlayer coupling modifies the dynamics in SAF
bilayers. We consider several geometries: single SAF skyrmions in square and rectangular confinement, unequal layer thicknesses, and strips containing multiple skyrmions. The
antiferromagnetic coupling strongly modifies the low-frequency dynamics. The square geometry exhibits two nearly degenerate gyrotropic modes, where in each both layers have the same rotation sense. In rectangular geometries, we instead find nearly linear SAF skyrmion translation emerging from opposite gyration sense in the two layers. These translational modes become the characteristic low-frequency excitations of SAF skyrmion chains. For skyrmion chains, we identify collective translational and breathing modes with standing-wave-like spatial profiles. Beyond
ferromagnetic-like breathing modes, the SAF geometry supports breathing oscillations in which the two layers oscillate out of phase. We further demonstrate signal propagation along extended SAF skyrmion chains with propagation velocities comparable to
ferromagnetic skyrmion chains. These results provide a systematic description of the collective dynamics of SAF skyrmions arising from the interplay of
geometric confinement, intralayer, and interlayer coupling.
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All authors Kauser Zulfiqar, Martin Lang, Samuel J. R. Holt, Swapneel Amit Pathak, Florian Bruckner, Hans Fangohr
Statistical Mechanics · Cross-listed from q-bio.NC
Early psychosis shows deviations in scaling behaviour within a critical regime
Irem Topal, Paola Moreno Ancalmo, Guillermo Montaña-Valverde et al. (+2 more)
Accumulating evidence suggests that large-scale
brain activity exhibits scale-invariant dynamics consistent with operation in a near-critical regime. Such dynamics have been associated with long-range correlations, efficient information processing, and the emergence of collective organization. While altered criticality-related measures have been reported in psychiatric disorders, previous findings remain fragmented across observables and modalities, making it unclear whether different scaling measures capture a common alteration of large-scale
brain dynamics. Here, we investigated scaling properties in resting-state fMRI data from 77 human participants (27 female and 50 male), comprising individuals with early psychosis and healthy controls. We combined a phenomenological renormalization group (PRG) framework with power spectral density (PSD) and detrended fluctuation analysis (DFA) to characterize collective dynamics across scales. In healthy controls, resting-state activity exhibited nontrivial scaling behavior consistent with critical-like organization. Early psychosis participants showed non-trivial scaling behavior, but with systematic shifts in scaling exponents across multiple observables. These findings indicate a reorganization of collective dynamics in early psychosis, with spatial and temporal scaling properties showing distinct alterations that may reflect different changes in proximity to criticality. More broadly, our results suggest that combining coarse-graining approaches with temporal scaling analyses provides a principled framework for studying large-scale
brain dynamics in psychiatric disorders.
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All authors Irem Topal, Paola Moreno Ancalmo, Guillermo Montaña-Valverde, Philipp Homan, Wolfram Hinzen
Materials Science
Optical Signature of Moiré Superlattices Formed by Twisted SrTiO$_3$ Membranes
T. A. M. Ragib Shahriar, Fumikazu Murakami, Xing He et al. (+11 more)
Moiré superlattices formed at the interfaces of mismatched
lattices have attracted significant interest over the past decade due to their large tunability of band parameters and interactions among electrons,
spins, and
lattices. Superlattices made from twisted perovskite
oxides may have strong structure and potential modulation, but evidence of such modulation over macroscopic areas, particularly at large twisting angles, has not been clearly demonstrated so far. Here, we fabricated millimeter-scale twisted
oxide bilayers at $36^\circ$ angle, close to the simple coincidence site
lattice condition $\Sigma5$, from freestanding SrTiO$_3$ membranes. We discovered new low-frequency vibrational modes whose Raman activity, according to molecular dynamics simulations, is greatly enhanced by an asymmetric, twisted interface between the SrO and TiO$_2$ layers. Such an interface is energetically favorable from first-principles calculations and is corroborated by the observation of strong second harmonic generation from the interface comparable to that from the SrTiO$_3$ surface throughout the
bilayer region. The results are consistent with interlayer coupling enhanced by high-temperature annealing and confirmed by cross-sectional scanning transmission electron microscopy imaging. Our work sheds light on the structural behavior of twisted
oxides and provides directions for tuning their phononic and nonlinear optical properties in future studies.
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All authors T. A. M. Ragib Shahriar, Fumikazu Murakami, Xing He, Konnor Koons, Xinyan Li, Bumseop Kim, Shihan Qin, Varun Harbola, Jochen Mannhart, Yimo Han, Ruijuan Xu, Shengxi Huang, Andrew Rappe, Hanyu Zhu