Superconductivity
Entropy stabilization and effect of A-site ionic size in bilayer nickelates
Jia-Yi Lu, Jia-Xin Li, Xin-Yu Zhao et al. (+5 more)
The discovery of high-temperature superconductivity in La$_3$Ni$_2$O$_7$ under high pressure has sparked a surge of research into Ruddlesden-Popper (RP) nickelates. Currently, stabilizing the
bilayer RP phases with smaller $A$-site ions remains a significant challenge. In this work, we have successfully synthesized medium- and high-
entropy bilayer nickelates, La$_{1.2}$Pr$_{0.6}$Nd$_{0.6}$Sm$_{0.6}$Ni$_2$O$_{7-\delta}$ and La$_{0.67}$Pr$_{0.67}$Nd$_{0.67}$Sm$_{0.33}$Eu$_{0.33}$Gd$_{0.33}$Ni$_2$O$_{7-\delta}$, by utilizing the concept of configuration
entropy stabilization. The high-
entropy nickelate exhibits the smallest unit-
cell volume and the largest orthorhombic distortion reported to date. The chemical pressure induced by the smaller A-site ions significantly enhances the NiO$_6$ octahedral rotation/distortion and shortens the interlayer Ni-Ni interatomic spacing. Physical property measurements reveal bad electrical conductivity alongside a markedly elevated density-wave transition temperature. Notably, the superconducting transition temperature extrapolated from structural correlations is projected to exceed 100 K. Our work not only demonstrates
entropy stabilization of
bilayer nickelates, but also reveals the effect of $A$-site-ion size on the
crystal structure and physical properties, opening a new pathway for developing nickelate
superconductors and tuning their electronic properties.
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All authors Jia-Yi Lu, Jia-Xin Li, Xin-Yu Zhao, Ya-Nan Zhang, Yi-Qiang Lin, Kai-Xin Ye, Hui-Qiu Yuan, Guang-Han Cao
Soft Condensed Matter
A geometric framework for curvature-dependent collective behavior of polar active agents on curved surfaces
Tatsuo Shibata
In biological systems, active
agents such as actomyosin and
cells move and interact on curved surfaces, exhibiting diverse phenomena. These observations have motivated studies of how
curvature shapes their collective behavior. Here, using a
geometric framework, a minimal model is presented for interacting active
agents on curved surfaces with Vicsek-like polar
alignment. A transition between disordered and ordered states occurs on spheres as well as on oblate and prolate spheroids. As the deviation from sphericity increases, the transition point shifts to higher
alignment strengths, and swarming localizes to an equatorial belt away from the poles, indicating that
curvature heterogeneity influences the emergence of the polar-ordered state.
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Superconductivity
Field-free Josephson diode and tunable $\phi_0$-junction in chiral kagome antiferromagnets
Jin-Xing Hou, Chuang Li, Lun-Hui Hu et al. (+1 more)
The recent realization of superconducting proximity effect in
chiral antiferromagnets (cAFMs) opens a new route to nonreciprocal superconducting transport of fundamental interest and practical importance. Using microscopic modeling and
symmetry analysis, we show that Josephson junctions formed by conventional $s$-wave
superconductors (SCs) and cAFMs on the kagome
lattice exhibit Josephson diode effects and anomalous phase shifts ($\phi_0$-junction state) when space inversion $\mathcal{I}$, time-reversal $\mathcal{T}$, and combined mirror-time-reversal $\mathcal{TM}_z$
symmetries are simultaneously broken. We propose two setups to realize these phenomena and achieve high diode efficiency. (i) An SC/cAFM/SC junction with
spin-orbit coupling, which enables a field-free diode effect with a robust tunable $\phi_0$-junction state. (ii) An SC/cAFM/cAFM$^\prime$/SC junction, where two cAFM layers with different in-plane order orientations, under an out-of-plane Zeeman exchange field, produces significant diode effect and anomalous phase shifts. These results establish a direct link between $\mathcal{TM}_z$
symmetry breaking and nonreciprocal superconductivity, suggesting cAFMs as versatile platforms for
symmetry-engineered Josephson diodes and tunable $\phi_0$-junctions.
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All authors Jin-Xing Hou, Chuang Li, Lun-Hui Hu, Song-Bo Zhang
Strongly Correlated Electrons
Magnetic-field-induced insulating behavior in black phosphorus under pressure
Kazuto Akiba, Yuzuki Sega, Yuichi Akahama et al. (+3 more)
We investigated the out-of-plane magnetoresistance of pressurized black phosphorus (BP) with a longitudinal field configuration. Despite the absence of the Lorentz force in the present configuration, we observed a significant enhancement of magnetoresistance marked with a clear onset field in both the semiconducting (1.1 GPa) and semimetallic (1.3 GPa) phases. The insulating behavior observed near the
semiconductor-semimetal transitio pressure is possibly associated with emergence of an excitonic phase, which has been suggested in a recent theoretical study. BP under finely tuned pressure can be a candidate to realize the field-induced electronic phase transition in a moderate
magnetic field below 9 T.
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All authors Kazuto Akiba, Yuzuki Sega, Yuichi Akahama, Yuta Seo, Tomoki Machida, Masashi Tokunaga
Superconductivity
Beyond dpa: an atomistic framework for a quantitative description of radiation damage in YBa2Cu3O7
Federico Ledda, Daniele Torsello, Davide Gambino et al. (+8 more)
Radiation damage in high-temperature cuprate
superconductors represents one of the main technological challenges for their deployment in harsh environments, such as fusion reactors and accelerator facilities. Their complex
crystal structure makes modeling irradiation effects in this class of materials a particularly demanding task, for which existing damage models remain inadequate. In this work, we develop an atomistic-based approach for describing primary radiation damage in YBa2Cu3O7, by coupling Molecular Dynamics and Binary Collision Approximation simulations in a way that makes them complementary. When integrated with Primary Knock-on Atom spectra obtained from Monte Carlo codes, our results establish a framework for multiscale modeling of radiation damage, enabling quantitative estimates of several damage descriptors, such as defect production, defect clustering, and the effective damaged volume for any specific irradiation conditions where collision cascades dominate. This computational approach is suitable for the prediction of irradiation effects in any complex functional
oxide, with applications ranging from aerospace to
nuclear fusion and high-energy physics.
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All authors Federico Ledda, Daniele Torsello, Davide Gambino, Flyura Djurabekova, Fabio Calzavara, Niccolò Di Eugenio, Ville Jantunen, Antonio Trotta, Erik Gallo, Kai Nordlund, Francesco Laviano
Quantum Gases · Cross-listed from nlin.PS
Numerical Identification of Stationary States and Their Stability in a Model of Quantum Droplets
Sun Lee, Panayotis G. Kevrekidis and Wenrui Hao
In this work, we are motivated by a recent variant of the nonlinear Schrodinger (NLS) equation describing cold, dilute atomic condensates with
quantum fluctuation effects. Our goal is to develop robust numerical methods capable of uncovering diverse stationary solutions in such NLS models. Specifically, and in line with recent theoretical and experimental interest, we focus on ultracold
quantum droplets in Bose mixtures influenced by the Lee Huang Yang
quantum fluctuation correction and study these systems in one and two dimensional settings. To this end, we deploy several numerical techniques. The homotopy grid method allows systematic refinement from coarse to fine spatial discretizations in one dimension, while the dimension by dimension homotopy approach extends one-dimensional solutions to two-dimensional domains. These methods effectively detect broad families of stationary states, many of which have not been previously reported, to the best of our knowledge. Furthermore, they enable the monitoring of solution continuation and bifurcation phenomena. During our investigation, we encounter unusual bifurcation events, including nonstandard pitchforks and saddle-center bifurcations, which exhibit novel stability transitions. For example, we identify continuous pathways connecting
vortex and dark
soliton stripe branches, absent in the standard cubic defocusing model. Overall, the presence of competing mean-field and
quantum fluctuation interactions leads to a richer bifurcation structure than in traditional cubic NLS systems. These findings suggest that similar complex bifurcation and stability phenomena may appear in other settings, including higher-dimensional systems or models with competing nonlinearities such as cubic-quintic interactions, highlighting the importance of further theoretical and numerical exploration.
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Superconductivity
Visualizing Pair-breaking Scattering Interference in Bulk FeSe
Matthew Toole, Nileema Sharma, James McKenzie et al. (+3 more)
Spatially periodic modulations of the superconducting gap have been recently reported in diverse materials and are often attributed to pair density wave order. An alternative mechanism, termed pair-breaking scattering interference (PBSI), was proposed to produce gap modulations without finite-momentum pairing. Here we investigate signatures of PBSI in bulk FeSe using scanning tunneling microscopy with superconductive tips, enabling enhanced energy resolution and Josephson tunneling. Subsurface
magnetic scatterers with Yu-Shiba-Rusinov states are identified in FeSe, around which we observe particle-hole symmetric gap modulations accompanied by spatial modulation of the Josephson current. Those modulations have wavevectors consistent with intra-pocket PBSI. We further demonstrate that phase-referenced quasiparticle interference imaging offers an independent and direct probe of PBSI beyond gap mapping. These results establish PBSI as a viable origin of gap modulations in
superconductors lacking preexisting charge/
spin density wave orders, and motivate further investigation of the intriguing gap modulation phenomenology.
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All authors Matthew Toole, Nileema Sharma, James McKenzie, Fangjun Cheng, Sheng Ran, Xiaolong Liu
Materials Science
On-demand phase-field modeling: Three-dimensional Landau energy for HfO2 through machine learning
Yusuke Tamura, Kairi Masuda and Yu Kumagai
The unexpected emergence of ferroelectricity in HfO2 at reduced dimensions has attracted considerable
attention, as it provides a pathway toward the realization of ultrasmall ferroelectric devices. Ab initio calculations suggest that this effect arises from a unique mode coupling, in which an antipolar displacement mode stabilizes a robust polar distortion. Based on these insights, Landau-Devonshire energy models have been proposed using such
lattice modes as order parameters. However, most existing models are limited to a simplified one-dimensional model because of the computational cost of ab initio calculations and the limitations of conventional Landau
polynomials. Here, we constructed a three-dimensional Landau-Devonshire potential for HfO2 by employing the tetragonal, antipolar, and polar modes as coupled order parameters, based on the latest machine-learning technologies. We generated a large-scale
dataset of energies over a three-dimensional structural space, with the computational cost drastically reduced through the use of machine-learning interatomic potentials, and trained a multilayer perceptron (MLP) to learn the relationship between the order parameters and the energy. The energy predicted by the MLP successfully captures the characteristic coupling behavior whereby the antipolar modes induce the polar mode. Furthermore, by extending this MLP-based Landau potential to a position-dependent functional, that is, to a phase-field modeling framework, we revealed that the polarization magnitude in thin films decreases compared with the bulk state, while the critical strain required for the onset of spontaneous polarization increases due to surface effects. This study presents a new framework for the on-demand construction of Landau energy and phase-field modeling using the latest machine-learning techniques, enabling multiscale analysis of complex ferroelectric phenomena.
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Strongly Correlated Electrons
Atomic-scale control of substrate-spin coupling via vertical manipulation of a 2D metal-organic framework
Benjamin Lowe, Bernard Field, Dhaneesh Kumar et al. (+9 more)
Two-dimensional (2D) materials with frustrated
crystal geometries can host strongly correlated electrons, potentially leading to a range of exotic many-body
quantum phases such as Mott
insulators,
quantum spin-
liquids, and Kondo
lattices. The ability to control exchange-coupling within these systems is therefore highly desirable. Here, we use an atomically sharp scanning tunneling microscope probe to vertically manipulate a 2D Mott insulating kagome metal-organic framework (MOF) featuring Kondo-screened local
magnetic moments on Ag(111). We show that by controlling the adsorption height of the MOF, we can also controllably and reversibly change the strength of Kondo coupling between the MOF's local
spins and the substrate's conduction electrons. This mechanical control of Kondo coupling could be extended to other forms of interlayer exchange coupling, potentially allowing for atomic-scale design or control of spintronics technologies.
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All authors Benjamin Lowe, Bernard Field, Dhaneesh Kumar, Daniel Moreno Cerrada, Oleksandr Stetsovych, Julian Ceddia, Andrés Pinar Solé, Amelia Domínguez-Celorrio, Jack Hellerstedt, Sinéad M. Griffin, Pavel Jelínek, Agustin Schiffrin
Statistical Mechanics · Cross-listed from nlin.AO
Emergence of higher-order interactions in systems of coupled Kuramoto oscillators with time delay
Narumi Fujii, Keisuke Taga, Riccardo Muolo et al. (+2 more)
We show that higher-order interactions naturally emerge from time-delayed pairwise coupling in Kuramoto oscillators. By expanding the delayed pairwise coupling to the second order, we derive a delay-free Kuramoto model possessing both pairwise and three-body interactions. Numerical simulations and stability analysis demonstrate that the three-body Kuramoto model and the time-delayed pairwise Kuramoto model exhibit qualitatively consistent synchronization transitions under appropriate conditions. In particular, the bistability arising in the time-delayed Kuramoto model is accounted for by the three-body interactions. Our findings reveal that time delays can be recast effectively as higher-order interactions, providing an insight into how coupling delays shape collective dynamics.
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All authors Narumi Fujii, Keisuke Taga, Riccardo Muolo, Bob Rink, Hiroya Nakao
Quantum Gases
Emergent topological properties in spatially modulated sub-wavelength barrier lattices
Giedrius Žlabys, Wen-Bin He, Domantas Burba et al. (+3 more)
We investigate topological phenomena in a spatially modulated Dirac-$\delta$
lattice, where the scattering potential varies periodically in space. Changing the potential modulation frequency leads to Hofstadter's butterfly-like energy spectrum and enables the emergence of topological transport regimes characterized by non-trivial Chern numbers. We show how the considered modulated system is connected to the Hofstadter model via the Harper equation. By adiabatically varying spatial modulation parameters, we demonstrate controllable
quantum transport and verify the topological nature of these effects through Wannier center displacement and bulk invariant calculations. We also propose an experimentally feasible realization of such a system using optically controlled three-level atoms. Our findings showcase spatially engineered Kronig-Penney-type systems as versatile platforms for investigating and exploiting different topological
quantum transport regimes.
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All authors Giedrius Žlabys, Wen-Bin He, Domantas Burba, Sarika Sasidharan Nair, Thomas Busch, Tomoki Ozawa
Strongly Correlated Electrons
Tunable Topological Phases in an Organic One-Dimensional Mott Chain: Odd-Haldane (S = 1/2) and Haldane (S = 1)
Khalid N. Anindya and Hong Guo
Establishing
symmetry-protected topological (SPT) phases with interactions in chemically realistic systems remains an open challenge. We show that a single, synthetically plausible organic one-dimensional chain, tunable via chemical modification of its radical sites, hosts two such phases: an odd-Haldane phase of a dimerized $S=\tfrac{1}{2}$ Heisenberg chain and a Haldane phase of an $S=1$ chain realized when Hund coupling locks two $S=\tfrac{1}{2}$
spins per monomer into $S=1$. Density-functional theory places the active
manifold deep in the Mott regime ($U/t\!\approx\!126$), justifying a
spin-only Heisenberg description; a compact $(t,U)\!\to\!J$ mapping then fixes exchange couplings. Exact diagonalization and DMRG reveal a consistent SPT fingerprint across both phases, including a quantized many-body Zak phase, even-degenerate
entanglement spectrum, protected edge
spins, and characteristic triplon/Haldane features in $S^{+-}(q,\omega)$. Our results identify a chemically programmable molecular platform for interacting SPT physics in one dimension and suggest concrete spectroscopic routes to organic Haldane
spin chains for nanoscale
quantum devices.
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Materials Science
In situ XRD Study of Strain Evolution in AlGaN/GaN HEMT at High Temperatures up to 1000 {\deg}C
Botong Li, Bobby G. Duersch, Hunter Ellis et al. (+6 more)
The thermal stability and structural
evolution of a GaN high-electron-mobility transistor (HEMT)
heterostructure grown on a Si (111) substrate were investigated using in situ high-temperature X-ray diffraction (HT-XRD), reciprocal space mapping (RSM), Raman spectroscopy, and rocking-curve (RC) analysis at varying temperatures. The
heterostructure, consisting of a p-GaN cap, an AlGaN barrier, and a GaN channel supported by two AlGaN/AlGaN superlattice (SL) buffer layers, maintained clear and periodic satellite peaks up to a temperature of 1000 deg C, confirming excellent structural integrity. Symmetric and asymmetric RSM results reveal that both the Si and GaN diffraction peaks shift to lower angles with increasing temperature, consistent with thermal expansion, and show no significant broadening or relaxation throughout the heating process. The c-
lattice constant follows the theoretical expansion predicted by the multi-frequency Einstein model, whereas the a-
lattice expansion is slower due to in-plane strain constraints imposed by the underlying Si substrate and buffer layers. Rapid
lattice contraction during the fast-cooling stage induces a residual compressive strain of approximately 0.3 percent in the GaN channel after cooling. Raman spectra further confirm this strain state through a blue shift of approximately 1.5 cm-1 of the GaN E2 (high)
phonon mode, corresponding to an in-plane strain of about 0.2 percent. Rocking-curve analysis reveals an increase in both screw and edge dislocation densities by 28 percent and 12 percent, respectively. These results collectively demonstrate that the GaN HEMT
heterostructure exhibits robust crystalline stability up to 1000 deg C, with only minor strain redistribution and limited dislocation activity, providing experimental evidence for GaN device applications under high-temperature conditions.
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All authors Botong Li, Bobby G. Duersch, Hunter Ellis, Imteaz Rahaman, Aidan Belanger, Zlatan Aksamija, Brian Roy Van Devener, Kathy Anderson, Kai Fu
Materials Science
Artificial Intelligence-Enabled Holistic Design of Catalysts Tailored for Semiconducting Carbon Nanotube Growth
Liu Qian, Yue Li, Ying Xie et al. (+6 more)
Catalyst design is crucial for materials synthesis, especially for complex reaction networks. Strategies like collaborative catalytic systems and multifunctional catalysts are effective but face challenges at the nanoscale. Carbon nanotube synthesis contains complicated nanoscale catalytic reactions, thus achieving high-density, high-quality semiconducting CNTs demands innovative catalyst design. In this work, we present a holistic framework integrating machine learning into traditional catalyst design for semiconducting CNT synthesis. It combines knowledge-based insights with data-driven techniques. Three key components, including open-access electronic structure databases for precise physicochemical descriptors, pre-trained natural
language processing-based
embedding model for higher-level abstractions, and physical - driven predictive models based on experiment data, are utilized. Through this framework, a new method for selective semiconducting CNT synthesis via catalyst - mediated electron injection, tuned by light during growth, is proposed. 54 candidate catalysts are screened, and three with high potential are identified. High-throughput experiments validate the predictions, with semiconducting selectivity exceeding 91% and the FeTiO3 catalyst reaching 98.6%. This approach not only addresses semiconducting CNT synthesis but also offers a generalizable methodology for global catalyst design and nanomaterials synthesis, advancing materials science in precise control.
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All authors Liu Qian, Yue Li, Ying Xie, Jian Zhang, Pai Li, Yue Yu, Zhe Liu, Feng Ding, Jin Zhang
Soft Condensed Matter · Cross-listed from physics.bio-ph
Predicting the Interfacial Energy and Morphology of DNA Condensates
Sihan Liu and Andrej Košmrlj
The physics and morphology of biomolecular condensates formed through
liquid-
liquid phase separation underpin diverse biological processes, exemplified by the nested organization of nucleoli that facilitates ribosome biogenesis. Here, we develop a theoretical and computational framework to understand and predict multiphase morphologies in DNA-nanostar solutions. Because morphology is governed by interfacial energies between coexisting phases, we combine Flory-Huggins theory with coarse-grained molecular dynamics simulations to examine how these energies depend on key microscopic features of DNA nanostars, including size, valence, bending
rigidity, Debye screening length, binding strength, and sticky-end distribution. The phase behavior of DNA nanostars is quantitatively captured by a generalized
lattice model, in which the interplay between sticky-end binding energy and conformational
entropy determines the effective interactions. Focusing on condensates comprising two dense phases, we find that Janus-like morphologies are ubiquitous because the interfacial energies between the dense and dilute phases, $\gamma_{i\in\{1,2\}}$, are typically comparable. In contrast, nested morphologies are rare as they require a large asymmetry in $\gamma_i$, which arises only for highly dissimilar nanostars such as those differing markedly in valence or size. Moreover, the interfacial energy between the two dense phases, $\gamma_{12}$, can be modulated either discretely, by varying sticky-end distribution, or continuously, by tuning the crosslinker ratio; the former may even eliminate nested configurations. These findings establish physical design principles for constructing complex condensate architectures directly from microscopic molecular parameters.
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Strongly Correlated Electrons
Power-Law Suppression of Phonon Thermal Transport by Magnetic Excitations in a Molecular Quantum Spin Liquid
S. Fujiyama, K. Ueda and Y. Otsuka
We present large-scale ab initio
phonon calculations for the molecular
quantum spin liquid X[Pd(dmit)2]2. An unusually low average
phonon velocity ( 700 {m/s}) and optical modes below 10 cm^{-1} confine the Debye T^{3} regime to T < 2 K. As the transfer-integral anisotropy approaches the maximally frustrated regime (t'/t \to 1), the
lattice stiffens, ruling out
lattice softening as the origin of the
spin-
liquid state. By quantifying the additional suppression of the thermal conductivity from experimental data, we observe a power-law behavior consistent with two-dimensional
magnetic excitations with a nodal, approximately linear (Dirac-like) spectrum.
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Soft Condensed Matter · Cross-listed from physics.flu-dyn
Intermittent Motility of a Synthetic Active Particle in Changing Environments
Rudra Sekhri, Rahil N. Valani and Tapio Simula
We experimentally investigate the dynamics of synthetic active particles composed of gravitationally bouncing, superwalking droplets confined within an annular fluid bath. Driven by a topologically pumping dual-frequency waveform, the droplets exhibit alternating active (walking) and dormant (bouncing) phases, producing intermittent azimuthal motion. Tracking individual droplets reveals pseudolaminar chaotic dynamics in the time series of particle's angular position, characterized by laminar plateaus that are interrupted by short irregular bursts of activity. Increasing the driving amplitude induces a qualitative change in the active particle's intermittent dynamics, arising from a
symmetry-breaking transition in its Faraday-wave field environment: continuous SO(2)-symmetric "channelling" waves give way to discrete "trapping" patterns. These findings demonstrate how environmental
symmetry and spatiotemporal structure modulate motility and intermittency in synthetic active matter.
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Strongly Correlated Electrons
Recent progress in quantum spin liquids, fractional magnetization plateaus, and unconventional superconductivity in kagome lattices
Li-Wei He, Shun-Li Yu and Jian-Xin Li
The kagome
lattice, with its unique
geometric structure, has emerged as a leading platform for exploring
quantum many-body physics, particularly in the study of
quantum spin liquids (QSLs) and unconventional superconductivity. This review highlights recent advancements in the investigations of QSLs, fractional magnetization plateau phases in kagome antiferromagnets, and unconventional superconductivity in vanadium-based kagome
superconductors. We begin by examining the classical ground-state properties of the nearest-neighbor kagome
antiferromagnetic Heisenberg model and introducing recent experimental progress in the study of QSLs and fractional magnetization plateau phases. Next, we discuss the fermionic description of the QSL states, along with related gauge theory and the variational Monte Carlo (VMC) method. We then focus on discussing the VMC studies of QSLs and magnetization plateau phases in kagome antiferromagnets. For superconductivity in kagome systems, we first analyze the characteristics of the electronic structure and the possible associated electronic instabilities. Finally, we review recent experimental advances in unconventional superconductivity in AV$_3$Sb$_5$ (A = K, Rb, Cs), with a particular focus on
chiral superconductivity and pairing density waves.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Discrete time crystals enhanced by Stark potentials in Rydberg atom arrays
Jian-Jia Wang, Ling-Zhi Tang, Yan-Xiong Du et al. (+1 more)
Discrete time
crystals (DTCs) are non-
equilibrium phases in periodically driven systems that exhibit spontaneous breaking of discrete time-translation
symmetry. The stabilization of most DTC phases is achieved via the disorder-induced many-body localization. In this work, we propose an experimental scheme to realize disorder-free DTCs in a periodically driven Rydberg atom array. Our scheme utilizes a linear potential in the atomic detuning to enhance the DTC order, without being tired to (Stark) many-body localization. We numerically demonstrate that the Stark potential enhances the robustness of the DTC against the flip imperfections and extends its lifetime, which are independent of initial states. Thus, our scheme provides a promising way to explore DTCs in Rydberg atom arrays without disorder averaging and special state preparation.
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All authors Jian-Jia Wang, Ling-Zhi Tang, Yan-Xiong Du, Dan-Wei Zhang
Materials Science
Machine Learning Enabled Graph Analysis of Particulate Composites: Application to Solid-state Battery Cathodes
Zebin Li, Shimao Deng, Yijin Liu et al. (+1 more)
Particulate composites underpin many solid-state chemical and electrochemical systems, where microstructural features such as multiphase boundaries and inter-particle connections strongly influence system performance. Advances in X-ray microscopy enable capturing large-scale,
multimodal images of these complex microstructures with an unprecedentedly high throughput. However, harnessing these
datasets to discover new physical insights and guide microstructure optimization remains a major challenge. Here, we develop a machine learning (ML) enabled framework that enables automated transformation of experimental
multimodal X-ray images of multiphase particulate composites into scalable,
topology-aware graphs for extracting physical insights and establishing local microstructure-property relationships at both the particle and network level. Using the multiphase particulate cathode of solid-state lithium batteries as an example, our ML-enabled graph analysis corroborates the critical role of triple phase junctions and concurrent ion/electron conduction channels in realizing desirable local electrochemical activity. Our work establishes graph-based microstructure representation as a powerful paradigm for bridging
multimodal experimental imaging and functional understanding, and facilitating microstructure-aware data-driven materials design in a broad range of particulate composites.
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All authors Zebin Li, Shimao Deng, Yijin Liu, Jia-Mian Hu
Statistical Mechanics
Complete Decomposition of Anomalous Diffusion in Variable Speed Generalized Lévy Walks
Abhijit Bera and Kevin E. Bassler
Variable Speed Generalized Lévy Walks (VGLWs) are a class of spatio-temporally coupled
stochastic processes that unify a broad range of previously studied models within a single parametrized framework. Their dynamics consist of discrete random steps, or flights, during which the walker's speed varies deterministically with both the elapsed time and the total duration of the flight. We investigate the anomalous diffusive behavior of VGLWs and analyze it through decomposition into the three fundamental constitutive effects that capture violations of the Central Limit
Theorem (CLT): the Joseph effect, reflecting long-range increment correlations, the Noah effect, arising from heavy-tailed step-size distributions with infinite variance, and the Moses effect, associated with statistical aging and non-stationarity. Our results show that anomalous
diffusion in VGLWs is typically generated by a nontrivial combination of all three effects, rather than being attributable to a single mechanism. Strikingly, we find that within the VGLW framework the Noah exponent $L$, which quantifies the strength of the Noah effect, is unbounded from above, revealing a richer and more extreme landscape of anomalous
diffusion than in previously studied Lévy-walk-type models.
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Materials Science
Tuning Carrier Type and Density in Highly Conductive and Infrared-Transparent (Bi1-xSbx)2Te3 films
Xiangren Zeng, Shenjin Zhang, Zhiheng Li et al. (+7 more)
Infrared transparent conductors have long been sought due to their broad optoelectronic applications in the infrared wavelength range. However, the search for ideal materials has been limited by the inherent trade-off between electrical conductance and optical transmittance. Band engineering offers an effective approach to modulate carrier type and density, enabling concurrent tuning of both conductance and transmittance. In this work, we present a band engineering strategy that enables effective tuning of both infrared transmittance and electrical conductance in topological
insulator (Bi1-xSbx)2Te3, bridging the gap and paving the way for applying topological
insulators to infrared photoelectric devices. More importantly, with the combination of high carrier mobility and a large optical dielectric constant as suggested by previous report, Sb2Te3 achieves a high electrical conductance (~1000 S/cm) and outstanding infrared transmittance (92.3%) in the wavelength range of 8~13 um, demonstrating strong potential as an infrared transparent conductor. Our findings reveal that concurrent enhancement of both carrier mobility and optical dielectric constant is key to overcoming the conductance-transmittance trade-off. This work provides valuable insight for the exploration of high-performance infrared transparent conducting materials.
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All authors Xiangren Zeng, Shenjin Zhang, Zhiheng Li, Weiyue Ma, Renjie Xie, Yanwei Cao, Fengguang Liu, Fengfeng Zhang, Haichao Zhao, Xiong Yao
Materials Science
Why planar cracks fragment into echelon cracks
Olivia Ward and Aditya Kumar
Predicting the path and shape of growing cracks is fundamental to understanding of fracture. Under out-of-plane shear loading, an initially planar crack may spontaneously fragment into multiple cracks, forming a striking echelon crack pattern. Explaining this crack morphogenesis in brittle materials has been a long-standing open problem essential to developing a complete theory of crack growth. Here, through comparison with classical experiments, we show that a strength-constrained minimization of the sum of elastic and surface energies explains echelon crack formation. Results are presented for both soft and hard materials, confirming the model's general applicability to any brittle material. As a corollary, we show that, contrary to prevailing views, a purely energetic minimization model is insufficient to predict the growth of large cracks. We identify two key non-dimensional parameters governing crack fragmentation and orientation, and demonstrate that these reconcile the various energy-based and stress-based empirical criteria proposed in the literature for crack path.
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Materials Science
Confinement-induced Ultrafast Conductivity in 2D Perovskites resolved by correlative Terahertz-NIR Spectroscopy
Lion Krüger, Fabian Brütting, Michael Baumann et al. (+5 more)
Quantum wells made of two-dimensional organic-inorganic hybrid perovskites (2D-PKs) offer a high degree of flexibility in tailoring optoelectronic properties through carrier confinement and functional interlayers. Compared to their 3D counterparts, 2D-PKs exhibit tunable photoluminescence, excitonic binding at room temperature and enhanced structural stability. However, the dynamics of photo-induced charge carriers and their transport properties are highly intertwined due to the interplay of diverse excitation species, charge carrier cooling, transport, and radiative and non-radiative recombination. In this study, we employ optical-pump terahertz-probe spectroscopy (OPTP) to analyze the local conductivity dynamics of 2D and 3D methylammonium lead iodide (MAPI) perovskites at timescales down to picoseconds. Remarkably, we observe an intensity-dependent, 2D-specific buildup of an ultrafast, few-picosecond decay in local conductivity. By combining OPTP with transient absorption (TA) and picosecond time-resolved photoluminescence (TRPL), we demonstrate the disentanglement of photoconductivity and carrier population. This allows us to attribute the 2D-specific ultrafast THz response to delayed hot-carrier cooling and subsequent
exciton formation, which effectively reduces the free-carrier conductivity. This intensity-dependent, ultrafast THz response is a signature of the recently identified hot-carrier bottleneck in 3D MAPI, and this effect manifests itself in a unique form in the 2D material. These results encourage further investigations on the impact of functional organic interlayers and provide insights into designing tunable carrier responses for ultrafast devices via adapted
heterostructures and confinement.
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All authors Lion Krüger, Fabian Brütting, Michael Baumann, Moritz B. Heindl, Maximilian Spies, Anna Köhler, Alexander JC Kühne, Georg Herink
Strongly Correlated Electrons
Imaging Electron-Hole Asymmetry in the Quantum Melting of Generalized Wigner Crystals
Emma Berger, Michael Arumainayagam, Zhihuan Dong et al. (+12 more)
Two-dimensional moiré materials provide a versatile platform to explore phase transitions in strongly correlated systems. Using scanning tunneling microscopy (STM) we have imaged the density-driven melting of generalized Wigner
crystals (GWCs) and Mott
insulators (MIs) in electron-doped, near-60{\deg} twisted MoSe2
bilayers featuring a triangular moiré superlattice. We observe striking electron-hole asymmetry in GWC melting: hole-doped GWCs yield interaction-driven disordered states whereas electron-doped GWCs melt into delocalized
liquid-like states. This asymmetry arises from the broken particle-hole
symmetry of the moiré superlattice, which produces electron and hole
Fermi pockets with different momentum geometries upon GWC condensation. MI states melt without such asymmetry, consistent with the absence of a
symmetry-breaking density modulation. This work provides direct visualization of the novel emergent phases that appear as GWCs undergo
quantum melting transitions.
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All authors Emma Berger, Michael Arumainayagam, Zhihuan Dong, Lucas Schneider, Tianle Wang, Greyson Nichols, Salman Kahn, Rwik Dutta, Gaoqiang Wang, Takashi Taniguchi, Kenji Watanabe, Mit H. Naik, Michael P. Zaletel, Feng Wang, Michael F. Crommie