Materials Science
Crystallizing Substrates Drag Supported Nanoparticles
Cheng-Yu Chen, Duncan Burns, Peter W. Voorhees et al. (+1 more)
When a solid support undergoes crystallization, the advancing amorphous-to-crystalline transformation front separates regions of distinct surface energy, creating a moving interfacial energy boundary. A supported nanoparticle straddling such a boundary experiences an asymmetric particle-substrate interfacial energy environment that constitutes a lateral thermodynamic driving force for migration. Here, using in situ transmission electron microscopy to track Pt nanoparticle motion statistically, paired with time-resolved diffraction and 4D-STEM analysis to characterize support crystallization, we demonstrate that propagating crystallization fronts in amorphous AlO$_x$ thin films actively drag supported Pt nanoparticles over long distances. Temporal correlation between the onsets of support crystallization and rapid particle migration, together with 4D-STEM virtual crystallinity maps, establishes that the front drives particle motion. Phase-field simulations confirm that particle-substrate interfacial energy contrast alone sustains particle drag, and identify
curvature gradients along the particle surface as the mechanism by which the advancing front redistributes mass and displaces the particle. These results establish a general mechanism by which any propagating surface-energy boundary on a substrate can act as a deterministic driver of supported nanoparticle transport.
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All authors Cheng-Yu Chen, Duncan Burns, Peter W. Voorhees, Eric A. Stach
Superconductivity
Phase Formation and Thermal Stability of Superconducting Platinum Silicide Thin Films on Silicon
Tharanga R. Nanayakkara, Ananya Chattaraj, Mingzhao Liu et al. (+1 more)
Platinum silicide (PtSi) thin films are promising for silicon-based superconducting
quantum devices due to their compatibility with CMOS fabrication, air stability, and superconducting transition temperature near 1 K. We report a systematic study of PtSi phase formation, microstructure, and interface quality as a function of annealing temperature and duration, characterizing films using grazing-incidence X-ray diffraction, X-ray reflectivity, and electrical transport measurements. Phase-pure PtSi forms within minutes by rapid thermal processing at 600 {\deg}C and is stable under extended annealing, while 30 s anneals across 300-600 {\deg}C yield equivalent film quality with consistent microstructure and superconducting properties. X-ray reflectivity reveals that interfacial roughening is an intrinsic consequence of the Pt2Si-to-PtSi conversion step rather than a result of elevated temperature or prolonged annealing. These results establish a robust processing window for PtSi formation in silicon-based superconducting device fabrication flows.
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All authors Tharanga R. Nanayakkara, Ananya Chattaraj, Mingzhao Liu, Charles T. Black
Materials Science
Agentic multi-fidelity learning of quasiparticle and excitonic properties
Arnab Neogi, Aaron Forde, Christopher A. Lane et al. (+2 more)
Many-body GW-Bethe-Salpeter equation calculations are essential for accurate simulations of electronic structure and optical properties in modern low-dimensional nanomaterials. However, these methods are computationally demanding and can exhibit localized numerical instabilities or convergence failures that are difficult to detect within high-throughput workflows. We introduce an
agent-guided multi-fidelity framework for correcting GW-Bethe-Salpeter excited-state landscapes in strained MoS2-WS2
bilayers. Across stacking registries, strain branches and reciprocal-space samplings, the workflow identifies spike-like excursions, near-zero-gap collapse and cross-fidelity inconsistencies associated with fragile long-wavelength dielectric screening. A structural
agent evaluates calculations by assigning confidence weights and selectively using a small number of high-accuracy reference points. Machine learning models then transfer information across related systems and apply Gaussian process corrections to recover improved quasiparticle gaps and
exciton binding energies, with calibrated uncertainty estimates. The approach corrects numerically induced artifacts without erasing physical strain dependence and substantially improves agreement with higher-fidelity references relative to a no-
agent baseline. These results show that reliable surrogate learning for excited-state materials requires explicit diagnosis of numerical fragility, not direct interpolation of raw first-principles data points. The proposed framework is readily transferable to other optoelectronic nanomaterials characterized by strong
quantum confinement, such as
quantum dots, nanoribbons, layered two-dimensional
semiconductors, and hybrid perovskite nanostructures.
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All authors Arnab Neogi, Aaron Forde, Christopher A. Lane, Sergei Tretiak, Jian-Xin Zhu
Soft Condensed Matter
Exact mean-field phase diagram for self-avoiding active particles in a lattice
Felipe Hawthorne, Cristiano F. Woellner and José A. Freire
We investigate motility-induced phase separation in a
lattice gas of self-propelled particles with hard-core exclusion, where an internal director biases particle hopping along the
lattice coordination directions while undergoing rotational
diffusion, together with a thermal-like translational
diffusion. Rather than employing
stochastic simulations, we adopt a master-equation formalism within a general mean-field approximation. By linearizing the mean-field master equation around the homogeneous stationary state and applying Bloch's
theorem, the stability analysis is reduced to a $z$-dimensional tight-binding
eigenvalue problem. A perturbation expansion in the wavenumber near $\vk = 0$ then yields the spinodal surface in closed analytical form for six Bravais
lattices: linear, square, hexagonal, simple cubic, body-centered cubic, and face-centered cubic. The influence of
lattice geometry is shown to enter exclusively through a single coefficient $\mathcal{A}$ which we evaluate exactly for each case. We further show that translational
diffusion smooths the interface between the dense and dilute phases. Finally, we determine the rotational probability currents associated with the inhomogeneous stationary states, a distinctive signature of the broken detailed balance underlying active-system dynamics.
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Materials Science
Redox-Active Halide Materials for Cathode Applications
Zhuohan Li and Gerbrand Ceder
Electrochemically redox-active halide (eREAL) materials are an emerging class of materials that combine high Li-ion conductivity with transition-metal redox activity, making them promising candidates for cathode or catholyte applications. As a redox-active catholyte, they could significantly increase the energy density of solid-state batteries. In this work, we perform first-principles calculations on Li-M-Cl (M = 3d transition metals) ternaries to establish such a theoretical foundation for their stability and electrochemical activity. We map the phase stability of eREAL structures with varying metal-to-Cl ratio, transition-metal species, oxidation states, and anion frameworks, and compute cation and anion redox potentials. We find that the high ionicity of metal-Cl bonds elevates cation redox potentials above those of conventional
oxide cathodes, but also will promote Cl oxidation and Cl-Cl dimerization at high voltages, which may limit the stability of these materials. Anion substitution effectively tunes both cation and anion redox potentials, with F substitution standing out as a viable route to extend the reversible voltage window. Beyond the anion redox issue, eREAL compounds generally exhibit flat voltage profiles, which potentially poses an electrochemical compatibility challenge when paired with active materials that operate at different voltage values or over wider voltage ranges. Collectively, our study provides a comprehensive analysis for redox behavior of eREAL materials, paving the way for their rational design and optimization in next-generation battery applications.
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Materials Science · Cross-listed from physics.optics
Deep-level engineering in aluminum nitride (AlN) enables reliable photodetection in extreme conditions
Jiahao Dong, Zhenjing Liu, Sara Tulchinsky et al. (+1 more)
Semiconductor photodetectors are conventionally optimized for sensing weak optical signals, and they typically saturate at low-to-moderate light intensity. Here, we demonstrate AlN photodetectors that exhibit non-saturating linear response to ultra-bright, sub-bandgap light exceeding 40 $\mathrm{W/cm^2}$ (over 400 Suns). The photodetector further shows undistorted linear response at elevated temperature, up to at least 300 $\mathrm{^\circ C}$. This exceptional performance originates from photoresponse mediated by point defects with energy levels deep in the bandgap (deep levels) at the metal-AlN Schottky junction. Through dopant design and contact engineering, we demonstrate that a narrow space-charge region is essential for enabling ultra-bright light detection and accurate measurement. These results establish a strategy for engineering ultra-wide bandgap (UWBG)
semiconductor devices for reliable operation in extreme conditions to meet emerging needs in industrial process control, thermal and
nuclear power generation, and aeronautics and spaceflight.
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All authors Jiahao Dong, Zhenjing Liu, Sara Tulchinsky, Rafael Jaramillo
Superconductivity · Cross-listed from quant-ph
Floquet Entanglement Generation in Parametrically Driven Coupled Superconducting Qubits
Gustavo M. Meneses A., Daniel Dominguez and María José Sánchez
We investigate the dynamical generation of
entanglement in a system of two superconducting
qubits coupled through a parametrically driven longitudinal interaction. Using Floquet theory and exact numerical simulations, we analyze the time
evolution of the system initialized in a separable ground state. Our results reveal a nontrivial mechanism for
entanglement generation, fundamentally distinct from the conventional resonant excitation to an entangled eigenstate. We show that this mechanism emerges when two initially separable eigenstates are mixed by the periodic driving under multiphoton resonance conditions. Since the effect cannot be captured within a standard rotating-wave approximation, we employ generalized Van Vleck near-degenerate perturbation theory to derive an effective analytical description. Within this framework, we demonstrate that the sustained
entanglement originates from the hybridization of the dominant Floquet states, namely those with the largest overlap with the initial ground state. Furthermore, the degree of
entanglement can be efficiently controlled through the driving amplitude. In particular, for specific amplitudes, the
entanglement is fully suppressed. We term this phenomenon as coherent destruction of
entanglement.
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Quantum Gases
Inverse supersymmetry in finite temperature Bose-Fermi mixtures
Zachary Gazzillo and Carlos A. R. Sá de Melo
We investigate nearly degenerate Bose-
Fermi mixtures and show that the breaking of generalized supersymmetry (gSUSY) between
bosons and
fermions, with up to two internal states, manifests itself through the emergence of fermionic Goldstino modes with up to four
flavors. In particular, we draw a distinction between typical supersymmetry (SUSY), where
bosons have pseudospin 0 and
fermions have pseudospin 1/2, and inverse supersymmetry (iSUSY), where
bosons have pseudospin 1/2 and
fermions have pseudospin 0. In such systems, we highlight that the Goldstino pseudospin is carried by either its constituent
fermion (SUSY) or
boson (iSUSY). We then distinguish between these two cases by depicting their differing effects on the spectral functions of the bosonic and fermionic atomic species. Lastly, we propose
radio-frequency- or microwave-spectroscopy experiments, analogous to momentum (angular) resolved photoemission in condensed matter physics, to measure the pseudospin-dependent spectral functions and detect the emergence of Goldstino modes in mixtures of $^{39}$K and $^{40}$K.
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Disordered Systems and Neural Networks
Length-resolved Operator Growth and Path-Entropy Obstructions to Many-Body Localization
J. Sirker
For the disordered Ising chain with transverse and longitudinal fields, where couplings and fields are drawn from strictly positive distributions, Cao~\cite{Cao} has shown that the moments $\mu_{2k} = \|[H,\sigma^z_0]^{(k)}\|_2^2$ grow almost factorially, $\mu_{2k}^{1/(2k)}\sim k/\ln k$, and thus asymptotically at the maximal allowed rate. We generalize this result by resolving the operator norm in support length and show that the weight at length $\ell_k \sim k/\ln k$ already exhibits almost factorial growth, $\|[H,\sigma^z_0]^{(k)}_{\ell_k}\|_2 \gtrsim (k/\ln k)^k$. This implies maximal spatial delocalization of local operators and, in particular, rules out dynamical locality—the strongest form of many-body localization—at any disorder strength. We further establish rigorously a finite-size crossover scale $L\sim (W/J)^2$, where $W$ is the disorder and $J$ the coupling strength. For $L\lesssim (W/J)^2$ numerical studies only access a pre-asymptotic regime. Finally, we identify a structural path-
entropy obstruction to perturbative LIOM constructions, based on the almost factorial branching of operator content and independent of resonance effects; the same mechanism strongly suggests ballistic real-time operator spreading, so sub-ballistic or localized dynamics would require a presently unidentified cancellation principle acting on almost factorially many disorder-dependent paths with random amplitudes.
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Materials Science
Machine learning assisted molecular dynamics of charge-transfer mechanisms at Li/Ga-doped Li$_7$La$_3$Zr$_2$O$_{12}$ (LLZO) interfaces
Arseniy S. Burov, Artem M. Abakumov and Dmitry A. Aksyonov
Interfacial charge transfer between solid electrolytes (SEs) and Li metal is a key factor limiting all-solid-state battery performance. Conventional density functional theory and nudged elastic band calculations are performed at 0 K along a single minimum-energy path and therefore neglect concerted multi-ion motion and finite-temperature effects, which can lead to inaccurate activation barriers. Here, we trained moment tensor potentials (MTPs) for garnet LLZO systems (t-LLZO, c-LLZO, and Ga-LLZO) and Li metal, enabling machine-learning molecular dynamics (MLMD) simulations of Li$^+$
diffusion in the bulk and across Li/SE interfaces. We also introduce a residence-time window method that filters out ion rattling at the interface and isolates genuine charge-transfer events. The resulting charge-transfer activation energy at the Li/Ga-LLZO interface is only $167 \pm 18$ meV, below the 200 meV barrier for vacancy-mediated Li migration in bulk Ga-LLZO. The corresponding intrinsic charge-transfer resistance is $\sim 10^{-5}\ \Omega\ \mathrm{cm}^{2}$, almost four orders of magnitude below the lowest experimentally reported $R_{\mathrm{ct}}$. These results indicate that intrinsic charge transfer across the Li/Ga-LLZO interface is not rate-limiting, and that Li transport within the electrolyte instead governs the overall kinetics. Taken together, our findings clarify the fast interfacial kinetics in Li/LLZO systems, and the proposed methodology can aid further interface optimization in solid-state batteries.
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Statistical Mechanics · Cross-listed from math.PR
REM universality and Poisson-Dirichlet Gibbs weights for linear random energy
Francesco Concetti and Simone Franchini
We study the
Hamiltonian $H_n(h,\sigma)=\sum_{i=1}^n h_i(\sigma_i-m), $ where $(h_i)$ are i.i.d.\ real random variables and $(\sigma_i)$ are i.i.d.\ Ising
spins. We consider the energy levels obtained after an independent thinning that retains an exponential number of configurations ($e^{O(n)}$). We prove that, after an $(h_i)$-dependent centering, the resulting point process converges in distribution to a Poisson point process with exponential intensity. Thus, the energy levels asymptotically has the one of the Random Energy Model (REM). Our results extend previous ones, where REM universality for this model was established only either for energy fluctuations of order $e^{-O(n)}$ or for $e^{o(\sqrt n)}$ randomly selected configurations. We also identify the limiting Gibbs weights, which converge to a Poisson–Dirichlet law, and the quenched free energy, which exhibits a freezing transition at $\beta=\tilde\lambda$. The proofs are presented here in compressed form; full details are given in the companion preprint.
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Mesoscale and Nanoscale Physics
Caterina Zerba, Léo Mangeolle and Michael Knap
Direct evidence of
exciton condensation in
semiconductor heterostructures remains elusive. Here we propose charge transport of doped carriers as a probe of
exciton condensation in transition-metal dichalcogenide
heterostructures and identify distinct experimental signatures. First, condensation suppresses the phase space for carrier scattering, leading to a reduction in resistivity, that provides a general diagnostic of
exciton condensation. Second, in
heterostructures with a tunable solid-state Feshbach resonance, condensate-induced hybridization between doped carriers and trion bound states qualitatively modifies transport. In particular, near resonance, this hybridization yields a negative effective mass and a corresponding sign reversal of the
Hall resistivity. These results establish charge transport as a promising route for detecting and characterizing
exciton condensation in
semiconductor heterostructures.
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Mesoscale and Nanoscale Physics
Phase diagram of magnetic $S^3$ Skyrmions on three-dimensional lattices and the toroidal antiSkyrmion
Niccolò Francini, Stefano Bolognesi, Sven Bjarke Gudnason et al. (+1 more)
Magnetic Skyrmions are planar
solitons stabilized by the Dzyaloshinskii-Moriya interaction (DMI) and realized in
chiral magnets. We study their natural three-dimensional generalization: a sigma model from $\mathbb{R}^3$ to $S^3$ with a four-component magnetization vector, stabilized by a one-derivative term which is a generalized DMI. We utilize two SO(3)-invariant generalized DMIs discovered recently: an "$\alpha$-term" supporting a spherically symmetric hedgehog Skyrmion and a "$\beta$-term" supporting an axially symmetric Skyrmion that splits into two half-Skyrmions connected by a
magnetic string of negative tension, a phenomenon we call "anti-confinement". We derive a cubic-
lattice discretization that reproduces both continuum theories at long wavelengths and use Monte Carlo simulations to map the finite-temperature phase diagram. We identify
spin-spiral,
magnetic-string-
lattice, Skyrmion-
lattice, and antiSkyrmion-
lattice phases, as well as a mixed-
topology regime with fractional $S^3$ charges localized at string bends. We find, for the first time in the literature to the best of our knowledge, a toroidal (anti-)
soliton of unit charge. Our results establish a theoretical and computational framework for three-dimensional topological
magnetic textures in systems whose order-parameter
manifold is $S^3$.
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All authors Niccolò Francini, Stefano Bolognesi, Sven Bjarke Gudnason, Roberto Menta
Statistical Mechanics · Cross-listed from quant-ph
Exact metastability in a class of driven-dissipative quantum many-body systems
David D. Noachtar and Aashish A. Clerk
Metastability in many-body
quantum systems and its associated exponentially-long timescales have been the subject of considerable recent interest. Here, we focus on a class of driven-dissipative many-body open
quantum systems described by a Lindbladian having hidden time-reversal
symmetry (a form of
quantum detailed balance). Examples include boundary-driven interacting
spin chains, bosonic
lattice models and driven-dissipative collective
spin models. We suggest that for such systems, slow timescales in the vicinity of a dissipative first-order phase transition can be analytically predicted using a special purification of the non-
equilibrium steady state. We show the accuracy of our
conjecture through detailed studies of a dissipative transverse-field Ising model with collective and local decay, and a driven-dissipative nonlinear cavity model. Our results allow quantitative insights into metastability and slow dynamics for a range of systems, including cases where semiclassical or path-integral instanton approaches are intractable.
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Materials Science
MatMind: A Structure-Activity Knowledge-Driven Generative Foundation Model for Materials Science
Zhan'ao Yao, Boxuan Zhang, Jingyuan Shu et al. (+10 more)
Progress in AI-driven
crystal materials science has so far been carried by narrow architectures purpose-built for individual tasks – graph neural networks for property prediction,
diffusion and flow-matching models for
crystal generation – each excelling within its niche yet unable to act as a shared backbone across the full spectrum of materials problems. Generative large
language models offer a fundamentally different paradigm, in which structural representation, quantitative prediction, and structure-activity
reasoning can be unified within one model, but the materials community has yet to see this paradigm realized at a level competitive with established narrow specialists. Here we present MatMind, a generative foundation model purpose-built for
crystal materials science under this paradigm, developed through the coordinated activation of structure-activity knowledge and physics-informed feedback within a progressive training framework – combining structure-activity knowledge injection, a dual-head architecture that jointly trains
language reasoning and numerical regression in a shared representation space, and multi-objective physics-informed reinforcement learning over stability, novelty, and structural diversity. Across three task families, MatMind attains the lowest mean absolute error on energy above hull, bulk modulus, and band gap – surpassing graph neural network predictors purpose-built for these tasks – reaches an S.U.N. rate of 65.3% on unconditional
crystal generation, and achieves a comparable multiplicative improvement on magnetization-density-conditioned generation, where only 21 positive samples exist within over 600000 training entries. By matching or surpassing narrow specialists on their own ground while operating within a single unified model, MatMind shows that the LLM-based paradigm can serve as a viable backbone for
crystal materials science going forward.
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All authors Zhan'ao Yao, Boxuan Zhang, Jingyuan Shu, Xiaoyu Wu, Rongyan Wang, Linjing Li, Dajun Zeng, Yudong Yao, Tingwei Chen, Youwei Wang, Xiaolin Zhao, Jiahui Shi, Jianjun Liu
Strongly Correlated Electrons
Non-Abelian braiding in Abelian Fractional Quantum Hall Phases from realistic interactions
Ha Quang Trung and Bo Yang
We propose a method of realizing non-Abelian braiding of fractionalized quasiholes in the Laughlin fractional
quantum Hall phase at $\nu=1/3$ with realistic two-body interactions within the lowest Landau level. It is numerically shown that low-lying gapped excitations near $\nu=1/3$ are contained almost entirely within the null space of the three-body Moore-Read model
Hamiltonian. They are thus
quantum fluids of non-Abelian quasiholes that are in principle physically accessible. In particular, Laughlin ground state can be described as a fluid of “$\psi$-type" quasiholes formed by binding a
magnetic flux with a Majorana
fermion (MF), and the Laughlin quasiholes are described by the “$1$-type” quasiholes, which are
magnetic fluxes without a MF attached. Within the Laughlin phase, Laughlin quasiholes can be locally fractionalized into non-Abelian quasiholes, when the strong attraction between them is overcome by properly designed one-body electronstatic trapping potentials. Extensive numerics with proper finite-size scaling corroborate this physical picture, and our study points to the possibility of realizing non-Abelian braiding within an Abelian topological phase in experiment without the need for fine-tuning realistic electron-electron interaction.
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Superconductivity
Bulk Superconductivity driven by Disorder-Induced Delocalization in 4Hb-Ta(S$_{1-x}$Se$_x$)$_2$
Lu Chen, Sae-Hee Ryu, Avior Almoalem et al. (+10 more)
The unconventional
superconductor 4Hb-TaS$_2$ is a natural
heterostructure that can be broadly understood as interleaving Mott-like and metallic layers. We study the properties of this material as a function of quenched disorder in the form of Se/S substitution and find that while disordered samples show bulk superconductivity, clean samples do not. We show that a disorder-driven delocalization of carriers in the Mott-like ($1T$-) layer forms a new
Fermi surface that is absent in the cleanest samples. This suggests that one of the primary drivers for superconductivity is the fragility of the Mott state, whose delocalization brings to life a sea of strongly correlated electrons.
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All authors Lu Chen, Sae-Hee Ryu, Avior Almoalem, Yuanqi Lyu, Koh Yamakawa, Luke Pritchard Cairns, Ryan Day, Ehud Altman, Daniel Podolsky, Dung-Hai Lee, 4 Vidya Madhavan, Eli Rotenberg, James G. Analytis
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Driving Exchange Interaction in Spin Qubits with Quasi-Zero Pulses
Julian D. Teske, Remy L. Delva, Shobhan Kulshreshtha et al. (+6 more)
The implementation of high-fidelity
quantum gates for
spin qubits requires accurate control of exchange interactions between electrons confined in
quantum dots, but pulse distortions can limit this control accuracy. Although linear-dynamical distortions can be compensated for by appropriately convolving the control signal, determining the necessary convolution requires detailed knowledge of the distortion's transfer function, and therefore the calibration of numerous parameters. Alternatively, control pulses can be designed to have a net-zero time integral canceling out linear-dynamical pulse distortions. We generalize net-zero pulse designs to quasi-zero pulses allowing net-positive but reduced time integrals. Using these pulse designs, we systematically develop complete gate sets for exchange-only
qubits, and study the resulting tradeoffs between pulse duration, fidelity, and the required number of tunable parameters, both in simulation and experiment. We
benchmark the optimized gate pulses on Intel's Tunnel Falls six-dot device and show they achieve fidelities similar to those obtained with a full filtering approach, with identical pulse durations and fewer tuning parameters. This reduction in complexity opens the door to fast and easily automated calibration schemes compatible with large-scale commercial
quantum devices.
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All authors Julian D. Teske, Remy L. Delva, Shobhan Kulshreshtha, Yuval Baum, Florian Luthi, Fahd A. Mohiyaddin, Rostyslav Savytskyy, Thomas Watson, Pranav S. Mundada
Soft Condensed Matter
Flow of deformable droplets: self-pinned glasses and string-like flow
Achille Quarante, Michael Chiang, Davide Marenduzzo et al. (+1 more)
We investigate, through numerical simulations, the rheology of a dry suspension of deformable droplets under pressure-driven flow. The system exhibits two force-driven dynamical transitions. At low forcing, the suspension behaves as a yield-stress material: below a critical force, droplets remain arrested in an amorphous solid-like state. Our simulations suggest that yielding is controlled by droplet contacts and predict that the critical force strongly depends on deformability. Above yielding, the suspension does not flow steadily but rather enters an intermittent, stick-slip regime characterised by long-lived caging and non-Gaussian velocity fluctuations. This state can be interpreted as a "self-pinned” glass, in which slowly evolving droplet overlaps generate an effective rugged energy landscape that dynamically traps droplets and produces intermittent rearrangements reminiscent of near-critical dynamics in depinning models. At larger forcing, droplets deform sufficiently to continuously exchange neighbours, progressively annealing the overlap structure and driving a dynamic transition to a string-like, flowing state. Our results identify the restructuring of overlap networks as a generic mechanism which controls flow in driven suspensions of deformable particles.
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All authors Achille Quarante, Michael Chiang, Davide Marenduzzo, Giuseppe Negro
Statistical Mechanics
Fermion sign problem and the structure of Lee-Yang zeros. II. Finite temperature results for a model system without interactions
Ran-Chen He, Jia-Xi Zeng, Shu Yang et al. (+3 more)
Beyond the analysis of the Lee-Yang (LY) zero of $\xi$ at $0$ K presented by our previous work [He et. al. Phys. Rev. E 113, 24115 (2026)], it is important but intricate to understand how these zeros evolve with temperature ($T$). Here, we use an analytically solvable noninteracting one-dimensional particle-on-a-ring model to address this. We determine the trajectories of these zeros and analyze how their
evolution with $T$ reshapes the analytic structure of the partition function. In particular, the zero originating from $\xi=-1$ at $T=0$ remains close to $-1$ at low $T$, where it governs the sign factor and strongly constrains continuation along the real $\xi$ axis. This explains why both direct extrapolation and implicit schemes such as contour-based fitting can fail in the low-$T$ regime, even at high fitting order, while becoming reasonable again once the relevant zeros move away at higher $T$s. Furthermore, based on the
polynomial structure of the partition function, we propose a new fitting strategy for low-$T$ fermionic properties. The key is to first obtain reliable high-$T$ fermionic properties by continuing sign-problem-free data in $\xi\in[0,1]$ to $\xi=-1$, and then extend this information toward lower $T$ through $T$-fitting of the $\xi$-independent remainder $\phi(\beta)=Z_{\text{F}}$. These results provide a solvable
benchmark for diagnosing the validity of analytic continuation and suggest a possible route toward treating more realistic interacting fermionic systems.
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All authors Ran-Chen He, Jia-Xi Zeng, Shu Yang, Cong Wang, Qi-Jun Ye, Xin-Zheng Li
Materials Science
Near-room-temperature magnetoelectric coupling engineered through inversion-breaking tilts in a bulk perovskite polytype
Struan Simpson, Urmimala Dey, Martin R. Lees et al. (+3 more)
Systematic strategies to design properties such as ferroelectricity or magnetoelectric coupling are well established in simple perovskite materials, but they remain scarce in more complex framework structures. Using a hexagonal polytype of the ternary manganite AMnO3 (A = Ba, Sr, Ca) as a model system, we introduce a
symmetry-guided design principle in which an inversion-breaking rigid-unit mode (RUM) serves as a single structural instability generating both polar and
ferromagnetic orders within a bulk material.
Symmetry analysis and first-principles calculations reveal that co-operative tilts of the Mn2O9 bioctahedral dimers generate both a spontaneous polarization and a
ferromagnetic moment. High-resolution diffraction and
magnetic susceptibility measurements show the structural and
magnetic orders persist as high as 450 K and 280 K, respectively, highlighting the untapped potential of framework structures which deviate from simple perovskite motifs to be designed to host useful ferroic properties. Our approach establishes a transferable
symmetry-based framework to engineer ferroelectric and magnetoelectric states across chemically diverse framework architectures.
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All authors Struan Simpson, Urmimala Dey, Martin R. Lees, Ivan Da Silva, Nicholas C. Bristowe, Mark S. Senn
Materials Science
Scalable Prediction of Complex Surface Reconstructions under Operating Conditions via Harmony-Search-Based Global Optimization
Shi-Yang Chen and Xiao-Ming Cao
The dynamic structural
evolution of catalyst surfaces under operating conditions dictates catalytic performance, yet capturing these reconstructions atomically remains challenging. Global optimization based on machine learning interatomic potentials (MLIPs) is promising, but scaling to large-scale, low-
symmetry operando systems is hindered by expansive search spaces and potential energy surface (PES) inaccuracies. Herein, we present Harmony-search-based Atomic Structural Global Optimization (HASGO), a framework integrating universal MLIPs with a harmony search
algorithm. HASGO overcomes the problem of PES softening by incorporating a multi-head replay fine-tuning protocol. Moreover, the
stochastic structural perturbation step in its
algorithm offers a fault-tolerant strategy to enhance the robustness of global convergence. These enable HASGO to identify intricate surface
oxide overlayers that align with atomic-resolution microscopy, thereby resolving the square-pyramidal subsurface O5 motif on Ag(100) during ethylene epoxidation. This scalable framework provides a robust approach for uncovering operando structures, accelerating the rational design of industrial catalysts.
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Mesoscale and Nanoscale Physics
Polar and quadratic magneto-optical Kerr effects in nonmagnetic/ferromagnet bilayers for spin-orbit torque measurements
Yukihiro Marui, Masashi Kawaguchi, Kohji Nakamura et al. (+1 more)
Recent studies have revealed that
spin Hall magnetoresistance (SMR) contributes to both the anomalous and planar
Hall resistances in nonmagnetic metal (NM)/
ferromagnetic metal (FM)
bilayers. This effect becomes pronounced when the NM layer exhibits a large
spin Hall angle, as in W/CoFeB
bilayers. In such systems, the ratio of planar to anomalous
Hall resistances, normally small in single CoFeB layers, can approach unity. This unusually large ratio complicates the determination of
spin-torque efficiency using harmonic
Hall voltage measurements. To overcome this limitation, magneto-optical Kerr effect (MOKE) measurements have been proposed as an alternative approach. Here, we investigate the polar and quadratic MOKE components, which correspond to, respectively, the anomalous and planar
Hall resistances in the low-frequency limit to clarify whether the MOKE measurements are suitable for characterizing the
spin-torque efficiency. We find that the ratio of quadratic to polar MOKE signals in NM/FM
bilayers is significantly smaller than the corresponding
Hall resistance ratio, indicating that SMR contributes negligibly to the MOKE response in the visible range. Consequently, the
spin-torque efficiency extracted from MOKE measurements agree well with those expected from the
spin Hall angle of the NM layer. These results clarify the reason why MOKE measurements provide reliable determination of the
spin-torque efficiency.
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All authors Yukihiro Marui, Masashi Kawaguchi, Kohji Nakamura, Masamitsu Hayashi
Soft Condensed Matter
Hydrogel mechanics below swelling equilibrium
A. Chao Correas, Y. Feng, R. W. Style et al. (+1 more)
Hydrogels are versatile soft materials whose behavior arises from complex
polymer-network-fluid interactions. Combining theory and experiments, we show that their mechanics simplify greatly below swelling
equilibrium. In this regime, mixing and pore pressures effectively control local hydration, relegating
polymer-network elasticity to accommodate the deformed shape. This mechanical hierarchy renders partially-dried hydrogels analogous to incompressible solids with environment-driven target volumes, enabling a staggered mechanical description that accurately captures their state and behavior.
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All authors A. Chao Correas, Y. Feng, R. W. Style, D. S. Kammer
Statistical Mechanics
Topologically Enforced Lifshitz Multicriticality in One Dimension
Kuang-Hung Chou and Xue-Jia Yu
Recent advances have revealed that
topology can further enrich the universality classes of
quantum phase transitions, thereby extending beyond the traditional paradigms of statistical and condensed matter physics. However, multicriticality between topologically distinct
quantum critical lines remains insufficiently explored. In this Letter, we systematically construct and investigate a novel class of topologically enforced Lifshitz multicritical points in one dimensional
chiral symmetric fermionic systems. Such multicriticality is driven solely by changes in the
topology of neighboring critical lines, beyond previously recognized multicritical points that are typically induced by changes in critical exponents. More importantly, the topologically enforced multicriticality identified here can host robust topological degeneracies while surprisingly exhibiting a breakdown of the Li Haldane bulk boundary correspondence-a phenomenon we elucidate through a simple physical picture.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Ferroelectrical Switching as a Probe of Quantum Damping in Magnetic Spin Systems
Yuefei Liu, Anna Delin, Olle Eriksson et al. (+3 more)
While damped
spin dynamics is important for the understanding of
magnetic materials, clear signatures of
quantum corrections to the Gilbert damping mechanism remain elusive. We propose a route to distinguish
quantum and classical Gilbert
spin damping using ferroelectric control of a
magnetic dimer. Ab initio calculations for dimers on ferroelectric substrates show that polarization reversal switches the inter-
spin exchange between
ferromagnetic and
antiferromagnetic regimes. We formulate a magnetization-based diagnostic that relates magnetization traces to
entanglement dynamics, which enables ferroelectrical on/off control of dimer
entanglement. Material-informed
quantum Landau-Lifshitz-Gilbert simulations illustrate how the signature of magnetization dynamics can, in principle, be used to infer the existence of
quantum Gilbert
spin damping. This minimal and non-volatile platform connects first-principles modeling to experimentally accessible observables and provides a starting point for voltage-controlled
quantum entanglement in
magnetic spin networks.
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All authors Yuefei Liu, Anna Delin, Olle Eriksson, Erik Sjöqvist, Kaiyou Wang, Qirui Cui
Soft Condensed Matter
Resolving Light-Induced Structural Rearrangements in Responsive Microgels
Fabrizio Camerin, Megha Emerse, Gianpaolo Gallo et al. (+6 more)
Optically-responsive microgels offer a versatile platform for designing adaptive soft materials with coupled light and thermal responsiveness. Control over the crosslinking degree is particularly appealing as it can regulate not only particle size but also stiffness, thereby enabling remote tuning of key material functionalities. However, the internal structural changes that couple molecular photoresponsive mechanisms to mesoscopic properties remain poorly resolved. Here, we investigate different light-responsive microgels containing covalently incorporated coumarin moieties, which impart optical sensitivity through UV-induced cycloaddition, by combining dynamic light scattering, small-angle
neutron scattering, and molecular dynamics simulations. We show that light irradiation alters not only particle size but also the internal
polymer density distribution and subsequent thermal response. Before irradiation, the microgels exhibit a
star-like architecture with a dense core and extended polymeric arms. After irradiation, the network evolves toward a markedly more compact structure. This transformation cannot be rationalized simply as an equivalent to an increase in crosslinking density during synthesis, as observed in the thermal response, revealing light as a powerful tool to regulate microgel architecture and multifunctional responsiveness.
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All authors Fabrizio Camerin, Megha Emerse, Gianpaolo Gallo, Najet Mahmoudi, Gregory Smith, Emanuela Zaccarelli, Lucio Isa, Marco Laurati, Jacopo Vialetto
Strongly Correlated Electrons
Direct High-Magnetic-Field Coupling to Stripe Order in a Cuprate Superconductor
Leonardo Martinelli, Izabela Biało, Jens Oppliger et al. (+47 more)
Superconductivity in cuprates emerges out of a complex normal state that hosts density waves, pseudogap physics, and strange metal properties. Here, we access this normal state by synchronizing free-electron
laser x-rays with high-
magnetic-field pulses up to 44 T. We observe a linear increase in charge order amplitude and correlation length that persists far above the
vortex melting transition. This behavior is incompatible with standard phase competition between charge order and superconductivity. By means of conventional hard x-ray diffraction and magnetostriction, we show that applied fields also enhance monoclinic
lattice distortions. However, this magnetoelastic response is weaker and an epiphenomenon of the stripe order enhancement. Combined with recent observations of field-linear
spin freezing, our results point to a direct coupling between
magnetic field and the
spin component of stripe order in the high-field normal state – a mechanism independent of superconductivity suppression that has so far remained hidden from scattering probes.
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All authors Leonardo Martinelli, Izabela Biało, Jens Oppliger, Julia Küspert, Orion Gerguri, Sandro Brunner, Benedikt Eggert, Mark H. Fischer, Jochen Geck, Marein Rahn, Ellen Fogh, Jaewon Choi, Atsuhiko Miyata, Oleksandr Prokhnenko, Zahirul Islam, Fernando Igoa Saldaña, Martin v. Zimmermann, Rachel Nickel, Kurt Kummer, Nicholas B. Brookes, Adheena Painganoor, Paola Caterina Forino, Rasmus Toft-Petersen, Niels Bech Christensen, Xunyang Hong, Qisi Wang, Tohru Kurosawa, Naoki Momono, Migaku Oda, Dmitri V. Novikov, Azat Khadiev, Thomas Herrmannsdörfer, Ana Kurtanidze, Katharina Ollefs, Zuzana Konôpková, Michał Andrzejewski, Minxue Tang, Ulf Zastrau, Alexander Pelka, Hauke Höppner, Jolanta Sztuk-Dambietz, Vratko Rovensky, Torsten Laurus, Erik Brambrink, Björn Näser, Marcin Sikora, Cornelius Strohm, Carsten Baehtz, Shingo Yamamoto, Johan Chang
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Performance analysis of classical adiabatic annealing on Ising machines
Jacob Lamers, Guy Verschaffelt and Guy Van der Sande
Ising machines are a promising approach to solve combinatorial optimization problems. They map these problems onto the Ising model and search for low-energy configurations. However, navigating the rugged energy landscapes of these systems remains difficult. To improve this
navigation, classical adiabatic annealing has been proposed in the literature as a heuristic optimization method for classical Ising machines. Using this technique, the
Hamiltonian of the Ising machine is gradually transformed from an easily solvable
Hamiltonian to the target
Hamiltonian. However, its purported effectiveness is primarily motivated by an analogy to
quantum adiabatic annealing, and systematic benchmarking has remained limited. In this work, we analyze the classical adiabatic annealing technique using continuation methods. Motivated by insights from this analysis, we propose an optimized annealing strategy we refer to as hybrid classical adiabatic annealing. We
benchmark our proposed strategy using MaxCut instances with up to 800
spins and problems with external fields, for which it achieves a marginal improvement for a limited set of problems. We conclude that, although theoretically motivated and occasionally beneficial, the hybrid strategy does not offer a sufficient practical advantage over simpler, existing techniques.
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Materials Science
Six Open Questions in Machine-Learned Interatomic Potential Foundation Models
Isabel Creed, Tim Rein, Ingvars Vitenburgs et al. (+21 more)
Machine-learned interatomic potentials (MLIPs) have had a profound impact on molecular modelling in recent years, promising to resolve the long-standing tension between the scale and accuracy of simulations. There has been a proliferation of new models and designs, and recently the paradigm of “foundational” MLIPs has become prevalent. Broadly speaking, foundation models are trained on large diverse
datasets and promise to work well for new systems with minimal updates required. However, in such a new and fast moving field, there are many unanswered questions. In this article, we set out to articulate and explore what we see as the most important among these questions. We start by developing a working definition for foundational MLIPs and use this definition to frame the subsequent open questions. Despite the rapid progress in the field of MLIP models, we believe that these are fundamental questions which will continue to define cutting edge research in MLIPs in the years to come.
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All authors Isabel Creed, Tim Rein, Ingvars Vitenburgs, Wojciech G. Stark, Viktor Ellingsson, Ahmed Y. Ismail, Guangyu Liu, Yuchen Lou, Bradley A. A. Martin, Cyprien Bone, Matthew A. H. Walker, Mueen Taj, Shirui Wang, Kelvin Wong, Ruiqi Wu, Prakriti Kayastha, Bingqing Cheng, Aditi Krishnapriyan, Michele Ceriotti, Marcel F. Langer, Jarvist Moore Frost, Alex M. Ganose, Venkat Kapil, Keith T. Butler