Materials Science · Cross-listed from cs.LG
Atomistic Language Models Understand and Generate Materials
Sathya Edamadaka, Krithik Ramesh, Ju Li et al. (+1 more)
Atomistic structure and natural
language have long been modeled separately, with
language models either calling atomistic models as tools or being fine-tuned on lossy textual encodings that discard atomistic information. We introduce Atomistic
Language Models (ALMs) to pursue native multimodality, in which a single
language backbone understands atomistic structures, generates materials from natural
language, and optimizes
crystal structures as instructed by text. By unifying a pretrained atomistic encoder, large
language model, and denoising
diffusion model through purely continuous projectors and staged training, ALMs achieve state-of-the-art results on
crystal structure prediction and de novo generation. ALMs are enabled by a continuous bridge that maps
language model
embeddings directly into the steering space of atomistic
diffusion, and are assisted by Text-to-
Crystal Feynman-Kac (T2C-FK), a particle-based sampler that scores partial denoising trajectories to enforce stoichiometric targets at inference time. To evaluate the ability of ALMs to optimize and generate materials from natural-
language prompts and 3D atom-coordinate inputs, we introduce ALM Bench, the first
benchmark for text-conditioned
crystal generation and optimization. Code, training data, and model weights will be released soon.
Read the full abstract ▾
All authors Sathya Edamadaka, Krithik Ramesh, Ju Li, Rafael Gómez-Bombarelli
Soft Condensed Matter
Quasi-one-dimensional motion of an active MXene sheet driven by chemo-hydrodynamic waves
Hui Wang, Huan Liu, Ling Yuan et al. (+4 more)
Signal-driven motion is widespread in natural and artificial systems, yet quantitative characterization of how transient chemo-hydrodynamic waves are converted into mechanical driving forces remains limited. Here, we investigate the self-propulsion of a MXene sheet asymmetrically coated with catalase in hydrogen peroxide solution. By combining dual-view particle image velocimetry experiments and numerical simulations reveal that active motion of the sheet is driven by chemo-hydrodynamic waves and exhibits direct-wave motion, the driving force of which is analyzed in terms of the shear stress on the sheet surface caused by chemo-hydrodynamic waves. This work suggests theoretical principles for designing and controlling hydrodynamically driven active motion.
Read the full abstract ▾
All authors Hui Wang, Huan Liu, Ling Yuan, Zihao Liu, Meng Zhang, Irving R Epstein, Qingyu Gao
Strongly Correlated Electrons
Importance of effective Coulomb interactions for $T_c$ in cuprates
Jakša Vučičević, Upendra Kumar, Chia-Nan Yeh et al. (+2 more)
Cuprate
superconductors exhibit the highest observed superconducting $T_c$ at atmospheric pressure. However, the magnitude of $T_c$ varies significantly between different cuprates. At present, it is unclear what properties of the
crystal structure affect $T_c$ most strongly, yet such an understanding must underpin any efforts toward high-$T_c$ materials design. To address this issue, we perform a large scale systematic study, employing a combination of data collection, state-of-the-art numerical methods, and statistical analysis. We identify about 40 different cuprate compounds, and we compile detailed data about their $T_c$'s and
crystal structures from literature and the available databases. Using a fully automated procedure, for each compound we compute the DFT bandstructure and downfold it to two of the most commonly studied low-energy
lattice models, namely the single-band Hubbard and the three-band Emery models. The downfolding is based on the approach of MLWFs and cRPA. Finally, we apply a thorough and unbiased statistical analysis to investigate the correlations between the experimentally measured $T_c$'s and the computed parameters of our theoretical models. Our data indicates that more sophisticated models might be needed to describe all cuprates on the same footing. Nevertheless, we find that $T_c$ scales well with simple functions of model parameters. We confirm a previously observed trend that $t'$ in the single-band model correlates with the experimental $T_c$, and we find that $T_c$ appears to vanish below a finite value of $t'$, in agreement with recent ground-state calculations for the Hubbard model. However, we find that the coupling strength also plays a role: throughout our entire
dataset, $T_c$ correlates the most with the Coulomb coupling on the $p$-orbitals in the 3-band model, highlighting the importance of the oxygen sites in the copper-
oxide planes.
Read the full abstract ▾
All authors Jakša Vučičević, Upendra Kumar, Chia-Nan Yeh, Miguel A. Morales, Malte Rösner
Statistical Mechanics
From Landau Equation and Large Deviations to Efficient Simulations of Dynamical Fluctuations
Anwar El Rhirhayi, Jean-Baptiste Fouvry and Julien Barré
The (deterministic) Landau equation captures the mean long-term
evolution of dynamically hot long-range interacting finite-$N$ systems. Though successful, this kinetic equation fundamentally ignores dynamical fluctuations. Building upon Large Deviation Theory, we present a physically-consistent system of Langevin equations that simultaneously recovers the mean Landau dynamics and accurately captures the corresponding fluctuations among different realizations. We show in particular how these Langevin equations can be derived from Rostoker's principle in the limit of weak two-body deflections. We extensively validate these equations against tailored direct $N$-body simulations, showing an exquisite level of agreement.
Read the full abstract ▾
Materials Science
Floquet-induced anisotropic magnetoresistance and anomalous Hall effect in 2D $d$-wave altermagnets with Rashba spin-orbit coupling
Mohsen Yarmohammadi, Pieter M. Gunnink, Jairo Sinova et al. (+1 more)
Altermagnets (AMs) combine momentum-dependent
spin splitting with zero net magnetization, making them promising for spintronics. Periodic driving enables dynamic
symmetry engineering beyond static, material-specific control. We show that Floquet engineering in 2D $d$-wave AMs with out-of-plane Néel order and Rashba
spin-orbit coupling unlocks
equilibrium-forbidden transport responses. Monochromatic driving produces purely out-of-plane magnetization, yielding longitudinal anisotropic magnetoresistance (AMR) and an anomalous
Hall effect, whereas bichromatic driving generates both in-plane and out-of-plane magnetizations and additionally activates transverse AMR via the second harmonic of the secondary beam. Comparable static
magnetic fields would require hundreds of tesla, avoided in Floquet driving. These effects persist across linear, circular, and mixed light polarizations and are tunable via light parameters. Our results establish multi-color Floquet engineering for controlling magnetization and
symmetry-protected transport in AMs.
Read the full abstract ▾
All authors Mohsen Yarmohammadi, Pieter M. Gunnink, Jairo Sinova, James K. Freericks
Materials Science
Strain induced magnetic phase transitions in Fe3GeTe2 monolayer
Anjali Jyothi Bhasu, Satish Kumar, Mátyás Török et al. (+11 more)
We investigate the
magnetic properties of a monolayer of Fe3GeTe2 as a function of the
lattice constant by combining first-principles calculations with atomistic
spin dynamics simulations. The calculated
magnetic exchange interactions reveal a competition between
ferromagnetic and
antiferromagnetic couplings, with the latter being significantly strengthened under compressive strain.
Stochastic Landau-Lifshitz-Gilbert simulations reveal a substantial decrease in the Curie temperature with decreasing
lattice constant, and predict a transition of the
magnetic ground state from a
ferromagnetic configuration to a conical
spin-spiral state. We introduce a simple
spin-model which explains the stabilization of the spiral phase due to competing exchange interactions. We found multiple
magnetic phase transitions involving
ferromagnetic, conical
spin-spiral, and planar Neel states, depending on both the
lattice constant and the temperature. The absence of Dzyaloshinskii-Moriya interactions is found to significantly reduce the Neel temperature, while leaving the Curie temperature largely unaffected. Our findings reveal the importance of
lattice distortions in controlling complex
magnetic phases and their
evolution with temperature.
Read the full abstract ▾
All authors Anjali Jyothi Bhasu, Satish Kumar, Mátyás Török, Dániel Tibor Pozsár, Bendegúz Nyári, László Udvardi, Gabriel Martínez-Carracedo, Balázs Nagyfalusi, Amador García-Fuente, Jaime Ferrer, Zoltán Tajkov, László Oroszlány, Levente Rózsa, László Szunyogh
Mesoscale and Nanoscale Physics
Topological Hall Effect in Antiferromagnetic Co doped Fe$_3$GaTe$_2$
Shyam Raj Karullithodi, Yeonkyu Lee, Vadym Kulichenko et al. (+8 more)
Fe$_3$GaTe$_2$ is van der Waals (vdW) ferromagnet with a Curie temperature $T_C$ ranging from 350 K to 380 K, followed upon cooling by a ferrimagnetic transition near room temperature. Substituting Fe with Co was previously reported to induce antiferromagnetism (AFM) at a Co fraction dependent Neel temperature $T_N$. In this work, we confirm the overall phase diagram of the Fe$_{3-x}$Co$_x$GaTe$_2$ series as a function of $x$ and temperature via magnetization and electrical transport measurements. For $x \simeq 0.6$ the
Hall effect is observed to mimic the magnetization as the AF ground state is suppressed by the external
magnetic field via a metamagnetic transition, thus displaying an anomalous
Hall response. At low temperatures, we also observe a pronounced topological
Hall signal peaking at $\mu_0H$ = 4 T, or within the metamagnetic transition region of fields. This observation points to the presence of
magnetic field-induced
chiral spin textures, such as skyrmions upon approaching magnetization saturation.
Magnetic force microscopy (MFM) reveals the emergence of nearly circular
magnetic domains, with diameters on the order of 100 to 200 nm, within the
antiferromagnetic phase. A detailed analysis of the MFM images indicates that the topological
Hall effect is closely linked to the field-induced stabilization of
magnetic domain structures, likely exhibiting
chiral textures. This observation suggests the possible formation of skyrmions already in the AFM phase, i.e., AFM skyrmions, that evolve into
ferromagnetic (FM) ones upon increasing the
magnetic field. Consequently, Co-doped Fe$_3$GaTe$_2$ might provide a platform to investigate the transformation of skyrmions, initially coupled antiferromagnetically into
ferromagnetic skyrmions, and to explore its impact on the topological and skyrmion
Hall effects.
Read the full abstract ▾
All authors Shyam Raj Karullithodi, Yeonkyu Lee, Vadym Kulichenko, W. Kice Brown, Sang-Eon Lee, Chanyoung Lee, Jinyoung Yun, Gregory T. McCandless, Julia Y. Chan, Jeehoon Kim, Luis Balicas
Superconductivity · Cross-listed from physics.comp-ph
AI-accelerated metallized $\sigma$-bonding screening for superconductor discovery
Zechen Tang, Wen-Han Dong, Baochun Wu et al. (+11 more)
The computational discovery of
phonon-mediated
superconductors is hindered by the prohibitive cost of density functional perturbation theory (DFPT). Here, guided by the metallized $\sigma$-bonding picture, we introduce the $\sigma$-bonding density of states ($\sigma$DOS) as an efficient physical descriptor to identify high-transition-temperature ($T_{\mathrm{c}}$)
superconductors from density functional theory (DFT)-level electronic structure without explicit DFPT calculations. The evaluation of $\sigma$DOS can be further accelerated by a deep-learning DFT
Hamiltonian method, enabling efficient large-scale screening for
superconductors. Screening 2 million materials, we identify B$_{13}$Se as an ambient-pressure
superconductor candidate with predicted $T_{\mathrm{c}} > 40$~K, together with a family of high-$T_{\mathrm{c}}$ B$_{13}X$ candidates, supporting the effectiveness of this discovery strategy. By bridging physics priors with AI acceleration, this study delivers an efficient and generalizable route for computational materials discovery in the AI era.
Read the full abstract ▾
All authors Zechen Tang, Wen-Han Dong, Baochun Wu, Jian-Feng Zhang, Yuxiang Wang, Yang Li, Honggeng Tao, Qiyu Zeng, Chong Wang, Chen Si, Zhong-Yi Lu, Wenhui Duan, Tao Xiang, Yong Xu
Strongly Correlated Electrons · Cross-listed from quant-ph
Entanglement-entropy analysis of critical and topological quantum phases in a frustrated spin-1/2 Heisenberg ladder
Azadeh Ghannadan, Hana Vargová, Jozef Genzor et al. (+2 more)
We investigate the ground-state phase diagram of a frustrated
spin-1/2 Heisenberg ladder in the transverse
magnetic field with an anisotropic inter-rung exchange coupling $\alpha$. This bond-anisotropic parameter continuously interpolates among the Ising-like limit $\alpha=0$, the isotropic point $\alpha=1$, and the XY-dominated regime $\alpha \gg 1$. Using density-
matrix renormalization group calculations within a
matrix-product-state framework, we analyze bipartite
entanglement, magnetization, and
spin correlations to characterize the emergent
quantum phases. We identify six distinct ground-state phases, including rung-singlet, Haldane-like, Tomonaga-Luttinger
liquid, canted Ising-ordered, XY-polarized, and ordered
ferromagnetic states. While magnetization and local correlations provide a first insight into phase classifications, the finite-size scaling of the
entanglement measures offers a more sensitive and unified diagnostics of both gapped and gapless regimes. In the gapless regime, we extract the central charge $c \simeq 1$, confirming Tomonaga-Luttinger
liquid behavior, while at the transition between the canted Ising and
ferromagnetic phases, we observe $c \simeq 1/2$, consistent with the Ising universality. Finally, we find that both the Haldane-like behavior and the extended critical Tomonaga-Luttinger
liquid regime are strongly confined to the vicinity of the isotropic point $\alpha = 1$.
Read the full abstract ▾
All authors Azadeh Ghannadan, Hana Vargová, Jozef Genzor, Roman Krčmár, Andrej Gendiar
Soft Condensed Matter
Exotic topological defects and director fields in free-floating spherical ferroelectric nematic liquid crystal shells
Churchill B. Agoni, Ema Pilih, Luka Cmok et al. (+5 more)
Ferroelectric nematic (NF)
liquid crystals exhibit polar
symmetry and large polarization, giving rise to phenomena absent in conventional apolar nematics. We investigate NF
liquid crystals confined to free-floating spherical shells with tangential boundary conditions, enforcing a total topological defect charge of +2. We
conjecture that ferroelectric nematics avoid splayed configurations with half-integer defects, common in apolar nematic shells, instead concentrating the topological charge into escaped azimuthal +1 defects requiring only bend and twist. Indeed, at room temperature in the NF phase, our thin RM734+DIO shells with inner and outer aqueous poly(vinyl alcohol) solutions develop an azimuthal director field around two antipodal +1 bend-twist defects. The non-centrosymmetric nature and the azimuthal director configuration of the shells in the NF phase are confirmed also through second-harmonic generation microscopy. At intermediate temperature the antiferroelectric Nx phase generates a new exotic texture rife in zigzag lines in the shells. In the regular N phase at high temperature, the shells develop the usual four +1/2 disclinations located near the thinnest point. Our study highlights the rich platform offered by spherical shells to study the behavior of exotic
liquid crystals subject to topological constraints, possibly opening new paths to apply the highly responsive ferroelectric nematic phase
Read the full abstract ▾
All authors Churchill B. Agoni, Ema Pilih, Luka Cmok, Calum J. Gibb, Jordan Hobbs, Richard Mandle, Irena Drevensek-Olenik, Jan P.F. Lagerwall
Mesoscale and Nanoscale Physics
In-plane and out-of-plane magnetic field driven Josephson diode effect in magic-angle twisted four-layer graphene
Marta Perego, Sayan Banerjee, Mohamad Abu El Hija et al. (+8 more)
The superconducting diode effect offers a powerful probe into the fundamental
symmetries of
quantum materials. Recent studies on twisted
graphene diodes have predominantly focused on
bilayer or trilayer systems under out-of-plane
magnetic fields. Here, we demonstrate both out-of-plane and in-plane driven Josephson diode effects in a magic-angle twisted four-layer
graphene junction, i.e., an even number of layers. We observe the emergence of a diode effect at zero out-of-plane field, tuned by an increasing in-plane
magnetic field. This result points to the presence of strong in-plane orbital coupling, which is highly sensitive to the specific layer parity of the structure. Our findings provide experimental insights into the
symmetry-breaking mechanisms of even-layer twisted
graphene, establishing in-plane
magnetic fields as a vital tool for unravelling their microscopic properties.
Read the full abstract ▾
All authors Marta Perego, Sayan Banerjee, Mohamad Abu El Hija, Clara Galante Agero, Alexandra Mestre-Torà, Giovanni Zhang, Takashi Taniguchi, Kenji Watanabe, Mathias S. Scheurer, Thomas Ihn, Klaus Ensslin
Statistical Mechanics · Cross-listed from quant-ph
Synchronization in the quantum regime
Finn Schmolke and Eric Lutz
Can synchronization – the widespread spontaneous emergence of coordinated dynamics in classical nonlinear systems – also occur in the
quantum regime? This question has recently sparked intense research into collective behavior and temporal self-organization in
quantum systems. Typical
quantum features such as the linearity of time
evolution and the presence of
quantum noise seem to hinder the appearance of synchrony at the microscopic level. At the same time,
quantum coherence and
quantum correlations may provide novel mechanisms for enhancing synchronization beyond its classical counterpart. We here survey recent theoretical and experimental advances in
quantum synchronization, ranging from the characterization of synchronous oscillations and genuinely nonclassical forms of synchrony to many-body synchronization on
quantum networks.
Read the full abstract ▾
Soft Condensed Matter
Thermoresponsive self-oscillating hydrogel: spatially lumped model, relaxation dynamics and mechanical output
Yunjie Wang, Ling Yuan, Yang Li et al. (+5 more)
Thermoresponsive gels with a lower critical solution temperature (LCST) can undergo self-oscillation driven by a thermal flux through repeated cycles of positive feedback, driven by heating-induced collapse, and negative feedback, characterized by deformation recovery due to collapse-induced suppression of heating and heat dissipation to the environment. In order to explore the detailed bifurcation structure of a thermosensitive self-oscillating gel and understand its mechanical output of peristaltic motion and net displacement, we develop a minimal spatially lumped two-variable phenomenological model whose
equilibrium parameters are constrained by poly(N-isopropylacrylamide) (PNIPAAm) swelling data. A supercritical
Hopf bifurcation creates stable small-amplitude oscillations near a fold of the swollen
manifold, and canard-mediated growth transforms this branch into relaxation oscillations. Singular analysis relates the amplitude to fast jumps and the period to drift along slow
manifolds, while continuation separates the
Hopf boundary from the maximal-canard locus. For the representative maximum-power relaxation cycle considered here, the loaded model predicts greater work than a harmonic volume trajectory with the same stroke, period, and viscous load, with output concentrated in the fast collapse and re-swelling transitions. The net displacement during peristaltic locomotion of the thermoresponsive self-oscillating gel results from the work difference between collapse and re-swelling. These results provide a theoretical basis for designing autonomous thermoresponsive self-oscillating gel actuators whose oscillatory waveform and power output can be controlled through thermal feedback and mechanical loading.
Read the full abstract ▾
All authors Yunjie Wang, Ling Yuan, Yang Li, Lin Ren, Yuhan Wang, Xiaol Lv, Irving R Epstein, Qingyu Gao
Mesoscale and Nanoscale Physics
Bose-Einstein Condensation of Three-Dimensional Exciton-Polaritons
Junhui Cao and Alexey Kavokin
We develop a band-structure-based theory of
exciton-polaritons in a three-dimensional inverse-opal photonic
crystal doped with
semiconductor quantum dots. Starting from a
symmetry-selected bright photonic branch near the photonic gap edge, we construct an
exciton-
photon Hamiltonian and obtain a lower-polariton band with a W-point global minimum and a nearby X-point van-Hove-enhanced density of states. We show that the W valleys determine the
equilibrium Bose-Einstein condensation threshold, while the X-point saddle provides a finite excited-state capacity that renormalizes the critical temperature when the W-X offset is thermally accessible. By tuning the
exciton resonance and the light-matter coupling, the relative W-X ordering can be reconstructed, leading to a strong variation of the critical temperature. We further formulate a momentum-resolved Boltzmann model for driven-dissipative kinetics. Under non-resonant pumping, reservoir feeding, radiative decay, and inter-sector relaxation can produce either W-dominated condensation, a mixed W-X regime, or an X-dominated nonequilibrium coherent state. Our results establish three-dimensional photonic-
crystal polaritons as a platform where condensation is controlled not only by the band minimum but also by valley geometry, van-Hove-enhanced phase space, and relaxation pathways.
Read the full abstract ▾
Disordered Systems and Neural Networks
Communication Heterogeneity and Collective Consensus in Neural Cellular Automata
Nishit Singh
Reaching global agreement from purely local interactions is a defining problem of collective intelligence, and most models of it assume that all
agents share a single communication protocol. We ask what happens when they do not. Using a Neural Cellular Automaton in which a population of
cells must solve the density classification task, agreeing on a global majority that no individual can observe, we introduce “
languages” as sub-populations that read one another's messages through a translation with a tunable “linguistic distance”. We find that linguistic distance slows consensus, that it produces mild divergence between groups rather than full fragmentation, and that a collective whose shared rule was trained under diverse protocols is robust to mismatch; a homogeneously trained one is not. The findings hold on both a ring and a two-dimensional grid, and admit a natural reading as Ising relaxation, in which a foreign-
language region acts as a boundary defect that leaves the system in a higher-energy, partially ordered state. These patterns are qualitatively consistent with effects reported in human group studies, suggesting that distance between communication protocols is a minimal mechanism sufficient to produce them, without anything
language-specific.
Read the full abstract ▾
Materials Science
Atomistic Mechanisms of Hard Carbon Formation from Polyvinylidene Chloride
Litong Wu, Zitong Wu, Zakariya El-Machachi et al. (+1 more)
Hard carbons are a class of disordered materials with widespread application in energy storage. Despite decades of research, their atomistic formation mechanisms have remained elusive, due to the difficulty of both in situ experimental characterization and first-principles simulations. Here, we describe the formation mechanism of hard carbon from the thermal decomposition of polyvinylidene chloride (PVDC), using first-principles-quality simulations with a bespoke machine-learned interatomic potential model. Our results indicate a two-stage process, consisting of (i) radical-mediated dehydrochlorination, which generates reactive unsaturated carbon sites, and (ii) progressive carbon-carbon cross-linking followed by thermally activated rearrangement into an extended sp$^{2}$-bonded network. We provide an atomistic account of non-hexagonal ring motifs emerging during pyrolysis, supporting the empirically-derived theory that these motifs induce the intrinsic
curvature that frustrates graphitic ordering in hard carbons.
Read the full abstract ▾
All authors Litong Wu, Zitong Wu, Zakariya El-Machachi, Volker L. Deringer
Mesoscale and Nanoscale Physics
Moiré-Enhanced Plasmonics in Non-Hermitian Twisted Bilayer Graphene
Andrianos Sygrimis and Giorgos P. Tsironis
We study plasmonic excitations in twisted
bilayer graphene within a non-Hermitian framework that incorporates effective gain and loss. Using a non-Hermitian extension of the Bistritzer–MacDonald continuum model together with a biorthogonal Kubo formalism for the optical conductivity, we determine how the moiré electronic structure enters the plasmonic response of the active
bilayer. We find that non-Hermiticity modifies the collective spectrum, yielding optical and acoustic plasmon branches, with the acoustic branch exhibiting strong subwavelength confinement. In the parity-time-symmetric configuration, gain–loss engineering can reduce the effective spatial damping and enhance the propagation length within the ideal linear model. The same regime produces strongly localized transverse-
magnetic near fields. We argue that the enhancement is not a generic consequence of adding gain to a
bilayer, but results from the combined influence of moiré-band reconstruction, biorthogonal optical
matrix elements, and non-Hermitian modification of the plasmon pole. We also discuss the limitations imposed by disorder, substrate loss, gain saturation, and stability of the parity-time-symmetric regime. These results identify twisted
bilayer graphene as a promising, but experimentally demanding, platform for tunable non-Hermitian plasmonics in moiré
quantum materials.
Read the full abstract ▾
Soft Condensed Matter
Many-body attractions do not stabilize gas-liquid phase separation in aqueous dispersions of charged colloids within the Poisson-Boltzmann framework
Thijs ter Rele, René van Roij and Marjolein Dijkstra
Attractive three-body interactions have been reported for like-charged colloids in low-salt suspensions, based on both finite-element Poisson-Boltzmann calculations and direct experimental measurements, and have been proposed as a mechanism to drive colloidal clustering. However, these Poisson-Boltzmann calculations typically neglect charge regulation and higher-order many-body effects. Here, we construct machine-learned (ML) many-body interaction potentials for charge-regulating colloids, trained on finite-element Poisson-Boltzmann calculations, to accurately capture three-body and higher-order contributions. We find that the three-body contribution to the many-body potential as obtained from Poisson-Boltzmann calculations on isolated colloid triplets is strongly attractive, consistent with previous work, whereas the four-body contribution for an equilateral pyramid configuration of four colloids is repulsive. We then construct ML many-body potentials for charged colloids using finite-element Poisson-Boltzmann calculations on clusters of 13 colloids, and find that the incorporation of higher-body interactions weakens the cohesive nature of the interactions. We identify a parameter regime exhibiting gas-
liquid or gas-solid phase separation using the ML potentials in molecular dynamics simulations. However, when we include clusters of 48 colloids in the training data, the cohesion diminishes further, and molecular dynamics simulations using these potentials no longer include broad phase separation in aqueous dispersions of charged colloids. Finally, we compute the potential of mean force of pairs and triplets of colloids using primitive model simulations. We find that the resulting potentials are in good agreement with those obtained from the Poisson-Boltzmann calculations, thereby supporting the validity of the Poisson-Boltzmann approach for determining many-body interactions.
Read the full abstract ▾
Materials Science · Cross-listed from physics.optics
Bounds on the Topological Charge of Photonic Systems
F. R. Prudencio, I. Souza and M. G. Silveirinha
Topology has become a central concept in understanding physical phenomena, leading to important advances in condensed matter and photonics. Recent work has established a universal upper bound on the energy gap of Chern
insulators in electronic systems, revealing a fundamental connection between
topology,
quantum geometry, and optical absorption. Here, we generalize this framework to photonic systems, deriving rigorous upper bounds on gap Chern numbers without requiring explicit topological analysis. Our approach enables the estimation of the topological charge of band gaps in both dispersive and nondispersive regimes.
Read the full abstract ▾
Superconductivity
Quantum-Geometry-Induced Superconductivity near a Fractional Chern Insulator
Haoyu Hu and Lei Chen
Recent moiré experiments and numerical studies of interacting Chern bands have revealed fractional Chern
insulators, charge-density-wave order, and superconductivity as proximate correlation-driven phases in topological systems. How these phases compete or intertwine, and how
quantum geometry shapes their interplay, remain open questions. Here we present an analytic study of competing correlation-driven phases in a partially filled Chern band using a coupled-wire construction and bosonization. The key ingredient is the coexistence of interaction channels that favor, respectively, a fractional Chern
insulator (FCI) and a closely related anti-FCI (aFCI) state. The aFCI channel is specific to
lattice Chern bands and is enhanced by the
quantum geometry of the underlying band structure. We show that when both FCI and aFCI scattering channels are present, their interplay generates an effective coupling that drives a superconducting instability near the FCI phase. The same mechanism can also favor a charge-density-wave phase, depending on microscopic parameters. Using a perturbative renormalization-group analysis, we obtain the phase diagram and identify a superconducting regime adjacent to the FCI phase. We further estimate the superconducting transition temperature and show that it is enhanced by
quantum geometry. Our results establish
quantum geometry as an organizing principle for the interplay among FCI, aFCI, and superconducting correlations.
Read the full abstract ▾
Materials Science
Room-Temperature Noncolinear Ferroelectricity in van der Waals WO$_2$Cl$_2$ with a Wide Bandgap
Yu Xing, Ning Ding, Zhipeng Wang et al. (+21 more)
Low-dimensional ferroelectrics are attractive for their promising prospects in nanoelectronics. Compared with widely-used ferroelectric perovskites, most low-dimensional ferroelectrics exhibit several inborn weaknesses such as small bandgaps (mostly <2 eV, i.e.
semiconductors-like) or faint polarizations (e.g. $<1$ $\mu$C/cm$^2$ for sliding ferroelectrics even if their bandgaps can be large). Here we experimentally demonstrate the room-temperature ferroelectricity of van der Waals WO$_2$Cl$_2$ . The well-tested d0 rule inherited from ferroelectric perovskites leads to a large dipole (~3 eÅ) from the off-center displacement of W$^6+$ ion and a wide bandgap of 2.80 eV. Its ferroelectricity is proved by multiple characterizations including second harmonic generation, piezoresponse force microscopy, and ferroelectric hysteresis loops. More interestingly, the exotic noncollinear dipole order is directly observed at the atomic level by integrated differential phase contrast scanning transmission electron microscopy. Our work paves an alternative route for low-dimensional ferroelectrics to pursue excellent ferroelectric performance and distinct physics of polarity.
Read the full abstract ▾
All authors Yu Xing, Ning Ding, Zhipeng Wang, Zhiwen Pan, Lei Guo, Guowei Du, Yangrui Liu, Xiaoxing Cao, Ran Su, Mengting Jiang, Xuezhi Ma, Xiyu Chen, Junchao Zhang, Xinyu Yang, Haoran Ye, Honghong Yao, Rui Feng, Dexiang Chen, Le-Ping Miao, Yumeng You, Zejun Li, Dongsheng Song, Linglong Li, Shuai Dong
Materials Science
SALMON 2.3: Implementation of divide-and-conquer ground-state initialization for large-scale real-time TDDFT
Shunsuke Yamada and Tomohito Otobe
In large-scale real-time time-dependent density functional theory (TDDFT), preparing the ground-state electronic structure can be more expensive than the subsequent time propagation, limiting simulations of nonequilibrium electron dynamics in realistic systems containing thousands of atoms. This bottleneck is especially important for disordered materials,
liquids, nanostructures, and heterogeneous condensed-matter systems, where nonlinear and strong-field phenomena such as high-harmonic generation and light-induced phase transitions require explicit real-time treatment. SALMON is an open-source first-principles code for light-matter interaction simulations based on real-time TDDFT on real-space grids, supporting massively parallel calculations with MPI combined with OpenMP or GPU acceleration. In SALMON 2.3, we implement a divide-and-conquer density functional theory (DC-DFT) scheme and combine it with a postprocessing method that reconstructs spatially extended Kohn-Sham orbitals of the entire system. These reconstructed global orbitals are used directly as initial states for the standard real-time, real-space TDDFT module of SALMON. The resulting workflow connects efficient DC-DFT ground-state preparation to conventional real-time TDDFT. The DC-DFT self-consistent-field procedure exhibits linear scaling with system size, addressing a major bottleneck in large-scale electron-dynamics simulations while retaining the robustness and broad applicability of SALMON's established time-propagation scheme. We describe the computational procedure, parallelization strategy, and input/output design. Weak-scaling tests using Si supercells on Fugaku confirm the linear-scaling behavior. Accuracy tests for a 512-atom amorphous Si system and a bulk H2O
liquid system containing 4134 atoms demonstrate that the workflow enables practical large-scale real-time TDDFT simulations.
Read the full abstract ▾
Statistical Mechanics
Asymptotic hydrographs and anomalous dispersion in mass-conserving storage cascades
Henrique Santos Lima, Márk Honti and Balázs Sándor
Sums of independent exponential random variables lead to the Erlang distribution, providing a direct probabilistic route from exponential waiting times to the integer-shape gamma law. This paper investigates how this classical construction changes when the exponential waiting-time density is replaced by the $q$-exponential density of nonextensive statistics. Our main result is an analytical asymptotic expression for the
outflow of a mass-conserving cascade of reservoirs driven by a $q$-exponential waiting-time kernel. In the critical case $q=5/3$, the large-cascade flow rate converges to a stable Lévy density whose time argument is shifted by a Galilean-type transformation. This shifted Lévy law gives the asymptotic hydrograph of the cascade. We also found that for the entire regime $1<q<2$ the macroscopic dynamics are governed by $\alpha$-stable Lévy laws. This proves that anomalous non-Gaussian dispersion can emerge from pure mass-conserving convolutional chains without invoking fractional derivatives.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Propagating edge and interfacial states in corrugated graphene: Robustness and configurability
Adel Belayadi, Dawei Zhai and Nancy Sandler
Periodically strained
graphene provides a versatile platform to realize moiré-like electronic structures. We show that the interplay between strain-induced pseudomagnetic field and a displacement-field-controlled scalar potential enables the formation of isolated narrow bands. Some of the low-energy bands are topological, carrying valley-opposite Chern numbers. Remarkably, despite a vanishing total Chern number, propagating in-gap edge states emerge in various nanoribbon geometries that preserve valley
symmetry. We elucidate the distinct mechanisms responsible for edge states in the zero-energy and higher-energy gaps and demonstrate their robustness against disorders, despite lacking conventional topological protection. Leveraging these properties, we propose device architectures in which a displacement field switches the zero-energy gap and its associated edge channels on and off. Furthermore, split-gate geometries generate topological interfacial states that coexist with the edge modes and can be spatially reconfigured. These results establish strain superlattices as a powerful platform for engineering topological electronic states and electronic transport.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Mechanically Exfoliated Metallic Delafossite PdCoO2 Nanomembranes: Quantum Transport and Electrical Evaluation Toward Interconnect Applications
Chengyu Zhu, Pahuni Jain, Yi Zhang et al. (+6 more)
Metallic delafossite
oxides have drawn
attention for their ultralow resistivity and coherent electronic transport. However, mesoscopic transport studies are hindered by the limited access to high quality nanoscale devices. Here, we report single crystalline PdCoO2 nanomembranes, enabling exploration of quasi two dimensional (2D) transport. Shubnikov de Haas and Aharonov Bohm oscillations under different
magnetic field orientations are observed at low temperatures, from which the electron effective mass and electron phase coherence length are extracted. Beyond
quantum transport, the electrical performance of PdCoO2 toward interconnect applications is evaluated. A nearly thickness independent room temperature resistivity is observed for flakes down to 40 nm thickness. The nanomembranes exhibit a breakdown current density up to 113 MA cm-2, with excellent thermal stability and electromigration resistance. These results demonstrate that mechanically exfoliated PdCoO2 flakes preserve the high crystalline and electronic quality of bulk
crystals in the quasi-2D limit, providing a useful platform for mesoscopic transport studies and interconnect applications.
Read the full abstract ▾
All authors Chengyu Zhu, Pahuni Jain, Yi Zhang, Junghyun Koo, Weideng Sun, Yaotian Li, Alexander McLeod, Chris Leighton, Gang Qiu
Materials Science
M. Winter, A. Pignedoli, A. S. Sukhanov et al. (+18 more)
In most helimagnets, an applied
magnetic field aligns the propagation direction of a helical
spin texture with the field, resulting in a conical state and obscuring the unwinding process. Here, we access a complementary regime in the anisotropic
chiral magnet Mn$_{1.4}$PtSn, where
crystal symmetry constrains the propagation direction of the
spin modulation. Using resonant elastic X-ray scattering in a vector magnet, we track the
evolution of quasi-one-dimensional
spin textures that propagate along a
chiral crystallographic axis while the
magnetic field is applied perpendicular to this direction. Together with micromagnetic simulations, our measurements reveal a transformation from the zero-field $\pi$-
chiral soliton lattice into a fan-like state. In this state, the propagation direction remains transverse to the applied field, while the
spins oscillate about the field direction. During magnetization, the modulation length decreases continuously with the field and approaches the field-polarized state. Simulations indicate that magnetostatic interactions in finite samples play a key role in stabilizing this behavior. Our results provide evidence for a fan-like regime in a
chiral magnet and highlight how field orientation can be used to control one-dimensional
spin textures.
Read the full abstract ▾
All authors M. Winter, A. Pignedoli, A. S. Sukhanov, M. Azhar, A. Tahn, B. Achinuq, J. R. Bollard, V. Ukleev, C. Luo, F. Radu, S. Wintz, M. Weigand, A. Mistonov, P. Vir, J. Geck, C. Felser, G. van der Laan, T. Hesjedal, K. Everschor-Sitte, B. Rellinghaus, M. C. Rahn
Mesoscale and Nanoscale Physics
Electrically Programmable Correlated Topology and Magnetism in a Moiré Trilayer
Christiano Wang Beach, Courtney Baier, Kaijie Yang et al. (+15 more)
Strong electron-electron interactions underlie a wide range of
quantum many-body phenomena, including magnetism, superconductivity, and charge fractionalization. A central goal is to achieve in situ control over
lattice geometry, bandwidth, and band
topology within a single platform. Here we realize such an electrically programmable
quantum many-body system in an alternating twisted trilayer MoTe$_2$, where an out-of-plane displacement field continuously modifies the layer polarization, effective
lattice, and
topology of the moiré bands. At zero displacement field, the system realizes a triangular
lattice hosting a correlated
insulator at one hole per moiré unit
cell ($\nu = -1$). Doping this state produces strongly asymmetric
magnetic responses: double-exchange-like ferromagnetism for $|\nu| > 1$, and signatures of
spin polarons and antiferromagnetism for $|\nu| < 1$. At large displacement field, interlayer hybridization reconstructs the electronic structure into a honeycomb
lattice with a flat Chern band, supporting integer and fractional Chern
insulators. Magneto-optical measurements further reveal the signatures of gap closure and Landau-level formation from a
spin-polarized
Fermi surface near the crossover between the two regimes. These results establish a unified, electrically tunable platform in which correlated magnetism and topological states emerge from a single controllable band structure.
Read the full abstract ▾
All authors Christiano Wang Beach, Courtney Baier, Kaijie Yang, Huiyuan Zheng, Yueyao Fan, Weijie Li, Shuai Yuan, Yifan Zhao, Yue Sun, Chaowei Hu, Takashi Taniguchi, Kenji Watanabe, Jiun-haw Chu, Liang Fu, Ting Cao, Satoshi Okamoto, Di Xiao, Xiaodong Xu
Statistical Mechanics · Cross-listed from physics.chem-ph
Generalized Mpemba effect in diffusion-controlled spin-dependent delayed fluorescence
Kazuhiko Seki
The Mpemba effect is commonly associated with anomalous thermal relaxation, in which a system prepared at a higher temperature reaches
equilibrium faster than one prepared at a lower temperature. In modern formulations, however, its defining feature is broader: a state initially farther from
equilibrium can relax faster than a closer one, or, equivalently, relaxation trajectories can cross. Here, we show that
magnetic-field-dependent delayed fluorescence in triplet-fusion systems realizes a generalized Mpemba effect driven by external control of
spin-selective kinetics. Using a
diffusion-controlled geminate-recombination extension of the Johnson–Merrifield model, we demonstrate that delayed-fluorescence trajectories obtained at different
magnetic fields cross when geminate fusion is effective. We further derive a compact kinetic criterion for such crossing in terms of the competition between intermediate-time decay rates and long-time power-law amplitudes. This criterion captures the interplay between effective fast and slow relaxation contributions. Within this kinetic framework, the final state is independent of the external control parameter and is defined as the fully relaxed state in which no separated triplet population remains. The generalized Mpemba effect therefore arises from the redistribution of transient relaxation pathways associated with geminate recombination, whereas bulk
diffusion-controlled processes contribute only to the final relaxation. These results link anomalous relaxation in
spin-dependent photokinetics to modern formulations of the generalized Mpemba effect and show how trajectory crossing can emerge in systems governed by
diffusion-controlled geminate recombination and non-Markovian kinetics.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Observation and Control of Spontaneous Magnon Emission from Spin Ensembles in 2D Hexagonal Boron Nitride
Ling-Jie Zhou, Jayakrishnan M. P. Nair, Senlei Li et al. (+10 more)
Hybrid systems consisting of color centers and
magnetic materials provide an appealing solid-state platform for advancing the burgeoning
quantum technological revolution. Exploring novel coupling mechanisms between optically active
spin defects and
quantum degrees of freedom is directly relevant in this context. Here, we report observation and control of spontaneous
magnon emission from boron-vacancy centers in 2D hexagonal boron nitride (hBN) to a proximal ferrimagnet in the near-zero temperature limit. The spontaneous
magnon emission process is overshadowed by thermal
magnon effect as temperature increases, reflecting the crossover from a spontaneous-emission-dominated
magnon reservoir to a thermally occupied
spin bath where absorption and stimulated processes restore balance. By increasing the
spin defect density, we further present that spontaneous
magnon emission into a common
spin bath could help establish
magnon-mediated correlations in dense hBN
spin ensembles. Our results are quantitatively captured by theoretical modeling, bringing insights into understanding
qubit-
magnon coupling, correlated
spin dynamics, and many-body physics of color centers in the
quantum regime.
Read the full abstract ▾
All authors Ling-Jie Zhou, Jayakrishnan M. P. Nair, Senlei Li, Thomas Poirier, Yiran Zhao, Zelong Xiong, Sumedh Rathi, Jingcheng Zhou, Zhigang Jiang, Hailong Wang, James H. Edgar, Benedetta Flebus, Chunhui Rita Du