Statistical Mechanics · Cross-listed from physics.soc-ph
Transfer Dynamics and Spectral Cascades in Graph-Coupled Kuramoto Networks
Marcin Kowalczyk, Pietro Liò and Zbigniew R. Struzik
This work introduces a spectral transfer formalism for nonlinear synchronisation dynamics to resolve how internal dynamical activity redistributes across network scales, moving beyond traditional global observables like the Kuramoto order parameter. By projecting Kuramoto phase dynamics onto the eigenbasis of the graph
Laplacian, we construct a time-dependent transfer
matrix and derive novel network metrics, including the spectral flux, which quantifies directional redistribution between structural dynamical scales rather than physical transport across nodes. Numerical simulations on modular and hierarchical networks reveal highly structured, intermittent spectral transfer episodes characterised by forward and inverse spectral cascades, directional reversals, and complex interaction geometries. Crucially, we demonstrate a clear separation between macroscopic coherence and microscopic spectral interactions, showing that highly organised, fluctuating internal redistribution dynamics persist even beneath nearly stationary and featureless global synchronisation states. This framework extends conventional synchronisation analysis and establishes a multiscale approach for interpreting network dynamics as an evolving process of spectral reorganisation.
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Materials Science · Cross-listed from physics.geo-ph
Shape matters: DEM investigation of geometry-controlled mechanical response in irregular rock fragments under static and dynamic loading
Athena Bahramiyarahmadi and Rick Chalaturnyk
Mechanical characterization of subsurface rock formations typically requires standardized cylindrical core specimens, which are often unavailable from fractured or unconventional reservoir sequences. This study uses a Discrete Element Method (DEM) framework calibrated to Sulphur Mountain Formation siltstone to investigate how fragment geometry governs mechanical response in irregular rock particles, which are direct analogues of drill cuttings. Nineteen specimens (18 procedurally generated irregular geometries and one reference Brazilian disk), normalized to a 10 mm bounding sphere radius, were tested under quasi-static (Brazilian-type) and dynamic (Short Impact Load
Cell) loading modes. Four mechanical outputs of failure force (Ff), apparent strength ({\sigma}f), apparent stiffness (Ka), and stiffness (E) were regressed against seven retained shape descriptors. Results show that force-based quantities are strongly controlled by the surface-area-to-volume (SA/V) ratio under static loading (Adj. R2 = 0.69), while area-normalized quantities ({\sigma}f and E) are geometrically insensitive. Dynamic loading amplifies
geometric sensitivity for failure force and introduces an independent role for surface concavity depth. These findings establish a preliminary quantitative framework for interpreting mechanical measurements from irregular rock fragments when a standardized core is unavailable.
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Strongly Correlated Electrons
Intrinsic anomalous Hall effect in the surface conduction regime of non-magnetic narrow-gap insulator FeSi
Yong-Cheng Pan, Hwai-Chi Lin, Li-Han Wang et al. (+6 more)
The realization of an intrinsic anomalous Hall effect (AHE) in the absence of bulk magnetism is a rare phenomenon, requiring a spontaneous breaking of the time-reversal
symmetry within the boundary states without a thermodynamic phase transition. Here, we report a robust, zero-field-hysteretic intrinsic AHE confined to the low-temperature surface-conduction regime of the prototypical narrow-gap
insulator FeSi. By systematically investigating single
crystals grown via Czochralski and chemical vapor transport methods with controlled thicknesses and surface preparations, we demonstrate that low-temperature electrical conductivity correlates with surface roughness and anti-correlates with sample thickness, confirming the emergence of surface conducting states (CSS) below $T_{\rm CSS} \simeq 55-75\text{ K}$. Meanwhile, a robust, field-hysteretic and temperature-independent anomalous Hall conductivity is found below $T_{\rm AHE}\simeq45-70\text{ K}$, implying the presence of
magnetic order in the surface conduction regime. Bulk
magnetic susceptibility and specific-heat measurements reveal no thermodynamic phase transitions, verifying that the sample interior remains a non-
magnetic insulator. Analyses of conductivity scaling and effective three-dimensional conductivity reveal the intrinsic nature of this surface-driven AHE, evidencing the presence of an emergent
magnetic order within the metallic surface of a non-
magnetic bulk
insulator. These findings establish FeSi as a compelling platform to investigate the interplay between strong electron correlations and anomalous Hall transport.
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All authors Yong-Cheng Pan, Hwai-Chi Lin, Li-Han Wang, Chia-Nung Kuo, Han-Shiuan Lin, Che-Ning Yeh, Chin-Shan Lue, Anne de Visser, Yu-Te Hsu
Materials Science
Ferromagnetic resonance and magnetic anisotropy in YbMn$_\text{6}$Sn$_\text{6}$
Philipp Schwenke, Kyle W. Fruhling, David Weffling et al. (+3 more)
The RMn$_\text{6}$Sn$_\text{6}$ (R = rare earth) family of kagome magnets exhibits a rich variety of
magnetic states and unconventional electronic and
magnetic properties. While the static
magnetic properties of these materials have been extensively investigated, their magnetization dynamics remain less explored. Here, we investigate the
magnetic anisotropy and dynamic magnetization of ferromagnetic YbMn$_\text{6}$Sn$_\text{6}$ using angle-dependent ferromagnetic resonance (FMR) spectroscopy and DC magnetization measurements. The angular dependence of FMR reveals the expected uniaxial anisotropy along the crystallographic c-axis, which is the global magnetically hard axis. In addition, we identify a pronounced twofold anisotropy within the ab-plane, which is independently confirmed by angle-dependent DC magnetization measurements. The observed uniaxial anisotropy in the ab-plane indicates a breaking of the expected sixfold rotational
symmetry in the
magnetic response that is attributed to growth induced anisotropy.
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All authors Philipp Schwenke, Kyle W. Fruhling, David Weffling, Vitaliy I. Vasyuchka, Fazel Tafti, Mathias Weiler
Materials Science
Morphological evolution of an Au crystalline domain in a nano-particle investigated by Bragg coherent diffraction imaging
Seonghyun Han, Saehyun Kang, Ouyoung Kwon et al. (+4 more)
Understanding the dynamic structural
evolution of metallic nanoparticles is crucial for tailoring their functional properties. In this study, we utilized three-dimensional coherent X-ray diffraction to investigate the morphological transformation of Au nanocrystalline domains in a multi-domain nanoparticle during in-situ annealing. By combining Bragg coherent diffraction imaging with autocorrelation function analysis, we observed a transformation from an anisotropic multi-domain configuration toward a single crystalline
equilibrium morphology. Above 600 degrees Celsius, a small subsidiary domain merged into the primary domain, which was continuously coarsened at 625 degrees Celsius, resulting in a more isotropic morphology. Finally, at 635 degrees Celsius, the low-energy {111} and {100} facets emerged, and the
crystal shape converged toward an
equilibrium truncated octahedral geometry. This work demonstrates a framework for interpreting complex domain dynamics, offering fundamental insights into domain growth and
equilibrium shape formation.
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All authors Seonghyun Han, Saehyun Kang, Ouyoung Kwon, Wonsuk Cha, Hyon Chol Kang, Chan Kim, Do Young Noh
Statistical Mechanics · Cross-listed from physics.soc-ph
Dynamics-structure interchangeability in binary opinion models on multiplex networks
Julian Sienkiewicz and Anna Chmiel
We examine the interchangeability between two duplex systems with opinion dynamics: one characterized by different dynamics parameters $a_1$ and $a_2$ on each layer and full node overlap, and the second with the same parameter $a_1$ on both layers but only partial node overlap $r$. We introduce a general framework for identifying the critical line between the ordered and disordered phases, thereby translating one system into another. The description is supported by several examples of opinion dynamics models and a rigorous measure of the distance between the stationary solutions of the rate equations in both settings. Our results show that even large values of $r$ are sufficient to obtain very good correspondence between the two settings.
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Disordered Systems and Neural Networks
Topological Fingerprints of Commensurate Order in Twisted Moiré Lattices
Collin J. Kovacs, Jiangxu Li, Yang Zhang et al. (+3 more)
Moiré patterns in twisted bilayer materials exhibit long-range periodic order that is highly sensitive to twist angle. Identifying commensurate angles from real-space atomic structures remains challenging, as spectral and
geometric methods emphasize global periodicity and are sensitive to disorder and finite-size effects. Here, we introduce a data-driven topological framework that quantifies moiré periodicity by treating atomic configurations as point-cloud data and extracting multiscale signatures using persistent homology. At the core of our approach is a small-neighborhood separation filter that removes redundant local motifs in persistence diagrams while preserving key structural features, enabling sharp minima in Wasserstein distances between twisted and untwisted reference configurations that accurately recover commensurate angles. We
benchmark this framework against
geometric and spectral similarity measures and show that the resulting topological descriptors remain stable under positional disorder ranging from weak to strong perturbations in the bond length. We further transfer these descriptors using a constrained Gaussian process surrogate to sparsely sampled configurations of a twisted MoTe$_2$ dichalcogenide bilayer. These results establish topological descriptors with neighborhood separation as a robust framework for identifying commensurate order in moiré systems and tracking commensurate structural similarity under disorder, sparsity, and finite-size effects.
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All authors Collin J. Kovacs, Jiangxu Li, Yang Zhang, Konstantinos D. Vogiatzis, Adrian Del Maestro, Vasileios Maroulas
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Scalable simulation of non-Markovian quantum transport by stochastic-phase bath reduction
Zhen Huang, Lin Lin and Pinchen Xie
Accurate simulations of non-Markovian
quantum transport remain limited to small systems, and a key bottleneck is that each system site requires an independent set of
quantum bath orbitals. We introduce the
Stochastic Phase
Algorithm (SPA), which replaces the independent local Gaussian baths in single-quasiparticle Holstein models by $R$ shared
quantum baths with
stochastic site-dependent phases. We prove that phase averaging reproduces the target two-point bath correlation
matrix for every $R$, while increasing $R$ systematically suppresses errors from higher-order cross-site correlations. We obtain a fixed-time $O(R^{-1})$ trace-norm error bound with a prefactor independent of system size and connectivity. This spatial compression applies directly to
unitary baths and can be combined with coupled-Lindblad spectral compression [Phys. Rev. Lett. 136, 090403 (2026)], which represents each shared environment by a very small number of coupled, damped
quantum modes fitted to its thermal bath correlation over the simulation window. Numerically, SPA converges against direct
unitary benchmarks on a $3\times3$
lattice, enables full-state-vector
quantum-bath dynamics on a $100\times100$
lattice, and, with $R=1$, closely reproduces near exact
benchmarks for
exciton populations in bacteriochlorophyll aggregates and carrier mobility in rubrene.
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Quantum Gases · Cross-listed from physics.optics
A photonic integrated comb engine for ultracold quantum gases
Wei Sun, Xiaoying Yan, Jinbao Long et al. (+18 more)
Cold atoms underpin
quantum sensing, simulation and computation, but their coherent control demands highly stable optical fields whose generation, referencing and power scaling remain formidable integration challenges. While photonic integrated
circuits have yielded compact visible
lasers and high-$Q$ microresonators have enabled chip-scale optical frequency combs, these crucial technologies have largely remained functionally fragmented. Consequently, the coherent manipulation of ultracold
quantum gases using a fully integrated
laser-comb source has yet to be realized. Here we demonstrate a scalable, hybrid-integrated microcomb engine at 780 nm that seamlessly bridges frequency synthesis, atomic referencing and power amplification to achieve
quantum state control of a Bose–Einstein condensate. By self-injection locking of electrically driven III–V
lasers to high-$Q$ Si$_3$N$_4$ microresonators, we generate coherent platicon microcombs featuring 20- and 100-GHz mode spacings. Absolute referencing of the microcomb to an $^{85}$Rb transition actively suppresses long-term frequency drift from over 200 MHz to the 100-kHz level across 2,000 s. A selected comb tooth is subsequently injection-amplified to 102 mW, entirely preserving the microcomb's pristine coherence and stability. We utilize this synthesized field to construct an optical
lattice, drive coherent two-
photon Raman transitions, and prepare stationary
spin–orbit-coupled and Raman-
lattice states within an $^{87}$Rb condensate. By providing a synchronized optical grid, this atom-referenced microcomb can allow multiple optical-control channels to scale without a proportional multiplication of independent frequency references. Our work establishes a fully integrated frequency-synthesis architecture essential for realizing deployable, large-scale atomic
quantum systems.
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All authors Wei Sun, Xiaoying Yan, Jinbao Long, Sanli Huang, Zhixin Duan, Hao Tan, Zhenyuan Shang, Zeying Zhong, Jiahao Sun, Yue Hu, Shichang Li, Baoqi Shi, Yi-Han Luo, Shuyi Li, Chen Shen, Hanqing Liu, Xiangbin Su, Haiqiao Ni, Zhichuan Niu, Shengjun Yang, Junqiu Liu
Mesoscale and Nanoscale Physics
Dynamic moiré-like band modulation in Dirac materials via multi-beam optical interference
Evelyn P. Sinaga, Rizky Setiawan, Herri Trilaksana et al. (+2 more)
We propose a purely optical Floquet framework to dynamically generate moiré-like superlattices and quasicrystalline potentials in a gapped Dirac material, entirely bypassing the need for physical twisting. The interference of three coherent circularly polarized beams produces a triangular, valley-dependent Floquet mass landscape that folds the Dirac spectrum into a mini-Brillouin zone, driving pronounced valley-selective miniband reconstruction. We further show that the bands near the Fermi level undergo a light-driven topological phase transition. Remarkably, interfering five or seven beams yields non-crystallographic spatial patterns, giving rise to optical quasicrystals with similar valley contrasting features. Although this purely optical approach provides a versatile route to band engineering, reaching deep subwavelength modulation requires overcoming the free-space diffraction limit. To overcome this limitation, we consider highly confined, linearly polarized surface plasmon polariton fields with controlled relative phases. Their phase-controlled interference generates a spatially alternating chiral mass with zero spatial average. Consequently, the two valleys exhibit degenerate energy spectra while hosting opposite valley-resolved miniband Chern numbers. Our findings establish a reconfigurable, all-optical platform for dynamically engineering moiré-like bands, quasicrystalline electronic states, and valley-dependent
topology without mechanical twisting.
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All authors Evelyn P. Sinaga, Rizky Setiawan, Herri Trilaksana, Lukas P. A. Krisna, Eddwi H. Hasdeo
Strongly Correlated Electrons · Cross-listed from math.NA
Computation of anisotropic singular sums from high-order derivatives of Epstein zeta functions
Andreas A. Buchheit and Jonathan K. Busse
The precise and efficient evaluation of large-scale
lattice sums involving power-law kernels is a fundamental computational problem in the simulation of classical and
quantum systems with long-range interactions. While methods for spatially isotropic kernels, some based on Epstein zeta functions, have advanced considerably in recent years, the anisotropic case has lagged behind, despite its broad relevance to both fundamental and effective interactions such as the dipole interaction in
magnetic materials. In this work, we solve this issue by defining and analyzing anisotropic Epstein zeta functions for which we derive stably computable representations obtained from wave vector derivatives of
lattice sums over isotropic interaction kernels. These functions find direct application in the analytical and numerical study of anisotropically interacting
lattice systems. Going further, they provide the correction term in an exact equivalence between discrete
lattices and their continuous analogs in a recent generalization of the classical Euler-Maclaurin summation formula to
lattices and summands involving power-law kernels. Their connection to high-order derivatives of zeta functions can be used to improve convergence rates of numerical
algorithms, for instance in micromagnetics, or to provide rapidly convergent expansions suitable for precomputations of generalized zeta functions. We derive a stably computable representation of anisotropic Epstein zeta functions, including the possibility for analytically removing Rayleigh–Wood singularities, and we develop a numerical
algorithm for their stable evaluation for any
lattice, power-law decay exponent and anisotropy order. We
benchmark the
algorithm against closed-form identities, direct summation and multi-precision results, obtaining machine precision across various
lattices, power-law exponents, and anisotropy orders.
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Soft Condensed Matter · Cross-listed from math.AP
The Naito–Okuda–Ouyang Biconcave Red Blood Cell Profile as a Finite-Energy Unbranched Weak Immersion with Point-Force Residues
Hao Wu
The axisymmetric profile \(\sin\psi(\rho)=c_0\rho\log(\rho/\rho_B)\) introduced by Naito, Okuda, and Ouyang is an exact solution of the unconstrained Helfrich shape equation for every \(\rho>0\), but its mean
curvature diverges logarithmically at the dimple center. A covariant local analysis shows that in Cartesian graph coordinates the immersion is nondegenerate and belongs to \(W^{2,p}\) for every finite \(p\); it is \(C^{1,\alpha}\) for every \(\alpha<1\), but neither \(C^{1,1}\) nor \(C^2\). The conformal factor has a finite nonzero limit, so the point has branch multiplicity one and is not a branch point in the sense used in weak-immersion compactness theory. The Helfrich energy is finite, whereas the complete Euler–Lagrange operator carries the distributional residue \(\E_{\CH}=4\pi c_0\delta_p\) under the convention specified below. Hence the profile is a classical solution on the punctured surface and a finite-energy weak immersion, but it is not a free weak critical point of the unforced Canham–Helfrich functional. Stationarity is restored after adding the corresponding point-force potential or under a pinned-point constraint. Area and volume multipliers cannot cancel the Dirac residue. The apparent sign discrepancy between the shape equation used in the original papers and the modern convention is explained by the opposite definition of mean
curvature. These results delimit precisely what can and cannot be inferred from modern existence and regularity
theorems for Canham–Helfrich minimizers.
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Materials Science
Three-photon photoemission on metallic transition metal dichalcogenide NiTe$_{2}$
Cheng-Tien Chiang, Mukesh Singh, Yu-Jhen Chuang et al. (+6 more)
Three-
photon photoemission (3PPE) signals on NiTe$_{2}$ are observed for the first time upon ultraviolet excitations. In the energy range beyond two-
photon excitations, an energy-momentum dispersive feature is clearly identified with characteristic light polarization dependence. Based on its dispersion, spectral width, as well as intensity as a function of the parallel momentum, this dispersive 3PPE feature could be ascribed to an image potential resonance overlapping with an unoccupied Ni $4s$ -Te $4d$/$5p$ bulk band in accordance with the electronic band structure. Our results underlie higher-order non-linear photoemission on metallic transition metal dichalcogenides and facilitate future ultrafast studies of coherent electron dynamics in anisotropic, two-dimensional systems.
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All authors Cheng-Tien Chiang, Mukesh Singh, Yu-Jhen Chuang, Chia-Nung Kuo, Prabesh Bista, Yu-Chan Lin, Chen-Bin Huang, Ming-Chiang Chung, Chin Shan Lue
Materials Science
Solid-State Dealloying Enables Local Symmetry Breaking in Ternary Intermetallic Thin Films
Mizuki Ohno, Reiley Dorrian, Veronica Show et al. (+2 more)
Metastable
quantum materials often occupy narrow composition windows with local
symmetries distinct from competing
equilibrium structures. These features open pathways for realizing qualitatively new electronic properties within a similar chemical subspace while at the same time complicating their deterministic synthesis. Here we illustrate a post-growth solid-state dealloying process using epitaxial ternary thin films in the La–Ag–Ge chemical space to realize a diffraction-averaged centrosymmetric superconducting structure. The process converts polar $P6_3mc$-LaAgGe into diffraction-averaged centrosymmetric AlB$_2$-type $P6/mmm$ La-Ag-Ge through net Ag loss during annealing at 800–900 $^\circ$C. Atomic-resolution electron microscopy reveals local Ag–Ge displacements of both signs relative to the planar configuration, consistent with local inversion-
symmetry-breaking distortions. The converted films exhibit composition-dependent superconductivity with critical temperatures below 1 K and in-plane upper critical fields that exceed the weak-coupling Pauli-field estimate by a factor of approximately 6 in the thinnest superconducting films. These results establish epitaxial solid-state dealloying as a route to phase-selective synthesis of metastable phases, offering control over atomic-scale structural configurations and their interplay with emergent electronic properties.
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All authors Mizuki Ohno, Reiley Dorrian, Veronica Show, Salva Salmani-Rezaie, Joseph Falson
Statistical Mechanics · Cross-listed from physics.comp-ph
Optimal limits on weak integrability breaking and protected thermal memory near qutrit exchange
Hanbing Liang and Fujun Liu
Although integrability does not universally require a continuous one-site
symmetry, we rigorously prove that every jointly analytic, regular Yang-Baxter deformation of the qutrit exchange interaction necessarily retains a nontrivial, analytically varying one-site charge. Breaking this local
symmetry imposes a fundamental physical constraint on approximate conservation, governed by the optimal uniform bound $\delta^3 \le C\varepsilon$ that explicitly relates the minimal one-site
symmetry defect $\delta$ to the local current-conservation residual $\varepsilon$. While breaking all one-site charges strictly forbids an exact integrable completion, an optimally compensated nearest-neighbor interaction saturates this cubic limit and anomalously extends the guaranteed infinite-temperature energy-current correlation window to order $|\lambda|^{-3}$ in the perturbation strength $\lambda$. Furthermore, we reveal a fundamental resonance obstruction for intrinsic conversion perturbations that strictly prevents any exact first-order repair of a broken one-site charge on any finite ring. Nevertheless, we demonstrate that the complete eight-dimensional charge
memory matrix remains thermodynamically protected and approaches the identity for timescales $t=o(|\lambda|^{-3/2})$, a robust feature of the full infinite-temperature dynamics when the thermodynamic limit is taken before weak coupling.
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Statistical Mechanics · Cross-listed from quant-ph
Certifying fermionic Gaussian states (and a little more) with optimal precision dependence
Ninnat Dangniam, Laphas Premcharoen, Metrasit Sripech et al. (+1 more)
Fermionic Gaussian states are the workhorse reference states for
qubit-based
quantum simulation of fermionic systems, yet existing certification protocols either proceed via fidelity estimation, leading to suboptimal sample complexity in the target precision $\epsilon$, only apply to Haar-typical states, or require adaptive measurements on a large fraction of
qubits. We give an adaptive protocol that certifies any $d$-mode pure fermionic Gaussian state using $O(d^2\epsilon^{-1})$ copies, single-
qubit measurements with only one
qubit measured adaptively per copy, and $O(d^3)$ classical processing time per copy. The $\epsilon^{-1}$ dependence is optimal for the certification problem, even among strategies using entangled measurements. The sample complexity is controlled by the spectral gap of a $d\leftrightarrow d-2$ down-up walk—a Markov chain studied in the theory of high-dimensional expanders, equivalent to a two-site Glauber dynamics in statistical physics—relating certification efficiency to relaxation time to
equilibrium. The worst-case bound is tight for this protocol and is attained by physically relevant states, including ground states of the fully dimerized Su-Schrieffer-Heeger (SSH) chain and BCS pair states. In contrast, numerics up to $d=14$ suggest that $O(d \epsilon^{-1})$ copies suffice to certify Haar-typical Gaussian states, a factor of $d$ improvement over the worst-case bound. Finally, because the bound depends only on the target's computational-basis distribution, the protocol extends to efficiently phase-dressed states—states obtained by injecting an efficiently computable diagonal phase to Gaussian states—with the same sample complexity. The class includes a continuous family of four-mode non-Gaussian magic states for matchgate computation.
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All authors Ninnat Dangniam, Laphas Premcharoen, Metrasit Sripech, Thiparat Chotibut
Mesoscale and Nanoscale Physics
Active control of THz plasmon propagation in a one-dimensional electronic waveguide
Thomas Vasselon, Uzer Ahmad, Clément Geffroy et al. (+14 more)
Quantum nanoelectronics is pushing towards ever higher operating frequencies in order to realise
quantum technologies capable of processing information at unprecedented speeds. A particularly promising direction is the development of flying electron
qubits, which offer the prospect of
quantum operations on picosecond timescales. Achieving in-flight
quantum control in this regime would establish a fundamentally new paradigm for studying
quantum entanglement and enable a novel form of
quantum information processing based on propagating electronic wavepackets. Here we report a first step towards this goal by injecting ultrashort electron wavepackets into an engineered
quantum nanoelectronic device. We demonstrate active control over the propagation speed of an electron wavepacket with a temporal duration as short as 4 ps in a quasi-one-dimensional electron waveguide with a length ranging from 10 $\mathrm{\mu}$m to 40 $\mathrm{\mu}$m. This advance provides a key building block for ultrafast
quantum operations using flying electrons. Beyond its technological implications, our approach offers a platform for exploring the intrinsic dynamical processes that govern
quantum transport and coherence in nanoscale electronic systems.
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All authors Thomas Vasselon, Uzer Ahmad, Clément Geffroy, Lucas Mazzella, Matteo Aluffi, Seddik Ouacel, Jashwanth Shaju, Kevin Bredillet, Nathan Roussel, Jean-François Roux, Pierre-Baptiste Vigneron, Arne Ludwig, Andreas D. Wieck, Matias Urdampilleta, Hermann Sellier, Giorgos Georgiou, Christopher Bäuerle
Materials Science
Disentangling spin polarization from driven circular ionic motion in EuTiO$_3$
Clifford J. Allington, Matthew J. Lutz, Enoch Ho et al. (+30 more)
Coherently driven circular ionic motion has been reported to produce large helicity-dependent optical responses attributed to transient magnetization. However, the microscopic nature and magnitude of this phenomenon, sometimes referred to as dynamical multiferroicity, remain strongly debated. Here, we directly study the connection between ionic circulation induced by a high-field circular terahertz (THz) drive and its effect on the
spin system of EuTiO$_3$ using X-rays. This material exhibits an optical response consistent with the putative
magnetic signal observed in related non-
magnetic materials. Furthermore, the presence of Eu$^{2+}$ ions enables the use of X-ray
magnetic circular dichroism (XMCD) to test for the creation of transient
spin polarization. Simultaneously, ultrafast X-ray diffraction (XRD) measures the circular ionic motion from which we determine the mechanical angular momentum. We find a classical ionic contribution of $3\times10^{-8}~\mu_B$ from XRD and upper limits of $0.03~\mu_B$ and $0.11~\mu_B$ from the sensitivity of XMCD at the europium $M_5$ and $L_2$ edges, probing the $4f$ and $5d$ shells of Eu$^{2+}$, respectively. These observations show that large-amplitude circular ionic motion in this system is not accompanied by a detectable
spin polarization despite the clear signature in the optical data, with the XMCD upper bounds and classical contribution differing by many orders of magnitude.
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All authors Clifford J. Allington, Matthew J. Lutz, Enoch Ho, Fabian Graf, Martina Basini, Hiroki Ueda, Michael Grimes, Alexander B. Elliott, Megan F. Biggs, Ravi Finn, Shih-Wen Huang, Merideth A. Henstridge, Matthias C. Hoffmann, Takahiro Sato, Roberto Alonso-Mori, Diling Zhu, Quynh L. Nguyen, Vincent Esposito, Jeffrey T. Babicz Jr., Elizabeth Skoropata, Biaolong Liu, Eugenio Paris, Arnau Romaguera Camps, Elia Razzoli, Roman Mankowsky, Flavio Capotondi, Nicolas Jaouen, Daniele Pergolesi, Milan Radovic, Matteo Savoini, Steven L. Johnson, Jeremy A. Johnson, Urs Staub
Mesoscale and Nanoscale Physics
Local time-reversal-invariant topological markers in two dimensions
Thomas Klein Kvorning, Miguel F. Martínez and Julia D. Hannukainen
Local topological markers provide a real-space characterization of topological phases and are suited to noncrystalline models. We derive a local topological marker, the Chern-Simons descendant marker, for characterizing the
topology of two-dimensional time-reversal-invariant near-Gaussian states from the one-particle density
matrix \(\rho\). We construct an auxiliary three-dimensional state characterized by the local Chern-Simons marker, and use dimensional reduction to obtain the Chern-Simons descendant marker for the original two-dimensional state. This derivation introduces a local Hermitian involution \(S\) that is odd under time reversal. When \([S,\rho]=0\), the local Chern-Simons descendant marker reduces to half the difference of the local Chern markers in the \(S=\pm1\) sectors. Constructing an \(S\) that commutes exactly with \(\rho\) generally requires fine-tuning, but this is not needed—the local Chern-Simon marker remains well defined whenever \(\Gamma=\{\rho,S\}-S\) has a spectral gap around zero, even when \([S,\rho]\neq0\). This leaves the practical problem of identifying a suitable \(S\) for a given state, which, importantly, is straightforward even when
spin is not a candidate. We show this by considering both strong Rashba and Dresselhaus
spin-orbit coupling, for which knowledge of the physical origin of the state reduces the general problem of choosing $S$ to a one-parameter family \(S(\theta)\). We evaluate the optimal angle $\theta$ maximizing the spectral gap of $\Gamma$ analytically assuming translation invariance, and find that the gap of $\Gamma$ remains open for a broad range of angles around the optimum. The same value of \(\theta\) remains valid in disordered systems, providing an easy way to obtain choice of \(S\) for evaluating the local Chern-Simons descendant marker of the state.
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Soft Condensed Matter
State-Resolved Integral of First-Passage Times for Multi-Site Polymer Adsorption
Yifan Huang and Qiyun Tang
Understanding the interfacial structure of multi-site
polymer adsorption is critical for the rational design of functional nanomaterials. However, the distribution of chains attached via one, two, or more anchor points has remained inaccessible to experiments and conventional simulations. Experiments typically measure ensemble averages such as total adsorbed mass, while molecular dynamics simulations are limited to timescales far shorter than the relevant adsorption processes. To address this challenge, we introduce the State-Resolved Integral of First-Passage Times (SR-IFS) method. This approach decouples fast intra-layer conformational adjustments from the slow kinetics of external chain exchange, enabling quantitative prediction of the time-dependent distribution of attachment states ($p_1$, $p_2$, $p_3$) within a multi-site adsorbed layer. Using 3-arm
star-like
polymers as a model system, we show that the interfacial state distribution evolves from an initial prevalence of three-point attachments to a more heterogeneous mixture over long time scales, and that the
equilibrium distribution can be systematically tuned by adjusting the monomer binding energy. The SR-IFS method provides access to this state-resolved information, offering a connection between microscopic kinetics and macroscopic interfacial properties.
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Quantum Gases
Quantum dynamics of spinful impurity in ideal Bose gas
O. Hryhorchak and V. Pastukhov
We discuss the quench dynamics of an isolated system composed of a single spinful impurity in the transverse Rabi field and bath of non-interacting three- and two-dimensional
bosons. Specifically, we consider the
evolution of
bosons and a
spin-$\frac{1}{2}$ particle, initially prepared in a Bose-Einstein condensate state and a
magnetic ground state, respectively, with the
spin-dependent contact
boson-impurity interaction switched on. Applying an original mean-field-like approximation, which naturally reflects the statistical effects of the bosonic bath, we calculate time-dependent components of the average impurity
spin and the overlap of the wave function between initial and arbitrary time moments. A key prediction is a substantial speed-up in the decoherence (thermalization) dynamics of the
spin degree of freedom compared to results obtained with the Chevy-like ansatz.
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Other Condensed Matter · Cross-listed from hep-lat
Larger physical volume and bounds on the number of matter fields in noncompact gauge theories on a lattice
Fabrizio Palumbo
The work was motivated by the numerical result that in a pure SU(2) gauge theory the ratio R of the effective non-compact and compact
lattice spacing is larger than 1 and increasing with decreasing gauge coupling, as well as the expectation that it should further increase extending the parameter space. This means that with a noncompact regularization, at given number of
lattice sites and comparable scaling, one can obtain a larger physical volume, whose importance for the control of size effects has long been known. We confirm qualitatively results and expectation by a perturbative evaluation of the effective
lattice spacing in an expansion in the Plank constant of non-compact pure SU(2) and Abelian gauge theories, but we find in addition that R reaches the maximum value of sqrt(2). Including matter fields we find that R increases ( still up to sqrt(2) ) or decreases depending on the difference between the number of scalar and spinor degrees of freedom, and there are bounds on such a difference.
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Disordered Systems and Neural Networks
Rank-One Signal Recovery in Sparse Wishart Noise
Preben Forer, Urte Adomaityte and Pierpaolo Vivo
We study the high-dimensional recovery of a signal vector $\mathbf{x}$ in the presence of sparse Wishart-like noise. We define an $N \times N$
matrix $A = J+(\theta/N)\mathbf{xx}^{\top}$, where $\mathbf{xx}^{\top}$ is the rank-one deformation of the random noise
matrix $J$. We consider a Wishart-like
matrix $J={X}^{\top} X$, where $X$ is a sparse $M \times N$ random
matrix with entries $X_{ij} = c_{ij}W_{ij}$, with $c_{ij}$ regulating the density of non-zero elements, and $W_{ij}$ the bond weights. Using the replica method, we compute analytically the top eigenpair statistics of $A$, and their dependence on the signal strength $\theta$, the rectangularity ratio $\alpha=\sqrt{M/N}$, and the average connectivity of the noise. The spectral observables are expressed in terms of a system of Recursive Distributional Equations, which are efficiently solved via a Population Dynamics
algorithm. They allow us to compute the average largest
eigenvalue $\langle\lambda_1\rangle_{A}$, the average top eigenvector component density, and the average overlap between the top eigenvector of $A$ and $\mathbf{x}$. We identify a critical threshold $\theta_{\mathrm{crit}}$–depending on the average connectivity of the noise–that marks a BBP-like phase transition: below this value, $\langle\lambda_1\rangle_{A}$ is unaffected by the signal, and the overlap vanishes. Thus, the signal is not recoverable from the top eigenvector of $A$. For $\theta>\theta_{\mathrm{crit}}$, the signal-related outlier
eigenvalue becomes $\langle\lambda_1\rangle_{A}$ and the overlap is nonzero, allowing for recovery of the signal. The results are in excellent agreement with numerical diagonalisation. We show that in the dense limit, the recovery threshold and eigen-statistics converge to the results predicted by the classical BBP transition for additive rank-one deformations of dense Wishart
matrices.
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Materials Science
Compositionally Engineered Non-Equimolar LaCoO$_3$-Based High-Entropy Perovskites with Enhanced Thermoelectric Performance
Jitendra Kumar, David Bérardan, Diana Dragoe et al. (+2 more)
The decoupling of
phonon and electron transport remains a central challenge in the development of high-performance TE materials. Configurational-
entropy maximization is widely invoked as a design principle for decoupling
phonon and electron transport. This study investigates compositionally engineered LaCoO$_3$-based high-
entropy perovskites to determine whether thermoelectric transport can be improved by tuning cation identity and concentration rather than maximizing configurational
entropy. La$_{1-x}$Sr$_x$(CoFeMnCrNi)O$_3$ ($x=0.0$–$0.2$) and selected non-equimolar A- and B-site perovskite compositions were prepared by solid-state reaction. The obtained samples are predominantly single-phase, as confirmed by X-ray diffraction and Rietveld refinement, consistent with the calculated size-disorder parameters. Multication disorder introduces substantial mass and strain-field fluctuations that promote
phonon scattering. All samples exhibit p-type, thermally activated electrical transport consistent with adiabatic SPH. Sr substitution progressively reduces the hopping barrier and $\rho$, whereas non-equimolar B-site engineering partially recovers electrical transport while retaining low k. La$_{0.9}$Sr$_{0.1}$Co$_{0.4}$Cr$_{0.3}$Ni$_{0.1}$Fe$_{0.1}$Mn$_{0.1}$O$_3$, featuring a Co-rich and Cr-rich B-site composition, combines Co-associated mixed valence and
spin-state degeneracy that sustain a large alpha with Cr-mediated control of carrier concentration and a reduced polaron hopping barrier of 0.19eV. This composition achieves a power factor of 40–43 $\mu$W/(m K$^2$) and a $zT\sim0.072$ at 1100K, approximately 2.7 times that of its equimolar analogue. These results demonstrate that targeted cation chemistry and mass contrast, rather than configurational-
entropy maximization alone, provide an effective strategy for balancing electronic and
phonon transport in multicomponent oxide TE.
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All authors Jitendra Kumar, David Bérardan, Diana Dragoe, Nita Dragoe, Ashutosh Kumar
Statistical Mechanics
Universal splitting of nonequilibrium phase transitions in driven Potts heat engines
Vitória T. Henkes, Gustavo A. L. Forão, Andre C. Barato et al. (+1 more)
We investigate nonequilibrium phase transitions and thermodynamic properties of driven Potts models coupled to two thermal reservoirs at different temperatures. The interplay with the multi-state structure of the Potts model leads to distinct phase-transition scenarios. The proposed driving scheme breaks the
symmetry between the Potts states and gives rise to multiple transitions within the ordered phases, where the phases are characterized by different numbers of stable fixed points. This number can vary from $q$ fixed points to $1$ fixed point, corresponding to $q-1$ distinct transitions. The driving scheme strongly affects the thermodynamic operation regimes, allowing the system to operate as a heat engine. We demonstrate that these phenomena persist for both a mean-field (MF) model and a two-dimensional model, confirming the robustness of the results with respect to dimensionality. For the MF case, we also develop a phenomenological description in the strongly ordered regime that yields analytical expressions for the power, heat currents, and efficiency. Our results show how multi-state collective interactions, nonequilibrium driving, and thermal bias jointly generate a rich phase structure and the emergence of a collective heat engine.
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All authors Vitória T. Henkes, Gustavo A. L. Forão, Andre C. Barato, Carlos E. Fiore
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Beyond Antibunching: Photon Correlation Analysis Reveals Blinking Origin
Patricia Kallert, Santiago Bermúdez-Feijóo, Giorgio De Pascalis et al. (+18 more)
A variety of
quantum emitters compete in the quest for the best single-
photon source for photonic
quantum technologies. Consequently, only a consistent approach to analyze the second-order auto correlation function allows comparison of the multi-
photon contribution ($g^{(2)}(0)$) of different sources. However, the community employs different and inconsistent methods for blinking sources, leading to incomparable
benchmarks of source quality. Here, we use the emission of an inherently non-blinking
quantum dot (QD) and apply artificial blinking through two different mechanisms: masking the recorded raw data in post-processing and emulation of a blinking system by gating the
laser excitation pulses. We then compare the $g^{(2)}(0)$ values with the non-blinking result. For the analysis, we investigate five
estimators of $g^{(2)}(0)$ actively used in the literature. While fitting the envelope of the correlations on long-time scales with the correct blinking model is the best choice, normalizing to the Poisson level gives by far the worst proximity. Furthermore, we test our predictive model to identify the underlying blinking mechanism of a QD in a circular Bragg grating cavity.
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All authors Patricia Kallert, Santiago Bermúdez-Feijóo, Giorgio De Pascalis, Nicolas Claro-Rodriguez, Ioannis Caltzidis, Normen Auler, Eva Berger, Rebecca Aschwanden, Tobias Krieger, Saimon. F. Covre da Silva, Sandra Stroj, Quirin Buchinger, Michele B. Rota, Thomas Hummel, Sven Höfling, Armando Rastelli, Rinaldo Trotta, Dirk Reuter, Sonja Barkhofen, Klaus D. Jöns, Tobias Huber-Loyola
Statistical Mechanics
Optimal Evasion from a Resetting Searcher
Ami Taitelbaum, Matan Shporer, Shlomi Reuveni et al. (+1 more)
Returning to a familiar location can help a searcher find its target—but how should the target move to avoid being found? We address this question for a resetting Brownian searcher and a mobile target fluctuating around a home location. Keeping the target's typical exploration range fixed, we find that the mean capture time is maximized at an intermediate correlation time: rapid motion promotes encounters, whereas slow motion leaves the target effectively stationary. Between these extremes, persistent excursions away from the searcher's reset point can substantially delay capture. Analytical limiting results explain this optimum, while numerical solutions reveal an approximately linear relation between the maximal mean capture time and the optimal correlation time across many decades. These findings identify temporal correlations as a resource for evasion, allowing a target to prolong survival by changing how it moves rather than where it roams.
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All authors Ami Taitelbaum, Matan Shporer, Shlomi Reuveni, Michael Assaf
Mesoscale and Nanoscale Physics
Helical Anomaly from Concurrent $\mathbb{Z}$ and $\mathbb{Z}_2$ Topology in an Acoustic Semimetal
Hou-Yin Li, Hua-Shan Lai, Jian-Lan Xie et al. (+3 more)
Topological classification constitutes a cornerstone of modern condensed-matter physics. Historically, topological systems have been predominantly characterized by invariants confined to a single topological class, such as topological
insulators with a $\mathbb{Z}_2$ invariant and Weyl semimetals with an integer ($\mathbb{Z}$) topological charge. While such classification frameworks in principle permit gapless phases in which bulk and boundary degeneracies are protected by distinct invariants, this regime has received limited focused
attention, as coordinating the requisite
symmetries within a single band structure is highly nontrivial. Here, we realize such concurrent $\mathbb{Z}$ and $\mathbb{Z}_2$
topology in a two-dimensional acoustic semimetal, revealing pseudospin-selective topological bulk modes arising from the interplay between these distinct invariants, termed helical anomaly bulk states (HABSs). Our
lattice design exploits layer, sublattice, and gauge-staggered degrees of freedom, enabling modular control of effective time-reversal, chiral, and particle-hole
symmetries. The resulting system exhibits bulk degeneracies protected by an integer $\mathbb{Z}$ invariant and Kramers-like boundary degeneracies protected by a $\mathbb{Z}_2$ invariant, forming twisted boundary arcs. Crucially, finite-size systems manifest helical or anti-helical edge states coexisting with HABSs, a distinctive signature absent in single-invariant
topologies. Our results establish HABSs as a characteristic signature of concurrent
topology and demonstrate a new regime where bulk and boundary invariants jointly govern topological transport beyond conventional single-class frameworks.
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All authors Hou-Yin Li, Hua-Shan Lai, Jian-Lan Xie, Xiao-Chen Sun, Yan-Feng Chen, Cheng He
Soft Condensed Matter
Active Self-Consistent Field Theory for Ornstein-Uhlenbeck Polymers
Yuliang Huang, Chun-Lai Ren and Qiyun Tang
We develop an active self-consistent field theory (ASCFT) for studying the steady-state behavior of active Ornstein–Uhlenbeck
polymers. Starting from the
stochastic equations of motion under the unified colored noise approximation, we derive an effective
Hamiltonian that extends the classical
polymer field theory to non-
equilibrium systems. The resulting free energy functional incorporates both the Flory–Huggins interaction parameter $\chi N$ and the persistence time $\tau$ of the active noise, enabling a unified description of thermodynamic and activity-driven effects. To solve the governing equations, we implement a stable implicit-explicit numerical scheme that handles the fourth-order term induced by activity. Our simulations reveal that increasing activity suppresses microphase separation, with the density modulation amplitude decaying as $\Delta\phi \propto \tau^{-1/2}$ for large $\tau$. This scaling is independent of copolymer composition and is confirmed by an asymptotic analysis of the free energy functional in the large-$\tau$ limit. The ASCFT framework provides a new theoretical tool for predicting and designing the non-
equilibrium morphologies of active
polymer systems, bridging the gap between traditional self-consistent field theory and active matter physics.
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Strongly Correlated Electrons · Cross-listed from math-ph
Frustration-Free Models for Topological Holography: Fusion Spin Chains as Boundary Algebras
Zhengwei Liu and Zishuo Zhao
We introduce a class of $2d$
quantum spin systems based on a
unitary spherical fusion category with a chosen object. These models have frustration-free, reflection positive, but generally non-commuting local interactions, generalizing the Levin-Wen string-net models. Based on the theory developed in arXiv:2510.20662, we explicitly realize the Temperley-Lieb-Jones
algebra, and more generally fusion
spin chains as their boundary
algebras.
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