Statistical Mechanics
Cover time statistics of one-dimensional Brownian motion under stochastic resetting
Anirban Ghosh and Sanjib Sabhapandit
We investigate the effect of
stochastic resetting on the statistics of the cover time of a one-dimensional Brownian motion with a
diffusion constant $D$, confined to a finite interval of length $L$. The cover time $t_c$, defined as the minimum time required for the particle to visit every point of the interval at least once, exhibits a non-monotonic dependence on the scaled reset rate $\rho = rL^2/4D$. The scaled mean cover time $4D\langle t_c\rangle/L^2$ initially decreases with increasing $\rho$, attains a minimum at an optimal value $\rho^*$, and then increases with $\rho$, indicating an optimal resetting rate that minimizes the search duration. Furthermore, we derive an exact analytical expression for the cover time distribution, including its asymptotic limits, which agree well with numerical simulations. These results demonstrate that
stochastic resetting serves as an efficient mechanism for optimizing cover-time processes in confined geometries.
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Materials Science
In-situ operation of amorphous circuits under heavy-ion irradiation
Xuanzhe Sha, Shun Liao, Xiaoxi Li et al. (+10 more)
Radiation-hardened electronics using
semiconductors beyond silicon are essential for computation and control in extreme environments. Yet complex digital
circuits based on such material platforms operating in situ under heavy-ion irradiation remain largely unexplored. Here, we show a timing
circuit based on amorphous thin-film
semiconductors at the 100-transistor scale, and demonstrate its robust operation through a functional "Hello World" ASCII output sequence. Beyond static device characterization, we evaluate the
circuit under powered heavy-ion irradiation using tantalum ions, providing an operationally relevant assessment of radiation tolerance at the system level. Under a high particle flux of 2.5 x 10^3 ions cm^-2 s^-1, the
circuit maintains stable operation during the irradiation test, achieving a total fluence of 1 x 10^6 ions cm^-2, establishing a milestone of prolonged powered digital operation under extreme conditions. Our work expands the design space of radiation-tolerant electronics, highlighting amorphous
semiconductors as a promising foundation for digital
circuits deployed in harsh environments.
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All authors Xuanzhe Sha, Shun Liao, Xiaoxi Li, Chengyuan Li, Jianli Liu, Yu Pan, Wenhai Wang, Yu Ye, Chengxin Zhao, Liyi Li, Hanwen Wang, Zheng Vitto Han, Jianming Lu
Materials Science · Cross-listed from physics.chem-ph
Rigorous extension of semilocal collinear functionals to noncollinear DFT using $SU(2)$ rotations
Konstantin Gaul
In the presence of
spin-orbit coupling and in geometrically frustrated materials, a noncollinear treatment the magnetization density is essential. However, in density functional theory most exchange–correlation functional approximations were originally developed for locally collinear magnetization. Many practical approaches to noncollinear DFT have emerged over the past decade. However, a first-principles connection between widely used semilocal collinear functionals and their noncollinear generalizations remains lacking. In this work, a locally exact relation between collinear and noncollinear exchange–correlation functionals is derived at the level of gradient expansions within a $u(2)$
matrix representation of the energy functional. Within this framework, collinear semilocal variables naturally acquire distinct dependencies on transverse and longitudinal magnetization gradient components. The widely used Scalmani–Frisch scheme emerges as a first-order approximation. The transformation of collinear functional derivatives to noncollinear space is implemented through numerically robust $SU(2)$ rotations. A consistent description of local
magnetic torques is demonstrated for the prototypical
spin-frustrated Cr$_3$ cluster. The approach further extends to fully nonlocal functionals and provides a direct route towards numerically stable relativistic response calculations. The influence on
magnetic properties in presence of
spin-orbit coupling is illustrated through calculations of hyperfine couplings in the high-
spin ground states of uranium and the uranium ion.
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Mesoscale and Nanoscale Physics
Surface lone-pair polarization probed by quantum-geometric transport in tellurium
Nathanael N. Batista, Wendel S. Paz, Manuel Suárez-Rodríguez et al. (+10 more)
Stereochemically active lone pairs are ubiquitous microscopic sources of polarity in molecules and solids, but their collective behavior in
crystals is often hidden by
symmetry or confined to surfaces. Here we show that
quantum-geometry transport provides a sensitive probe of surface lone-pair polarization in trigonal tellurium. This surface polarization appears microscopically as an inversion-odd dipolar component of the
crystal potential, which shifts the center of mass of Bloch wavepackets and produces
quantum-
geometric corrections to their velocity. We describe this lone-pair polar texture through a minimal three-component
lattice model, and we show that the resulting linear and nonlinear transport coefficients probe, respectively, the second and first moments of the net polarization field. Because rectified voltages in tellurium flakes are directly proportional to the surface lone-pair polarization, our results provide a microscopic route to understanding and engineering polarization-driven,
quantum-
geometric electronic devices based on tellurium allotropes.
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All authors Nathanael N. Batista, Wendel S. Paz, Manuel Suárez-Rodríguez, Pierpaolo Fontana, Victor Velasco, Marcus V. O. Moutinho, Chang Niu, Peide D. Ye, Marco Gobbi, Fèlix Casanova, Luis E. Hueso, Caio Lewenkopf, Marcello B. Silva Neto
Materials Science
Topological Interstitial-Electron Conductor
Tingli He, Xiaoming Zhang, Chaoxi Cui et al. (+5 more)
Electron transport in solids arises primarily from two mechanisms: freely moving bulk electrons in metals, and gapless boundary states in topological
insulators. Here, we report a new mechanism discovered in electrides. The topological interstitial-electron conductors (TIECs) proposed here are insulating electrides, but host interstitial electrons (IEs) distributed within
crystal voids that traverse the entire unit
cell. Without being tightly bound to real ions, the IEs generally experience low periodic potential barrier along the void channels. As a consequence, by applying a weak electric field sufficient to overcome the IE barriers but far below the system's dielectric breakdown threshold, one can expect that the TIECs would generate a persistent current contributed by the IEs and propagating along the void channels. We identify a family of realistic altermagnetic electrides, $A_5X_3$ ($A$ = Ca, Sr, Ba, Yb; $X$ = As, Sb), as TIECs. Remarkably, for $A_5X_3$ materials, the periodic potential barrier of the IEs along the void channels are ultralow, ranging from 13.43 to 67.96 meV per formula unit. This renders our proposal readily accessible to experimental verification. We further demonstrate that when the IEs of $A_5X_3$ undergo periodic motion along the channels, topological surface states will emerge at the boundary perpendicular to the channel direction, and continuously move across the bulk band gap. This pumping-like behaviour not only corroborates the topological nature of TIECs, but also rationalizes the finite-electric-field induced electronic transport within the band theory. Our findings expand the classification of electronic conductors, uncover unexplored transport properties of electrides, and establish a new material platform for low-power electronic devices.
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All authors Tingli He, Xiaoming Zhang, Chaoxi Cui, Yilin Han, Yang Wang, Wei Jiang, Zhi-Ming Yu, Yugui Yao
Mesoscale and Nanoscale Physics
Fast coherent control of a charge qubit on solid neon with a spin-qubit-compatible resonator
Jun Wang, Yiran Tian, Ivan Grytsenko et al. (+7 more)
Electrons floating in
vacuum provide a clean platform for
quantum information processing owing to their isolation from material defects. In particular, electrons on solid neon have emerged as a promising
qubit platform because of their potentially long coherence times. Here, toward
spin-
qubit realization, we couple a single electron on solid neon to a
magnetic-field-compatible superconducting NbTiN nanowire resonator. We realize a charge
qubit and demonstrate microwave readout and coherent control, with Rabi frequencies up to 76 MHz, an order of magnitude larger than in previous studies. Under strong driving, we observe a
qubit frequency shift from nonlinear interactions with the intense microwave field. Deterministic electron trapping at an intended position remains challenging due to solid neon surface roughness; we characterize the electron's position from its differential coupling to distinct electrodes. Although not trapped at an intended position, our estimates indicate that
spin-
qubit demonstrations remain feasible.
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All authors Jun Wang, Yiran Tian, Ivan Grytsenko, Asher Jennings, Beatriz Pérez González, Xianjing Zhou, Hirotaka Terai, Dafei Jin, Monica Benito, Erika Kawakami
Mesoscale and Nanoscale Physics
The geometry of the CISS effect
P. Hedegård, A. Kazimir, C. Lamers et al. (+3 more)
Using scanning tunneling microscopy, and a careful selection of
chiral molecules and anchoring groups, we systematically carried out a series of magnetoresistance experiments. We observed a reversal of the signal upon changing the magnetization direction, the molecular chirality, and the molecular orientation. The orientation of the molecules and the magnetization of the substrate are vectors, and by associating an axial vector with the molecule, the observations can be explained. Other recent experiments, among them null experiments showing no CISS related magnetoresistance can be explained using our framework. The physical interpretation is, that the polar electrical polarization of the molecule cannot play a direct role, while the axial
magnetic polarization vector operator is a much more realistic candidate. This vector plays an important role in the creation of a
magnetic moment in the interface between molecule and metallic lead.
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All authors P. Hedegård, A. Kazimir, C. Lamers, L. T. Baczewski, T. N. H. Nguyen, C. Tegenkamp
Materials Science
A Self-Evolving Machine-Learning-Based Kinetic Monte Carlo Method for Modelling Thin-Film Growth
Jyri Kimari, Flyura Djurabekova and Kostas Sarakinos
We present a kinetic Monte Carlo (KMC) simulation framework parameterized by automatically sampling machine-learning (ML) for modeling thin-film growth atom by atom. Given an interatomic potential energy function, the KMC
algorithm builds an ML-based regression model for rate parameters on runtime, being trained on the local atomic environments encountered during the system
evolution. New environments are continuously added to the training set in a self-evolving manner at points where the ML model estimates high uncertainty. As the simulation progresses, the ML model gains confidence, and the quick estimation of rates increasingly overtakes the relatively-expensive nudged elastic band calculations, promoting computational efficiency while retaining high fidelity description of the atomic
diffusion kinetics. As a test case, we simulate the sub-monolayer growth of Ag on Ag {111}, where we demonstrate adatom islands forming in shapes and densities in accordance with the underlying atomistic interaction model, the theoretical framework, and available experimental results related to thin-film nucleation and growth.
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Mesoscale and Nanoscale Physics
Interplay of Cl Substitution and He$^{+}$ Irradiation in CrSBr$_{1-x}$Cl$_{x}$
Satyam Sahu, Adeel Bukhari, Arijit Kayal et al. (+8 more)
Two-dimensional
magnetic semiconductors provide a promising platform for exploring the interplay between disorder,
lattice dynamics, and resonant light–matter interactions. Among them, CrSBr exhibits strong in-plane anisotropy and pronounced resonance-enhanced Raman scattering. Here, we investigate the effects of Cl substitution and He$^{+}$ irradiation on the vibrational response of CrSBr using polarization-resolved Raman spectroscopy. Cl substitution activates additional
phonon modes associated with local
symmetry breaking, while He$^{+}$ irradiation introduces distinct defect-related scattering channels and enhanced
phonon broadening. The combined effects of
alloy disorder and externally introduced defects lead to strong anisotropic reconstruction of the Raman spectra and modification of the nonlinear Raman response under near-resonant 1.96 eV excitation. Power-dependent measurements reveal robust superlinear scaling of both intrinsic and substitution-induced
phonon modes, indicating persistent resonance-enhanced electron–
phonon coupling even in defect-engineered samples.
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All authors Satyam Sahu, Adeel Bukhari, Arijit Kayal, Valerie Černá, Bing Wu, Aljoscha Söll, Gregor Hlawacek, Zdeněk Sofer, Martin Kalbáč, Matěj Velický, Otakar Frank
Strongly Correlated Electrons
Complex Magnetic Behavior of the Ce sawtooth chains in CeRhSn$_2$
P. Opletal, J. Fikáček, E. Duverger-Nédellec et al. (+8 more)
Conflicting reports exist on the ground state of the intermetallic compound CeRhSn$_2$. This can be rooted in the sawtooth-like arrangement of two inequivalent Ce sites in the unit
cell, which suggests potential
geometric magnetic frustration. To resolve, we conducted a comprehensive study on high-quality single
crystals of CeRhSn$_2$ by means of magnetization ($M$), specific heat ($C_p/T$), and resistivity ($\rho$). The system exhibits strong
magnetic anisotropy, confirming the $b$-axis as the easy
magnetic axis. We establish three successive transitions, an AFM order at $T_{N} = 3.65$K, a first-order FM order at $T_{C} = 1.7$K and final transition, at $T = 1.5$K. The transition temperatures are highly field-directional dependent: in a
magnetic field, the lowest transition is immediately suppressed while $\mathbf{H} \parallel b$ rapidly merges $T_{C}$ and $T_{N}$ into a single second-order transition. Conversely, $\mathbf{H}\parallel c$ suppresses the FM order and reduces $T_{N}$. Additional ab initio calculations affirm the FM ground state of CeRhSn$_2$. The observation of an enhancement of the Sommerfeld coefficient ($\gamma = 76.5$mJ/mol$\cdot$K$^2$) may arise from
geometric frustration, but it is most consistently attributed to weak Kondo hybridization as frustration cannot be conclusively established through our data.
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All authors P. Opletal, J. Fikáček, E. Duverger-Nédellec, A. Thamizhavel, Z. Hossain, R. Tarasenko, V. Tkáč, D. Legut, Bin Shen, P. Gegenwart, J. Custers
Quantum Gases
Functional methods for quantum thermodynamics
Sibo Wang, Samuel Degen and Haozhao Liang
The functional renormalization group provides a nonperturbative and systematically improvable route to constructing density functionals for
quantum many-body systems from microscopic
Hamiltonians. Here we advance this program by benchmarking functional-renormalization-group density functional theory (FRG-DFT) against the exact thermodynamics of the single-site Bose-Hubbard model. This model provides an ideal testing ground because it is analytically solvable, yet remains subtle in the imaginary-time coherent-state path integral, where a naive continuum treatment generates a spurious self-interaction. We show that a careful Hubbard-Stratonovich derivation identifies the self-interaction correction term that must be included in the FRG-DFT flow to recover the exact thermodynamics. We then systematically compare several closures of the resulting hierarchy of flow equations for the free energy, chemical potential, and connected density correlators over broad ranges of density, temperature, and interaction strength. The
benchmark shows that the free energy is comparatively robust, whereas the chemical potential and fluctuation observables provide much sharper diagnostics of the hierarchy closure. A maximum-
entropy closure gives the most accurate overall description and reproduces even the low-temperature oscillatory structure of the connected two-density correlator. These results identify two general requirements for functional approaches to
quantum thermodynamics: the renormalization group flow equation must retain the equal-time contact subtraction to avoid spurious self-interactions, and any closure of the hierarchy must preserve the statistical consistency of density correlators. This work provides a controlled foundation for deriving ab initio density functionals for
quantum many-body systems across condensed-matter, ultracold-atom, and
nuclear physics, as well as
quantum chemistry.
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Materials Science
Clustering in atom probe tomography data: coordination number metric, percolation-based parameter scaling, and size effects
Mykola Lazarev and John Banhart
The ability to identify nanometer-scale
nuclei of new phases in atom probe
tomography (APT) is often limited by the sensitivity of clustering
algorithms to user-defined control parameters. Conventional approaches typically rely on the Euclidean distance metric and consider only solute atoms, thereby discarding the solvent atoms that contain most of the spatial information. Here, we introduce a coordination-number metric based on the composition and apply it to higher-order clustering. Using various metrics, we investigate percolation in typical APT structures. By scaling clustering properties to the corresponding percolation thresholds, we define a self-similar variable that is almost invariant with respect to metrics, clustering parameters, and structural disorder. This variable provides a relevant description of clustering and enables the formal transfer of optimal parameters between clustering methods. We also study the characteristic clustering behavior in small precipitates and quantify how the precipitate-
matrix interface alters the composition spectrum and broadens the clustering curve. Finally, using simulations that incorporate finite spatial resolution, detection efficiency, and other APT reconstruction artifacts, we show that the approach based on coordination numbers effectively compensates for heterogeneous dilations and outperforms solute-density-based methods in all tested scenarios.
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Soft Condensed Matter
Finite-inertia effects in Langevin dynamics of a lopsided elastic dumbbell using exponential-time differencing schemes
Lei Song, Dingyi Pan and Nhan Phan-Thien
Inertia effects in the Langevin dynamics of a lopsided elastic dumbbell are investigated using exponential-time-differencing (ETD) integrators for the corresponding stiff
stochastic equations at small mass limit. Starting from the bead-level underdamped Langevin model, we formulate the dynamics in modal coordinates, highlighting two distinct friction scales: an additive friction $\zeta_{\rm trans}=\zeta_1+\zeta_2$ controlling translation ($\zeta_i, i=1,2$ are the friction factor on bead $i$), and an effective internal friction $1/\zeta_{\rm eff}=1/\zeta_1+1/\zeta_2$ controlling configurational relaxation, with relaxation time $\tau_R=\zeta_{\rm eff}/H$ for a Hookean spring of stiffness $H$. We
benchmark ETD against Euler–Maruyama and overdamped Brownian dynamics using
equilibrium statistics, time-domain autocorrelations, and frequency-domain power spectra of the end-to-end vector. When time is rescaled by $\tau_R$, configurational and orientational relaxation curves collapse across asymmetry ratios, showing that the dominant long-time structural dynamics remains close to the overdamped description. Inertial signatures are instead confined to short-time transients, high-frequency modifications of the configurational spectrum, and a transient coupling between translational and internal modes. This study provides a practical and accurate route for lopsided dumbbells across overdamped and weakly underdamped regimes, and clarify how mass and friction asymmetry affect the translational and internal dynamics.
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Materials Science
Spin-Spiral Enhancement of Ultrafast Light-Polarization-Robust Magnetization
Yirui Lu, Zeyu Jiang and Bing Huang
Ultrafast light-driven magnetization, a frontier in
quantum magneto-optics, has traditionally relied on circularly polarized
lasers to provide external angular momentum. While increasing efforts have aimed to achieve light-polarization-robust (LPR) magnetization that is insensitive to the form of external light excitation, the underlying mechanism remains largely unclear. Here, we establish the
symmetry-constrained rule for LPR magnetization in
antiferromagnetic systems. Through real-time time-dependent density functional theory calculations, we observe the strong LPR magnetization in
spin-spiral magnets and its suppression in collinear antiferromagnets, confirming our theory. Strikingly,
laser excitation induces real-space demagnetization, rotation, and oscillation of atomic
spins in
spin-spiral monolayer NiI$_2$, whereas rotation is largely suppressed in conventional collinear antiferromagnets. Our work reveals a novel microscopic pathway for ultrafast magnetization that is independent of light polarization, paving the way for advanced femtosecond
spin control.
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Materials Science · Cross-listed from physics.acc-ph
Explicit Turn Resolution with Anisotropic Homogenisation for Efficient 3D Magneto-Thermal Finite-Element Simulation of Large-Scale No-Insulation HTS Magnets
Louis Denis, Erik Schnaubelt, Julien Dular et al. (+3 more)
No-insulation (NI) and metal-insulation (MI) high-temperature superconducting (HTS) magnets require three-dimensional (3D) models to describe the current distribution around critical current defects. In this work, we design and validate the EXTRA homogenisation method, standing for explicit turn resolution with anisotropic homogenisation method. It allows 3D magneto-thermal finite-element (FE) simulations of large-scale magnets to be performed with high accuracy at a reasonable computational cost. The method combines the anisotropic homogenisation of turn-to-turn contact layers (T2TCLs) and their neighbouring winding turns with the explicit resolution of specific T2TCLs. In particular, the inner- and outermost winding turns and adjacent contact layers are explicitly resolved to properly describe the current distribution near current leads. In addition, the method is able to simulate local $J_{\textrm{c}}$ defects for a broad range of turn-to-turn contact resistances, provided the winding turns and T2TCLs next to the defect are explicitly resolved. For efficiency, the resolved T2TCLs are modelled using the surface contact approximation. The consistency of the proposed method is first verified on a 50-turn single pancake
benchmark. It is shown to reproduce AC losses and temperature distributions obtained with a turn-resolved FE reference model, for both nominal operation and during thermal runaway. The computational efficiency of the EXTRA method is demonstrated with the simulation of a stack of three 150-turn pancake coils, for which computation time is reduced by a factor of up to 13 with respect to a turn-resolved FE reference model. Finally, the results of a large-scale 3D FE simulation, currently out of reach of turn-resolved models, are provided for an insert HTS magnet with 10,000 turns. The EXTRA method is open-source and input files to reproduce all results are made available.
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All authors Louis Denis, Erik Schnaubelt, Julien Dular, Mariusz Wozniak, Benoît Vanderheyden, Christophe Geuzaine
Quantum Gases
Dimensionality of a strongly interacting 2D-3D Fermi-Fermi mixture from the perspective of superfluid instability and excitation properties
Haruka Takeda, Saki Hirai, Shumpei Iwasaki et al. (+1 more)
We theoretically investigate strong-coupling properties of an attractively interacting
Fermi atomic gas, where the Cooper-pair formation occurs between atoms belonging to different dimensional bands. Including pairing fluctuations within the framework of the self-consistent $T$-
matrix approximation (SCTMA), we examine how the BCS-type superfluid phase transition temperature $T_\mathrm{c}$ varies as one moves from the 3D-3D to the 2D-3D system, in the wide parameter region with respect to the strength of the pairing interaction. In the 2D-3D limit, we find that, while the mean-field BCS theory predicts $T_\mathrm{c}>0$ in the strong-coupling regime, $T_\mathrm{c}$ is remarkably suppressed down to zero by pairing fluctuations that are strongly enhanced by the mixed-dimensionality of the system. As the origin of this, we clarify that the lower-dimensional (2D) component dominates the superfluid instability, so that the vanishing $T_\mathrm{c}$ is the same phenomenon as that in the 2D-2D case. We also point out that this can already be seen in the mean-field level, when one examines the propagation of the Goldstone mode. On the other hand, we find that the pseudogap phenomenon, which is known as a precursor of Cooper-pair formation, exhibits a 3D character of the 2D-3D system. These results indicate that the dimensionality of a strongly interacting
Fermi gas depends on what we observe.
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All authors Haruka Takeda, Saki Hirai, Shumpei Iwasaki, Yoji Ohashi
Mesoscale and Nanoscale Physics
Parity-induced generalized Brillouin zone without non-Hermitian skin effect
Alexander Felski
Acute spectral sensitivity to boundary conditions and the formation of a generalized Brillouin zone associated with complex quasimomenta are features frequently attributed to systems with non-trivial non-Hermitian
topology, showcasing the non-Hermitian skin effect. We show that, away from the thermodynamic limit, these features themselves are not uniquely tied to this phenomenon; they can similarly arise as parity-induced even-odd effects in non-Hermitian systems without skin effect. Despite an underlying generalized Brillouin zone description, wavefunctions remain delocalized. In addition, the effect can arise in skin-effect models as entirely separate distinguishable feature
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Statistical Mechanics
Competing heterogeneities shape ordering via higher-order interactions
Gangmin Son, Federico Battiston, Deok-Sun Lee et al. (+1 more)
Higher-order interactions admit richer structural heterogeneity than pairwise networks. To understand how heterogeneity impacts collective phenomena we develop a framework based on the cavity method and apply it to the simplicial Ising model on heterogeneous hypergraphs. Unlike in homogeneous structures, group size and node degree play fundamentally different roles: size heterogeneity sharpens the transition via large-group unanimity, while degree heterogeneity softens it as hubs cooperatively seed ordering with non-hubs. Under either type of heterogeneity, continuous–discontinuous double transitions can arise, where the
symmetry-breaking continuous transition is driven by pairs or by hubs, respectively. When both heterogeneities coexist, cross-order degree correlations further modulate the phase diagram, with anticorrelation delaying the group-driven discontinuous jump and broadening the hysteretic region. Our results reveal the intricate interplay between size and degree heterogeneities in collective phenomena beyond pairwise interactions.
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All authors Gangmin Son, Federico Battiston, Deok-Sun Lee, K.-I. Goh
Statistical Mechanics
Finite-time Scaling with Arbitrary Driving Rates: Bridging the Kibble-Zurek and De Grandi-Gritsev-Polkovnikov Limits
Shuai Yin
The pursuit of a universal description for nonequilibrium critical dynamics in
quantum many-body systems stands as a central frontier in modern statistical physics. For driven critical dynamics starting far from the critical point, the well-known Kibble-Zurek (KZ) scaling holds only when the driving rate lies below an upper bound. Here we study driven dynamics restricted to the critical region, and show that robust dynamic scaling behavior exists for arbitrary driving rates. We develop a generalized finite-time scaling (FTS) framework, which provides a unified understanding on the driven dynamics for the full range of quench rates, bridging the KZ scaling in the slow-driving regime and the De~Grandi-Gritsev-Polkovnikov (DGP) scaling in the sudden-quench limit. We verify this unified FTS form through numerical simulations in both
quantum critical and tricritical points. The good agreement between theoretical predictions and numerical results confirms the generality of our theory. Our work establishes a universal theory for nonequilibrium critical dynamics spanning the full range of driving rates, with broad implications for
quantum quench experiments and out-of-
equilibrium statistical mechanics.
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Mesoscale and Nanoscale Physics
Pure Spin Photocurrent in Altermagnetic Photovoltaic Battery
Qiang Li, Shibo Fang, Zongmeng Yang et al. (+11 more)
Altermagnets, featuring momentum-dependent
spin splitting without net magnetization, provide a promising platform for spintronic functionalities beyond conventional ferromagnets and antiferromagnets. Here, we propose an altermagnetic
spin photovoltaic battery consisting of a nonmagnetic semiconducting layer sandwiched between two altermagnetic electrodes. Using first-principles
quantum-transport simulations, we show that a V2Te2O/ZnSe/V2Te2O junction supports a pure
spin photocurrent for opposite Néel vectors in the two altermagnetic electrodes, with
spin-up and
spin-down photocurrents equal in magnitude and opposite in sign. The effect persists under both linearly and circularly polarized light and remains tunable with
photon energy and polarization angle. Our results establish a realistic route toward light-driven pure
spin-current generation in altermagnetic junctions.
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All authors Qiang Li, Shibo Fang, Zongmeng Yang, Xingyue Yang, Jianhua Wang, Rui Peng, Lin Zhu, Shuhua Wang, Dexing Liu, Min Zhang, Dahua Ren, Mai Zhang, Han Zhang, Yee Sin Ang
Statistical Mechanics
Activity-Enhanced Ordering in Fluctuation-Induced First-Order Transitions
Suvendra K. Sahoo
Fluctuations can drive otherwise continuous phase transitions to first order through the Brazovskii mechanism. We study how these fluctuation-induced transitions are modified in active systems by introducing nonequilibrium spatiotemporally correlated noise. We show that, while the transition remains fluctuation-induced first order, activity systematically suppresses these fluctuation effects, shifting the transition to higher temperatures and rendering it increasingly weakly first order. As a result, ordering is enhanced without inducing a spinodal instability of the isotropic phase, as confirmed by direct numerical simulations. In the strong-activity limit, fluctuation effects disappear and mean-field behavior is recovered. Our results identify activity as a generic control parameter for tuning the strength of fluctuation-induced first-order transitions.
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Mesoscale and Nanoscale Physics
Spin Hall effect in two-dimensional materials with inverted bands and Mexican-hat dispersion
Bagun S. Shchamkhalova and Vladimir A. Sablikov
We study the
spin Hall effect in two-dimensional topological
insulators with "Mexican hat" dispersion and a ring-shaped
Fermi surface which are formed due to the band inversion. Electron transitions between different isoenergetic contours and the
quantum metric of band states play an important role in the transport properties of such materials, since they largely determine the spatial distribution of the electron charges screening the
impurity potential and the scattering probability [Phys.B, 719, 417942 (2025)]. Here we study a
spin-dependent skew scattering, which is enabled by the second-order scattering processes, and show that the extrinsic
spin-
Hall current (SHC) can significantly exceed the intrinsic SHC arising from the Berry
curvature. Furthermore, due to Mexican-hat dispersion, the SHC exhibits a very unusual dependence on the
Fermi energy ($E_F$). The extrinsic SHC reaches a maximum at some $E_F$, then decreases with increasing $E_F$ and can even change a sign. This complicated behavior reflects an interplay of energy dependencies of such important factors as probabilities of inter- and intra-contour transitions, as well as different electron velocities in two contours.
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Soft Condensed Matter
Living Helices in Fluctuating Polymer Chains: Cooperative Nucleation, Dynamics, and Lifetime
Biman Bagchi
Helical segments in
polymer chains are often transient, finite, and dynamically evolving, yet their origin and stability remain incompletely understood. Here we develop a minimal coarse-grained statistical-mechanical theory that explains how such living helices emerge in fluctuating
polymer systems. Using a three-state model with cooperative interactions, we show that helix formation proceeds through a multistep nucleation mechanism. An initial constrained pre-
nucleus forms first, followed by cooperative stabilization that promotes the growth of finite helical segments. The resulting free-energy landscape naturally favors marginally stable helices whose size is determined by a competition between cooperative gains and nonlinear penalties arising from stiffness, torsional strain, and solvent fluctuations. By formulating the dynamics as a
stochastic process in segment size, we derive analytical expressions for both formation times and lifetimes within a mean first-passage framework. For representative parameters relevant to flexible
polymers and peptide segments, the theory predicts characteristic timescales in the nanosecond to sub-microsecond range. The present analysis supports a view of living helices as finite, mobile excitations whose stability is controlled by cooperativity, boundary motion, and solvent-induced fluctuations.
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Superconductivity
Terahertz Electrodynamics and Kinetic Inductance of Disordered Titanium-Vanadium Alloy Thin Films
Shekhar Chandra Pandey, Shilpam Sharma, Ashish Khandelwal et al. (+1 more)
Disordered
superconductors represent an important area in modern condensed matter physics, where superconductivity survives even in the presence of strong electron scattering and localization effects. Understanding how disorder modifies the high-frequency electrodynamic response is not only important from physics point of view, but is also essential for developing next-generation
quantum detectors and superconducting devices. In this work, we investigate the terahertz electrodynamics of disordered Ti40V60
alloy thin films using terahertz time-domain spectroscopy (THz-TDS) to understand the relationship between disorder, quasiparticle dynamics, and kinetic inductance. By analysing the complex conductivity, penetration depth and superfluid response, we show that structural disorder can be systematically used to tune the inductive response while maintaining a robust superconducting phase. Unlike conventional nitride
superconductors that require tightly controlled reactive growth conditions, Ti40V60
alloys provide a simpler and more adaptable route for tuning the superconducting energy scales directly through the deposition conditions. These findings establish Ti40V60
alloys as a promising material for kinetic inductance detectors and provide useful insights into the electrodynamics of strongly disordered
superconductors.
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All authors Shekhar Chandra Pandey, Shilpam Sharma, Ashish Khandelwal, M. K. Chattopadhyay
Disordered Systems and Neural Networks
Probing the many-body energy landscape of a soft glass with graph neural networks
Mehryar Jannesari Ghomsheh, Donald L. Koch and Sarah Hormozi
Many-body interactions govern the complex behavior of many amorphous materials, from metallic glasses to biological tissues, yet are often replaced by pairwise additive frameworks for computational efficiency. Here, we use classical density functional theory (DFT) to study a model soft glass of solvent-free
polymer-grafted nanoparticles (PGNs), where the absence of solvent forces grafted chains to uniformly fill the interstitial space, generating strong angular-dependent many-body interactions between the cores. We show that NequIP, an equivariant message-passing graph neural network (GNN), predicts the
equilibrium states with DFT-level accuracy, despite being trained only on high-energy, out-of-
equilibrium configurations. Systematic analysis of GNN hyperparameters offers physical insights into the range, anisotropy, and effective body order of interactions. GNN-driven Monte Carlo simulations recover
equilibrium structures in agreement with experiments and reveal locally favored icosahedral-like structures. Our results position machine-learned potentials as a tool for probing many-body glass physics beyond atomistic settings.
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Statistical Mechanics · Cross-listed from quant-ph
Eigenstate chaos in the presence of non-Abelian symmetries
Siddharth Jindal and Pavan Hosur
The eigenstate thermalization hypothesis (ETH) posits that energy eigenstates encode local properties of the microcanonical ensemble. Motivated by recent interest in the physics of non-commuting conserved charges and the non-Abelian ETH, we study chaotic eigenstates in the presence of
symmetries described by general compact Lie groups, such as SU(2). By applying non-Abelian
symmetry resolution, we develop a non-Abelian microcanonical
entropy and relate this
entropy to the
entanglement entropy of chaotic eigenstates. We find that microcanonical
entropy is closely related to the
symmetry-resolved
entanglement entropy, which differs from conventional
entanglement entropy by a universal logarithmic correction. Our results depend on the global Casimir charge, e.g. total
spin. At finite charge density, we find a logarithmic enhancement to conventional
entanglement entropy. At zero density, we find no such correction to
entanglement entropy, but a logarithmic reduction to microcanonical
entropy and
symmetry-resolved
entanglement entropy. We discuss the implications of our approach for non-Abelian eigenstate thermalization.
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Materials Science
Saturated and Anisotropic Magnetostriction in an Altermagnet
Zhiyuan Duan, Qiyun Xu, Peixin Qin et al. (+14 more)
Magnetostriction, a fundamental phenomenon bridging magnetism and mechanics, has enabled a broad spectrum of applications. For almost two centuries, it has been mainly investigated for ferromagnets. Regarding the magnetostriction of antiferromagnets (AFMs), limitedly known examples for both conventional collinear AFMs and noncollinear AFMs predominantly exhibit non-saturating
magnetic-field dependence. Herein, we report an easily saturated magnetostriction effect in a prototypical altermagnet - MnTe, which is an emerging class of collinear AFMs with special
crystal symmetries. For high-quality MnTe single
crystals, the magnetostriction saturates under a moderate field of ~0.7 T with an intriguing two-fold-
symmetry anisotropy. First-principles calculations reveal that the saturated and anisotropic magnetostriction originates from
symmetry-allowed coupling between elastic strain and its Néel order parameter. These findings break the traditional wisdom on
antiferromagnetic magnetostriction.
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All authors Zhiyuan Duan, Qiyun Xu, Peixin Qin, Li Liu, Guojian Zhao, Yuzhou He, Xiaoyang Tan, Sixu Jiang, Jingyu Li, Xiaoning Wang, Qinghua Zhang, Wenhui Duan, Yong Xu, Ziang Meng, Peizhe Tang, Chengbao Jiang, Zhiqi Liu
Superconductivity · Cross-listed from quant-ph
Geometric dependence of critical-current variation in Al/AlO${\rm _x}$/Al Josephson junctions: a model-based analysis
K. Kakuyanagi, N. Teran, H. Toida et al. (+1 more)
Achieving uniform critical current across Josephson junctions is essential for the large-scale integration of superconducting
quantum circuits. In this work, we statistically analyzed the variation of the critical current of Al/AlO${\rm _x}$/Al junctions using room-temperature tunnel resistance statistics, and identified the dominant contribution among the modeled sources of the variation based on their dependence on geometry and deposition conditions of junctions. Our model-based analysis reveals that fluctuations in the Al film thickness play the dominant role among the modeled contributing factors. Based on this analysis, we found that, in Dolan-bridge double-angle deposition, adopting a deposition angle of 30-degree for
bilayer junctions significantly improves uniformity, yielding a relative standard deviation of 1.2% (0.5%) across a 9.75 mm (1.5 mm) square region.
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All authors K. Kakuyanagi, N. Teran, H. Toida, S. Saito
Materials Science
Crystal Dislocations as Atomic Scale Ratchets
Wu-Rong Jian, Yifan Wang and Wei Cai
The
symmetry of a system's response to external stimuli is a fundamental concept in physics and materials science. At the microscopic scale, breaking this
symmetry to achieve a rectified response is exceptionally difficult to engineer and remains rare in nature. Conventional micromechanics models of crystalline solids often assume a symmetric response to applied stress, where reversing the load simply inverts the direction of defect velocity without altering its magnitude. In this work, we report an atomic-scale, geometry-rooted mechanism that breaks this
symmetry. Molecular dynamics simulations of face-centered cubic nickel reveal that dislocations containing atomic-scale jogs exhibit asymmetric mobility under opposite applied stresses: reversing the loading direction triggers significantly higher drag. This asymmetry arises from the coupling of two internal variables with different transformation parity: a non-affine displacement of an atom at the jog core, and a strain-like tensor associated with the advance of the dislocation. Because jogs are ubiquitous structures in plastic deformation, this discovery challenges classical descriptions of plastic deformation mechanisms, with direct implications for cyclic creep, and opens new pathways for defect engineering to enhance fatigue resistance.
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Superconductivity
Bending-like stress induced by solder joint under uniaxial tensile testing in 2G-HTS tapes: Impact and optimization approach
Dean Liu, Yue Wu, Haoliang Xiang et al. (+4 more)
The reversible stress limit (\mathit{R}_{rev}) of second-generation high-temperature superconducting (2G-HTS) tapes is a critical performance indicator, typically characterized through uniaxial tensile testing. In practice, the accuracy of the measured Rrev value is often compromised by stress concentration induced by the voltage tap solder joint. The present study investigates the underlying interference mechanism using integrated experimental and numerical methods. Mechanistic analysis reveals that under uniaxial tensile loading, the local
geometric inhomogeneity introduced by the solder joint induces an external, bending-like stress in the vicinity of the solder joint, transitioning from additional tensile stress in the zone adjacent to the joint to additional compressive stress in the zone remote from it. When the solder joint is attached to the front surface of the tape (the side closer to the superconducting layer), the superconducting layer experiences localized additional tensile stress, triggering premature damage and early \mathit{I}_{c} degradation. Consequently, an optimized back-surface soldering approach is proposed, which positions the superconducting layer in a localized compressive zone. Experimental validation demonstrates that the proposed approach effectively mitigates testing errors for various tape configurations. Notably, for the tape with a copper layer thickness of 5 {\mu}m, the measured \mathit{R}_{rev} increased from 546 MPa to 734 MPa, corresponding to a 42% increase, and moved closer to the actual value. The findings provide essential insights for the precision characterization of the electromechanical performances (EMPs) of 2G-HTS tapes.
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All authors Dean Liu, Yue Wu, Haoliang Xiang, Xiaofen Li, Caida Fu, Chiheng Dong, Yue Zhao