Statistical Mechanics
Yi-Jui Chiu and Cheng-Hung Chang
Colloidal
stochastic engines are often regarded as microscopic analogues of macroscopic pis ton cylinder heat engines. However, although they share some underlying physical principles, such systems remain far from being direct force generators from a practical perspective. Motivated by this limitation, the present study introduces a
polymer-based
stochastic engine that more closely mimics the operation of piston cylinder engines. In this setup, heat is converted into work through a cyclic process in which a
polymer is pulled into and out of a narrow channel under varying tem peratures. The work performed by the engine can be directly obtained from the cyclic trajectory in the force position diagram, analogous to the pressure volume diagram in traditional heat engines. Despite its much higher number of degrees of freedom compared to colloidal engines, the
polymer en gine nevertheless follows several characteristic features observed in such systems. Numerical results demonstrate consistency with universal low-dissipation bounds for e ciency, recovery of Carnot e ciency under regeneration, and low-dissipation scaling of work and power.
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Statistical Mechanics · Cross-listed from quant-ph
Exchange Fluctuation Theorems for Non-Markovian Baths in Quantum Collisional Model
Sayan Mondal, Sukrut Mondkar and Ujjwal Sen
The
quantum exchange fluctuation
theorem relates the probabilities of observing heat transfer along and against the temperature gradient between thermal baths at different temperatures. We investigate how this relation generalizes when the baths exhibit non-Markovian dynamics. Using a microscopic collisional model, bath
memory is generated through interactions between successive bath auxiliaries before each heat-exchange collision. We derive exchange fluctuation
theorems for both direct bath-bath interactions and probe-mediated heat exchange in the steady-state regime. As an illustrative example, we consider heat baths with
qubit auxiliaries and show that non-Markovian
memory enhances the probability of heat-transfer events against the temperature gradient, modifying the predictions made by the conventional Jarzynski-Wójcik exchange fluctuation
theorem. Our results establish a microscopic connection between environmental
memory and non-
equilibrium heat-exchange statistics.
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Materials Science
Advances and opportunities for automated robotic preparation of 2D materials and fabrication of 2D heterostructures
S. Davari, D. L. Duong, T. Faltermeier et al. (+7 more)
The mechanical exfoliation, transfer, and stacking of 2D atomic sheets from van der Waals
crystals synergize to enable atomic layer-by-atomic layer engineering of 2D
heterostructures with tailored properties that yield new exotic phenomena and states of matter. With the huge variety of van der Waals materials available, there is a limitless number of ways to couple 2D semiconducting, insulating,
magnetic, metallic, topological, etc. systems with one another. Experimental exploration of this vast space starts with the fabrication of high-quality 2D
heterostructures, which is commonly performed manually, relying on humans to execute delicate operations. Many scientific advancements have been achieved in this manner, revealing immense potential for further discovery and innovation of increasingly sophisticated 2D
heterostructures. However, soon, the complexity of the 2D
heterostructures that define the scientific state-of-the-art will exceed the capabilities of manual fabrication. Therefore, the demand for robotic instruments for preparing 2D materials and fabricating complex 2D
heterostructures with greater quality, at higher rates, and with better reproducibility is increasing. This review covers recent scientific, instrumentation, and processing advances rising to this challenge. Robotic instruments for mechanical exfoliation, optical metrology of 2D crystallites, stacking, as well as advancements in supporting technologies such as organic-free stamps,
vacuum-compatible processing tools, and artificial intelligence (AI) are covered. Looking forward, a new generation of AI-driven, automated advanced manufacturing tools is anticipated to emerge from these current advancements. These new tools will bridge the current state-of-the-art of 2D
heterostructure science to new scientific frontiers defined by precision fabrication of high-quality, complex, many-layer 2D
heterostructure systems.
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All authors S. Davari, D. L. Duong, T. Faltermeier, J. A. Goss, A. Hasani, D. Kotekar-Patil, J. Peabody, S. Wyss, H. O. H. Churchill, N. J. Borys
Materials Science
Soft-Phonon-Driven Effective Inversion-Symmetry Crossover in Quantum Paraelectrics
Xiaojiang Li, Guodong Zhao, Fei Yang et al. (+6 more)
Symmetry lays the foundation of condensed matter physics and its experimental manifestation provides fundamental insight into the collective behaviors of
quantum materials. Optical second-harmonic generation (SHG) is widely regarded as a fingerprint of inversion-
symmetry breaking, yet whether and how collective
lattice dynamics govern the nonlinear optical manifestation of local inversion-
symmetry breaking remains unknown. Here, combining optical SHG, diffuse X-ray scattering, and microscopic theory, we reveal a
phonon-regulated mechanism governing the temperature-dependent manifestation of local inversion-
symmetry breaking in
quantum paraelectric material KTaO3. We demonstrate that an oxygen-defect-mediated nonlinear optical channel is strongly coupled to the host soft polar mode, whose thermal fluctuations scramble the associated electronic phase coherence and thereby suppress the nonlinear manifestation of local inversion-
symmetry breaking at elevated temperatures. Consequently, the nonlinear response exhibits a temperature-driven crossover from a regime in which local inversion-
symmetry breaking is optically manifest to one that appears effectively centrosymmetric, without any accompanying structural change. Our findings revise the conventional picture of the temperature-dependent manifestation of inversion-
symmetry breaking in
quantum paraelectrics and establish a framework for understanding and engineering defect-mediated nonlinear optical responses in materials hosting low-energy polar excitations.
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All authors Xiaojiang Li, Guodong Zhao, Fei Yang, Seng Huat Lee, Richard D. Schaller, Jong-Woo Kim, Matthew Krogstad, Long-Qing Chen, Philip J. Ryan
Soft Condensed Matter
Spatially heterogeneous relaxational dynamics and the evolution of recoverable strain following flow cessation of a ductile nanocolloidal glass
Chloe W. Lindeman, James J. Griebler, Penelope Grace Kovakas et al. (+6 more)
We report a combined rheology and x-ray
photon correlation spectroscopy (XPCS) study of the structural and mechanical relaxation of a ductile, nanocolloidal glass following the cessation of shear flow. After the glass is sheared to 300% strain at various shear rates and then held at fixed strain, the stress undergoes a protracted, quasi-logarithmic decay with hold time that depends weakly on the initial strain rate. Recovery rheology measurements reveal that this stress relaxation is accompanied by a logarithmic decrease in the elastic component of the recoverable strain; hence, the rates of decrease of the stress and recoverable strain are proportional. XPCS measurements during the stress relaxation reveal dynamics dominated by a convection-like backflow that is divided into two dynamically distinct regions indicative of banded motion. In one region, the flow can be modeled by an affine strain, while in the other region the glass moves as a plug while undergoing slow, glassy relaxation. The rates of these dynamics approximately track the rate of loss of recoverable strain, indicating this motion is the predominant microscopic mechanism driving the conversion of recoverable to unrecoverable strain during stress relaxation. In contrast, XPCS measurements during strain recovery reveal purely affine flow with no evidence of heterogeneity and with strain rates that agree quantitatively with the rheometry measurements. Together, these results provide a unified microscopic picture connecting the evolving internal dynamics of a ductile glass to its macroscopic mechanical relaxation following flow cessation.
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All authors Chloe W. Lindeman, James J. Griebler, Penelope Grace Kovakas, Miaoqi Chu, Qingteng Zhang, Suresh Narayanan, James L. Harden, Simon A. Rogers, Robert L. Leheny
Materials Science
Accurate Evaluation of Nanoscale Spatiotemporal Dynamics with Electron Correlation Microscopy
Po-Cheng Kung, Ajay Annamareddy, Mark D. Ediger et al. (+2 more)
Electron correlation microscopy (ECM) can measure materials dynamics with nanoscale spatial resolution from intensity correlation functions. However, adopting X-ray
photon correlation spectroscopy (XPCS) normalization frameworks unchanged when calculating intensity correlations can introduce errors. Due to the constrained sampling volumes and larger speckle sizes in nanobeam electron diffraction, XPCS-style time-averaging and scattering-vector averaging introduce systematic artifacts, such as artificial anticorrelations or elevated baselines that lead to systematic errors in structural relaxation times and stretching exponents. This work presents physics-inspired, ECM-specific intensity normalizations over time- and azimuthal-averaged intensities of the first diffraction ring that limit those errors. The framework is validated using molecular dynamics simulations of a CuZr supercooled
liquid to
benchmark against the self intermediate scattering function, successfully reproducing relaxation times. When applied to experimental time-resolved 4D STEM
datasets of a Pt57.5Cu14.7Ni5.3P22.5 nanowire, the method correctly identifies highly stable, unchanging nanoscale crystalline phases that were erroneously misclassified as relaxing domains by previous frameworks. Other previous ECM research is reevaluated in light of these observation. This robust approach establishes an artifact-free pathway for evaluating localized spatiotemporal relaxation behaviors.
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All authors Po-Cheng Kung, Ajay Annamareddy, Mark D. Ediger, Dane Morgan, Paul M. Voyles
Mesoscale and Nanoscale Physics
Layer-Number-Controlled Symmetry Breaking and Surface-State Transport in Rhombohedral Graphene Multilayers
Bosai Lyu, Jian Zheng, Kai Liu et al. (+12 more)
Rhombohedral multilayer
graphene hosts layer-polarized flat bands, providing an intriguing platform for correlated and topological electronic states; however, the role of layer number in governing
symmetry breaking and surface screening remains elusive. Here we prepare rhombohedral
graphene multilayers and systematically conduct electrical transport measurements. We uncover an unconventional layer dependence of phase transitions: the critical displacement field (D$_{c}$) for the layer-
antiferromagnetic (LAF)-to-semimetal transitions remains constant across tetralayer to hexalayer
graphene, whereas the D$_{c}$ for semimetal-to-layer-polarized-
insulator (LPI) transition increases with layer number, defying unscreened Coulomb interaction models. In hexalayer
graphene, surface-state-dominated transport emerges, with Landau levels (LLs) and resistive peaks selectively controlled by adjacent gates, a signature of strong interlayer screening absent in thinner stacks. High
magnetic fields reveal valley-layer-locked LLs and dissipative states possibly from interlayer backscattering, highlighting the presence of decoupled surface states. Our findings establish layer number as a key tuning knob for engineering correlated and topological phases in rhombohedral
graphene multilayers.
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All authors Bosai Lyu, Jian Zheng, Kai Liu, Yulu Ren, Size Wu, Yating Sha, Shuhan Liu, Youngju Park, Kenji Watanabe, Takashi Taniguchi, Jinfeng Jia, Zhiwen Shi, Jeil Jung, Weidong Luo, Guorui Chen
Materials Science · Cross-listed from cs.CE
Predicting Mechanical Properties of Lignin-Containing Polyurethane Rigid Foams from Microstructure Using Convolutional Neural Networks
Ilige S. Hage, Charbel Y. Seif, Jose Enrico Q. Quinsaat et al. (+5 more)
Bio-based alternatives for conventional rigid foams have proven to be good substituents owing to their enhanced sustainability and competitive performance. However, because their manufacturing processes are complex and destructive testing is often impractical, this study investigates whether microstructural features can be correlated with mechanical properties in lignin-containing rigid polyurethane (PU) foams using machine-learning approaches. Various types and percentages of lignin-based polyols were investigated as a partial polyol replacement. Scanning electron microscopy (SEM) images and corresponding mechanical compression data were used to train a custom state-of-art dual-head convolutional neural network (CNN) targeting the specific prediction of density, specific compression modulus, specific yield strength, and specific compression strength. The CNN was optimized with a weighted multi-output loss function, achieving strong predictive performance R2 values ranging from 0.850 to 0.91 and correlation coefficients above 0.92 while maintaining mean absolute error percentages below 9%. This proves the trained network capability to predict and capture morphological features governing load bearing responses. On the other hand, Grad-CAM visualization revealed that the network focused its predictions on physically meaningful microstructural regions such as
cell walls and strut junctions, which confirm that the proposed network can be classified as an interpretable, non-destructive and data-driven framework for predicting and understanding bio-based PU foams mechanical behavior, hence reducing the inconvenience caused by time consuming manufacturing and destructive testing.
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All authors Ilige S. Hage, Charbel Y. Seif, Jose Enrico Q. Quinsaat, Daniel J. van de Pas, Richard Vendamme, Walter Eeversd, Karolien Vanbroekhovend, Elias Feghalid
Other Condensed Matter
Giant Effective Permeability in Drude Thin Films Probed by THz Time-Domain Spectroscopy
Gian Paolo Papari, Zahra Mazaheri, Antonio Vettoliere et al. (+7 more)
The electromagnetic response of metallic films is commonly analyzed in terahertz spectroscopy by assuming unit relative
magnetic permeability. In this work we show that this assumption introduces significant distortions in the electrodynamic
retrieval of highly conductive films. Aluminum and copper films, 10 nm thick, were investigated by terahertz time-domain spectroscopy in both transmission and reflection configurations. By applying a self consistent
retrieval method that independently determines the complex permittivity and permeability, we show that the Drude-type dielectric response is systematically accompanied by a permeability that strongly departs from unity. This deviation is intrinsically linked to the reactive impedance of the films, which clarifies the light induced onset of large screening currents within a transversally confined geometry. A phenomenological interpretation based on the Faraday Neumann Lenz mechanism and a lumped-element model of the film impedance accounts for the observed trends. These results indicate that the common assumption $\tilde{\mu}=1$ in non-
magnetic Drude films can lead to an incomplete or biased electrodynamic characterization in the terahertz regime.
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All authors Gian Paolo Papari, Zahra Mazaheri, Antonio Vettoliere, Carmine Granata, Roberto Russo, Giovanni Ausanio, Umar Farooq, Junaid Yaseen, Can Koral, Antonello Andreone
Superconductivity
Yttrium Superhydrides Revisited: Advanced Experimental and Theoretical Studies of YH$_6$, YH$_9$ and YH$_{10}$
Dmitrii V. Semenok, Pedro N. Ferreira, Di Zhou et al. (+10 more)
Yttrium polyhydrides are
benchmark materials in high-pressure superconductivity, yet several key properties of the Y-H system remain insufficiently characterized. Here we combine contact transport, contactless
radio-frequency measurements, pulsed-field experiments, and first-principles calculations to reinvestigate YH$_6$, YH$_9$, and YH$_{10}$ in the pressure range 140-213 GPa. Yttrium hydrides YH$_6$ ($\textit{$T_c$}$ = 218-221 K) and YH$_9$ ($\textit{$T_c$}$ = 235-237 K) demonstrate narrow superconducting transitions ($\textit{${\Delta}$T$_c$}$ = 2-5 K), approaching the limit imposed by thermal fluctuations. Pulsed-field measurements on YH$_6$ up to 60 T establish an extended superconducting phase diagram with a linear slope $\textit{dB$_{c2}$/dT}$ = -0.52 T/K, pronounced transition broadening above 30 T, and negligible normal-state magnetoresistance. We report the
radio-frequency AC susceptibility study of YH$_6$, providing evidence for superconductivity via high-frequency field screening in a contactless geometry. Experiments involving Pd incorporation, Pd thin-film sputtering, and Al alloying show strong suppression of high-temperature superconductivity, with no transitions detected above 78-120 K. Finally, using density-functional theory with the
stochastic self-consistent harmonic approximation, superconducting density-functional theory, and full-bandwidth Migdal-Eliashberg calculations, we show that anharmonic effects substantially reduce the predicted $\textit{$T_c$}$ of cubic YH$_{10}$ to approximately 260-270 K. These results strongly disfavor room-temperature superconductivity in binary yttrium superhydrides.
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All authors Dmitrii V. Semenok, Pedro N. Ferreira, Di Zhou, Fabian Jőbstl, Andrey V. Sadakov, Kirill S. Pervakov, Burkhan I. Massalimov, Toni Helm, Ryosuke Akashi, Vladimir M. Pudalov, Viktor V. Struzhkin, Christoph Heil, Ivan A. Troyan
Materials Science
Symmetry-Dependent Mechanical and Vibrational Response of Formamidinium Lead Halide Perovskites: A DFT Study
Mahdi Faghihnasiri, Carmine Autieri and Sara Memarzadeh
Formamidinium-based hybrid halide perovskites (FAPbX3, X = Cl, Br, and I) have attracted considerable
attention for optoelectronic applications owing to their outstanding optical and electronic properties. However, the influence of
crystal symmetry reduction on their mechanical behavior and stability has not yet been comprehensively understood. In this work, density functional theory (DFT) calculations were performed to investigate the structural, elastic, dynamical, and nonlinear mechanical properties of the cubic and ps-cubic phases of FAPbX3. The elastic constants, bulk, shear, and Young's
moduli, Poisson's ratio, sound velocities, and Debye temperature were evaluated and correlated with the second Piola-Kirchhoff stress-strain response under tensile and compressive loading. The results reveal that the effect of
symmetry reduction is strongly dependent on the halide composition. For FAPbCl3 and FAPbBr3, the transition from the cubic to the ps-cubic phase reduces the
lattice stiffness, decreases the acoustic
phonon velocities, and lowers the Debye temperature, whereas the opposite trend is observed for FAPbI3. The stress-strain analysis further reveals pronounced nonlinear, anisotropic, and asymmetric mechanical behavior, demonstrating that
symmetry reduction can either activate or suppress strain-accommodation mechanisms depending on the halide species, thereby governing the mechanical stability and the onset of structural softening. These findings provide microscopic insight into the relationship between
crystal symmetry,
lattice dynamics, and nonlinear mechanical response in formamidinium-based halide perovskites, offering useful guidance for the design of mechanically robust optoelectronic materials.
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Mesoscale and Nanoscale Physics
Large bias-tunable magnetoresistance from spin-dependent interlayer hybridization in van der Waals antiferromagnet CrSBr-based heterostructures
Sadeed Hameed, Aditya Kumar, Chengjie Yu et al. (+5 more)
We explore the large magnetoresistance (MR) in \ce{hBN}/few-layer-
graphene/\ce{CrSBr}/few-layer-
graphene heterostructures and reveal the mechanism behind its non-monotonic bias dependence. Using bias voltage and temperature as independent tuning knobs, we achieve MR up to \SI{350}{\percent} at \SI{20}{K}, characterized by symmetric M-shaped maxima around $\pm 0.5\,\mathrm{V}$. Continuous tuning of the magnetization angle $\theta$ via a hard-axis
magnetic field shows that the barrier band-edge offset varies linearly with $\cos(\theta/2)$, a first-order signature of
spin-dependent interlayer hybridization. This linear relationship rules out the Jullière model and a
spin-filter projection. We conclude that the
magnetic-configuration-dependent band edge, rather than electrode
spin polarization, dictates the large magnetoresistance in \ce{CrSBr} junctions.
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All authors Sadeed Hameed, Aditya Kumar, Chengjie Yu, Aravind P. Balan, Xinran Wang, Lichuan Zhang, Yuriy Mokrousov, Mathias Kläui
Materials Science
Many-Body Destabilization of Intermediate Oxygen-Hole States
Anirudh Adavi, Kayahan Saritas, Ming Lei et al. (+3 more)
Oxygen holes in transition-metal
oxides can appear as localized polarons,
symmetry-delocalized ligand holes, or intermediate states whose stability is controlled by subtle electron-correlation effects. In layered Na$_{2-x}$Mn$_3$O$_7$, hybrid density functional theory (DFT) predicts an unusual bond-centered split oxygen-hole polaron stabilized near ordered Mn vacancies. Here we resolve the nature of this state using
diffusion Quantum Monte Carlo (QMC). Although hybrid DFT favors the split configuration, QMC reverses the energetic ordering and identifies the localized oxygen polaron as the lower-energy state. The result is robust to the class of trial wavefunctions used, including hybrid and generalized-gradient DFT wavefunctions. Many-body
spin densities further show that the nominal split state partially collapses toward a localized polaron. Because localized and split configurations produce similar O K-edge spectral features, this qualitative failure is not resolved by conventional X-ray absorption signatures alone. These findings identify Na$_{2-x}$Mn$_3$O$_7$ as a stringent
benchmark for oxygen-hole polarons and reveal a failure mode of hybrid functionals in correlated
oxides.
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All authors Anirudh Adavi, Kayahan Saritas, Ming Lei, Das Pemmaraju, Paul R. C. Kent, Iwnetim I. Abate
Materials Science
Strain-controlled magnetism and magnetoelasticity in monolayer NiPS$_3$ and CrPS$_4$
Balázs Nagyfalusi, Alvaro Bermejillo-Seco, Linde de Jong et al. (+5 more)
We develop a first-principles framework for magnetoelastic coupling in two-dimensional magnets based on a strain-dependent Heisenberg model. In this approach, strain derivatives of the exchange interactions provide direct access to magnetostriction and to the
magnetic renormalization of the elastic tensor, establishing a microscopic link between
spin interactions and elastic response. We apply the method to monolayer NiPS$_3$ and CrPS$_4$, which exhibit contrasting magnetoelastic behavior. NiPS$_3$ shows weak and nearly isotropic
spin-
lattice coupling, consistent with a robust zigzag
antiferromagnetic ground state. In contrast, CrPS$_4$ displays strong anisotropic coupling, leading to strain-driven transitions between
spin-spiral and
ferromagnetic phases and significant changes in the critical temperature and elastic response. Our results demonstrate a general route to quantify magnetoelastic effects in low-dimensional magnets and highlight CrPS$_4$ as a promising platform for strain engineering of
magnetic order.
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All authors Balázs Nagyfalusi, Alvaro Bermejillo-Seco, Linde de Jong, Ritesh Das, Yaroslav M. Blanter, Herre S. J. van der Zant, Amador Garcia-Fuente, and Jaime Ferrer
Statistical Mechanics
Observable dependence and rate identifiability in false-vacuum decay of the quantum Ising chain
Boliang Yu, Ruixin Zhou and Hang Su
Extracting a thermodynamic nucleation rate from finite-time
quantum dynamics requires separating observable decay from
estimator and finite-size validity. We develop a multilevel identification framework for real-time tensor-network simulations of false-
vacuum decay in the one-dimensional
quantum Ising chain. Across twelve parameter points, the same coherent two-kink amplitudes semi-quantitatively predict both infinite-chain survival and magnetization dynamics: the survival coefficient has a median
lattice-to-theory ratio of 0.896, while the magnetization-area slope ratios span 0.767–0.931. By contrast, the microscopic nearest-neighbour bond response is coherence dominated:
vacuum–pair coherence contributes 60.0–81.5% across seven points with matched bond-dimension control, while substantial late-window slope discrepancies remain that cannot be removed by a scalar normalization. The analysis establishes finite-time survival and magnetization
benchmarks and identifies the additional finite-size and branch-validation requirements for a bulk thermodynamic rate interpretation. Within the two-kink model and under the adopted common normalization, the
lattice-resolved WKB action gives a median fixed-prefactor rate discrepancy of 4.13% from the coherent-bubble spectral calculation. These results distinguish finite-time
lattice–theory consistency from the additional observable and finite-size evidence required to identify a thermodynamic nucleation rate.
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Superconductivity
Light induced superconducting diode effect in patterned films
Evan M. Wilson, Hou-Tong Chen and Alexander V. Balatsky
Structured light offers a route to control superconducting transport without permanently modifying the material or applying a static bias. Here we show that structured optical driving can generate a superconducting diode response in patterned superconducting films with asymmetric holes. Using generalized time-dependent Ginzburg Landau simulations, we find that optical driving produces rectified dc photovoltages and zero bias directional supercurrent imbalance in a junction free geometry, with continuous-drive diode efficiencies of order $10^{-3}$ and pulsed efficiencies reaching $10^{-2}$. The response is controlled by both the hole array and the optical mode. Increasing the number of asymmetric holes enhances rectification, reversing circular helicity reverses the diode polarity, and the optical spatial mode strongly modifies the magnitude and polarity of the directional response. Pulsed excitation enhances the zero bias line cut current imbalance to the percent level. For linearly polarized illumination, the asymmetric metacrystal converts the drive into local
chiral supercurrent motion, inducing an inverse Faraday effect like mechanism for dynamical time reversal
symmetry breaking. These results establish patterned superconducting films as a viable platform for light-tunable superconducting diode behavior.
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Statistical Mechanics · Cross-listed from quant-ph
Spectrally local geometric response at the onset of many-body quantum chaos
George Mihailescu and Pablo M. Poggi
We introduce the spectral density of
geometric response, a measure of eigenstate sensitivity across an energy spectrum. Applied to many-body
quantum systems, it reveals an exponentially sensitive integrability-to-chaos crossover, where eigenbasis deformations first accumulate in localized spectral regions before spreading throughout the spectrum. Physically motivated random-
matrix ensembles reproduce this behaviour, whereas Gaussian ensembles do not, indicating universal features of the route to chaos that are absent from featureless random-
matrix models.
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Strongly Correlated Electrons
Thermodynamic Spectroscopy of Emergent Excitations in Quantum Spin Ice
Zhengbang Zhou, Tony An and Yong Baek Kim
Quantum spin ice (QSI) is a three-dimensional
quantum spin liquid where fractionalized spinons interact with emergent
photons. The XXZ model on the pyrochlore
lattice realizes such a $U(1)$
quantum spin liquid and a number of pyrochlore magnets have been investigated as candidate materials, but the detection of emergent excitations has been a major challenge. The specific heat is expected to show the higher-energy spinon excitations and a lower-energy anomaly at the ring-exchange scale, which sets both the
photon bandwidth and the energy of the emergent
magnetic monopoles (or visons). In reality, the lower-energy peak is obscured by the
nuclear Schottky anomaly in non-Kramers Pr-based systems, while it is not clearly resolved from the spinon contributions in Ce-based dipolar-octupolar systems. In this work, we propose a novel thermodynamic probe of the elusive ring-exchange energy scale. We show that in the presence of a weak perturbation coupled to the transverse component of the pseudospin degrees of freedom, the temperature derivative of an observable conjugate to such a weak perturbing force is highly sensitive to the ring-exchange energy scale. Using this scheme, it is shown that the difference between thermal expansion coefficients along the [100] and [010] directions should show a peak at the ring-exchange energy scale for non-Kramers QSI. Similarly, the temperature derivative of the magnetization, $dM/dT$, of dipolar-octupolar pyrochlores under a weak
magnetic field can also detect the same signal. Moreover, the sign of these signatures distinguishes the zero-flux and $\pi$-flux QSI states.
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Strongly Correlated Electrons
The Fate of Crystalline Topological Phenomena in the Continuum
Rajas Chari and Taylor L. Hughes
The continuum limit is a widely used theoretical construct for obtaining continuum field-theories of crystalline systems. We study the formulation of a continuum limit for gapped bosonic phases and ask whether their topological properties survive passage to the continuum. Using methods in algebraic
topology and category theory, we give a rigorous formulation of the continuum limit and construct a surjective global map relating crystalline topological phases across all finite point-group
symmetries to continuum invertible topological phases. Consequently, we find that some
lattice phases admit no continuum limit, while distinct
lattice phases that do admit a continuum limit can share the same continuum image, hence implying that some
lattice topological data can collapse. Conversely, we find that every continuum invertible phase admits a faithful crystalline realization. In addition to the general framework, we apply it to several examples, including studies of a 2D rotation-symmetric phase, higher-order topological phases, and the mixed
spin-
lattice anomaly of the deconfined
quantum critical point between an antiferromagnet and valence bond solid.
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Strongly Correlated Electrons
Quetzalcoatlite as a Disorder-Free Platform for Chiral Magnetism and Frustration
Aleksandar Razpopov, P. Peter Stavropoulos, Felix Flicker et al. (+2 more)
The natural mineral quetzalcoatlite Zn$_6$Cu$_3$(TeO$_6$)$_2$(OH)$_6$ $\cdot$ (Ag$_x$Pb$_y$Cl$_{x+2y}$) is a structurally ideal kagome magnet, providing a platform for exploring the interplay of
geometric frustration, chirality, and tunability in a disorder-free framework. Here, we present the (first) comprehensive ab initio study of its electronic and
magnetic properties. The electronic structure is dominated by localized half-filled Cu $d_{x^2-y^2}$ orbitals that become insulating through electronic correlations. Mapping the low-energy physics onto a Heisenberg model reveals that the magnetism is governed primarily by two exchange interactions: a nearest-neighbor intralayer kagome coupling and a next-nearest-neighbor interlayer coupling. Their competition stabilizes an unconventional three-dimensional
chiral magnetic state. Each kagome layer hosts a $\sqrt{3}\times\sqrt{3}$ order, while adjacent layers are rotated by $60^\circ$, producing a right-handed spiral along the crystallographic $c$-axis. This intrinsic
chiral order emerges naturally from the
crystal structure and
magnetic interactions, establishing quetzalcoatlite as a distinctive realization of
chiral magnetism on a perfect kagome
lattice. At the same time, the small energy scale of the exchange interactions places the material close to competing
magnetic regimes, suggesting that moderate pressure, chemical substitution, or structural modifications may strongly enhance frustration, suppress long-range order, and potentially drive the system toward a
quantum spin-
liquid state.
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All authors Aleksandar Razpopov, P. Peter Stavropoulos, Felix Flicker, Michael R. Norman, Roser Valentí
Statistical Mechanics
Geometry of Noisy Quantum Many-Body Dynamics with Continuous Symmetries: Entanglement and Correlations
Marco Lastres and Sanjay Moudgalya
We study
unitary quantum dynamics in noisy Brownian models with global continuous
symmetries, such as $U(1)$ and $SU(2)$, focusing on Rényi
entanglement entropies and hydrodynamic and non-hydrodynamic correlators. By mapping the averaged late-time dynamics to the low-energy physics of effective replica
Hamiltonians, we find that the
evolution is controlled by the
quantum geometry of their ground-state
manifolds, which is directly related to the geometry of $k$-commutants—the
symmetry algebra of $k$ replicas of the system. In interacting systems, these $k$-commutants are generically determined solely by the
symmetries of the system, independent of microscopic details of the noisy
evolution. This allows us to use the time-dependent variational principle (TDVP) to provide simple
geometric explanations for the sub-ballistic Rényi
entanglement growth and the anomalous decay of non-hydrodynamic correlators in interacting systems with continuous
symmetries. We find this behavior to be intimately connected to singularities within the $k$-commutant
manifolds, arising from frozen “void” states in the
Hilbert space that exist due to continuous on-site
symmetries. This also demystifies the important role of voids in the dynamics of these observables, previously identified in $U(1)$ symmetric systems. We compare these behaviors in interacting systems with Abelian and non-Abelian continuous
symmetries and in free-
fermion systems, which differ in the geometry of their $k$-commutants. Ultimately, this work provides a general
geometric framework for systematically studying observables in noisy systems with continuous
symmetries, including Haar-random
circuits.
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Superconductivity
Discriminating superconducting fluctuations from the pseudogap in Bi$_2$Sr$_2$Ca$_{n-1}$Cu$_n$O$_{2n+4+\delta} (n = 2,3)$: A magnetotransport study
Shunpei Yamaguchi, Nae Sasaki, Shintaro Adachi et al. (+13 more)
Understanding the normal state is essential for uncovering the mechanism of high-$T_c$ superconductivity. We investigate magnetotransport in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ single
crystals over a wide doping range. While the in-plane resistivity and
Hall coefficient show strong pseudogap-induced temperature dependence, the $T^2$
Hall-angle behavior and the modified Kohler's rule remain robust across all dopings. The onset temperatures of the pseudogap are clearly distinct from superconducting fluctuations, although they scale with the pseudogap magnitudes with a factor consistent with a $d$-wave
superconductor. These results demonstrate that the pseudogap does not arise from superconducting fluctuations and instead suggest that it may originate from preformed Cooper pairing in the BCS-BEC crossover regime.
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All authors Shunpei Yamaguchi, Nae Sasaki, Shintaro Adachi, Keiichi Harada, Yuki Teramoto, Shintaro Matsuda, Tomohiro Usui, Takenori Fujii, Takashi Noji, Itsuhiro Kakeya, Haruka Taniguchi, Michiaki Matsukawa, Atsushi Miyake, Hajime Ishikawa, Koichi Kindo, Takao Watanabe
Materials Science
Chemically Meaningful Textualization Enables Explainable Validation of Metal-Organic Frameworks by Large Language Models
Guobin Zhao and Xiao-Yan Li
Computation-ready metal-organic framework (MOF) databases are essential for high-throughput screening, yet many reported
crystal structures remain chemically unreasonable or disordered, compromising simulation fidelity. Existing validation approaches can identify non-computation-ready structures, but they often rely on heuristic rules, license requirement, or offer limited interpretability. Here, we show that large
language models (LLMs) can serve as interpretable validators of MOF structures when crystallographic information is transformed into chemically meaningful text. By benchmarking nine descriptors, we find that successful LLM-based validation depends not on the amount of structural information alone, but on whether local coordination, framework connectivity, and chemical context are organized into a linguistically learnable representation. Fine-tuned LLMs using specialized descriptors (mof2text) achieve performance comparable to graph-based models in identifying unreasonable MOFs. Importantly, these models extend beyond black-box classification by generating diagnostic rationales for likely error sources, including abnormal bonding, connectivity, and charge states, as well as error-category predictions for annotated
datasets. This work establishes chemically informed textualization as the key step that transforms LLMs from generic text models into practical and explainable tools for curating MOF databases.
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Quantum Gases
OpenMP Fortran programs for rotating dipolar Bose-Einstein condensates
Denis Mujo, Dušan Vudragović, Paulsamy Muruganandam et al. (+1 more)
In this paper we present Open Multi-Processing (OpenMP) Fortran 90/95 programs to solve the Gross-Pitaevskii equation for a rotating dipolar Bose-Einstein condensate (BEC) in two and three dimensions, which is a new version of our previous published programs for a dipolar Bose-Einstein condensate without rotation. After the recent experimental study of a rotating dipolar BEC [L. Klaus et al., Nature Phys. 18, 1453 (2022)], the present programs will be useful tools for related theoretical investigation. The
algorithm used is the split-step semi-implicit Crank-Nicolson scheme for imaginary- and real-time propagation to obtain stationary states and BEC dynamics, respectively, as in the previous version [L. E. Young-S. et al., Comput. Phys. Commun. 286 (2023) 108669].
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All authors Denis Mujo, Dušan Vudragović, Paulsamy Muruganandam, Sadhan K. Adhikari
Statistical Mechanics
Exact First-Passage Time Response Theory from Steady-State Response
Ruicheng Bao and Shiling Liang
The mean first-passage time (MFPT) provides a universal temporal measure of transport, reaction, search, and switching processes in physical, chemical, and biological systems. Understanding how MFPTs respond to perturbations is therefore crucial for prediction and control, yet a systematic theory has been lacking. We establish a compact theoretical framework for linear and nonlinear MFPT response in continuous-time Markov processes. The key tool is an exact correspondence that maps the intrinsically transient response of MFPTs onto the steady-state response of an auxiliary system. This correspondence yields exact and universal response relations for MFPTs between arbitrary state pairs, expressed entirely in terms of unperturbed MFPTs and steady-state probabilities. We then obtain a factorized physical decomposition of the MFPT response into linear upstream, linear downstream, and nonlinear contributions. Further corollaries include response-curve inference rules, fundamental bounds on MFPT responses, analytical expressions for higher-order responses of MFPTs and steady-state probabilities, and multi-rate response formulas. Additionally, our result offers computational advantages in calculating both MFPTs and steady-state distributions. Finally, a biologically motivated folding network is analyzed, and a recently reported paradox on MFPT is clarified.
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Statistical Mechanics · Cross-listed from quant-ph
Work distribution for strongly coupled many-body open quantum systems
H. T. M. Nghiem, T. A. Costi, S. Campbell et al. (+1 more)
The non-
equilibrium quantum thermodynamics of many-body open systems is notoriously rich, especially in the strong-coupling regime where strong system-bath correlations develop and interactions produce non-perturbative effects. Such systems can be described by `
quantum impurity models' where the system and bath are treated on an equal footing as a single composite. Paradigmatic examples are the
spin-
boson and Anderson
impurity models, in which system degrees of freedom interact with either bosonic or fermionic gapless baths. Here we study the
quantum work distribution function (WDF) of such systems following a quench. Capturing the full continuum of many-body excitations in the WDF requires a non-perturbative solution of the underlying non-
equilibrium quantum impurity problem. For this purpose, we extend the time-dependent numerical renormalization group (TDNRG) approach to the calculation of the WDF, which applies directly in the thermodynamic limit, can be used for arbitrary quench amplitudes at zero or finite temperature, and provides exponentially fine low-energy resolution. Our numerically-exact solution reveals power-law threshold behavior due to the Anderson orthogonality catastrophe when the work approaches its minimum value, with universal scaling collapse of the distribution below an emergent low-energy scale induced by system-bath correlations.
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All authors H. T. M. Nghiem, T. A. Costi, S. Campbell, A. K. Mitchell
Mesoscale and Nanoscale Physics
Floquet Engineering of Topological Phases and Magneto-Optical Response in a Driven $d$-wave Altermagnet
Muzamil Shah
We study how Floquet driving with linearly polarized light controls the
topology and magneto-optical response of a two-dimensional (2D) $d$-wave altermagnet. In the absence of linearly polarized optical field and under
spin conservation, we find that the system hosts a
spin-Chern (a
quantum-
spin-
Hall analog) phase with Chern numbers of opposite sign in the two
spin sectors. The irradiated optical field breaks the $C_{4z}\mathcal{T}$ crystalline antiunitary
symmetry between the
spin sectors.
Symmetry breaking originates from polarization-dependent Peierls phases, which renormalize hopping anisotropically along the two axes. The resulting
spin-selective gap closures produce intermediate Chern-insulating phases with $C=\pm1$. The drive amplitude $A_0$ determines the inversion thresholds, while rotating the polarization by $\pi/2$ swaps the
spin sectors and reverses the Chern number. Using the Kubo formalism, we compute the frequency-dependent longitudinal and
Hall conductivities and derive the corresponding Faraday and Kerr rotations for a free-standing conducting sheet. The longitudinal response tracks the Floquet-renormalized interband thresholds, whereas the optical
Hall response, together with the sign of the magneto-optical rotations, distinguishes the two opposite Berry-
curvature chiralities. Sizable Kerr angles occur only within narrow resonant windows and should be interpreted together with the reflected intensity and Kerr ellipticity. These results identify linearly polarized light as a
symmetry-selective handle for
spin-resolved band inversion, Chern-number switching, and contact-free optical detection in $d$-wave altermagnets.
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Strongly Correlated Electrons
Floquet Green's functions for lattice electrons driven by Gaussian quantum light
Atsushi Ono
We formulate Floquet Green's functions for noninteracting single-band
lattice electrons driven by a reservoir-stabilized single-mode Gaussian
quantum light source. The source is prescribed externally and is not updated by the many-electron polarization, while an active electronic probe still conditions the source
evolution through the Peierls coupling. The two time arguments of a Green's function share one source history: the lesser and greater components are obtained by convolving a shared-history four-endpoint kernel with the continuous bath kernels before the final source trace, while the bath canonical anticommutation relation yields an equal-time covariance that seeds the retarded and advanced one-leg propagations. The Peierls coupling is treated nonperturbatively within the prescribed-source model, and classical Floquet theory is recovered in the appropriate limit. Numerical calculations on a minimal one-dimensional model show finite-coupling
quantum-source corrections beyond a prescribed classical drive, together with spectral reconstruction and occupancy redistribution for squeezed
vacuum and squeezed coherent sources. The squeezing parameter and phase provide additional control knobs, beyond classical amplitude modulation, for both sideband structure and occupied weight. This work provides a theoretical framework for
quantum Floquet engineering of condensed matter with an externally prescribed
quantum light source.
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Mesoscale and Nanoscale Physics
Inferring stealthy hyperuniform correlations from quantum transport
Natanael C. Costa, Mauro S. Ferreira, Caio Lewenkopf et al. (+4 more)
Stealthy hyperuniform disordered systems exhibit strongly suppressed long-wavelength fluctuations, producing correlated disorder with unusual consequences for wave propagation. A central quantity characterizing these systems is the stealthiness parameter $\chi$, which controls the range of excluded
Fourier components in the disorder spectrum. However, in realistic settings, the microscopic disorder configuration may not be directly accessible, making it challenging to determine $\chi$ from structural information alone. Here, we propose a conductance-based inverse protocol to recover stealthy hyperuniform correlations from transport data. As a proof of concept, we study spinless
fermions in a one-dimensional tight-binding chain connected to clean semi-infinite leads, with on-site disorder generated by imposing a stealthy spectrum $S(k)=\Theta(|k|-K)$, where $K=2\pi\chi$. The energy-dependent transmittance is computed using a recursive Green's function method and compared with target spectra through a misfit function defined over an energy window. We show that the position of the sharp drop separating high- and low-transmittance regions is strongly controlled by $\chi$, while the disorder strength $W$ mainly affects the absolute magnitude of the transmittance. As a result, the misfit function displays a clear minimum close to the target stealthy parameter. Our results demonstrate that transmittance spectra can serve as fingerprints of stealthy hyperuniform disorder, providing a practical route to infer correlated-disorder parameters from transport measurements.
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All authors Natanael C. Costa, Mauro S. Ferreira, Caio Lewenkopf, Felipe A. Pinheiro, Paul J. Steinhardt, Salvatore Torquato, Carlo Vanoni
Disordered Systems and Neural Networks
Skin-Anderson Localization Transition in Strongly Coupled Disordered Non-Hermitian Chains
S Rahul
The interplay between disorder and non-Hermitian effects gives rise to a variety of intriguing localization phenomena. While disorder tends to localize the eigenstates through Anderson localization, non-Hermitian non-reciprocity promotes the formation of skin modes by driving the eigenstates toward the system boundaries giving rise to non-Hermitian skin effect (NHSE). In this work, we investigate the interplay between these competing mechanisms in a two-leg ladder consisting of a Hatano-Nelson chain coupled to a Hermitian chain via asymmetric inter-chain hopping, with strong disorder present in both chains. We show that tuning the asymmetry of the inter-chain coupling induces successive transitions in the nature of the eigenstates, from skin localization to Anderson localization and subsequently back to skin localization. Remarkably, the non-Hermitian skin effect re-emerges even though the energy spectrum exhibits a line-gap
topology, demonstrating that robust skin localization can persist beyond the conventional point-gap regime.
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