CMP Journal 2025-07-19
Statistics
Physical Review Letters: 4
Physical Review X: 1
arXiv: 58
Physical Review Letters
Enhanced Quantum Frequency Estimation by Nonlinear Scrambling
Research article | Information scrambling | 2025-07-18 06:00 EDT
Victor Montenegro, Sara Dornetti, Alessandro Ferraro, and Matteo G. A. Paris
Frequency estimation, a cornerstone of basic and applied sciences, has been significantly enhanced by quantum sensing strategies. Despite breakthroughs in quantum-enhanced frequency estimation, key challenges remain: static probes limit flexibility, and the interplay between resource efficiency, sensing precision, and potential enhancements from nonlinear probes remains not fully understood. In this Letter, we show that dynamically encoding an unknown frequency in a nonlinear quantum electromagnetic field can significantly improve frequency estimation. To provide a fair comparison of resources, we define the energy cost as the figure of merit for our sensing strategy. We further show that specific higher-order nonlinear processes lead to nonlinear-enhanced frequency estimation. This enhancement results from quantum scrambling, where local quantum information spreads across a larger portion of the Hilbert space. We quantify this effect using the Wigner-Yanase skew information, which measures the degree of noncommutativity in the Hamiltonian structure. Our Letter sheds light on the connection between Wigner-Yanase skew information and quantum sensing, providing a direct method to optimize nonlinear quantum probes.
Phys. Rev. Lett. 135, 030802 (2025)
Information scrambling, Quantum parameter estimation, Quantum sensing, Chaos & nonlinear dynamics
Kinematic Flow and the Emergence of Time
Cosmology | 2025-07-18 06:00 EDT
Nima Arkani-Hamed, Daniel Baumann, Aaron Hillman, Austin Joyce, Hayden Lee, and Guilherme L. Pimentel
Changes in strengths of cosmological correlations may give a way to think of time as an emergent entity.
Phys. Rev. Lett. 135, 031602 (2025)
Cosmology, Inflation, Quantum field theory, Quantum fields in curved spacetime, Scattering amplitudes
Large Kohn Anomaly and Phonon Collapse Induced by Charge Density Wave in ${\mathrm{UPt}}{2}{\mathrm{Si}}{2}$
Research article | Charge density waves | 2025-07-18 06:00 EDT
Jooseop Lee, Greta L. Chappell, Ryan E. Baumbach, Ayman H. Said, and Igor A. Zaliznyak
Using high-energy-resolution inelastic x-ray scattering, we observe anomalous softening and damping of the transverse acoustic phonon in ${\mathrm{UPt}}{2}{\mathrm{Si}}{2}$ as the system is cooled toward the charge density wave (CDW) transition temperature ${T}{\mathrm{CDW}}$. The phonon exhibits a marked Kohn-type anomaly around the CDW wave vector ${Q}{\mathrm{CDW}}$ and becomes overdamped within a finite momentum range already well above ${T}{\mathrm{CDW}}$. The dispersion anomaly is consistent with potential Fermi surface nesting, which together with the extended phonon collapse indicates strong electron-phonon coupling. The transition temperature estimated from the phonon softening is markedly lower than ${T}{\mathrm{CDW}}$, consistent with a primarily electronic instability rather than a phonon-driven transition. Our results establish ${\mathrm{UPt}}{2}{\mathrm{Si}}{2}$ as a prime example of a strongly correlated electron CDW system with exceptionally strong electron-phonon coupling driving phonon softening and collapse.
Phys. Rev. Lett. 135, 036705 (2025)
Charge density waves, Phonons, Strongly correlated systems, X-ray scattering
Ground States of the Mean-Field Spin Glass with 3-Spin Couplings
Research article | Optimization problems | 2025-07-18 06:00 EDT
Stefan Boettcher and Ginger E. Lau
We use heuristic optimization methods in extensive computations to determine with low systematic error ground-state configurations of the mean-field $p$-spin glass model with $p=3$. Here, all possible triplets in a system of $N$ Ising spins are connected with a bond. This model has been of recent interest, since it exhibits the ‘’overlap gap condition,’’ which should make it prohibitive to find ground states asymptotically with local search methods when compared, for instance, with the $p=2$ case better known as the Sherrington-Kirkpatrick model (SKM). Indeed, it proves more costly to find good approximations for $p=3$ than for the SKM, even for our heuristic. Compared to the SKM, the ground-state behavior for $p=3$ is quite distinct also in other ways. For the SKM, finite-size corrections for large system sizes $N\rightarrow \infty $, of both the ensemble average over ground-state energy densities and the width of their distribution, vary anomalously with noninteger exponents. In the $p=3$ case here, the energy density and its distribution appear to scale with $\mathrm{ln}N/N$ and $1/N$ corrections, respectively. The distribution itself is consistent with a Gumbel form. Even more stark is the contrast for the bond-diluted case, where the SKM has shown previously a notable variation of the anomalous corrections exponent with the bond density, while for $p=3$ no such variation is found here. Hence, for the 3-spin model, all measured corrections scale the same as for the random energy model (REM), corresponding to $p=\infty $. This would suggest that all $p$-spin models with $p\ge 3$ exhibit the same ground-state corrections as in the REM.
Phys. Rev. Lett. 135, 037402 (2025)
Optimization problems, Artificial neural networks, Disordered systems, Spin glasses
Physical Review X
Reconstructing the Wave Function of Magnetic Topological Insulators ${\mathrm{MnBi}}{2}{\mathrm{Te}}{4}$ and ${\mathrm{MnBi}}{4}{\mathrm{Te}}{7}$ Using Spin-Resolved Photoemission
Research article | Electronic structure | 2025-07-18 06:00 EDT
Xue Han, Jason Qu, Hengxin Tan, Zicheng Tao, Noah M. Meyer, Patrick S. Kirchmann, Yanfeng Guo, Binghai Yan, Zhi-Xun Shen, and Jonathan A. Sobota
A new way to reconstruct electron wave functions reveals how electron spin and orbital angular momenta combine to influence the exotic low-temperature behavior of magnetic topological insulators.
Phys. Rev. X 15, 031022 (2025)
Electronic structure, Spin-orbit coupling, Surface states, Topological materials, Antiferromagnets, Topological insulators, Angle-resolved photoemission spectroscopy, Spin-resolved photoemission spectroscopy
arXiv
Impact of electronic correlations on the superconductivity of high-pressure CeH9
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-18 20:00 EDT
Siyu Chen, Yao Wei, Bartomeu Monserrat, Jan M. Tomczak, Samuel Poncé
Rare-earth superhydrides have attracted considerable attention because of their high critical superconducting temperature under extreme pressures. They are known to have localized valence electrons, implying strong electronic correlations. However, such many-body effects are rarely included in first-principles studies of rare-earth superhydrides because of the complexity of their high-pressure phases. In this work, we use a combined density functional theory and dynamical mean-field theory approach to study both electrons and phonons in the prototypical rare-earth superhydride CeH$ _9$ , shedding light on the impact of electronic correlations on its critical temperature for phonon-mediated superconductivity. Our findings indicate that electronic correlations result in a larger electronic density at the Fermi level, a bigger superconducting gap, and softer vibrational modes associated with hydrogen atoms. Together, the inclusion of these correlation signatures increases the Migdal-Eliashberg superconducting critical temperature from 47 K to 96 K, close to the measured 95 K. Our results reconcile experimental observations and theoretical predictions for CeH$ _9$ and herald a path towards the quantitative modeling of phonon-mediated superconductivity for interacting electron systems.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 4 figures
Projective Representations, Bogomolov Multiplier, and Their Applications in Physics
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Ryohei Kobayashi, Haruki Watanabe
We present a pedagogical review of projective representations of finite groups and their physical applications in quantum many-body systems. Some of our physical results are new. We begin with a self-contained introduction to projective representations, highlighting the role of group cohomology, representation theory, and classification of irreducible projective representations. We then focus on a special subset of cohomology classes, known as the Bogomolov multiplier, which consists of cocycles that are symmetric on commuting pairs but remain nontrivial in group cohomology. Such cocycles have important physical implications: they characterize (1+1)D SPT phases that cannot be detected by string order parameters and give rise, upon gauging, to distinct gapped phases with completely broken non-invertible $ \mathrm{Rep}(G)$ symmetry. We construct explicit lattice models for these phases and demonstrate how they are distinguished by the fusion rules of local order parameters. We show that a pair of completely broken $ \mathrm{Rep}(G)$ SSB phases host nontrivial interface modes at their domain walls. As an example, we construct a lattice model where the ground state degeneracy on a ring increases from 32 without interfaces to 56 with interfaces.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th), Quantum Physics (quant-ph)
32 pages, 5 figures
Self-learning Monte Carlo Method: A Review
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Gaopei Pan, Chuang Chen, Zi Yang Meng
The Self-Learning Monte Carlo (SLMC) method is a Monte Carlo approach that has emerged in recent years by integrating concepts from machine learning with conventional Monte Carlo techniques. Designed to accelerate the numerical study of interacting many-body systems, SLMC significantly improves sampling efficiency by constructing an effective model – via machine learning methods – based on configurations generated by conventional Monte Carlo methods and then proposes global updates based on the effective model. This enhancement leads to a substantial reduction in autocorrelation time, especially near the critical region, where traditional methods typically suffer from critical slowing down and increased computation complexity. Moreover, SLMC maintains statistical accuracy by implementing a cumulative update scheme that rigorously satisfies the detailed balance condition. And more recent applications have extended the SLMC to convolutional neural networks with applications not only in condensed matter physics but also high-energy physics, quantum chemistry, and quantum simulations. The generic applicability and high computational efficiency make SLMC a powerful and scalable framework for quantum Monte Carlo simulations of strongly correlated electron systems, extending the reach of numerical investigations beyond the limitations of conventional techniques.
Strongly Correlated Electrons (cond-mat.str-el)
22 pages,10 figures, invited book chapter
Kinetics of Vacancy-Assisted Reversible Phase Transition in Monolayer MoTe$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Fei Shuang, Daniel Ocampo, Reza Namakian, Arman Ghasemi, Poulumi Dey, Wei Gao
We investigate the kinetics of phase transition between the 2H and 1T$ ^\prime$ phases in monolayer MoTe$ _2$ using atomistic simulations based on a machine learning interatomic potential trained on SCAN-DFT data, combined with mean field kinetic theory to interpret the underlying mechanisms. The transition is found to involve both diffusive and diffusionless mechanisms. Nucleation of 1T$ ^\prime$ phase is initiated by the coalescence of neighboring Te monovacancies into divacancies, which are found to be mobile and can interact with other Te vacancies to form small triangular 1T$ ^\prime$ islands. Growth of these islands proceeds either by incorporating pre-existing vacancies at the phase boundaries or, in their absence, by absorbing divacancies that migrate from the surrounding lattice. Once a critical island size is reached, vacancy-free growth becomes possible although with a higher activation barrier. Upon removal of external stimuli, the system reverts to 2H phase, during which Te vacancies reorganize into three-fold spoke-like vacancy lines at the island center. This reverse process and the subsequent 1T$ ^\prime$ \leftrightarrow$ 2H reversible transitions are diffusionless, rapid, do not require additional vacancies and can be driven by mild external stimuli. Although our analysis focuses on strain-induced transitions, the kinetic mechanisms are expected to be generalizable to other types of stimuli.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Nonreciprocal magnetic-field-induced second harmonic generation of exciton polaritons in ZnSe
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
J. Mund, D. R. Yakovlev, A. Farenbruch, N. V. Siverin, M. A. Semina, M. M. Glazov, E. L. Ivchenko, M. Bayer
We report on the optical second harmonic generation (SHG) on the 1S exciton-polariton resonance in bulk ZnSe that is subject to an external magnetic field applied perpendicular to the light wave vector $ \mathbf k$ (Voigt geometry). For the symmetry allowed geometry with the $ \mathbf{k}\parallel[111]$ crystal axes, the nonreciprocal dependence of the SHG intensity on the magnetic field direction is found. It is explained by an interference of the crystallographic and magnetic-field-induced SHG signals. Relative phases of these signals are evaluated from the rotational anisotropy diagrams. Phenomenological and microscopic models of the effect are developed. To the best of our knowledge, this is the first experimental observation of the nonreciprocal SHG in semiconductor crystals, and the first one for exciton-polaritons.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Spin Polarization driven by Itinerant Orbital Angular Momentum in van der Waals Heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Luis M. Canonico, Jose H. García, Aron W. Cummings, Stephan Roche
We report on the possibility of manipulating magnetic materials by using itinerant orbital angular momentum to produce out-of-plane spin polarization in van der Waals heterostructures. Employing a real-space formulation of the OAM operator within linear response theory, we demonstrate that in low-symmetry transition-metal dichalcogenide (TMD) monolayers, such as 1$ T{}_d$ -MoTe2, the current-induced itinerant OAM exceeds the spin response by three orders of magnitude. When TMDs are coupled with ferromagnets with negligible intrinsic orbital responses, the itinerant OAM generated by the orbital Rashba-Edelstein effect transfers across the interface, generating spin densities capable of inducing magnetization dynamics inside the ferromagnet. Our findings highlight the previously overlooked role of itinerant OAM in the generation of out-of-plane spin densities, which serves as an emerging mechanism for efficient electrical control of magnetization in low-power, ultracompact storage devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Anisotropic Multi-Q Order in CoxTaS2
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Jonathon Kruppe, Josue Rodriguez, Catherine Xu, James Analytis, Joseph Orenstein, Veronika Sunko
The cobalt-intercalated transition metal dichalcogenide Co$ _x$ TaS$ _2$ hosts a rich landscape of magnetic phases that depend sensitively on $ x$ . While the stoichiometric compound with $ x=1/3$ exhibits a single magnetic transition, samples with $ x\leq 0.325$ display two transitions with an anomalous Hall effect (AHE) emerging in the lower temperature phase. Here, we resolve the spin structure in each phase by employing a suite of magneto-optical probes that include the discovery of anomalous magneto-birefringence – a spontaneous time-reversal sensitive rotation of the principal optic axes. A symmetry-based analysis identifies the AHE-active phase as an anisotropic (2+1)\textbf{Q} state, in which magnetic modulation at one wavevector (\textbf{Q}) differs in symmetry from that at the remaining two. The (2+1)\textbf{Q} state naturally exhibits scalar spin chirality as a mechanism for the AHE and expands the classification of multi-Q magnetic phases.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Quenched Disorder in the Triangular Lattice Antiferromagnet YbZn$_2$GaO$_5$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Leshan Zhao, Tong Chen, Matthew B. Stone, Qiang Zhang, Colin L. Sarkis, S. M. Koohpayeh, Collin Broholm
We investigate the crystal electric field (CEF) excitations of Yb$ ^{3+}$ ions in powder samples of the triangular-lattice rare-earth-based antiferromagnet YbZn$ _2$ GaO$ _5$ using inelastic neutron scattering (INS). Three CEF excitations from the ground-state Kramers doublet were observed, each exhibiting significant broadening beyond instrumental resolution. Combining temperature-dependent INS and neutron powder diffraction, we identify a significant static contribution to this broadening and attribute it to heterogeneous coordination of Yb$ ^{3+}$ ions due to Ga$ ^{3+}$ /Zn$ ^{2+}$ site mixing. Rietveld refinement of neutron powder diffraction indicates that 35% of Ga occupies the Zn site and 60% of Zn occupies the Ga site. We show with a point charge model for the CEF Hamiltonian that heterogeneous coordination of Yb$ ^{3+}$ ions leads to broadened CEF peaks. First-principles calculations demonstrate that the random Ga$ ^{3+}$ /Zn$ ^{2+}$ distribution can produce the distortions of the YbO$ _6$ octahedra observed from neutron diffraction. Because the documented heterogeneity will extend to exchange interactions, our results suggest that disorder is a significant factor in the unusual magnetism previously reported in YbZn$ _2$ GaO$ _5$ , including broad low-energy magnetic excitations and the absence of magnetic ordering down to 0.3K.
Strongly Correlated Electrons (cond-mat.str-el)
Defect Interactions Through Periodic Boundaries in Two-Dimensional $p$-atics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Periodic boundary conditions are a common tool used to emulate effectively infinite domains. However, two-dimensional periodic domains are topologically distinct from the infinite plane, eliciting the question: How do periodic boundaries affect systems with topological properties themselves? In this work, I derive an analytical expression for the orientation fields of two-dimensional $ p$ -atic liquid crystals, systems with $ p$ -fold rotational symmetry, with topological defects in a flat domain subject to periodic boundary conditions in two-dimensions. I show that this orientation field leads to an anomalous interaction between defects that deviates from the usual Coulomb interaction, which is confirmed through continuum simulations of nematic liquid crystals ($ p = 2$ ). The interaction is understood as being mediated by non-singular topological solitons in the director field which are stabilized by the periodic boundary conditions. The results show the importance of considering domain topology, not only geometry, when analyzing interactions between topological defects.
Soft Condensed Matter (cond-mat.soft)
7 + 16 pages, 4 + 4 figures
Suppression of Thermal Conductivity via Singlet-Dominated Scattering in TmFeO$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
M. L. McLanahan, D. Lederman, A. P. Ramirez
We measured the thermal conductivity of the rare-earth orthoferrites, $ R$ FeO$ _3$ , where $ R$ = Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb and see an anomalous strong suppression for TmFeO$ _3$ . Using a Debye thermal transport model, we demonstrate that this suppression is due to resonant scattering between phonons and the Tm$ ^{3+}$ $ 4f$ singlet crystal field levels. The implications of these results are discussed in context of thermal conductivity studies in quantum magnets.
Materials Science (cond-mat.mtrl-sci)
Manuscript: 17 pages, 3 figures, 1 table; Supplemental: 6 pages, 5 figures, 1 table
Low-energy domain wall racetracks with multiferroic topologies
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Arundhati Ghosal, Alexander Qualls, Yousra Nahas, Shashank Ojha, Peter Meisenheimer, Shiyu Zhou, Maya Ramesh, Sajid Husain, Julia Mundy, Darrell Schlom, Zhi Yao, Sergei Prokhorenko, Laurent Bellaiche, Ramamoorthy Ramesh, Paul Stevenson, Lucas Caretta
Conventional racetrack memories move information by pushing magnetic domain walls or other spin textures with spin-polarized currents, but the accompanying Joule heating inflates their energy budget and can hamper scaling. Here we present a voltage-controlled, magnetoelectric racetrack in which transverse electric fields translate coupled ferroelectric-antiferromagnetic walls along BiFeO3 nanostrips at room temperature. Because no charge traverses the track, the switching dissipates orders of magnitude less energy than the most efficient spin-torque devices with more favourable scaling, making the scheme significantly more attractive at the nanoscale. We further uncover noncollinear topological magnetoelectric textures that emerge at domain walls in BiFeO3, where the nature of these topologies influences their stability upon translation. Among these are polar bi-merons and polar vertices magnetoelectrically coupled with magnetic cycloid disclinations and previously unobserved, topological magnetic cycloid twist topologies. We observe domain wall velocities of at least kilometres per second - matching or surpassing the fastest ferrimagnetic and antiferromagnetic racetracks and approaching the acoustic-phonon limit of BiFeO3 - while preserving these topologies over tens of micrometres. The resulting high velocity, low-energy racetrack delivers nanosecond access times without the thermal overhead of current-driven schemes, charting a path toward dense, ultralow-power racetrack devices which rely on spin texture translation.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Spin relaxation in a polariton fluid: quantum hydrodynamic approach
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
D. A. Saltykova, A. V. Yulin, I. A. Shelykh
Cavity polaritons, the elementary excitations appearing in quantum microcavities in the strong-coupling regime, reveal clear signatures of quantum collective behavior. The combination of unique spin structure and strong nonlinear response opens the possibility of direct experimental observation of a plethora of nontrivial optical polarization phenomena. Spin relaxation processes are of crucial importance here. However, a mathematical formalism for their coherent description is still absent. In the present paper, based on the quantum hydrodynamics approach for a two-component liquid, we derive the set of the corresponding equations where both energy and spin relaxation terms appear naturally. We analyze in detail how these terms affect the dynamics of spinor polariton droplets in the external magnetic field and the dispersion of elementary excitations of a uniform polariton condensate. Although we focus on the case of cavity polaritons, our approach can be applied to other cases of spinor bosonic condensates, where the processes of spin relaxation play a major role.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Pattern Formation and Solitons (nlin.PS), Quantum Physics (quant-ph)
12 pages + 15 pages of Supplementary Materials
Enhancement of Indistinguishable Photon Emission from a GaAs Quantum Dot via Charge Noise Suppression
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Priyabrata Mudi, Avijit Barua, Kartik Gaur, Steffen Wilksen, Alexander Steinhoff, Setthanat Wijitpatima, Sarthak Tripathi, Julian Ritzmann, Andreas D. Wieck, Sven Rodt, Christopher Gies, Arne Ludwig, Stephan Reitzenstein
The generation of indistinguishable single photons is a fundamental requirement for future quantum technologies, particularly in quantum repeater networks and for distributed quantum computing based on entanglement distribution. However, spectral jitter, often induced by charge noise in epitaxial quantum dots, leads to exciton dephasing, thereby limiting their practical usage in quantum applications. We present a straightforward approach to mitigate charge noise-induced decoherence in droplet-etched GaAs quantum dots embedded in an n-i-p diode structure and integrated deterministically into an electrically contacted circular Bragg grating resonator for emission enhancement. The quantum device allows for the stabilization of the charge environment by applying an external electrical field while producing a photon extraction efficiency of approximately (37 +- 2)%. Hong-Ou-Mandel two-photon interference measurements reveal a strong voltage dependence of the exciton dephasing time and interference visibility on the applied bias in excellent agreement with our theoretical predictions. Notably, the reduction in visibility from a maximum, charge-stabilized corrected value of 97 percent at the optimum bias point follows an inverse square dependence (proportional to 1/I^2) with increasing diode current (I) in forward direction. Under a quasi-resonant excitation scheme, we achieve a maximum exciton dephasing time (T2\ast) of approximately (6.8 +-0.5) ns, reaching nearly the Fourier limit (T2 = 2T1) without the need for complex echo schemes like Ramsey or Carr-Purcell-Meiboom-Gill sequences. These findings are consistent with theoretical predictions from rate equation modeling and quantum optical analysis as well as voltage-dependent linewidth measurements, demonstrating optimized electrical control of exciton dephasing.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Walking on Archimedean Lattices: Insights from Bloch Band Theory
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-18 20:00 EDT
Davidson Noby Joseph, Igor Boettcher
Returning walks on a lattice are sequences of moves that start at a given lattice site and return to the same site after $ n$ steps. Determining the total number of returning walks of a given length $ n$ is a typical graph-theoretical problem with connections to lattice models in statistical and condensed matter physics. We derive analytical expressions for the returning walk numbers on the eleven two-dimensional Archimedean lattices by developing a connection to the theory of Bloch energy bands. We benchmark our results through an alternative method that relies on computing the moments of adjacency matrices of large graphs, whose construction we explain explicitly. As a condensed matter physics application, we use our formulas to compute the density of states of tight-binding models on the Archimedean lattices. While the Archimedean lattices provide a sufficiently rich structure and are chosen here for concreteness, our techniques can be generalized straightforwardly to other two- or higher-dimensional Euclidean lattices.
Statistical Mechanics (cond-mat.stat-mech), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph)
27 pages
A Physics-Informed Data-Driven Discovery for Constitutive Modeling of Compressible, Nonlinear, History-Dependent Soft Materials under Multiaxial Cyclic Loading
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Alireza Ostadrahimi, Amir Teimouri, Kshitiz Upadhyay, Guoqiang Li
We propose a general hybrid physics-informed machine learning framework for modeling nonlinear, history-dependent viscoelastic behavior under multiaxial cyclic loading. The approach is built on a generalized internal state variable-based visco-hyperelastic constitutive formulation, where stress is decomposed into volumetric, isochoric hyperelastic, and isochoric viscoelastic components. Gaussian Process Regression (GPR) models the equilibrium response, while Recurrent Neural Networks (RNNs) with Long Short-Term Memory (LSTM) units capture time-dependent viscoelastic effects. Physical constraints, including objectivity, material symmetry, and thermodynamic consistency, are enforced to ensure physically valid predictions. After developing the general form of the surrogate model based on tensor integrity bases and response functions, we employed the nonlinear Holzapfel differential viscoelastic model to generate training data. Two datasets, one for short-term and another for long-term relaxation, are constructed to span a wide range of material memory characteristics. The model is trained and tested under diverse multiaxial loading conditions, including different stretch levels applied independently in the longitudinal and transverse directions, varying strain rates, and both tension and compression states, even beyond the training domain. Energy dissipation is explicitly analyzed at different strain rates for both datasets to verify thermodynamic consistency through the second law. The results show that the proposed framework accurately captures complex, nonlinear, and rate-dependent material responses. Moreover, it demonstrates strong robustness to synthetic noise, enabling generalizable and physically consistent predictions under realistic and variable loading scenarios.
Soft Condensed Matter (cond-mat.soft)
Extreme Thermal Insulation in Nano-Bubble Wrap Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Amalya C. Johnson, Sorren Warkander, Archana Raja, Fang Liu
Achieving ultra-low thermal conductivity under ambient conditions is a fundamental challenge constrained by classical heat transport limits and material design trade-offs. Here, we introduce a new class of nano-bubble wrap architectures that achieve exceptionally low thermal conductivity by integrating nanoscale gas confinement with atomically thin, weakly coupled van der Waals solids. Using scalable patterning of 2D monolayers into periodic nano-bubbles and nano-wrinkles, we construct materials with structural analogies to macroscopic bubble wrap but engineered at length scales much shorter than the mean free path of air and the mean free path of phonons in the atomically thin monolayers. Time-domain thermoreflectance measurements reveal out-of-plane thermal conductivities nearly an order of magnitude lower than that of air and commercial aerogels, reaching critical values below 0.001 W $ \cdot$ M$ ^{-1}$ K$ ^{-1}$ under room temperature and atmospheric pressure. This extreme thermal resistance arises from the combined suppression of gas-phase conduction, phonon transport, and interfacial coupling. Our findings establish nano-bubble wraps as a versatile platform for tuning heat flow in ultrathin materials and open new pathways for designing thermal metamaterials and energy-efficient technologies.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Stress Softening Damage in Strongly Nonlinear Viscoelastic Soft Materials A Physics Informed Data Driven Constitutive Model with Time Temperature Coupling
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Alireza Ostadrahimi, Amir Teimouri, Kshitiz Upadhyay, Guoqiang Li
This study presents a novel physics informed, data-driven modeling framework for capturing the strongly nonlinear thermo-viscoelastic behavior of soft materials exhibiting stress softening, with emphasis on the Mullins effect. Unlike previous approaches limited to quasi-static or isothermal conditions, our model unifies rate dependence, temperature sensitivity, large strain cyclic loading, and evolving damage mechanisms. Thermodynamic admissibility is ensured via a custom loss function that embeds the Clausius Duhem inequality and explicitly constrains the damage variable for physically realistic softening. A Temporal Convolutional Network is trained on high fidelity experimental data across multiple temperatures, strain rates, and stretch levels, enabling the model to capture rich thermomechanical coupling and history dependence. The framework generalizes to unseen thermo mechanical conditions, higher strain rates, and larger deformations, and remains robust to input noise. Validation against finite element simulations using Abaqus/Explicit demonstrates excellent agreement under cyclic loading and damage evolution, confirming the surrogate models effectiveness for advanced simulation workflows.
Soft Condensed Matter (cond-mat.soft)
Scalable tensor network algorithm for quantum impurity problems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Zhijie Sun, Ruofan Chen, Zhenyu Li, Chu Guo
The Grassmann time-evolving matrix product operator method has shown great potential as a general-purpose quantum impurity solver, as its numerical errors can be well-controlled and it is flexible to be applied on both the imaginary- and real-time axis. However, a major limitation of it is that its computational cost grows exponentially with the number of impurity flavors. In this work, we propose a multi-flavor extension of it to overcome this limitation. The key insight is that to calculate multi-time correlation functions on one or a few impurity flavors, one could integrate out the degrees of freedom of the rest flavors before hand, which could greatly simplify the calculation. The idea is particularly effective for quantum impurity problems with diagonal hybridization function, i.e., each impurity flavor is coupled to an independent bath, a setting which is commonly used in the field. We demonstrate the accuracy and scalability of our method for the imaginary time evolution of impurity problems with up to three impurity orbitals, i.e., 6 flavors, and benchmark our results against continuous-time quantum Monte Carlo calculations. Our method paves the way of scaling up tensor network algorithms to solve large-scale quantum impurity problems.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
8 pages, 6 figures
Collinear Antiferromagnetic Tunnel Junctions Implemented in Van der Waals Heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Wei-Min Zhao, Yi-Lun Liu, Liu Yang, Cheng Tan, Yuanjun Yang, Zhifeng Zhu, Meixia Chen, Tingting Yan, Rong Hu, James Partridge, Guopeng Wang, Mingliang Tian, Ding-Fu Shao, Lan Wang
Magnetic tunnel junctions (MTJs) are crucial components in high-performance spintronic devices. Traditional MTJs rely on ferromagnetic (FM) materials but significant improvements in speed and packing density could be enabled by exploiting antiferromagnetic (AFM) compounds instead. Here, we report all-collinear AFM tunnel junctions (AFMTJs) fabricated with van der Waals A-type AFM metal (Fe0.6Co0.4)5GeTe2 (FCGT) electrodes and nonmagnetic semiconducting WSe2 tunnel barriers. The AFMTJ heterostructure device achieves a tunneling magnetoresistance (TMR) ratio of up to 75% in response to magnetic field switching. Our results demonstrate that the TMR exclusively emerges in the AFM state of FCGT, rather than during the AFM-to-FM transition. By engineering FCGT electrodes with either even- or odd-layer configurations, volatile or non-volatile TMR could be selected, consistent with an entirely interfacial effect. TMR in the even-layer devices arose by Néel vector switching. In the odd-layer devices, TMR stemmed from interfacial spin-flipping. Experimental and theoretical analyses reveal a new TMR mechanism associated with interface-driven spin-polarized transport, despite the spin-independent nature of bulk FCGT. Our work demonstrates that all-collinear AFMTJs can provide comparable performance to conventional MTJs and introduces a new paradigm for AFM spintronics, in which the spin-dependent properties of AFM interfaces are harnessed.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Under review, submitted on March 6th, 2025
Hyperuniformity near jamming transition over a wide range of bidispersity
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Duc T. Dam, Takeshi Kawasaki, Atsushi Ikeda, Kunimasa Miyazaki
We numerically investigate hyperuniformity in two-dimensional frictionless jammed packings of bidisperse systems. Hyperuniformity is characterized by the suppression of density fluctuations at large length scales, and the structure factor asymptotically vanishes in the small-wavenumber limit as $ S(q) \propto q^{\alpha}$ , where $ \alpha > 0$ . It is well known that jammed configurations exhibit hyperuniformity over a wide range of wavenumbers windows, down to $ q^{\ast}\sigma \approx 0.2$ , where $ \sigma$ is the particle diameter. In two dimensions, we find that the exponent $ \alpha$ is approximately $ 0.6\text{–}0.7$ . This contrasts with the reported value of $ \alpha = 1$ for three-dimensional systems. We employ an advanced method recently introduced by Rissone \textit{et al.} \href{this https URL}{[Phys. Rev. Lett. {\bf 127}, 038001 (2021)]}, originally developed for monodisperse and three-dimensional systems, to determine $ \alpha$ with high precision. This exponent is found to be unchanged for all size ratios between small and large particles, except in the monodisperse case, where the system crystallizes.
Soft Condensed Matter (cond-mat.soft)
11 pages, 9 figures
Probing nontrivial fusion of Majorana zero modes via near-adiabatic coupling
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Jing Bai, Luting Xu, Wei Feng, Xin-Qi Li
We propose and simulate a near-adiabatically coupling probing scheme for nontrivial fusion of a pair of Majorara zero modes (MZMs). The scheme can avoid the complexity of oscillating charge occupation in the probing quantum dot, making thus practical measurements more feasible. We also show how to extract the information of nonadiabatic transition and fermion parity violation caused during moving the MZMs together to fuse, from the initial states prepared with definite fermion parity. All the simulations, including the effective coupling between the fusing MZMs, and their coupling to the probing quantum dot, are based on the lattice model of a Rashba quantum wire in proximity contact with an s-wave superconductor, under the modulation of mini-gate voltage control.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 6 figures
EPL 151, 16004 (2025)
Cryogenic magnetization dynamics in tensile-strained ultrathin yttrium iron garnets with tunable magnetic anisotropy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Jihyung Kim, Dongchang Kim, Seung-Gi Lee, Yung-Cheng Li, Jae-Chun Jeon, Jiho Yoon, Sachio Komori, Ryotaro Arkakwa, Tomoyasu Taniyama, Stuart S. P. Parkin, Kun-Rok Jeon
We report a significant reduction of low-temperature damping losses in tensile-strained, ultrathin Y3Fe5O12 (YIG) films grown by pulsed laser deposition, exhibiting ultralow damping constants and tunable magnetic anisotropy. Comparative broadband FMR measurements show that tensile-strained YIG films on Gd3Sc2Ga3O12 (GSGG) retain low damping even at nanometer thicknesses and cryogenic temperatures, outperforming relaxed films on Gd3Ga5O12. Based on static magnetometry measurements and microstructural characterization, we attribute these enhanced dynamic properties to the suppression of interdiffusion across the YIG/GSGG interface, resulting from enhanced chemical stability and favorable growth kinetics by the presence of Sc. Our findings highlight the importance of chemical and kinetic factors in achieving few-nanometer-thick YIG film with negligible low-temperature damping dissipation and perpendicular magnetic anisotropy for cryogenic spintronic applications.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
18 pages, 5 figures
Spin-reorientation Driven Temperature Dependent Intrinsic Anomalous Hall Conductivity in Fe$_3$Ge, a Ferromagnetic Topological Metal
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Susanta Ghosh, Tushar Kanti Bhowmik, Achintya Low, Setti Thirupathaiah
We investigate the temperature dependence of the intrinsic anomalous Hall conductivity in Fe$ 3$ Ge, which is a ferromagnetic topological metal. We observe a significant anisotropy in the anomalous Hall conductivity between in-plane and out-of-plane directions. We further identify that the total Hall conductivity is contributed extrinsically due to the skew-scattering mechanism and intrinsically due to nonzero Berry curvature in the momentum space. Most importantly, we demonstrate the temperature dependence of the intrinsic Hall contribution, a rare phenomenon to visualize experimentally, due to tuning the easy-magnetic axis from the out-of-plane to the in-plane with decreasing temperature. We also show that the extrinsic Hall conductivity decreases with temperature as $ \sigma{xy}^{ext}(T)=\frac{\sigma_{xy0}^{ext}}{(aT+1)^2}$ due to electron-phonon scattering.
Materials Science (cond-mat.mtrl-sci)
9 pages, 8 figures, Accepted for Publication in Phys. Rev. Materials
Three-dimensional spinless Euler insulators with rotational symmetry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Manabu Sato, Shingo Kobayashi, Motoaki Hirayama, Akira Furusaki
The Euler class is a $ \mathbb{Z}$ -valued topological invariant that characterizes a pair of real bands in a two-dimensional Brillouin zone. One of the symmetries that permits its definition is $ C_{2z}T$ , where $ C_{2z}$ denotes a twofold rotation about the $ z$ axis and $ T$ denotes time-reversal symmetry. Here, we study three-dimensional spinless insulators characterized by the Euler class, focusing on the case where additional $ C_{4z}$ or $ C_{6z}$ rotational symmetry is present, and investigate the relationship between the Euler class of the occupied bands and their rotation eigenvalues. We first consider two-dimensional systems and clarify the transformation rules for the real Berry connection and curvature under point group operations, using the corresponding sewing matrices. Applying these rules to $ C_{4z}$ and $ C_{6z}$ operations, we obtain explicit formulas that relate the Euler class to the rotation eigenvalues at high-symmetry points. We then extend our analysis to three-dimensional systems, focusing on the difference in the Euler class between the two $ C_{2z}T$ -invariant planes. We derive analytic expressions that relate the difference in the Euler class to two types of representation-protected invariants and analyze their phase transitions. We further construct tight-binding models and perform numerical calculations to support our analysis and elucidate the bulk-boundary correspondence.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
20 pages, 11 figures
Structure determination of flat honeycomb Bi grown on Ag(111)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Ziyong Zhang, Xiaobin Chen, Takeshi Nakagawa
Honeycomb bismuthene structures on Ag(111) were investigated using low-energy electron diffraction (LEED) and density functional theory. LEED I(V) analysis revealed that 0.5 monolayer (ML) of Bi forms an ultraflat honeycomb lattice with negligible buckling at ~120 K, which transforms into other structures upon warming to room temperature. A similar flat bismuthene structure also forms in Mn/Bi/Ag(111), which remains stable even at room temperature. Mn deposition on $ (p\times \sqrt{3})$ -rect Bi/Ag(111) induces Bi surface segregation, as confirmed by X-ray photoelectron spectroscopy, resulting in a p$ (2\times2)$ honeycomb bismuthene. The detailed structural investigation provides fundamental insights into the characterization of two-dimensional topological properties of bismuthene grown on Ag(111).
Materials Science (cond-mat.mtrl-sci)
Coulomb-mediated single-electron heat transfer statistics across capacitively coupled silicon nanodots
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Kensaku Chida, Antoine Andrieux, Katsuhiko Nishiguchi
Heat transfer mediated by the Coulomb interaction reveals unconventional thermodynamic behavior and broadens thermodynamics research into fields such as quantum dynamics and information engineering. Although some experimental demonstrations of phenomena utilizing Coulomb-mediated heat transfer have been reported, estimations of their performance, such as efficiency, and their theoretical evaluations necessitate qualitative evaluation of the transfer mechanism itself, which remains challenging. We present an experiment investigating single-electron dynamics in two electrostatically coupled silicon nanodots to quantify Coulomb-mediated heat transfer at the nanoscale. By estimating the Coulomb interaction strength between the dots using the cross-correlation measurements of the single-electron dynamics, we convert the single-electron dynamics into the statistics of Coulomb-mediated heat transfer. Conducting the experiment at equilibrium enabled us to obtain a fluctuating net-zero heat transfer between the dots. These heat transfer statistics are essential for exploring device functionalities from the perspective of stochastic thermodynamics and for verifying universal relations in nonequilibrium states.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech)
13 pages, 5 figures
Spontaneous Rotation of a Symmetric Inclusion in Chiral Active Bath
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Abhra Puitandy, Shradha Mishra
We study the dynamics of a circular passive inclusion, termed a torquer, in a bath of chiral active Brownian particles. Despite being geometrically symmetric and non-motile, the torquer exhibits persistent rotation due to spatially inhomogeneous torques arising from angularly biased collisions with active particles. This interaction-driven symmetry breaking does not rely on shape anisotropy or external forcing. Through simulations, we identify two distinct regimes of rotation: one dominated by density gradients at low chirality, and another by increased impact frequency at high chirality. Our results highlight how nonequilibrium interactions in chiral active media can induce motion in symmetric objects, offering a new perspective on symmetry breaking in active systems.
Soft Condensed Matter (cond-mat.soft)
There are 9 pages and 7 figures
Quantum Mechanical Approach for Modeling of Ternary Based Strained-Layer Superlattice
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Ternary-based InAs/InAs1-xSbx Strained-Layer Superlattice (SLS)material with type-II band alignment belongs to the 6.1 A family with reasonably small lattice mismatch with GaSb substrate for epitaxial growth. InAs/InAs1-xSbx SLS have been proven to have more advantages such as longer carrier lifetime, better control on growth and manufacturability, and being considered as an alternative material system for infrared photodetectors. In this article a quantum mechanical based modelling on electronic band structure of InAs/InAs1-xSbx is presented. A modified sp3s\ast empirical tight binding method along with implementing a virtual crystal approximation with a bowing of the s-on-site tight-binding energy, were incorporated. In this approach, a theoretical explanation of atomic segregation in superlattices is suggested and used in calculations. The simulations show good agreement with experimentally measured band gap of InAs/InAs1-xSbx superlattices.
Materials Science (cond-mat.mtrl-sci)
Quantum geometrical bound relations for observables
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
The quantum geometric tensor (QGT) provides nontrivial bound relations among physical quantities, as exemplified by the metric-curvature inequality. In this paper, we investigate various bound relations for different observables through certain generalizations of the QGT. First, by generalizing the parameter space, we demonstrate that bound relations hold for all linear responses. As an application, we show the thermodynamic inequality originating from the convexity of free energy can be further tightened. Second, by extending the projection operator, we establish a bound relation between the Drude weight and the orbital magnetization. The equality is exactly satisfied in the Landau level system, and systems with nearly flat bands tend to approach equality as well. We apply the resulting inequality to two orbital ferromagnets and support that the twisted bilayer graphene system is close to the Landau level system. Moreover, we show that an analogous inequality also holds for a higher-order multipole, magnetic quadrupole. Finally, we discuss the analogy between the QGT and the uncertainty principle, emphasizing that the existence of nontrivial bound relations necessarily reflects quantum effects.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech)
Enhancement of Josephson Supercurrent and $π$-Junction by Chiral Antiferromagnetism
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-18 20:00 EDT
Jin-Xing Hou, Hai-Peng Sun, Björn Trauzettel, Song-Bo Zhang
Magnetic order typically disrupts superconductivity, reducing the supercurrent. Here, we show that chiral antiferromagnetism, with non-relativistic spin-split bands and distinctive valley-locked spin texture, can instead significantly enhance Josephson supercurrents. This enhancement stems from the emergence of dominant equal-spin triplet pairing and strong fluctuations of singlet pairing in momentum space, both induced by chiral antiferromagnetism. We demonstrate these results in Josephson junctions composed of chiral antiferromagnetic metals and conventional superconductors on kagome lattices. Furthermore, we show that the enhanced Josephson supercurrent is stabilized in a $ \pi$ -junction state. These phenomena persist across a broad energy range and remain stable for different temperatures and junction lengths. Our results unveil a previously unexplored mechanism for enhancing supercurrent by strong magnetic order and provide crucial insights into the large Josephson currents observed in Mn$ _3$ Ge.
Superconductivity (cond-mat.supr-con)
14 pages, 14 figures
Energy Dynamics of a Nonequilibrium Unitary Fermi Gas
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-18 20:00 EDT
Xiangchuan Yan, Jing Min, Dali Sun, Shi-Guo Peng, Xin Xie, Xizhi Wu, Kaijun Jiang
We investigate the energy dynamics of a unitary Fermi gas driven away from equilibrium. The energy is injected into the system by periodically modulating the trapping potential of a spherical unitary Fermi gas, and due to the existence of SO(2,1) symmetry, the breathing mode is excited without dissipation. Through the long-lived breathing oscillation, we precisely measure the energy evolution of the nonequilibrium system during the trap modulation. We find the trapping potential and internal energies increase with modulation time and simultaneously oscillate nearly $ \textrm{180}^{\textrm{o}}$ out of phase. At large modulation amplitudes, the energy-injection efficiency is strongly reduced due to the trap anharmonicity. Unlike the equilibrium system, the measured energy evolution agrees well with predictions of the dynamic virial theorem. Our work provides valuable insights into the energy injection and redistribution in a non-equilibrium system, paving a way for future investigations of nonequilibrium thermodynamics.
Quantum Gases (cond-mat.quant-gas), Atomic Physics (physics.atom-ph)
11 pages, 7 figures
Magnetoelectric multiferroics: from fundamentals to transformative applications – a mini review
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Multiferroics, combining ferroelectric and magnetic orders, enable magnetoelectric (ME) coupling for advanced applications. This mini review explores single-phase and composite multiferroics, examining phenomenological, microscopic, nanostruc-tured, and quantum mechanisms driving ME effects. Phenomenological models quantify coupling coefficients, while microscopic approaches reveal spin-lattice in-teractions, including frustrated spin states and Dzyaloshinskii-Moriya contributions. Nanostructured systems, such as plasmonic skyrmion lattices and metasurfaces, en-hance ME effects for tunable birefringence and electromagnon amplification. Quan-tum heat engines utilize spin entanglement and topological protection in chiral chains and skyrmion lattices for efficient energy conversion. Applications include high-sensitivity magnetic sensors, tunable radio-frequency devices, energy-efficient MERAM, energy harvesters, quantum heat engines, and thermal diodes. Future re-search aims to optimize room-temperature ME coupling, scalability, coherence, and biocompatibility for innovations in sensing, quantum computing, and sustainable energy.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
This mini review has been accepted for publication in Rzeszow University of Technology Physics for Economy
Chemical vapor deposition synthesis of (GeTe)n(Sb2Te3) gradient crystalline films as promising planar heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
M. Zhezhu, A. Vasil’ev, M. Yapryntsev, E. Ghalumyan, D.A. Ghazaryan, H. Gharagulyan
Phase-change materials of the (GeTe)n (Sb2Te3) (GST) system are of high relevance in memory storage and energy conversion applications due to their fast-switching speed, high data retention, and tunable properties. Here, we report on a fast and efficient CVD-based method for the fabrication of crystalline GST films with variable Ge/Sb atomic content. In particular, the approach enables compositional control without changing the precursor, facilitating a gradient synthesis of Ge3Sb2Te6, Ge2Sb2Te5, and GeSb2Te4 phases in a single attempt. The analyses of their structural, optical, and electrical aspects highlight how compositional variation influences the film’s properties. Our findings demonstrate a straightforward approach enabling the preparation of gradient crystalline GST films with tunable morphology and functionality. These gradient films can potentially provide in-plane multilevel and gradual switching thresholds for memory applications and altered refractive index and absorption for optical modulation and filtering applications.
Materials Science (cond-mat.mtrl-sci)
Banding and polarization in driven multistable materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
We study a disordered network of bistable bonds subjected to periodic strain. The model is inspired by experiments on crumpled sheets and it features behaviors associated with glasses, including a complex energy landscape, memories, and large avalanches. At small strain amplitudes, the system quickly converges to a limit cycle where the system repeatedly cycles between a set of states. At large amplitudes, motion is erratic and does not converge to a limit cycle. The transition appears to be continuous, with diverging time scales. The nature of instabilities is different on both sides of the transition. At small strain amplitudes, instabilities are correlated only over a finite distance. Above the transition, instabilities are localized along diagonal bands. The distance between bands grows near the transition and appears to diverge. We propose a simple model that explains these observations. Below the transition, we propose a new ``order parameter’’ – the polarization of the instabilities along the driving direction.
Soft Condensed Matter (cond-mat.soft), Disordered Systems and Neural Networks (cond-mat.dis-nn)
Machine learning many-body potentials for charged colloids in primitive 1:1 electrolytes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Thijs ter Rele, Gerardo Campos-Villalobos, René van Roij, Marjolein Dijkstra
Effective interactions between charged particles dispersed in an electrolyte are most commonly modeled using the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential, where the ions in the suspension are coarse-grained out at mean-field level. However, several experiments point to shortcomings of this theory, as the distribution of ions surrounding colloids is governed by nontrivial correlations in regimes of strong Coulomb coupling (e.g. low temperature, low dielectric constant, high ion valency, high surface charge). Insight can be gained by explicitly including the ions in simulations of these colloidal suspensions, even though direct simulations of dispersions of highly charged spheres are computationally demanding. To circumvent slow equilibration, we employ a machine-learning (ML) framework to generate ML potentials that accurately describe the effective colloid interactions. These ML potentials enable fast simulations and make large-scale simulations of charged colloids in suspension possible, opening the possibility for a systematic study of their phase behaviour, in particular gas-liquid and fluid-solid coexistence.
Soft Condensed Matter (cond-mat.soft)
13 pages, 7 figures
Disorder-induced spin excitation continuum and spin-glass ground state in the inverse spinel CuGa$_2$O$_4$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Zhentao Huang, Zhijun Xu, Shuaiwei Li, Qingchen Duan, Junbo Liao, Song Bao, Yanyan Shangguan, Bo Zhang, Hao Xu, Shufan Cheng, Zihang Song, Shuai Dong, Maofeng Wu, M. B. Stone, Yiming Qiu, Ruidan Zhong, Guangyong Xu, Zhen Ma, G. D. Gu, J. M. Tranquada, Jinsheng Wen
Spinel-structured compounds serve as prototypical examples of highly frustrated systems, and are promising candidates for realizing the long-sought quantum spin liquid (QSL) state. However, structural disorder is inevitable in many real QSL candidates and its impact remains a topic of intense debate. In this work, we conduct comprehensive investigations on CuGa$ 2$ O$ 4$ , a spinel compound with significant structural disorder, focusing on its thermodynamic properties and spectroscopic behaviors. No long-range magnetic order is observed down to $ \sim$ 80 mK, as evidenced by magnetic susceptibility, specific heat and elastic neutron scattering measurements. More intriguingly, inelastic neutron scattering experiments reveal a broad gapless continuum of magnetic excitations around the Brillouin zone boundary, resembling the magnetic excitation spectra expected for a QSL. Nevertheless, a spin-freezing transition at $ T{\rm{f}} \approx $ 0.88 K is identified from the cusp in the dc susceptibility curves, where a bifurcation between zero-field-cooling and field-cooling curves occurs. Furthermore, ac susceptibility measurements show a peak close to $ T{\rm{f}}$ at low frequency, which shifts to higher temperature with increasing frequency. These results are evident that CuGa$ _2$ O$ _4$ has spin-glass ground state, consistent with the establishment of short-range order inferred from the specific heat measurements. Collectively, these results illustrate the crucial role of disorder in defining the excitation spectrum out of the disordered ground state. Our findings shed light onto the broader class of AB$ _2$ O$ _4$ spinels and advance our understanding of the spin dynamics in magnetically disordered systems.
Strongly Correlated Electrons (cond-mat.str-el)
Published in PRB, 11 pages, 5 figures
Phys. Rev. B 112, 035128 (2025)
Weyl nodes in CeRu$_4$Sn$_6$ studied by dynamical mean-field theory
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Jorūnas Dobilas, Martin Brass, Frank T. Ebel, Silke Pasche, Karsten Held
The heavy fermion compound CeRu$ _4$ Sn$ _6$ has recently shown to exhibit a spontaneous nonlinear Hall effect, indicating its topological nature. This is consistent with the lack of inversion symmetry that allows for the existence of Weyl nodes. Here, we employ density functional theory plus dynamical mean-field theory, which is state-of-the-art for such correlated materials, and study the topology of CeRu$ _4$ Sn$ _6$ . We find five inequivalent Weyl nodes of either type I or II, each having sixteen symmetry-related replicas. These Weyl nodes bridge the Kondo insulating gap, which is a direct but not an indirect gap. The closest Weyl points is only 0.5meV below the Fermi energy, and has a flat energy-momentum dispersion
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 9 figures
Magnetic Triple-q State in Antiferromagnetic Monolayer Interfaced with Bismuthene
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Chia-Ju Chen, Yu-Tung Lin, Chieh-Lin Lee, Nitin Kumar, Hung-Chin Lee, Yen-Hui Lin, Bo-Yao Wang, Stefan Bluegel, Gustav Bihlmayer, Pin-Jui Hsu
We have successfully fabricated the bismuthene covered Mn monolayer on Ag(111) by evaporating Mn atoms onto (pxroot3)-Bi/Ag(111) at room temperature. By using spin-polarized scanning tunneling microscopy (SP-STM), we have resolved the magnetic triple-q (3Q) state. In combination with density-functional theory (DFT) calculations, the 3Q3-like spin texture is the magnetic ground state for the bismuthene covered Mn monolayer/Ag(111). Interestingly, the uniaxial magnetic anisotropy of 3Q3 state triggered by the bismuthene on top of Mn monolayer/Ag(111) has been revealed, which is consistent with the switching of 3Q3up and 3Q3down domains observed by SP-STM measurements with external magnetic fields.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Laser-Induced Topological Toggle Switching at Room Temperature in the van der Waals Ferromagnet \ce{Fe3GaTe2}
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Charlie W. F. Freeman, Woohyun Cho, Paul S. Keatley, PeiYu Cai, Elton J. G. Santos, Robert J. Hicken, H. Yang, Hidekazu Kurebayashi, Murat Cubukcu, Maciej Dabrowski
We demonstrate room-temperature nucleation and manipulation of topological spin textures in the van der Waals (vdW) ferromagnet, Fe3GaTe2, through laser pulse excitation. By leveraging laser-induced heating and subsequent cooling, we access the skyrmion/bubble state at low fields and achieve toggle switching between two topological spin textures - skyrmion/bubble and labyrinth. Micromagnetic simulations reveal that this switching behaviour arises from laser-induced heating and cooling. Our findings highlight the potential of vdW ferromagnets for room temperature laser-controlled non-volatile memory storage applications.
Materials Science (cond-mat.mtrl-sci)
Harmonic generation of graphene quantum dots in Hartree-Fock approximation
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Kainan Chang, Ying Song, Yuwei Shan, Jin Luo Cheng
We theoretically investigate harmonic generation in graphene quantum dots under linearly polarized optical pulses, focusing on excitonic effects. Combining the tight-binding model and the single-particle density matrix approach, we derive a semiconductor Bloch equation under a static-screened Hartree-Fock approximation. This framework characterizes the electron-electron interaction through local Hartree potentials for direct Coulomb interaction and nonlocal Fock potentials for exchange interaction. Distinct confgurations of Hartree and Fock terms yield various approximation methods, including independent-particle approximation, mean-feld approximation, random phase approximation, and excitonic effects. We thoroughly analyze how these approximation methods affect the electronic energy levels, linear optical absorption, and nonlinear harmonic generation. Within excitonic effects, we present the dependence of harmonic generation on the geometric variations of graphene quantum dots (sizes, triangular/hexagonal shapes, and armchair/zigzag edges) and the amplitude and polarization of electric fields. Our findings show that excitonic effects significantly enhance optical responses of graphene nanostructures. For a dot ensemble formed by randomly oriented graphene quantum dots,
only odd-order harmonics exist along the polarization direction of the incident light. Crucially, harmonic generation in graphene quantum dots exhibits high tunability via geometric configuration, making them promising candidates for nonlinear optical nanodevices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
Enhanced Phonon-Assisted Tunneling in Metal – Twisted Bilayer Graphene Junctions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Radhika Soni, Suvronil Datta, Robin Bajaj, Saisab Bhowmik, Shinjan Mandal, Baladitya Suri, Kenji Watanabe, Takashi Taniguchi, Manish Jain, U. Chandni
We report planar tunneling spectroscopy measurements on metal-WSe$ _2$ -twisted bilayer graphene heterostructures across a broad range of gate and bias voltages. The observed experimental features are attributed to phonon-assisted tunneling and the significantly high density of states within the moiré bands. A notable finding is the enhanced phonon-assisted tunneling in twisted bilayer graphene compared to Bernal bilayer graphene, which arises from a more relaxed in-plane momentum matching criterion. Theoretical calculations of phonon dispersions enable us to identify low-energy phonon modes in both Bernal and twisted bilayers of graphene, thereby elucidating the underlying mechanism of tunneling. Our results establish planar tunneling as a versatile tool to further understand electron-phonon coupling in twisted van der Waals materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
25+12 pages, 4+5 figures
ACS Nano 2025
Mapping diverse hysteresis dynamics in scaled MoS$_2$ FETs using the universal method derived from TCAD modeling
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Yezhu Lv, Haihui Cai, Yehao Wu, Yu.Yu. Illarionov
Field-effect transistors (FETs) based on 2D materials have already reached the stage of trial FAB integration. However, reliability limitations caused by various defects present a serious obstacle for their smooth way forward, especially when scaling the device geometries. Still the ongoing research is mostly focused on pure technology aspects, while reliability is often recalled only when showing a randomly measured gate transfer curve to manifest that the hysteresis is “negligible”.In fact the hysteresis dynamics contain unique fingerprints of various mechanisms which may coexist or cancel each other, being more complex in scaled FETs, for instance because of simultaneous interaction of defects with the channel and top gate in thin insulators. To fill this gap, here by doing TCAD modeling for nanoscale MoS$ _2$ /HfO$ _2$ FETs we introduce the universal hysteresis mapping method which can correctly capture commonly measured diverse hysteresis dynamics such as conventional clockwise (CW) and counterclockwise (CCW) hysteresis, as well as CW/CCW switching and time separation. Next we extend this method to bias-temperature instabilities (BTI) and show a clear correlation between complex hysteresis dynamics and abnormal BTI recovery. Finally, we validate our mapping method using available experimental data for MoS$ _2$ FETs and demonstrate that it provides far more accurate results than a conventional constant current extraction of the hysteresis width, being also usable if a CCW hysteresis is caused by mobile ions.
Materials Science (cond-mat.mtrl-sci)
History-dependent and frequency-dependent dielectric nonlinearities induced by polar nanoregions in a thin film of 0.5 ( Ba 0.7 Ca 0.3 TiO 3 ) – 0.5 ( BaZr 0.2 Ti 0.8 O 3 )
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Kevin Nadaud (GREMAN), Guillaume Nataf (GREMAN), Nazir Jaber (GREMAN), Edgar Chaslin (GREMAN), Béatrice Negulescu (GREMAN), Jérôme Wolfman (GREMAN, CNRS)
In this article, dielectric nonlinearities in 0.5(Ba0.7 Ca0.3 TiO3 ) – 0.5(BaZr 0.2 Ti0.8 O3 ) thin film are studied using impedance spectroscopy and harmonic measurements, as a function of the AC measuring field, at different frequencies and upon cycling. The measurements reveal that the pinching of the hysteresis loop, characterized by a phase angle of the third harmonic close to –270 deg, is stronger for low frequencies. This confirms that the pinching is induced by the presence of polar nanoregions (PNRs), whose responses are also strongly dependent on frequency. When repeating the measurement, the PNR contribution changes since the phase angle of the third-harmonic response evolves from pinched to conventional relaxor. This shows that strong changes in the PNR configuration can be induced, even for low AC fields. First-order reversal curves (FORCs) confirm the presence of a pinched hysteresis loop. When repeating the FORC measurement a second time, the distribution drastically changes and corresponds to a soft ferroelectric. The asymmetry of the Preisach plane measured using FORCs is confirmed by a proposed measurement strategy: unipolar impedance measurements.
Materials Science (cond-mat.mtrl-sci)
Physical Review B, 2025, 112 (1), pp.014202
Ultrafast thermal boundary conductance under large temperature discontinuities of ultrathin epitaxial Pb films on Si(111)
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Christian Brand, Tobias Witte, Mohammad Tajik, Jonas D. Fortmann, Birk Finke, Michael Horn-von Hoegen
Heat transfer is a critical aspect of modern electronics, and a deeper understanding of the underlying physics is essential for building faster, smaller, and more powerful devices with an improved performance and efficiency. In such nanoscale structures the heat transfer between two materials is limited by the finite thermal boundary conductance across their interface. Using ultrafast electron diffraction under grazing incidence we investigated the heat transfer from ultrathin epitaxial Pb films to an Si(111) substrate under strong non-equilibrium conditions. Applying an intense femtosecond laser pulse, the 5-7 ML thin Pb film experiences a strong heat up by 10-120 K while the Si substrate remains cold at $ \approx$ 10 K. At such large temperature discontinuities we observe a significantly faster cooling for stronger excited Pb films. The decrease of the corresponding cooling time constant is explained through the thermal boundary conductance in the framework of the diffuse mismatch model. The thermal boundary conductance is reduced by more than a factor of three in comparison with Pb films grown on H-terminated substrates, pointing out the importance of the morphology of substrate, film and their interface.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Comparative Study of Strain-Engineered Thermoelectric Performance of 2D-Xene Nanoribbons
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Kalpana Panneerselvam, Swastik Sahoo, Bhaskaran Muralidharan
The quest for efficient and scalable thermoelectric materials has catalyzed intense interest in quasi 1D nanoribbons, where reduced dimensionality and structural tunability can decouple key transport parameters to enhance energy conversion. In this work, we present a unified comparative study of the thermopower in armchair nanoribbons derived from five archetypal 2D materials: graphene, silicene, germanene, stanene and phosphorene. Using a tight binding model parametrized by first principles inputs and solved within the Landauer Buttiker formalism, we compute strain and width dependent thermopower across nanoribbons classified by width families (3p, 3p+1, 3p+2) over a wide range of uniaxial tensile strain. Our results reveal that thermoelectric behavior is governed by a complex interplay of bandgap evolution, chemical potential asymmetry, and quantum confinement. While graphene and silicene exhibit pronounced family and width sensitive thermopower enhancement under moderate strain, heavier Xenes such as germanene and stanene show diminished responses. In particular, phosphorene nanoribbons emerge as exceptional, exhibiting remarkably high thermopower (62 kB/e), a consequence of their large, persistent bandgap and anisotropic electronic structure. Across all systems, the 3p+2 family transitions from near-metallic to semiconducting under strain, enabling dramatic activation of thermopower in previously inactive configurations. This systematic cross material analysis delineates the design principles for the optimization of TE in 1D nanoribbons, highlighting the strategic use of width control and strain engineering. Our findings identify phosphorene as an intrinsically superior thermoelectric material and position strained Xene nanoribbons as promising candidates for tunable, low-dimensional thermoelectric devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
12 pages, 9 figures
Designing binary mixtures of colloidal particles with simple interactions that assemble complex crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Beth Hsiao-Yen Wei, C. Levi Petix, Qizan Chen, Michael P. Howard, Jeetain Mittal
Computational methods for designing interactions between colloidal particles that induce self-assembly have received much attention for their promise to discover tailored materials. However, it often remains a challenge to translate computationally designed interactions to experiments because they may have features that are too complex, or even infeasible, to physically realize. Toward bridging this gap, we leverage relative-entropy minimization to design pair potentials for binary mixtures of colloidal particles that assemble crystal superlattices. We reduce the dimensionality and extent of the interaction design space by enforcing constraints on the form and parametrization of the pair potentials that are physically motivated by DNA-functionalized nanoparticles. We show that several two- and three-dimensional lattices, including honeycomb and cubic diamond, can be assembled using simple interactions despite their complex structures. We also find that the initial conditions used for the designed parameters as well as the assembly protocol play important roles in determining the outcome and success of the assembly process.
Soft Condensed Matter (cond-mat.soft)
Origin of circular and triangular pores in electron-irradiated hexagonal boron nitride
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Umair Javed, Manuel Langle, Vladimir Zobac, Alexander Markevich, Clara Kofler, Martin Paul, Clemens Mangler, Toma Susi, Jani Kotakoski
For nearly two decades, it has been known that electron irradiation of hexagonal boron nitride (hBN) in a transmission electron microscope leads to the formation of triangular pores. This has been attributed to the lower displacement threshold energy of boron, with or without the assistance of an inelastic scattering event, typically assuming that chemical etching caused by residual gases can be neglected. In this study, in contrast to previous high-vacuum experiments, we show that electron irradiation in ultra-high vacuum leads to circular pores, whereas even small amounts of oxygen in the atmosphere during the experiment change the pores into triangles. Ab initio calculations show that oxygen atoms preferentially attach to boron at the pore edge, supporting the hypothesis that they are preferentially etched during irradiation, resulting in nitrogen-terminated triangular defects. Our results explain the origin of triangular pores in hBN and demonstrate a deterministic way to create atomically-defined pores into 2D materials.
Materials Science (cond-mat.mtrl-sci)
13 pages; 10 figures and 2 tables
From the up-converting multimodal luminescent thermometer to ratiometric visual power density meter based on Er3+,Yb3+ emission
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Anam Javaid, Maja Szymczak, Lukasz Marciniak
This study demonstrates that thermally induced variations in the spectroscopic properties of Na3Sc2(PO4)3:Er3+, Yb3+ can be effectively harnessed for multimodal remote temperature sensing. As shown, Na3Sc2(PO4)3:Er3+, Yb3+ supports multiple ratiometric sensing modes based on the intensity ratios of (i) 2H11/2 -> 4I15/2 and 4S3/2 -> 4I15/2; (ii) 2H9/2 -> 4I13/2 and 4S3/2 -> 4I15/2; and (iii) green-to-red emission intensity ratio, achieving maximum relative sensitivities of 2.8% K-1, 3% K-1, and 1.8% K-1, respectively. The synergy between thermal changes observed in the green-to-red emission intensity ratio of Er3+ ions, combined with the efficient optical heating of Na3Sc2(PO4)3:Er3+, Yb3+ at elevated Yb3+ concentrations enables the development of a visual optical power density sensor, exhibiting relative sensitivities of SRx = 1.0% W-1 cm2 and SRy = 0.9% W-1 cm2 at 15 W cm-2 when quantified using CIE 1931 chromaticity coordinates. To the best of our knowledge, this is the first report of a visual luminescent optical power density sensor. Furthermore, it was demonstrated that Na3Sc2(PO4)3:Er3+, Yb3+ can be successfully applied for two-dimensional imaging of optical power density, thereby enabling spatial visualization of power distribution within an illuminated field.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Phase transitions of eutectic high entropy alloy AlCoCrFeNi2.1 under shock compression
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Sophie Parsons, Kento Katagiri, Hangman Chen, Anirudh Hari, Tharun Reddy, Sara J. Irvine, Laura Madril, Dorian Luccioni, Jie Ren, Wuxian Yang, Norimasa Ozaki, Alexis Amouretti, Ryosuke Kodama, Hirotaka Nakamura, Yusuke Nakanishi, Masato Ota, Yusuke Seto, Sota Takagi, Takuo Okuchi, Yuhei Umeda, Yuichi Inubushi, Kohei Miyanishi, Keiichi Sueda, Tadashi Togashi, Makina Yabashi, Toshinori Yabuuchi, Wanghui Li, Paul E. Specht, Penghui Cao, Wen Chen, Yogesh K. Vohra, Leora E. Dresselhaus-Marais
High entropy alloys (HEAs) are a new class of metals that exhibit unique mechanical performance. Among HEAs, additively manufactured eutectic high entropy alloys (AM-EHEAs) have recently emerged as candidate materials for use in extreme conditions due to their simultaneous high strength and ductility. However, the deformation and structural evolution of AM-EHEAs under conditions of high pressure have not been well characterized, limiting their use in extreme applications. We present dynamic compression experiments and molecular dynamics simulations studying the structural evolution of AM-EHEA AlCoCrFeNi2.1 when compressed to pressures up to 400 GPa. Our in-situ X-ray diffraction measurements capture the appearance of fcc and bcc phases at different pressure conditions, with pure- and mixed-phase regions. Understanding the phase stability and structural evolution of the AM EHEA offers new insights to guide the development of high-performance complex materials for extreme conditions.
Materials Science (cond-mat.mtrl-sci)
Preferential site ordering alters the magnetic structure of Sm$_3$Ru$4$Sn${13-x}$Ge$_x$ ($x = 0$-2)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Jacob W. Fritsky, Hui-Fei Zhai, Yifeng Zhao, Aryan Rauniyar, Antia S. Botana, Jason F. Khoury
An important aspect of materials research is the ability to tune different physical properties through controlled alloying. The Ln$ _3$ M$ _4$ X$ _{13}$ (Ln = Lanthanide, M = Transition Metal, X = Tetrel) filled skutterudite family is of interest due to the tunability of its constituent components and their effects on physical properties, such as superconductivity and complex magnetism. In this work, Sm$ _3$ Ru$ _4$ Sn$ _{13-x}$ Ge$ _x$ (x = 0 – 2) was synthesized via excess Sn-flux and characterized using powder and single-crystal X-ray diffraction, magnetometry, X-ray photoelectron spectroscopy, and heat capacity. Sm$ _3$ Ru$ _4$ Sn$ _{13}$ and its Ge-solid-solution members crystallize in the Pm-3n space group, which has two unique Wyckoff positions for the tetrel (X) site. In the solid solution members, Ge shows preferential occupancy for one of the two Wyckoff sites, reaching $ \sim$ 60$ %$ and 100$ %$ occupancy when x = 1 and 2, respectively. Magnetometry and heat capacity measurements of Sm$ _3$ Ru$ _4$ Sn$ _{13}$ indicated antiferromagnetic ordering at $ T_N$ = 7.3 K. However, Sm$ _3$ Ru$ _4$ Sn$ _{12}$ Ge and Sm$ _3$ Ru$ _4$ Sn$ _{11}$ Ge$ _2$ showed notably lower-temperature antiferromagnetic phase transitions with substantial peak-broadening at $ T_N$ = 5.5 K and 4.1 K, respectively. These data suggest that alloying Ge into Sm$ _3$ Ru$ _4$ Sn$ _{13}$ causes magnetic frustration within the structure, likely attributable to a change in the density of states from additional Ge $ p$ states at the Fermi level. This work demonstrates that preferentially alloying Ge in Sm$ _3$ Ru$ _4$ Sn$ _{13-x}$ Ge$ _x$ allows for more precise tunability of its magnetic structure, elucidating design principles for different quantum phases in intermetallic materials.
Materials Science (cond-mat.mtrl-sci)
36 Pages, 12 Figures
The carbon cost of materials discovery: Can machine learning really accelerate the discovery of new photovoltaics?
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-18 20:00 EDT
Matthew Walker, Keith T. Butler
Computational screening has become a powerful complement to experimental efforts in the discovery of high-performance photovoltaic (PV) materials. Most workflows rely on density functional theory (DFT) to estimate electronic and optical properties relevant to solar energy conversion. Although more efficient than laboratory-based methods, DFT calculations still entail substantial computational and environmental costs. Machine learning (ML) models have recently gained attention as surrogates for DFT, offering drastic reductions in resource use with competitive predictive performance. In this study, we reproduce a canonical DFT-based workflow to estimate the maximum efficiency limit and progressively replace its components with ML surrogates. By quantifying the CO$ _2$ emissions associated with each computational strategy, we evaluate the trade-offs between predictive efficacy and environmental cost. Our results reveal multiple hybrid ML/DFT strategies that optimize different points along the accuracy–emissions front. We find that direct prediction of scalar quantities, such as maximum efficiency, is significantly more tractable than using predicted absorption spectra as an intermediate step. Interestingly, ML models trained on DFT data can outperform DFT workflows using alternative exchange–correlation functionals in screening applications, highlighting the consistency and utility of data-driven approaches. We also assess strategies to improve ML-driven screening through expanded datasets and improved model architectures tailored to PV-relevant features. This work provides a quantitative framework for building low-emission, high-throughput discovery pipelines.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Impact of particle-size polydispersity on the quality of thin-film colloidal crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-18 20:00 EDT
Mariam Arif, Andrew B. Schofield, Fraser H. J. Laidlaw, Wilson C. K. Poon, Job H. J. Thijssen
Size polydispersity in colloidal particles can disrupt order in their self-assembly, ultimately leading to a complete suppression of crystallization. In contrast to various computational studies, few experimental studies systematically address the effects of size polydispersity on the quality of colloidal crystals. We present an experimental study of structural order in thin films of crystals vertically dried from colloidal dispersions with a systematically varying polydispersity. As expected, an increase in polydispersity leads to a deterioration in order with significant drops in the local bond-orientational order at 8% and 12% polydispersity. Our results align with previously suggested models of epitaxial-like growth of 2D layers during convective assembly. Our results can offer critical insights into the permissible limits for achieving colloidal crystals from more polydisperse systems such as those synthesized through more sustainable methods.
Soft Condensed Matter (cond-mat.soft)
10 pages, 5 figures
Partial decidability protocol for the Wang tiling problem from statistical mechanics and chaotic mapping
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-18 20:00 EDT
Fabrizio Canfora, Marco Cedeno
We introduce a partial decidability protocol for the Wang tiling problem (which is the prototype of undecidable problems in combinatorics and statistical physics) by constructing a suitable mapping from tilings of finite squares of different sizes. Such mapping depends on the initial family of Wang tiles (the alphabet) with which one would like to tile the plane. This allows to define effective entropy and temperature associated to the alphabet (together with the corresponding partition function). We identify a subclass of good alphabets by observing that when the entropy and temperature of a given alphabet are well-behaved in the thermodynamical sense then such alphabet can tile the infinite two-dimensional plane. Our proposal is tested successfully with the known available good alphabets (which produce periodic tilings, aperiodic but self-similar tilings as well as tilings which are neither periodic nor self-similar). Our analysis shows that the Kendall Tau coefficient is able to distinguish alphabets with a good thermodynamical behavior from alphabets with bad thermodynamical behavior. The transition from good to undecidable behavior is related to a transition from non-chaotic to chaotic regime in discrete dynamical systems of logistic type.
Statistical Mechanics (cond-mat.stat-mech), Information Theory (cs.IT), High Energy Physics - Theory (hep-th), Logic (math.LO)
22 pages, 24 figures
Improving photovoltaics by adding extra terminals to extract hot carriers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-18 20:00 EDT
Bruno Bertin-Johannet, Thibaut Thuégaz, Janine Splettstoesser, Robert S. Whitney
Photovoltaic cells usually have two terminals, one collecting electrons and the other collecting holes. Can more terminals improve such solar cells? Energy-filtering terminals could collect “hot” carriers (electrons or holes not yet relaxed to the band edge), with other terminals for low-energy carriers. For collection faster than carrier-phonon relaxation, we predict four-terminal cells with higher power output than optimal two-terminal cells – more than 40% higher for fast carrier collection. Similar effects will occur in multi-terminal thermoelectrics exploiting non-equilibrium distributions
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Suppression of the charge fluctuations by nonlocal correlations close to the Mott transition
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Irakli Titvinidze, Julian Stobbe, Marvin Leusch, Georg Rohringer
In this paper, we investigate the impact of nonlocal correlations on charge fluctuations in the two-dimensional single-band Hubbard model close to the Mott metal-to-insulator transition. At half-filling and for interaction strengths and temperatures where the system is in the Mott insulating phase, charge fluctuations are strongly suppressed. Under these conditions, dynamical mean-field theory (DMFT) calculations predict a strong enhancement of the charge susceptibility at small (electron or hole) doping. However, these DMFT results include only the effects of purely local correlations despite the importance of nonlocal correlations in two-dimensional systems. We have, hence, carried out dynamical vertex approximation (D$ \Gamma$ A) simulations which allow for the inclusion of such nonlocal correlation effects while retaining the local ones of DMFT. Our numerical data show that close to half-filling the large uniform charge susceptibility of DMFT is strongly suppressed by nonlocal fluctuations but gradually increases with (electron) doping. At a certain doping value charge fluctuations become eventually larger in D$ \Gamma$ A with respect to DMFT indicating that the absence of nonlocal correlations underestimates the mobility of the charge carriers in this parameter regime. This metallization effect is also reflected in an enhancement of the D$ \Gamma$ A kinetic and potential energies and a corresponding reduction of the (absolute value of the) D$ \Gamma$ A Matsubara self-energy with respect to DMFT.
Strongly Correlated Electrons (cond-mat.str-el)
14 pages, 11 figures
Artificial Intelligence for Quantum Matter: Finding a Needle in a Haystack
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-18 20:00 EDT
Khachatur Nazaryan, Filippo Gaggioli, Yi Teng, Liang Fu
Neural networks (NNs) have great potential in solving the ground state of various many-body problems. However, several key challenges remain to be overcome before NNs can tackle problems and system sizes inaccessible with more established tools. Here, we present a general and efficient method for learning the NN representation of an arbitrary many-body complex wave function. Having reached overlaps as large as $ 99.9%$ for as many as $ 25$ particles, we employ our neural wave function for pre-training to effortlessly solve the fractional quantum Hall problem for $ 20$ electrons with Coulomb interactions and realistic Landau-level mixing.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Expansion creates spin-glass order in finite-connectivity models: a rigorous and intuitive approach from the theory of LDPC codes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-18 20:00 EDT
Benedikt Placke, Grace M. Sommers, Nikolas P. Breuckmann, Tibor Rakovszky, Vedika Khemani
Complex free-energy landscapes with many local minima separated by large barriers are believed to underlie glassy behavior across diverse physical systems. This is the heuristic picture associated with replica symmetry breaking (RSB) in spin glasses, but RSB has only been rigorously verified for certain mean-field models with all-to-all connectivity. In this work, we give a rigorous proof of finite temperature spin glass order for a family of models with local interactions on finite-connectivity, non-Euclidean expander graphs. To this end, we bypass the RSB formalism entirely, and instead exploit the mathematical equivalence of such models to certain low-density parity check (LDPC) codes. We use code expansion, a property of LDPC codes which guarantees extensive energy barriers around ground states. Together with mild additional assumptions, this allows us to construct an explicit decomposition of the low-temperature Gibbs state into disjoint components, each hosting an asymptotically long-lived state associated with a local minimum of the landscape. Each component carries at most an exponentially small fraction of the total weight, and almost all components do not contain ground states – which we take together to define spin-glass order. The proof is elementary, and treats various expanding graph topologies on the same footing, including those with short loops where existing approaches such as the cavity method fail. Our results apply rigorously to diluted p-spin glasses for sufficiently large p, and while unproven, we also expect our assumptions to hold in a broader family of codes. Motivated by this, we numerically study two simple models, on random regular graphs and a regular tesselation of hyperbolic space. We show that both models undergo two transitions as a function of temperature, corresponding to the onset of weak ergodicity breaking and spin glass order, respectively.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn), Mathematical Physics (math-ph)
27+28 pages, 16+12 figures
Effective field theory for superfluid vortex lattice from coset construction
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-18 20:00 EDT
Aleksander Głódkowski, Sergej Moroz, Francisco Peña-Benítez, Piotr Surówka
Guided by symmetry principles, we construct an effective field theory that captures the long-wavelength dynamics of two-dimensional vortex crystals observed in rotating Bose-Einstein condensates trapped in a harmonic potential. By embedding the system into Newton–Cartan spacetime and analyzing its isometries, we identify the appropriate spacetime symmetry group for trapped condensates at finite angular momentum. After introducing a coarse-grained description of the vortex lattice we consider a homogeneous equilibrium configuration and discuss the associated symmetry breaking pattern. We apply the coset construction method to identify covariant structures that enter the effective action and discuss the physical interpretation of the inverse Higgs constraints. We verify that Kohn’s theorem is satisfied within our construction and subsequently focus on the gapless sector of the theory. In this regime, the effective theory accommodates a single gapless excitation–the Tkachenko mode–for which we construct both the leading-order and next-to-leading-order actions, the latter including cubic interaction terms.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con), High Energy Physics - Theory (hep-th)
20+7 pages