Materials Science
Universal Interatomic Potentials as Configuration-Space Generators for One-Shot and Iterative Fine-Tuning of Ab Initio-Accurate Material-Specific Models
Jonas Hänseroth, Aaron Flötotto and Christian Dreßler
Universal machine-learning interatomic potentials (MLIPs) are rapidly becoming general-purpose tools for atomistic simulation, but their role in quantitative materials modeling when reactive events are involved remains unsettled. We compare five universal MLIPs across seven chemically diverse systems and find that strong performance on standard
benchmarks does not guarantee accurate predictions of target observables. In particular, zero-shot models do not reliably reproduce reactive, transport, or high-barrier processes, exemplified here in particular by the sulfur-vacancy jump in MoS$_2$. We therefore propose a practical alternative: universal MLIPs are used to generate long molecular dynamics trajectories, the resulting configurations are sub-sampled and relabeled with DFT, and material-specific MLIPs are subsequently trained or fine-tuned on the resulting first-principles
datasets. This workflow converts universal models into efficient configuration-space generators while retaining ab initio reference labels for training. Across the tested systems, $2{,}000$ DFT-recalculated structures are often sufficient to obtain accurate fine-tuned or trained-from-scratch models. For the most challenging case, iterative self-training progressively refines the sampled configuration space and recovers the DFT MoS$_2$ potential energy profile with only $600$ first-principles calculations in total. The resulting workflow enables the generation of $1$ ns ab initio-quality trajectories - including training data generation and model creation - within three days.
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Soft Condensed Matter
Coupling Heterarchical Granular Dynamics and Computational Fluid Dynamics
Jiahuan Li, Shivakumar Athani, Alistair Gillespie et al. (+3 more)
Granular flows in ambient fluids exhibit grain-size-dependent segregation, which is difficult to capture efficiently with existing models, especially in large-scale systems involving more than a million grains. We develop a two-way coupled framework that integrates heterarchical granular dynamics (HGD) with a fluid-fraction-weighted incompressible Navier-Stokes solver. This heterarchical granular-fluid dynamics (HGFD) model extends a previous HGD model for quasi-static deformations by introducing inertial, force-balance-driven particle velocities and consistent fluid-solid momentum exchange. The coupling between the inertial HGD and the fluid solver is performed using a staggered explicit sequential scheme and co-located Eulerian fields. The framework is evaluated against experimental data of (i) single-particle settling to verify inertial relaxation, (ii) hindered settling to reproduce concentration-dependent settling and vertical size stratification, and (iii) representative cases covering three reported segregation types to assess regime sensitivity. These results establish HGFD as an efficient and consistent approach for simulating fluid-coupled granular segregation dynamics.
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All authors Jiahuan Li, Shivakumar Athani, Alistair Gillespie, Matthew J Cleary, Itai Einav, Benjy Marks
Materials Science
Hierarchical Unsupervised Clustering of Nanobeam Electron Diffraction Data Using Sparse Bragg-Vector Representations
Ian MacLaren, Ala Al-Afeef, Trevor Almeida et al. (+5 more)
If disk detection is applied to nanobeam electron diffraction
datasets, then the results are effectively a list of vectors describing the position of every diffraction peak in real and reciprocal space. This is the natural territory for the application of clustering
algorithms, and they are shown to be highly effective at decomposing such
datasets and automating imaging and analysis. In particular, this is found to work particularly well in a hierarchical clustering approach, where a first level is concerned with finding clusters of similar diffraction vectors and a second level with grouping those diffraction vector clusters that originate from the same real space area (i.e.
crystal or crystallographic variant). Examples are shown in both polycrystalline and single
crystal (with precipitates) systems. Additionally, automated separation of amorphous or deeply nanocrystalline components is also found to be possible in an optional third level of clustering, allowing composite images of both amorphous and crystalline components in partially crystallised samples to be easily and automatically generated. These advances promise to increase throughput in atomic structure analysis with nanobeam diffraction, and also make finding minor components much easier. They can also serve as a preliminary step towards more detailed crystallographic or
crystal size/shape distribution analysis.
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All authors Ian MacLaren, Ala Al-Afeef, Trevor Almeida, Rantej Bali, Shriyar Tariq, Emily Wackan, Luke Daly, Joshua F. Einsle
Mesoscale and Nanoscale Physics
Rotating Zeeman field as a tool for Majorana zero mode detection in topological superconducting wire
Piotr Stefański
We demonstrate that analysis of the
spin polarization of a
quantum dot (QD) attached to the topological wire can provide valuable insights into Majorana zero mode (MZM) formation and topological phase transition. Detection is realized by rotation of the Zeeman field in the wire, while retaining the Zeeman field direction in the dot intact. In the presence of Majorana mode, the effective QD
spin polarization at
Fermi energy changes significantly when the direction of the Zeeman field in the wire changes from parallel to perpendicular to the wire axis. It can be opposed to the wire in its trivial state, when
spin polarization remains practically constant while the
magnetic field is rotated. Similar unaltered
spin polarization is observed when QD
spin sub-level at
Fermi energy mimics MZM. Moreover, the characteristic non-linear dependence of the
spin polarization on the
magnetic field magnitude at its critical value identifies a topological phase transition in the wire. This feature is observed independently on the coupling strength of the wire to the dot and the angle of the Zeeman field.
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Materials Science · Cross-listed from cs.LG
Substitution-Based Analysis of Structural Novelty for Generative Models of Materials
Masahiro Negishi and Aron Walsh
There has been rapid progress in generative artificial intelligence (AI) models for inorganic
crystal design, which can efficiently generate large numbers of candidate compounds after being trained on databases of known
crystals. However, it remains unclear whether they genuinely expand the accessible materials search space beyond conventional strategies such as elemental substitution within known structure types. We address this question by developing a workflow to assess whether AI-generated
crystals are duplicates of training structures, reproducible by elemental substitution, or unmatched by either criterion. Applying this workflow to representative generative models reveals that 81-92% of chemically valid and metastable generated
crystals are either training duplicates or substitution-derived structures. This tendency is particularly strong in high-
symmetry crystal systems, even though many possible structural prototypes remain unexplored. Further analysis of the underlying structural fingerprints shows that low-
symmetry structures beyond duplication or substitution can be interpreted as interpolation in training-data-rich regions, while high-
symmetry duplicates appear to result from memorisation in training-sparse regions. Our findings highlight a limitation in the current generation of models that exhibit a bias towards known structural prototypes in the high
symmetry regions, but enable wider exploration of the low-
symmetry structural space.
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Materials Science
Toward in-situ/operando X-ray absorption spectroscopy and electrochemical characterization of solid oxide fuel cells
Renato A. N. de Oliveira, Rafael Galiza Yoshimura, Liliana Mogni et al. (+15 more)
The focus of the present work is the development of specialized experimental instrumentation compatible with synchrotron characterization for in-situ and operando symmetric intermediate temperature solid
oxide fuel
cells (IT-SOFC) studies at maximum temperatures of 800 C , exposed to reducing and oxidizing atmospheres, using fluorescence X-ray absorption spectroscopy (XAS) measurements in combination with electrochemical impedance spectroscopy (EIS) in the multipurpose Quati beamline at CNPEM/SIRIUS synchrotron facility [1]. Symmetric IT-SOFC are gaining importance due to their structural simplicity, as they allow for the use of identical materials on both sides of the fuel
cell electrolyte; the anode, and the cathode [ 2,3 ]. The symmetric configuration opens new opportunities for fundamental research of electrode materials and improves the versatility of SOFC electrochemical devices [2,3].
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All authors Renato A. N. de Oliveira, Rafael Galiza Yoshimura, Liliana Mogni, Maurico Arce, Diego G. Lamas, Lucia Toscani, Maria Belén Arcentales Vera, Esteban Elvis Asto Ramos, Magna Monteiro Schaerer, Celeste Z.A. Aquino, Marcia Carvalho de Abreu Fantini, Taofeeq Oladayo Bello, Tereza da Silva Martins, Danilo Waismann Losito, James Moraes de Almeida, Valeria Spolon Marangoni, Leopoldo Suescunand, Santiago Figueroa
Materials Science
Unconventional topological Hall response and anisotropic magnetotransport properties of a helical magnet EuAuAs
Anyesh Saraswati, Koyendrila Debnath, Shubhankar Roy et al. (+3 more)
Topological magnets with nontrivial
spin texture have attracted considerable interest because they display a rich spectrum of emergent
quantum phenomena. Here, we present a combined experimental and theoretical investigation of the
magnetic and magnetotransport properties of EuAuAs, an antiferromagnet with Néel temperature ($T_\mathrm{N}$) $\sim$ 6 K. The temperature and
magnetic field dependence of electrical resistivity and magnetization demonstrate that the charge transport in EuAuAs is strongly influenced by the
spin configuration of local Eu moments. Below $T_\mathrm{N}$, both longitudinal magnetoresistance (LMR) and transverse magnetoresistance (TMR) are positive at low fields but large and negative at high fields. With increasing temperature, TMR becomes positive above 60 K, whereas LMR remains negative up to 100 K. The low-field positive LMR and TMR originate from weak antilocalization (WAL). The WAL contribution in TMR is well captured by the Hikami-Larkin-Nagaoka model, whereas the LMR data are described by a generalized Altshuler-Aronov framework. Moreover, we observe a
giant topological
Hall effect arising from the scalar
spin chirality, which is further supported by the helical
magnetic structure obtained from the ab-initio calculations. The observed anisotropy in longitudinal resistivity and magnetoresistance underscores the very nature of the
Fermi surface of the EuAuAs, as confirmed by first-principles calculations. These results establish EuAuAs as a unique platform for exploring the interplay between electronic structure and noncoplanar
spin texture in a centrosymmetric helical magnet.
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All authors Anyesh Saraswati, Koyendrila Debnath, Shubhankar Roy, Barun Ghosh, Nitesh Kumar, Prabhat Mandal
Materials Science
Reduced-Order Modelling of Defect Transport using Surrogate Kinetics: Application to U$_x$Pu$_ {1-x}$N
Peter Hatton
Defect transport in chemically disordered materials is a difficult phenomenon to model since migration energetics depend strongly on the local chemical environment, producing a distribution of transition barriers that cannot be exhaustively enumerated. Here, we develop a reduced-order approach to modelling defect
diffusion in compositionally complex materials using environment-dependent surrogate kinetics. Migration energetics for actinide vacancies, nitride vacancies, and actinide-nitride divacancies in U$_x$Pu$_{1-x}$N are generated using the Hop-Decorate workflow across thousands of chemical configurations. These data are distilled into compact surrogate functions that predict migration barriers and energy differences from simple descriptors based on local coordination counts. The surrogate models reproduce the atomistic
dataset with low error and enable efficient evaluation of migration rates during
lattice kinetic Monte Carlo simulations. Long-time diffusivities computed across temperature and composition reveal strongly non-linear behaviour arising from two dominant mechanisms: species-controlled migration on the actinide sublattice and environment-dependent trapping on the nitride sublattice. Although demonstrated for U$_x$Pu$_{1-x}$N the framework provides a general and computationally efficient approach for modelling defect transport in chemically disordered materials and for integrating atomistic kinetics into higher-scale simulations.
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Strongly Correlated Electrons
Angular-time evolution and edge-spin dynamics in the Haldane phase of the S=1 bilinear-biquadratic chain
Takuma Kaise and Kouichi Okunishi
We investigate the angular-time
evolution – a parameter-time
evolution generated by the
entanglement Hamiltonian – for the bipartitioned ground state of the S=1 bilinear-biquadratic chain under the open boundary condition with the up edge
spin. Using a
matrix-product-state representation of the ground-state wavefunction, we calculate the angular-time
spin correlation functions $\langle S_n^{\alpha }(\tau )S_{n'}^{\alpha }(0)\rangle$ in the Haldane phase, and extract its dominant oscillation mode attributed to the nearly two-fold-degenerate
entanglement spectrum associated with the $\mathbb{Z}_2 \times \mathbb{Z}_2$
symmetry. We also compute the effective edge-
spin dynamics under a uniform
magnetic field applied to the system part and numerically verify its correspondence to the dominant angular-time mode by precisely comparing the subsystem-size dependence of their amplitudes.
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Mesoscale and Nanoscale Physics
Fingerprints of an Imbert-Fedorov-like effect in the tunneling transmission of Rarita-Schwinger semi-metals
Otman Bouladiane, Ahmed Jellal, Hocine Bahlouli et al. (+2 more)
We study tunneling through a square barrier in a rotationally symmetric Rarita-Schwinger semi-metal and identify fingerprints of an Imbert-Fedorov-like effect in the tunneling transmission. The problem is intrinsically multichannel at all energies because there exist two propagating sectors with
spin projections $m=1/2$ and $m=3/2$. We derive the transmission amplitudes analytically and compare the single-channel and coherent mixed-incidence cases in the two channels. Interestingly, we observe that tunneling at high energy shows a bias towards scattering into
spin projection $3/2$ contributions. For single-channel injection, we find that the transmission remains symmetric under a mirror transformation of the incident angle. In contrast, for the coherent superposition, we find a directional asymmetry in the transmission probability $T(k_y)\neq T(-k_y)$. Importantly, this effect does not originate from an anisotropy of the dispersion. Instead, it arises from the phase structure of the multicomponent scattering states. The two
spin projection sectors exhibit different scattering and barrier-propagation phases, which enter as interference terms when both channels appear as a coherent superposition. This interference term is identified as the cause of the broken mirror
symmetry. We therefore discover an analog of the Imbert-Fedorov effect, at the level of interface-induced phase differences between internal wave components. Our result demonstrates that asymmetric tunneling can already occur in transport experiments, even in an idealized, isotropic multiband system, and should therefore not be automatically attributed solely to explicit band anisotropy.
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All authors Otman Bouladiane, Ahmed Jellal, Hocine Bahlouli, A. Al Luhaibi, Michael Vogl
Mesoscale and Nanoscale Physics
Universality of dimensional crossovers in topological insulators
Lumen Eek, Zeb Osseweijer and Cristiane Morais Smith
We investigate dimensional crossovers in minimal tight-binding models of three-dimensional (3D) topological
insulators subject to
geometric confinement. While thin films are commonly understood to host a crossover from a 3D strong topological
insulator to a two-dimensional (2D)
quantum spin Hall phase via hybridization of surface states, we demonstrate that this picture is incomplete once bulk confinement effects and boundary termination are fully taken into account. Using
lattice models, we show that reducing the system size induces a strongly non-monotonic dependence of the
topology on thickness and microscopic parameters, leading to a sequence of topological phase transitions that is highly sensitive to surface termination. In particular, we find a cascade of dimensional reduction from a 3D topological
insulator to a 2D
quantum spin Hall phase and ultimately to a one-dimensional phase consisting of end states of Kramers pairs protected by inversion
symmetry. Remarkably, we show that both the 2D and 1D topological phases can emerge even when the corresponding 3D bulk phase is topologically trivial. Our results reveal an unexpected universality in the phase diagrams of 3D-to-2D and 2D-to-1D crossovers, pointing toward a unified framework for
topology under dimensional reduction.
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Other Condensed Matter
Nonlinear Static Screening of Positive Charges in an Electron Gas: Contact Hartree Energy
M. Sherafati, G. Rodway-Gant and A. X. Chen
Electron screening of positive charges in metals is most strongly nonlinear in the static near-field regime. We revisit the static screening of a
proton embedded in a homogeneous electron gas, focusing on the induced electron density and the contact Hartree energy $U_{\rm H}(0)$. Although evaluated at the
impurity site, $U_{\rm H}(0)$ is a nonlocal radial moment of the induced density in a formulation applicable to both linear-response and nonlinear density-functional descriptions. We compare Thomas–
Fermi, random-phase-approximation, and local-field-corrected dielectric screening with nonlinear density-functional-theory
benchmarks. The Estreicher–Meier local-density-approximation parametrization closely reproduces the contact Hartree energies from our direct LDA calculations and from Almbladh et al. [\href{https://doi.org/10.1103/PhysRevB.14.2250}{Phys. Rev. B 14, 2250 (1976)}], separating hydrogenic core and Friedel-oscillation contributions. The contact energy and on-top density are nearly insensitive to the choice between modern
quantum-Monte-Carlo-consistent local-field factors. We then analyze Yukawa, hydrogenic, and Hulthén screened Coulomb potentials using a variable-phase formulation constrained by the Friedel sum rule. These model potentials provide a useful phase-shift representation of static screening, but a single Friedel constraint does not determine the nonlinear contact Hartree energy quantitatively. The results establish a one-center nonlinear screening
benchmark for
protons in jellium and a baseline for future two-center screening calculations in metallic environments.
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Mesoscale and Nanoscale Physics
Tomography of Transport Pathways in Selective-Area-Grown Nanowires Using Angle-Resolved Conductance Fluctuations
Christian E. N. Petersen, Damon J. Carrad, Daria Beznasyuk et al. (+1 more)
Understanding the spatial distribution of carriers is important for interpreting transport in nanoscale devices. Here, we apply conductance fluctuation
tomography to planar selective-area-grown InAs nanowires in both normal-normal and normal-
superconductor device geometries. By tracking the
evolution of conductance-interference features as a function of
magnetic-field strength and orientation, we extract information about the geometry of phase-coherent transport pathways. Using theory to distinguish between bulk-dominated transport, coherent near-surface transport across facets, and transport confined to individual facets. The measurements are consistent with transport dominated by a near-surface accumulation layer in InAs. Devices with normal contacts show behavior consistent with coherent transport across the nanowire apex, whereas hybrid normal-
superconductor devices exhibit signatures of more facet-dependent transport. These results demonstrate how universal conductance fluctuations can be used as a tomographic probe of phase-coherent transport pathways in
semiconductor nanostructures.
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All authors Christian E. N. Petersen, Damon J. Carrad, Daria Beznasyuk, Thomas S. Jespersen
Materials Science · Cross-listed from physics.app-ph
Physics-governed executable modelling of triboelectric nanogenerators
Hongfa Zhao, Baiqiao Wang, Tiancong Zhao et al. (+7 more)
Predictive modelling of triboelectric nanogenerators (TENGs) remains fragmented across analytical theories, finite-geometry solvers and disconnected simulation workflows. These disparate approaches must be unified into an executable framework to advance quantitative TENG research.Here we introduce a charge-defined modelling framework and implement it as TENG-CLAW, a physics-governed platform for traceable TENG simulation. The framework establishes a self-consistent electrostatic hierarchy in which triboelectric charges, pre-charging charges and compensating electrode charges serve as defining state variables.This hierarchy connects the infinite plate analytical limit for near-uniform fields with finite-geometry numerical formulations required for edge-dominated devices. Built on this basis, TENG-CLAW converts user-defined research requests into physically admissible simulation tasks, so that generated outputs are tied to explicit charge states, boundary conditions, solver routes and reusable artifacts across spatial, temporal, field-level, comparative and reporting workflows. This work establishes a rigorous computational basis for interpreting TENG mechanisms and provides reproducible research infrastructure for simulation and physics-guided device design.
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All authors Hongfa Zhao, Baiqiao Wang, Tiancong Zhao, Chun Jin, Hanlin Zhou, Mingrui Shu, Minyi Xu, Liwei Lin, Wenbo Ding, Zhong Lin Wang
Statistical Mechanics
Deviance from a pink noise regime in the temporal organization of semantic relations in psychosis
Paola Moreno Ancalmo, Emre Bora, Rieke Roxanne Mülfarth et al. (+5 more)
The notion of pink noise refers to 'scale-invariant' temporal dynamics, where fluctuations exhibit similar statistical structure across time scales. Departures from a regime associated with such scale-free organization toward uncorrelated 'white' noise or overly persistent 'brown' noise have been widely identified as markers of pathology across physiological and cognitive domains. Whether comparable alterations characterize the temporal organization of
language remains largely unexplored. We address this question in the domain of psychosis, where
language anomalies are pervasively documented. Specifically, we apply detrended fluctuation analysis (DFA) to quantify temporal scaling in BERT-derived continuous cosine-similarity time series capturing trajectories through semantic space, using clinical transcripts from patients and controls across three independent
datasets. DFA scaling exponents were extracted to characterize the strength of long-range temporal correlations. Across all
datasets, patients exhibited significantly elevated scaling exponents relative to controls, indicating abnormally strong long-range correlations with excessive persistence in semantic fluctuations. This temporal analysis opens a window into the multi-timescale organization of meaning as it unfolds in discourse. The results reveal a signature of altered temporal scaling in
speech, consistent with deviations from criticality in physiological domains, paralleling known departures from criticality in
brain function in psychosis and suggesting possible links between these two domains.
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All authors Paola Moreno Ancalmo, Emre Bora, Rieke Roxanne Mülfarth, Svenja Seuffert, Tilo Kircher, Frederike Stein, Philipp Homan, Wolfram Hinzen
Mesoscale and Nanoscale Physics
Strongly anisotropic Rytova-Keldysh interaction and the ground state of 2D excitons
Andrei Galiautdinov
The classic Rytova-Keldysh potential describes the non-local dielectric screening of Coulomb interactions in ultrathin two-dimensional (2D) materials. Recently, the corresponding potential for arbitrary in-plane anisotropy was derived in integral form, with numerical studies suggesting that an effective isotropic approximation remains robust for highly directional systems. In this paper we provide the analytical foundation for these observations by mapping the complete spatial landscape of the strongly anisotropic Rytova-Keldysh interaction. By applying the method of steepest descent and momentum-space coordinate scaling to the exact one-dimensional integral representation, we derive closed-form asymptotic expressions for the potential across all spatial regimes. We find that the intermediate-range screening exhibits a non-trivial amplitude scaling driven by the direction of weakest polarizability, while the short-range limit produces an anisotropic logarithmic well governed by the
geometric mean of the principal polarizabilities. Finally, utilizing this short-range confinement, we implement an anisotropic Gaussian variational ansatz to solve the Wannier equation, providing a closed-form analytical expression for the
exciton ground-state binding energy that explicitly captures the competition between the effective mass and dielectric tensors.
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Superconductivity
Structural symmetry effects on the competition of density waves and superconductivity in bilayer nickelates
Steffen Bötzel, Aiman Al-Eryani, Jun Zhan et al. (+4 more)
We investigate the interplay between
spin-density-wave (SDW) order and superconductivity in the
bilayer nickelate La$_3$Ni$_2$O$_7$ using the functional renormalization group~(fRG) applied to multiorbital weak-coupling models of both the ambient- and high-pressure
crystal structures. As Hund's coupling increases, the leading instability evolves from superconductivity to an SDW state with ordering vector $\mathbf{Q}_1 \approx (\pi/2,\pi/2)$ (equivalently $\mathbf{Q}_Y \approx (0,\pi)$ in the orthorhombic $Amam$ unit
cell), in agreement with experimental observations. Surprisingly, the ambient- and high-pressure structures exhibit nearly identical non-interacting susceptibilities and leading fRG instabilities, indicating that the emergence of superconductivity under pressure cannot be explained solely by changes in the low-energy electronic structure. Instead, our results identify the suppression of orthorhombicity as a key ingredient for superconductivity. As the system approaches the tetragonal limit,
symmetry-related SDW fluctuations become nearly degenerate, frustrating long-range
magnetic order while enhancing pairing interactions. These findings highlight
lattice symmetry as a central tuning parameter of the competing ordered states in
bilayer nickelates and suggest that reducing orthorhombicity through uniaxial strain could stabilize bulk superconductivity already at ambient pressure.
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All authors Steffen Bötzel, Aiman Al-Eryani, Jun Zhan, Xianxin Wu, Frank Lechermann, Michael M. Scherer, Ilya M. Eremin
Strongly Correlated Electrons
Spiral spin liquid resilient to quantization in the frustrated honeycomb antiferromagnet GdZnPO
Xun Chen, Rui Bian, Yuqian Zhao et al. (+4 more)
Frustrated magnets host strong
quantum fluctuations that can suppress conventional
magnetic order and give rise to exotic
quantum phases such as
spin liquids. In some cases, however,
quantum fluctuations lift classical degeneracies and stabilize ordered states via an order-by-
quantum-disorder mechanism. The
spin-7/2 honeycomb antiferromagnet GdZnPO has recently been proposed as a spiral
spin-
liquid candidate arising from cooperative fluctuations among a subextensively degenerate
manifold of spiral states. Here, we investigate the local magnetization and
spin dynamics in GdZnPO using
nuclear magnetic resonance. In an intermediate field regime between $\sim$3 T and the saturation field ($\sim$12 T), we observe a spatially uniform magnetization and persistent low-energy
spin dynamics down to 0.033 K, with no detectable
symmetry breaking, providing spectroscopic evidence for a
spin-
liquid state. At lower fields below $\sim$3 T, a weak stripe order emerges below $\sim$0.25 K; however, strong fluctuations persist, as indicated by a nearly temperature-independent and unusually large
spin-
lattice relaxation rate in the low-temperature limit. Our results demonstrate that
spin-7/2 quantization weakly lifts the spiral degeneracy, stabilizing subtle
magnetic order while preserving robust dynamics and
spin-
liquid phenomenology. These findings establish GdZnPO as a promising platform for exploring
spin liquids in high-
spin frustrated magnets down to the lowest accessible temperatures.
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All authors Xun Chen, Rui Bian, Yuqian Zhao, Haijun Liao, Weiqiang Yu, Yi Cui, Yuesheng Li
Materials Science · Cross-listed from physics.acc-ph
Powder Spreading and Layer Deposition in Metal Powder Bed Fusion
Antonello Astarita
Powder spreading and layer deposition are fundamental stages of Powder Bed Fusion (PBF) technologies and play a critical role in determining process stability and final component quality. This chapter examines the mechanisms governing powder-bed formation, highlighting the interactions between powder characteristics, process parameters, and machine architecture. Particular
attention is devoted to the influence of particle size distribution, morphology, cohesion, flowability, layer thickness, recoater velocity, and environmental conditions on powder-bed quality. The resulting powder-bed is discussed as a process state variable whose characteristics, including packing density, surface coverage, effective layer thickness, and spatial homogeneity, directly affect energy absorption, melt-pool stability, defect formation, and mechanical performance. The chapter also reviews the application of the Discrete Element Method (DEM) for modelling powder spreading phenomena and quantifying powder-bed quality metrics. Finally, the role of powder reuse, lifecycle management, and future developments involving process monitoring, digital twins, and data-driven optimization strategies is discussed, emphasizing the growing importance of powder engineering in advanced metal additive manufacturing.
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Disordered Systems and Neural Networks
Scalable Physics-Inspired Transformers for Spin Glasses
Lu Zhong, Wenli Duan, Jing Liu et al. (+2 more)
Efficient sampling of the Boltzmann distribution in frustrated
spin glasses is central to statistical mechanics and combinatorial optimization. Despite advances in machine-learning-based approaches, two issues persist: limited understanding of why variational models fail to benefit from increased scale, unlike the monotonic scaling law of large
language models; and high computational cost on large systems that negates advantages over classical sampling methods. Here, we develop a physics-inspired
transformer with interpretable sparse
attention and
spin-tailored positional
embeddings to address these challenges. By further leveraging FlashAttention for parallel ancestral sampling, it achieves up to two orders of magnitude speedup over vanilla variational autoregressive networks, enabling neural-network simulations of
spin-glass systems to unprecedented sizes on a single GPU. It can resolve full probability distributions, free energies, and overlap statistics across temperatures, for Sherrington-Kirkpatrick and 2D or 3D Edwards-Anderson models, where existing machine-learning methods encounter limitations at certain temperatures. This framework thus establishes a scalable paradigm for frustrated
spin-glass systems.
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All authors Lu Zhong, Wenli Duan, Jing Liu, Pan Zhang, Ying Tang
Materials Science · Cross-listed from physics.optics
Large-Area Patternable Solar-Powered Bistable Organic Crystalline Film for Nonlinear Optical Communication
Ankur Khapre, Avulu Vinod Kumar, Haseeba Nasreen Punathil et al. (+5 more)
Reversible control of
crystal symmetry offers a powerful route to programmable optical functionality. However, achieving solid-state bistability between centrosymmetric and non-centrosymmetric crystalline phases remains a formidable challenge; examples of materials that enable stable switching of second-order nonlinear optical (NLO) responses are exceptionally rare. Here we report a
solar-powered,
symmetry-bistable organic material based on the photoisomerizable molecule (E/Z)-2-(4-(4-bromophenyl)thiazol-2-yl)-3-(4- (dimethylamino)phenyl)acrylonitrile (E/Z-BTDPA). The crystallizable E- and Z-isomers adopt distinct molecular packing arrangements that reversibly toggle between these states, controlling second-order NLO activity. The E-form exhibits strong second-harmonic generation (SHG), whereas the Z-form is SHG-inactive and displays twophoton luminescence. This bistable behavior is retained in flexible thin films, where sunlight-driven photoisomerization enables reversible photoswitching of the second-order electric susceptibility (ḩi} 2), large-area optical patterning, and real-time NLO communication via waveform generation and text-string transcription at telecommunication wavelengths. This sustainable strategy bypasses rigid inorganic architectures, establishing photoinduced
symmetry bistability as a scalable paradigm for all-optical computing and advanced communication networks.
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All authors Ankur Khapre, Avulu Vinod Kumar, Haseeba Nasreen Punathil, Biswajit Kumar Barman, Bedanta Kumar Deka, Shilpa Mangalassery, Sri Ram G Naraharishetty, Rajadurai Chandrasekar
Materials Science · Cross-listed from physics.chem-ph
Reaction-Network-Level Discovery of Ammonia Synthesis Catalysts via Ten-Million-Scale Generative Exploration
Ruili Li, Rui Qi, Shuoqi Zhang et al. (+5 more)
Catalyst discovery for ammonia synthesis is inherently a reaction-network challenge because catalytic performance is governed not by a single adsorbed intermediate, but by a surface's orchestrated compatibility with multiple distinct intermediates across competing dissociative and associative pathways. However, navigating ultra-large chemical spaces under such multi-intermediate constraints remains a formidable bottleneck for conventional screening workflows. Here, we report a reaction-network-level catalyst discovery framework driven by ten-million-scale generative exploration. By coupling adsorbate-specific generative
Transformers with high-throughput machine learning potentials, we systematically map the structure-property landscapes of four critical intermediates (N*, NH*, NNH*, and HNNH*). Scale-dependent overlap analysis shows that the full four-intermediate compatibility space remains strongly under-sampled at conventional 105-106 generative scales, emerging exclusively under ten-million-scale exploration. By generating approximately 15 million configurations per adsorbate, followed by structural compression and machine-learning-potential predictions, we identified 279 highly potential target materials. This sparse compatibility space successfully recovers traditional Fe- and Ru-based motifs while uncovering previously unexplored catalyst families. Representative DFT calculations validate pathway-dependent mechanisms: Fe-V emerges as a dissociative-pathway lead by significantly lowering the initial N2 dissociation barrier, whereas Al-Pd-Zr efficiently stabilizes associative intermediates as an associative-pathway lead. These findings establish multi-intermediate reaction-network compatibility as a robust criterion for discovering advanced catalysts from multi-million generative chemical spaces.
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All authors Ruili Li, Rui Qi, Shuoqi Zhang, Qingli Tang, Qingqing Mao, Ritankar Das, Beien Zhu, Yi Gao
Soft Condensed Matter
Hydrodynamic Phase Separation and Morphological Evolution in Chiral Active-Passive Mixtures
Mayurakshi Deb and Rajesh Singh
The collective behavior of passive particles within
chiral active matter has emerged as a significant area of soft matter research. However, most existing studies focus on systems where chirality is imposed by external torques rather than intrinsic activity. In this work, we study emergent dynamics in a suspension of active spinners and passive colloids by computing many-body hydrodynamic interactions via Ewald summation. By systematically exploring a broad range of area fractions and rotational velocities, we identify distinct phase-separation regimes sensitive to the system's kinematic parameters. Specifically, we report the emergence of unique structural morphologies, including the formation of passive particle
vortices surrounding phase-separated active spinners and the development of large-scale active-passive bands. We characterize the underlying dynamics by analyzing the temporal
evolution of characteristic length scales and the non-
equilibrium velocity distributions of the passive particles. Our findings provide new insights into the role of long-range hydrodynamic couplings in governing the self-organization of non-
equilibrium condensed matter.
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Materials Science
Coherent seeding and control of dynamical ferroelectricity by phonon anharmonicity
Junhan Huang, Yongkang Ju, Xinbo Wang et al. (+12 more)
Optical control of
quantum materials has progressed along two separate directions: creating non-
equilibrium states inaccessible at
equilibrium, and coherently controlling ultrafast dynamics with multi-pulse protocols. Ferroelectricity is especially attractive in this context because its order parameter, macroscopic polarization, directly links inversion-
symmetry breaking to functional response. Yet light-induced ferroelectricity has so far been confined to
quantum paraelectrics near the ferroelectric instability, where critical fluctuations obscure the formation of a homogeneous ferroelectric state and complicate its deterministic coherent control. Unifying these capabilities – preparing a
symmetry-broken state and then coherently steering its functionality – remains a central challenge. Here we show that intense terahertz excitation of a soft
phonon mode induces a ferroelectric state in centrosymmetric PbTe, a thermoelectric material with strong
lattice anharmonicity but no ferroelectric transition at finite temperature. The light-induced
symmetry-broken state can be realized up to about 100 K, without relying on local dipolar fluctuations. Experiment and theory together reveal that terahertz-driven anharmonic coupling between degenerate transverse optical
phonons underlies this ferroelectric induction. Furthermore, we demonstrate coherent amplification and suppression of the induced polarization via a double-pulse-excitation protocol. These results establish terahertz-driven anharmonic mode coupling as a general strategy for controlling mode-mediated functionalities in
quantum materials, opening a route to ultrafast information processing.
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All authors Junhan Huang, Yongkang Ju, Xinbo Wang, Li Yue, Hao Wang, Qiaomei Liu, Tianchen Hu, Yuchen Cui, Liyu Shi, Shangfei Wu, Sijie Zhang, Dong Wu, Peizhe Tang, Tao Dong, Nan-Lin Wang
Materials Science
Interfacial melting as a thermodynamic indicator of solid-state synthesizability
Zihan Zhang, Mengyi Chen, Qianxiao Li et al. (+1 more)
Computational materials discovery commonly ranks candidate materials by their thermodynamic stability on the formation energy convex hull, yet many predicted-stable phases resist synthesis. We propose that solid-state synthesizability through interfacial-melt-mediated routes requires an additional thermodynamic condition: the interfacial melt at the target composition must itself remain locally stable against spinodal decomposition. We examine this in the classical Fe–B system, where thermodynamically stable FeB$_4$ has been reported under high-pressure synthesis but not in low-pressure synthesis attempts. Using melt–quench molecular dynamics driven by a fine-tuned machine-learning interatomic potential, we find that, at ambient pressure, the B-rich interfacial melt near the FeB$_4$ composition develops a concave free-energy landscape, signaling a demixing instability that is corroborated by the concentration–concentration structure factor and correlated with low-energy icosahedral and pentagonal-pyramidal boron motifs. In contrast to FeB$_4$, metastable Fe$_3$B and Fe$_{23}$B$_6$ remain synthesizable because their corresponding melts are stable. Applied pressure introduces a convex $PV$ contribution that strongly suppresses this instability, reducing the
curvature at the FeB$_4$ composition to within the uncertainty of our fit at 1800~K, consistent with the experimental synthesis boundary. Comparison with CrB$_4$ further shows that weaker melt instability correlates with easier experimental synthesis. Interfacial-melt stability, which atomistic simulations can assess via the low-$k$ concentration–concentration structure factor, is thus proposed as a practical thermodynamic screening descriptor of synthesizability for AI-assisted materials discovery.
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All authors Zihan Zhang, Mengyi Chen, Qianxiao Li, Peichen Zhong
Materials Science
Thermal Transport in SiC with Intrinsic Defects and Mg Transmutation Products
Chen Shen, Yang Su, Maciej P. Polak et al. (+5 more)
Silicon carbide is a leading candidate material for advanced
nuclear energy systems, but irradiation-induced defects and transmutation products can severely degrade its thermal conductivity. In fusion environments, Mg is predicted to be a major solid transmutant in SiC, yet it is not well understood how different Mg-related defects affect
phonon transport. Here, we develop a machine-learning interatomic potential, MLIP4SiC-Mg, for 3C-SiC containing intrinsic point defects, Mg-related defects, and Mg-defect complexes. The potential is trained on a large DFT
dataset and reproduces DFT energies, forces, equation-of-state behavior,
phonon dispersions, and
lattice thermal conductivities with near-DFT accuracy. Combined with Green-Kubo molecular dynamics, force-error correction, and a resistance-based treatment for dilute defective systems, MLIP4SiC-Mg enables quantitative thermal-conductivity calculations in large defective supercells. The corrected thermal conductivity of pristine 3C-SiC is 421 W/(mK) at 300 K, in good agreement with available experimental data. All defects considered strongly reduce thermal conductivity, but their scattering strengths are highly configuration dependent. V_C and Mg_TC act as strong
phonon scatterers, whereas isolated Mg_Si is comparatively weak. Residual thermal resistivity analysis shows that defect-induced thermal resistance is not strictly linear with concentration and should be treated as an effective temperature- and concentration-dependent scattering metric. Mg_Si-V_C clustering enhances scattering relative to isolated Mg_Si, but reduces the total excess resistance relative to spatially separated Mg_Si and V_C defects. These results clarify the configuration-dependent role of Mg transmutation in irradiation-degraded SiC and provide an atomistic framework for quantifying defect-controlled heat transport in
nuclear ceramics.
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All authors Chen Shen, Yang Su, Maciej P. Polak, Rafi Ullah, Nuohao Liu, Mary Alice Cusentino, Dane Morgan, Izabela Szlufarska
Strongly Correlated Electrons
Isometrization of Tensor Network States via Gauge Propagation
Zhiyu Jiang and Hiroshi Ueda
We introduce a gauge-propagation approach for approximately converting generic tensor-network states into an isometric tensor-network form with a prescribed orthogonality center. In one dimension, this propagation is exact because the non-isometric factor produced by a QR or singular-value decomposition is supported on a single virtual bond. In higher-dimensional networks, however, a local step can have several outgoing directions, and the residual factor is generally not separable into independent single-bond contributions. We address this local obstruction by approximating a local tensor, or a contracted local cluster, by structured terms consisting of an isometric factor multiplied by a tensor product of output-leg factors. The isometric factor is retained at the current site or cluster, while the output-leg factors are absorbed into neighboring tensors along the propagation directions. This construction applies to general local input-output partitions for which the input-side dimension is no smaller than the output-side dimension and provides a local truncation criterion for gauge propagation.
Benchmarks on random tensors show that the proposed decomposition is effective in the low-term regime and that the residual decreases for larger local clusters. For the loop-gas tensor representation of the Kitaev
spin liquid, two structured terms reduce the local residual to numerical precision, and the same cluster refinement further lowers the leading-term truncation error and reduces error accumulation during gauge propagation on a finite honeycomb network. These results identify a propagation-compatible local decomposition as a useful building block for approximate isometrization and as a potential initializer or preconditioner for variational isoTNS
algorithms.
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Strongly Correlated Electrons
Strain-tuned orbital-dependent electronic correlations in FeTe thin films
Hyunjee Song, Sangjae Lee, Keun-Yeol Park et al. (+8 more)
Iron chalcogenides exhibit rich phenomena which are governed by orbital-dependent electronic interactions and strong electronic correlation. In particular, many studies have explored orbital selectivity in FeTe through Se doping. Here, applying tensile strain to thin films allows us to precisely control the system without other
impurities that may arise from chemical doping to investigate the emergent behaviors in FeTe. Using angle-resolved photoemission spectroscopy, we observe a spectral weight transfer between $d_{\rm xy}$ and $d_{\rm z^{2}}$ orbitals, evidence of an orbital-selective Mott phase (OSMP). Beyond OSMP, we reveal hitherto unobserved strain-induced effects, distinct from chemical doping. The
evolution of $d_{\rm xz}$ orbital demonstrates how electron hopping mechanism plays an important role in defining the electronic properties of the system. Our findings highlight a direct correlation between epitaxial strain and the
evolution of electronic structures in FeTe.
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All authors Hyunjee Song, Sangjae Lee, Keun-Yeol Park, Jaehyun Park, Suyoung Lee, Yeonjae Lee, Jinyoung Kim, Jaeung Lee, Celesta S. Chang, Younsik Kim, Changyoung Kim
Soft Condensed Matter
Hierarchical Granular Metamaterials
James Utama Surjadi, Bastien F. G. Aymon, Ayan Kumar et al. (+4 more)
Granular materials dissipate energy efficiently through intergranular interactions, yet their disordered, dense nature precludes precise control and integration into lightweight systems. Architected materials offer tunable mechanical responses at low densities but tend to localize stress, limiting dissipation efficiency. Here, we introduce hierarchical granular metamaterials that reconcile these trade-offs through three levels of design: lightweight architected grains engineered with hollow elliptical inclusions,
crystal-inspired grain packings, and functional gradients and defects within grain tessellations. These metamaterials exhibit simultaneous increases in impact energy absorption per unit mass and reductions in transmitted peak force at low densities, outperforming conventional architected materials. In situ nanomechanical experiments and nonlinear computational models reveal that enhanced lateral grain expansion drives recruitment of neighboring grains, amplifying plastic and frictional dissipation. Multiscale impact experiments confirm that these mechanisms persist across length scales, constituent materials, and dimensionalities. Beyond mechanical performance, we demonstrate that spatially programmable inter-grain contact networks enable deterministic routing of deformation, which extends to electrical transport pathways independently of packing geometry. By combining granular principles with architected material design, this work establishes a paradigm for multifunctional metamaterials whose contact
topology, mechanical response, and transport properties can be programmed independently.
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All authors James Utama Surjadi, Bastien F. G. Aymon, Ayan Kumar, Lei Wu, Jet Lem, Ken N. Kamrin, Carlos M. Portela
Mesoscale and Nanoscale Physics
Modulating radiative heat and momentum transfer via the thermal Purcell effect
Liyao Jiao, Yaohua Liu and Gaomin Tang
The thermal Purcell effect describes the modification of the local density of states of the fluctuating electromagnetic field induced by a Fabry-Pérot cavity, leading to the enhancement or suppression of radiative transport quantities. Using fluctuational electrodynamics, we investigate nonequilibrium radiative heat, linear-momentum, and angular-momentum exchange between a magneto-optic nanoparticle and a Fabry-Pérot cavity. Analytical expressions for the spectral densities reveal that
geometric confinement modifies the electromagnetic local density of states, producing distinct behaviors for different transport quantities. Specifically, sub-wavelength confinement enhances radiative heat and angular-momentum transfer, but suppresses the lateral force. Additionally, interference between cavity modes causes all transfer quantities to oscillate spatially with particle position. At the cavity center, mirror
symmetry enforces a parity decomposition of electromagnetic fluctuations resulting in a vanishing lateral force, whereas heat transfer and torque remain finite through combined even and odd modal contributions. These results demonstrate that cavity engineering provides selective control over nanoscale energy and momentum transfer via structured electromagnetic fluctuations.
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