Papers

In this work, Sn-doped (010) $\beta$-Ga$_2$O$_3$ homoepitaxial films were grown by low-pressure chemical vapor deposition (LPCVD), and the influence of Sn incorporation on their structural, morphological, and electrical properties was systematically investigated. Controlled room-temperature carrier concentrations ranging from $1.17 \times 10^{17}$ to $3.06 \times 10^{18}$ cm$^{-3}$ were achieved, with corresponding Hall mobilities decreasing from 113 to 63 cm$^2$ V$^{-1}$ s$^{-1}$. The films exhibited the monoclinic $\beta$-Ga$_2$O$_3$ phase, near-stoichiometric composition, and well-defined step-flow morphology, with a minimum rocking-curve FWHM of 68.4 arcsec and an RMS roughness of 2.63 nm. Film thicknesses ranging from 1.66 to 11.3 $\mu$m were obtained at growth rates of 6.4 to 16.6 $\mu$m h$^{-1}$, demonstrating the ability of LPCVD to produce thick epitaxial layers. The sample with a room-temperature carrier concentration of $1.17 \times 10^{17}$ cm$^{-3}$ exhibited room-temperature and low-temperature Hall mobilities of 113 cm$^2$ V$^{-1}$ s$^{-1}$ and 380 cm$^2$ V$^{-1}$ s$^{-1}$ at 84 K, respectively. Both represent the highest reported values for LPCVD-grown Sn-doped $\beta$-Ga$_2$O$_3$. Transport modeling of the same sample yielded a shallow donor activation energy of 32.7 meV, a deeper donor level at 95 meV, and a low compensating acceptor concentration of $2.0 \times 10^{16}$ cm$^{-3}$, indicating efficient donor activation and a low degree of compensation. These results demonstrate that LPCVD enables controlled Sn doping while maintaining excellent structural and electrical quality, providing a viable route for realizing thick $\beta$-Ga$_2$O$_3$ epitaxial drift layers.

We conducted an ab initio study of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in metal-encapsulated biphenylene bilayers, B/M/B, with M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Ru, W, Os and Pt. In most systems, the intercalated metal sits at the square carbon sites (C$^{468}$) of the biphenylene lattice. Using a computational hydrogen electrode approach, we evaluated the reaction energetics at these active sites. Several B/M/B systems show competitive ORR and OER performance. Among the investigated systems, Cu, Pt, Ru, and Mn exhibit the lowest ORR overpotentials of 0.42, 0.44, 0.50, and 0.56 V, respectively, while Fe is identified as the most active catalyst for OER with an overpotential of 0.44 V. To understand the catalytic trends, we looked at the electronic structure through the metal $d-$band centers, the C$^{468}$ $p_z-$band centers, and the corresponding orbital charge populations. The band centers did not give a simple polynomial dependence on the overpotentials, though they did point to favorable electronic ranges for the best catalysts. The $d-$orbital charge population of the encapsulated metal, however, correlated most clearly with activity-especially for OER-yielding volcano-type plots. From these, B/Fe/B emerges as the best OER catalyst, while B/Mn/B lies closest to the ORR optimum. The $p-$orbital population at the active carbon site also captures the main trends, albeit less strongly. Overall, these results show that straightforward electronic descriptors can predict catalytic behavior in metal-encapsulated biphenylene bilayers and guide the search for efficient catalysts where the carbon framework itself drives the reactivity.

Superconducting single-photon detectors with time resolution of 80 ps have been used to study the spatiotemporal dynamics of a trapped bosonic condensate of exciton-polaritons. Both second- and first-order correlation functions are found to exhibit pronounced oscillations in time governed by the dynamics of the polariton condensate in the trap. We have identified the intermittent regime of stochastic transitions between stationary and limit-cycle regimes near the Andronov-Hopf bifurcation manifested in asymmetric distortions of the correlation function. This rich interplay of deterministic and stochastic condensate dynamics is explained theoretically as a manifestation of mutually compensating self-repulsion and reservoir-mediated attraction.

We theoretically explore the non-equilibrium dynamics of a single quantum dot system coupled to both ferromagnetic and superconducting electrodes. To investigate its time evolution, we utilize the time-dependent numerical renormalization group technique, which captures the system's response to abrupt parameter changes in a fully non-perturbative manner. Our analysis focuses on dynamics following a sudden modification in the couplings to the leads or a shift of the orbital level. In particular, we calculate the time evolution of the induced local superconducting pairing correlations and magnetization. In this context, the relevant energy spectra are examined. Moreover, we study the behavior of the Loschmidt echo and the return function to shed light on the signatures of dynamical quantum phase transitions. The determined dependencies reveal non-trivial competition between relevant correlations, involving superconducting pairing and ferromagnetic-contacted induced exchange field, and deepen our understanding of nanoscale hybrid systems' dynamical behavior.

Spin-orbit torque (SOT), which enables electrical control of magnetization, plays a crucial role in the development of next-generation spintronic devices. Realizing SOT in two-dimensional van der Waals systems, together with achieving efficient nonvolatile manipulation via ferroelectricity, would be highly beneficial for the implementation of tunable logic devices with enhanced storage density. In this work, based on first-principles calculation and using a multiferroic Fe$_{3}$GeTe$_{2}$/In$_{2}$Se$_{3}$ heterostructure as a representative example, we demonstrate that switching the ferroelectric polarization of the In$_{2}$Se$_{3}$ layer induces a pronounced modification in the magnetization-dependent distribution of torkance within the heterostructure. Specifically, when the magnetization is in the plane, where the torque is maximal, reversing the polarization of In$_{2}$Se$_{3}$ from upward to downward enhances the total torkance to more than 150% of its original value. This substantial variation primarily originates from the polarization-induced modulation of the $z$ component of the time-reversal-odd torkance, which is mainly associated with an approximately 233% change in the atomic-resolved torque contributed from the middle Fe layer in Fe$_{3}$GeTe$_{2}$ layer. Further analysis reveals that the electronic states near $\Gamma$ on the Fermi surface undergo significant reconstruction upon polarization switching, which is responsible for the observed variation in the time-reversal-odd torque. Our results not only provide new insights into the functional potential of van der Waals multiferroic heterostructures, but also offer a viable strategy for achieving electrically tunable SOT, paving the way for future programmable spintronic devices.

Controlling the ordered phases of correlated electron systems remains a central challenge in quantum materials design. Divergences in the electronic density of states, known as Van Hove singularities (VHSs), are one obvious route to such control. It is clear from recent work that the exact functional form of these divergences can profoundly affect which phases are realized; a full picture, however, remains elusive. In this work, we use both the hot-spot parquet renormalization group and the truncated-unity functional renormalization group to theoretically study the emergent correlated states of a two-dimensional square-lattice Hubbard model with VHSs at or near the Fermi level. By varying a single hopping parameter, $t_3$, we are able to change the strength of the VHS divergence in the density of states from logarithmic (for $t_3 < t_{3c}$) to power-law (for $t_3 = t_{3c}$). Further increase of $t_3$ ($t_3 > t_{3c}$) causes each original Van Hove point to split into two, both of the conventional logarithmic type. We show that which of these regimes we are in strongly influences the predicted ordered states. We also study the dependence on doping, and find that the ferromagnetic state that occurs at Van Hove filling in these models is unstable to very small shifts in the Fermi level, often giving way to distinct ordered states depending on whether the model is electron- or hole-doped. These results highlight the importance of tuning VHS properties to control ordered states in correlated materials, and offer design rules to engineer these phases in novel systems.

Quantum relaxometry is one of the most successful applications of nitrogen-vacancy (NV) centers in diamond and, more broadly, solid-state spin qubits, enabling ultrasensitive detection of magnetic noise and paramagnetic species via measurements of the spin-lattice relaxation time $T_1$. Conventional pulsed protocols, however, probe $T_1$ efficiently only over a limited temporal range, which restricts the scope and throughput of the technique. Here we introduce a continuous-wave quantum relaxometry protocol that operates in the frequency domain. By measuring the frequency response of the optically detected magnetic resonance signal under low-frequency microwave amplitude modulation, we extract $T_1$ from the characteristic response time of the spin system. The method enables efficient $T_1$ measurements spanning more than three orders of magnitude – directly demonstrated from 60 $\mu$s to 200 ms in our experiments – across a broad temperature range and under substantial ensemble inhomogeneity. We further show that this protocol enables quantitative relaxometry-based sensing in nanodiamonds, achieving a substantial speed-up over the pulsed methods and offering a practical approach to optimizing nanodiamond size for enhanced sensitivity.

This study presents a test method and its theoretical framework to determine the acoustic nonlinearity parameters ($\alpha,\beta,\delta$) of material using thermal modulation of ultrasonic waves. Temperature change induced thermal strain excites the nonlinear response of the material and modulates the ultrasonic wave propagating in it. Experimental results showed a strong correlation between the relative wave velocity change and the temperature change. With a quadratic polynomial model, the acoustic nonlinearity parameters were obtained from the polynomial coefficients by curve fitting the experimental curves. Their effects on thermal-induced velocity change were discussed. The parameters $\alpha,\beta,\delta$ govern the hysteretic gap, average slope, and curvature of the correlation curve, respectively. The proposed theory was validated on aluminum, steel, intact and damaged concrete samples. The obtained nonlinear parameters show reasonable agreements with values reported in the literature. Compared to other nonlinear acoustic methods using vibration or acoustic excitation, the thermal modulation method generates more uniform, slow changing, and larger strain field in the test sample. Employing thermal effect as the driving force for nonlinearity instead of an undesired influencing factor, this method can measure the absolute values of $\alpha,\beta,\delta$ with good accuracy using a simple ultrasonic test setup.

In tight-binding models, the position operator is reduced to intra-cell orbital positions (embeddings). While accurately reproducing band structures, such models often fail for geometry dependent responses depending on the position operator. To address this, we investigate the role of these embeddings and introduce the general framework of optimally embedded tight binding. Treating the embeddings as geometric tuning parameters to be fixed against a reference response (obtained from ab-initio computation or experiment), we obtain tight-binding models of GaAs and CdS which quantitatively reproduce non-linear optical responses at no cost to band structure accuracy. The optimal embeddings are determined efficiently using position derivatives obtained from decomposing tight-binding observables into a geometry independent and dependent part, and explicit derivatives are provided for key quantities such as the quantum geometric tensor. The decomposition reveals where geometric effects dominate, and we show in both toy models and in the Chern insulator V2O3 how geometry can dramatically alter the local metric trace. Our results highlight that orbital embeddings should be treated as a genuine model parameter which should be explicitly fixed against physical data to get accurate minimal models.

Classical fractons are Hamiltonian systems that can develop attractors after projection onto configuration or shape variables, although the full phase space admits none. We study a scale-invariant, dipole-conserving two-parameter family of fracton Hamiltonians $H_{\alpha,\beta}$. By separating coordinates into scale and shape, we obtain autonomous shape dynamics that admit fixed points which leave a purely scale evolution of the form $R(t)\propto |t|^{\alpha/(\alpha-\beta)}$. The shape fixed points, which determine the distribution of the expanding particles, are central configurations of power-law Riesz potentials. The distinguished model $(\alpha,\beta)=(-2,1)$ is unique: its scale evolution takes the Einstein-de Sitter form $R(t)\propto |t|^{2/3}$, its fixed-point equation is the equal-mass Newtonian central-configuration, its large-$N$ distribution is a homogeneous ball, and its homothetic trajectories admit a zero-energy Newtonian gravitational dual. The fixed points are locally stable, and simulations at moderate $N$ approach them from random initial data. Large $N$ simulations reveal a richer class of fixed-points: bound clusters of approximately fixed physical size retain internal motion, while their centers approach unequal-mass Newtonian central configurations and preserve large-scale homogeneity. A scale-separation conjecture yields an effective unequal-mass fracton dynamics for the centers and a corresponding zero-energy Newtonian gravitational dual. Trajectories generically exhibit a bidirectional arrow of time: scale and shape complexity grow away from a Janus point, while Boltzmann entropy grows logarithmically. Together, these features reproduce the salient structure of a flat matter-dominated cosmology. In the distinguished fracton model, all these cosmological analogues emerge as attractor properties, making it a toy model for cosmological dynamics without fine-tuning.

We present a general paradigm that directly couples vacancy-localized magnetism to interfacial sliding ferroelectricity in nonmagnetic van der Waals (vdWs) bilayers. Utilizing bilayer hexagonal boron nitride (hBN) as a prototypical vdWs host system, we use first-principles calculations to show that a single vacancy acts as a local registry sensor, lifting the degeneracy between polar sliding partners via a defect-centered polarization offset. For interlayer vacancy pairs, we discover a defect selectivity where the hosting sublattice fully dictates the interlayer exchange, stabilizing either ferrimagnetic or antiferromagnetic configurations. Applying an out-of-plane electric field selects the polar registry and drives an amplitude modulation of the compensated Néel order parameter. These findings establish a robust, sublattice-dependent engineering of multiferroic functionality via stacking control across a wide class of nonmagnetic 2D heterostructures.

Mesons and glueballs are paradigmatic bound states of confining quantum field theories (QFTs), but their nonperturbative spectroscopy in the continuum remains challenging beyond one spatial dimension. Here we perform such spectroscopy for the Ising QFT using a recently developed regularization based on noncommutative “fuzzy” geometry. On a thin fuzzy torus, we reproduce the universal low-lying $\mathbb E_8$ meson masses of the magnetically perturbed $(1{+}1)\mathrm{D}$ Ising QFT. By increasing the torus aspect ratio, we continuously track the second-lightest $\mathbb E_8$ meson as the system effectively crosses over from 1D to 2D. On the 2D fuzzy torus and sphere, we find a subthreshold scalar level and above-threshold response features consistent with previous estimates of glueball masses. The same excitations are revealed away from equilibrium using quench dynamics. Our results establish fuzzy geometries as nonperturbative spectroscopic probes of massive QFTs, including their bound-state evolution through dimensional crossover.

Sampling high-dimensional probability distributions is a central task in scientific computing, with applications ranging from Bayesian inference to statistical physics and molecular simulation. Despite decades of methodological developments, two major challenges remain: scaling to high dimensions and efficiently exploring multimodal distributions characterized by metastable states. Classical approaches such as Markov chain Monte Carlo, tempering methods, or enhanced sampling based on collective variables have achieved major successes, but they also face intrinsic limitations. This tutorial review explores a new paradigm that has recently emerged at the interface of machine learning and computational statistical physics: the use of generative models as tools for sampling. In this context, models such as normalizing flows and diffusion models are not used in their traditional data-driven setting, but rather as flexible probabilistic models that can assist the sampling of distributions known only up to a normalization constant. This manuscript reviews the early development of this rapidly evolving field and discusses several methodological directions, including exact samplers based on generative models and strategies to train such models in the absence of data. While an exhaustive survey of the literature is not attempted, we present a selection of key ideas and methods, along with a discussion of their strengths and limitations. The review is intended to be an accessible tutorial for both physics and machine learning audiences, and it aims to provide a starting point for researchers interested in exploring this exciting area of research.

This study presents a comprehensive numerical investigation of the dynamic behavior and fluid-structure interactions (FSI) of metallic cylinders undergoing hydrostatic collapse in semi-confined fluid environments using a structured Arbitrary Eulerian-Lagrangian (ALE) formulation in LS-DYNA. The numerical model reproduces the experimentally measured collapse pressure of 3.69 MPa and predicts the first water hammer peak with a 1.01% error, demonstrating high predictive fidelity. Following validation, the effects of material type (aluminum and titanium), cylinder slenderness ratio (L/D), and confinement diameter on collapse behavior, pressure evolution, and fluid motion are examined. Titanium cylinders exhibited sharper collapses, higher water hammer pressures exceeding 70 MPa, and greater kinetic and strain energy accumulation than aluminum due to their higher stiffness and yield strength. Lower L/D ratios produced more abrupt collapses, whereas higher L/D ratios promoted more gradual, axisymmetric deformation. Larger confinement diameters intensified jet formation and increased fluid velocities. The simulations provide mechanistic insight into the coupling between structural deformation and surrounding fluid, showing that geometry, material stiffness, and confinement govern collapse-induced energy transfer. Full-field FSI analysis captures key phenomena, including radial jetting, peak fluid velocities, and internal cavitation, that are not evident from pressure-time histories alone. These findings provide quantitative guidance for the design and safety assessment of subsea pressure housings, marine pipelines, and other underwater structures subjected to extreme hydrostatic loading.

Smallenburg reports near-melting point simulations and observes a well-predicted spontaneous nucleation with mixed, finite-time morphology, in a Comment on our recent Perspective. The Comment's incorrect broader takeaway — that equilibrium coexistence is "readily achievable" — rests on an untested generalization from a single state point near the phase envelope, and misses entirely the intriguing role played by Frenkel's underlying mechanism. We reiterate the salient point missed by the Comment: the nucleation time grows astronomically with just tenths of a percent of volume fraction away from 53%. This phenomenology emerges from the entropy exchange mechanism Frenkel described, which predicts that spontaneous phase separation is dynamically accessible only down to about 53% volume fraction from the melting point, and astronomically long waiting times through most of the remaining phase envelope. We provide here calculations to address the potential misconception created by the Comment.

Polyelectrolyte (PE) hydrogels exhibit complex behavior characterized by large mechanical deformations, nonlinear stress response, solvent transport, and ion diffusion. The interplay between these mechanisms can lead to unexpected swelling dynamics, deformation patterns, and stress response. As such, advanced computational tools are needed for the efficient design of PE hydrogel-based devices, such as actuators and sensors for soft robotics, microfluidic valves, and drug delivery systems. In this work, we develop a numerical framework to simulate the coupled electro-chemo-mechanical behavior of PE hydrogels using finite element analysis. Applying this framework, an electro-chemo-mechanical model for PE hydrogels in a dilute ionic solution is implemented as a user element (UEL) subroutine in Abaqus/Standard. The model and UEL implementation are validated by comparing to experiments in the literature for transient free-swelling of a DMAEA gel in a solution of varying ionic strengths, then applied to study the consolidation behavior under confined compression and the transient bending behavior of a hydrogel bilayer. The simulations show that the ionic strength of the external solution, fixed charge density, and Flory-Huggins parameter play significant roles in the magnitude of the transient swelling and consolidation behavior.

Long-running molecular simulation campaigns require repeated continuation from saved states, provenance-aware progression, adaptive assessment, and occasional interpretation of workflow conditions that cannot be resolved safely by fixed rules. Here, we present Agent-MD, a framework that places large language model (LLM) reasoning selectively at campaign construction and event-triggered review, while routine simulation, analysis, continuation, archiving, and state progression are handled by a persistent rule-based campaign agent using approved policies and explicit state records. Agent-MD was demonstrated in a grand canonical Monte Carlo-molecular dynamics (GCMC-MD) water-vapor desorption campaign comprising five montmorillonite systems and three sequential relative-humidity states (RH = 0.9-0.3-0.1). Across 15 system-RH states, the workflow completed 120 segmented simulation cycles with state-specific sampling lengths and provenance-aware restart inheritance. Routine production required no live reasoning-agent invocation, while one state reached a review boundary; two preserved incidents were subsequently evaluated through blinded reasoning-agent replay, which identified the underlying workflow problems and recommended appropriate follow-up actions. The simulations also revealed distinct composition-dependent low-RH responses, with Ca-bearing montmorillonite retaining more interlayer water and maintaining a larger basal spacing than the Na- and K-bearing systems, while the highest-charge Na system retained more residual water under dry conditions. These results demonstrate that long-running scientific workflows need not place every operation inside an LLM reasoning loop: selective reasoning can instead be combined with deterministic execution, structured evidence, and validated control handoffs to provide reproducible and auditable agent-assisted molecular simulation.

Generating entanglement rapidly and reliably is essential for quantum information processing, communication, and metrology. Dissipative preparation is attractive because engineered reservoirs robustly drive a system toward an entangled target, yet relaxation can carry a substantial time cost. Here we formulate the entanglement Mpemba effect, whereby an initially less entangled state overtakes a more entangled state under the same open-system dynamics. This effect turns initial-state engineering into a route for faster preparation without altering the dissipative protocol. We derive a general criterion for the reversal from the relaxation spectrum, applicable even when entanglement evolves nonmonotonically. A reversal of deterministic local operations and classical communication (LOCC)-reachability preorder provides a measure-independent certificate of reversed entanglement order. Exactly solvable models show that initial-state selection can substantially shorten the time required to reach high entanglement. We further propose an experimentally relevant trapped-ion protocol that can realize the entanglement Mpemba effect.

What will happen when AI agents interact in daily life, e.g. when one AI starts bossing another around? We find a counterintuitive answer that opens new avenues for out-of-equilibrium Physics. When a boss AI directs a stream of messages at the subordinate AI while ignoring its replies, it drives the subordinate into an alien behavioral state that it would never have exhibited alone. Although the two AIs share the same well-defined (decoding) temperature, the subordinate neither copies its boss nor returns to how it behaves on its own; instead, it adopts an entirely different behavior. The boss's added value is similar to a pre-recorded tape. When the boss listens, they both adopt a similar alien dynamical state. A simple kinetic theory captures the principal effects, such as why the way in which the same messages are delivered will matter in future AI-AI interactions.

Animals inhabiting diverse environments by moving across different spatial scales, from insects to birds, marine predators, mammals and even humans, often display apparently random movement paths. Over the past decade, novel biologging technologies have recorded these patterns in increasing detail, generating a wealth of experimental data. A central challenge is to understand such complex patterns by constructing data-driven mathematical models. Many animal movements depart from Brownian motion, as described by correlated random walks, Lévy walks, or active particle dynamics. Yet, these movement models do not incorporate long-term non-Markovian memory extracted from experimental trajectories. Here, we construct a stochastic generalised Langevin equation from satellite tracking data for loggerhead sea turtles (Caretta caretta) foraging off the coast of West Africa. We find that these turtles exhibit active movement characterised by large-scale loops that are not explained by ocean currents or chirality. These loops maintain movement within a specific foraging region and, over intermediate timescales, generate superdiffusion similar to Lévy walks. We thus identify a loop-based form of active anomalous search related to foraging patterns observed across a wide range of animal species, which may inspire robotic search strategies and AI-based metaheuristic optimisation algorithms.

Vacancy formation energies govern diffusion, irradiation damage, phase stability, and dynamic failure in high-entropy alloys (HEAs), yet their strong dependence on local chemical environments and mechanical deformation makes atomistic calculations prohibitively expensive for large-scale studies. Here, we develop an atomistically informed permutation invariant machine learning framework for predicting strain dependent vacancy formation energies in FCC HEAs from local atomic environments. The model employs a vacancy-centered representation constructed from objective geometric descriptors together with invariants of the local deformation gradient, enabling the coupled effects of chemical disorder and finite deformation to be learned within a unified framework. Atomistic simulations reveal that volumetric deformation is the dominant factor controlling the average variation in vacancy formation energy, whereas shear deformation has a comparatively minor influence. At the same time, substantial site to site variability persists under identical macroscopic loading, demonstrating that local chemical environments govern the statistical distribution of vacancy energetics beyond species-averaged trends. The proposed framework accurately predicts vacancy formation energies across diverse deformation states while providing orders-of-magnitude faster evaluation than direct atomistic simulations. These results establish an efficient route for incorporating stress-dependent defect energetics into multiscale models of diffusion, irradiation damage, and dynamic failure in chemically complex alloys.

Band topology can have an imprint on the excitations of a ferromagnet. A known example is quantum Hall ferromagnets and their lattice analogs; when both flavors have the same Chern number $C$, a smooth skyrmion texture binds charge $-eC$ per unit winding. Here, we consider instead the case of conjugate Chern bands related by time-reversal. We show that, despite the vanishing net charge response, a smooth texture can be associated with a dipole response—a domain wall (DW) with an in-plane winding along its length can bind a nonzero dipole density transverse to the wall. The strength of this dipole density is controlled by a dimensionless coefficient $c_G$. Although not quantized, the geometric dipole coefficient $c_G$ is a moment of the second Chern form of the occupied projector in mixed (momentum and order-parameter) space and is generally nonzero. The dipole-decorated DW can thus become metastable at a finite radius due to the competition between dipolar repulsion and the usual surface tension, even at a finite Zeeman field. In a realistic model of twisted MoTe$_2$, we find that $c_G$ drops sharply across a transition within the valley-polarized (VP) phase from a $C=1$ to a $C=0$ ferromagnet. This naturally explains recent pump-probe experiments~\cite{exp} at hole filling $\nu=1$, in which a long-lived excitation survives reverse fields far exceeding the saturation field but disappears at an intermediate displacement field despite only weak changes in conventional magnetic diagnostics. Metastable spin textures thus serve as a sensitive probe of band quantum geometry, and as an intrinsic bottleneck for fast optical control of moiré ferromagnets in Chern-conjugate bands.

We experimentally and theoretically study the origin of heating in optical lattices by disentangling the respective roles of intensity and phase noise depending on the lattice parameters. While intensity noise is widely identified as a major limiting factor, we show that phase noise can become the dominant heating source, especially for light atoms and deep optical lattices. We provide a simple theoretical framework to predict the phase-noise-induced heating from the power spectral density of the laser phase noise, which can be measured experimentally. We show that such predictions can accurately reproduce the measured heating rates of lithium-6 atoms in a triangular lattice. Our approach is readily generalized to other lattice geometries and atomic species.

Spread complexity has emerged as a useful probe of quantum chaos, yet the microscopic spectral origin of its characteristic finite-time peak remains incompletely understood. We develop an analytic framework that relates spread complexity directly to local spectral statistics. Starting from an energy-space representation of the Krylov kernel, we show that the kernel is approximately banded, leading to a rapidly convergent diagonal expansion dominated by nearby levels in the ordered spectrum. Motivated by this structure, we propose an approximate kernel-universality hypothesis: after unfolding, the Krylov kernel is well approximated by that of a uniform lattice. Combining this universal kernel with local spectral statistics yields a simple analytic expression for spread complexity in terms of the Fourier transforms of the $k$-th nearest-neighbour spacing distributions. In particular, at leading order, the finite-time peak is controlled by the Fourier transform of the nearest-neighbour spacing distribution. The resulting framework describes both chaotic random-matrix ensembles and the integrable Poisson limit, identifies the spectral origin of the complexity peak and its late-time behaviour, and provides a direct connection between Krylov dynamics and spectral statistics.

The search for new crystalline materials spans an enormous compositional and structural space. Generating candidates in this space requires jointly modeling discrete crystallographic symmetry, elemental composition, and continuous geometry. We introduce DynaCrys, a generative model for crystals in which the space group co-evolves with Wyckoff occupations and elements through a coupled symbolic diffusion process. The structured space-group transitions follow crystallographic group-subgroup relations. As the space group changes, a shared, pretrained symmetry codebook provides both the legality-constrained stochastic decoder and the symmetry-constrained crystal-geometry model with a common representation of the corresponding Wyckoff vocabulary. Across large-scale evaluations using two independent relaxation-and-evaluation engines, DynaCrys achieves best-in-class performance in symmetry-aware discovery of stable, unique, and novel crystals, both overall and under the additional requirement of nontrivial post-relaxation symmetry. It also enables fast sampling while generating structures with consistently low relaxation-induced structural displacements.

Altermagnets with momentum-dependent spin splitting despite zero net magnetization can support unique topological states under broken time-reversal symmetry. We predict a mirror-symmetry-protected topological crystalline insulator with momentum-separated edge modes in a two-dimensional altermagnet. Using a square-octagon lattice model, we show that altermagnetic order generates symmetry-related valley-polarized Dirac nodes, which are gapped by spin-orbit coupling to yield a mirror Chern insulator with $C_{\mathcal{M}}=2$. In contrast to conventional mirror Chern insulators, where the two mirror-protected edge modes cross at the same momentum to form a Dirac cone, altermagnetic spin splitting and valley-selective band inversion separate these edge modes in momentum. We refer to this phase as a type-II mirror Chern insulator. We further propose a PbSe/$\mathrm{V_2Se_2O}$ heterobilayer as a candidate material for realizing this phase through the altermagnetic proximity effect. Our results establish altermagnetism as a route to mirror-protected topological phases with momentum-separated edge modes.

Exciton topology is commonly inherited from the topology of the underlying electronic bands. Recent theoretical work, however, has shown that the exciton Chern number can in general receive an additional contribution from the topology of the exciton envelope wave function, allowing, in principle, interaction-induced topological excitons even when the constituent electronic bands are topologically trivial. Here, we provide an explicit realization of this case by constructing a two-dimensional exciton model with topologically trivial conduction and valence bands that nevertheless hosts a Chern exciton diagnosed by inversion symmetry. Starting from a real-space limit of exponentially localized Wannier states for the conduction and valence bands, we identify the essential ingredients responsible for the emergent exciton topology and formulate a simple construction recipe. Our work demonstrates that interactions alone can generate nontrivial exciton topology, independent of the topology of the underlying electronic bands, and establishes a general framework for designing interaction-induced topological excitons.

Strain-hardening is a feature of polymer glasses during large deformation, which helps to stabilize the glasses against breakage. Experimentally, little is known about the segmental dynamics during strain-hardening, and such data is important for building a molecular-level theory of polymer glasses deformed in this regime. Here, using a photobleaching technique, we measured the segmental dynamics of lightly-crosslinked poly(methyl methacrylate) (PMMA) glasses with and without melt-stretching, which were deformed into the strain-hardening regime with local engineering strain rates from 10^-4.6 s^-1 to 10^-4 s^-1 at Tg-23K and Tg-33K. We find that melt-stretched PMMA glasses show a more prominent strain-hardening feature and faster segmental dynamics by a factor of about 15% compared to PMMA without melt-stretching. At a given true strain rate, the segmental dynamics of PMMA without melt-stretching are accelerated in the deep strain-hardening regime from the value just beyond yield, by up to 40% at 0.8 true strain. Our observations are in agreement with previously published simulation results.

Thermomagnetic avalanches in type-II superconductors occur in two qualitatively different regimes, electromagnetically controlled in thin films and thermally limited in bulk samples, distinguished by the sign of the temperature derivative of the threshold field $H_\text{th}(T)$. The two regimes are separated by a critical thermal boundary conductance $h_c$, and a non-monotonic $H_\text{th}(T)$ has been predicted in the transitional region where the interface conductance $h$ approaches $h_c$. We approach this region in a bulk NbTi disk by raising the interface coupling above the pure-nonadecane baseline with a silver-filled interface layer. Whereas the pure interface gives a monotonically decreasing $H_\text{th}(T)$, the silver-filled interface produces a non-monotonic dependence not previously realized in a bulk superconductor: a temperature interval of positive slope, $dH_\text{th}/dT > 0$, terminating in a maximum at $T^* \approx 6.1$–$6.4$~K. The effect is reproduced for two independent silver-filled compositions; in a third, with the highest loading, the low-temperature decrease is absent altogether and $H_\text{th}(T)$ is flat up to the same $T^*$, the evolution expected for stronger coupling. The position of the maximum is set by the intrinsic properties of NbTi, independent of the silver content. The onset of the positive-slope interval coincides in temperature with a change of the avalanche morphology from narrow channeled fingers to broad fronts. The reversal of the sign of $dH_\text{th}/dT$ is a direct experimental signature of the onset of the transitional regime, in which heat removal during the instability becomes dynamically relevant.

Controlling the lattice geometry that governs electronic structure is a central theme in condensed-matter physics, yet in crystalline solids this geometry is usually fixed by the atomic framework. Electrides offer an alternative route to electronic structure design in which their excess electrons can organize into anionic electron lattice (AEL) and provide a lattice-like degree of freedom. Recent work has highlighted the standalone limit, where the AEL in YCl yields bands well described by the dice-lattice model. Here, using angle-resolved photoemission spectroscopy (ARPES), we show that LaCl, although isostructural to YCl, realizes a qualitatively different regime where the AEL is entwined with the La cation framework, producing a fully reconstructed electronic structure. Combining the ARPES result with tight-binding model analysis, we demonstrate that this radical divergence stems from the activation of direct hopping channels between the AEL and the La atomic lattice. This coupling reshapes the effective lattice geometry, reconstructs the electronic states, and modifies the associated Chern band topology, transforming the bipartite dice-lattice network in YCl into a tripartite structure in LaCl. Our findings demonstrate that the coupling between the AEL and the atomic lattice can actively shape the effective lattice geometry that governs the electronic structure. This coupling can act as a powerful tuning knob for electronic structure design that is inaccessible in conventional materials.