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Physics Condensed Matter

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Thursday 25 June

Materials Science

A Hybrid Quantum Mechanics Machine Learning Forcefield (QM/ML) Framework for Accurate Solute-Dislocation Interaction Simulations

Solute-dislocation interactions play a central role in controlling microstructural evolution and mechanical behaviour of structural materials, yet conventional atomistic modelling approaches struggle to combine the chemical accuracy with computational scalability. In the nuclear industry, these challenges become particularly acute, as experiments reveal strong correlations between solute segregation and irradiation-induced dislocation loops. However, theoretical insight remains limited because density functional theory (DFT) simulations are prohibitively expensive at relevant length scales, while traditional semi-empirical interatomic potentials lack the chemical fidelity required for predictive solute-defect calculations. Here, we introduce a hybrid quantum-mechanics/machine-learning (QM/ML) simulation framework that couples DFT with neural-network machine learning interatomic potentials (MLIPs), enabling accurate atomistic dislocation simulations at reduced computational cost. We demonstrate the QM/ML framework's capability by reproducing the experimentally observed Sn and Fe segregation to dislocation loops in Zr and investigating magnetically complex solute-dislocation interactions in steel. These results establish the approach as a transferable, high-fidelity tool for modelling irradiation-induced defect structures and benchmarking emerging MLIPs.
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All authors Junting Zhang, Colleen Reynolds, Ryan S. Stroud, Jana Smutna, Daniel J. M. King, Andrew P. Horsfield, Mark R. Wenman

Materials Science

Giant and Broadband Circular Dichroism from Particle-Hole Symmetry Breaking in Weyl Semimetals

Circular dichroism originates from symmetry breaking of material structure, leading to differential absorption of left- and right-circularly polarized light. However, circular dichroism in most materials is inherently weak and spectrally narrow, especially in the mid-to-far infrared. Here, we uncover giant infrared circular dichroism in the magnetic-field-forced Weyl semimetal Mn(Bi,Sb)2Te4, driven by extreme particle-hole symmetry breaking. Helicity-resolved magneto-infrared spectroscopy reveals circular dichroism exceeding 3000 mdeg (~130 mdeg/nm) with above-degree response extending over the 6-13 {\mu}m spectral range. The optical resonances are enhanced by a strong band nesting effect intrinsic to the Landau levels of type-II Weyl dispersion. A symmetry-based kp model reproduces these magneto-infrared responses and demonstrates that magnetization-induced asymmetric spin-orbit coupling generates particle-hole symmetry breaking, suppressing spin-up, parity-even wavefunction components in the valence Landau band and thereby producing pronounced optical helicity selectivity. Our findings establish particle-hole symmetry breaking as an effective route toward helicity-resolved optical control in quantum materials.
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All authors Xiangyu Jiang, Zeping Shi, Yuhan Du, Haonan Chen, Jiayu Wang, Wenbin Wu, Guangyi Wang, Congming Hao, Mingfan Yao, Mingsen Zhou, Xin Chen, Chenyao Xu, Zhongbo Yan, Cheng Zhang, Hai-Zhou Lu, Junhao Chu, Xiang Yuan

Materials Science

Hydrogen segregation around a straight screw dislocation in bcc iron

The interaction between hydrogen and screw dislocations in bcc iron is central to understanding hydrogen embrittlement. A major challenge lies in the high-dimensional parametric landscape governing this interaction. In this work, we perform a comprehensive set of molecular simulations using a reliable neural network interatomic potential, systematically exploring hydrogen binding across dislocation core structures (easy and hard cores), site types, and concentrations. From these energetics, we construct a thermodynamic framework that quantifies the statistical relevance of the various trapping configurations, thereby significantly reducing the complexity of the problem. Our results show good agreement with the limited density functional theory data available in the literature. We further delineate the validity domain of an elastic dipole description of hydrogen-dislocation interactions, providing a simplified yet physically grounded modeling approach. Finally, we demonstrate that the easy-core configuration plays a key role in rationalizing experimental hydrogen solubility limits. These findings establish a consistent multiscale foundation for incorporating hydrogen-dislocation interactions into larger-scale models of plasticity and embrittlement.
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All authors Margot Lucas, Marie Landeiro Dos Reis, Sylvain Queyreau, Xavier Feaugas

Materials Science

Controlled chemical vapor deposition for synthesis of emerging Mo(W)Te2 systems

The Group-VI transition metal ditellurides offer a rich platform for correlated and topological phenomena, yet their structural polymorphism and instability complicate the creation of single crystals and heterointerfaces. Here, we introduce a confined-space chemical vapor deposition (CVD) strategy that lowers the growth temperature window and, when combined with tailored precursor configurations and stepwise thermal ramps, enables the deterministic synthesis of high-quality single crystals, alloys, and lateral/vertical heterostructures. High-resolution aberration-corrected STEM provides atomic characterization of lattice-matched Mo(W)Te2 lateral heterostructure, revealing nearly atomically sharp, compositionally well-defined seamless boundaries. This approach avoids the thickness nonuniformity and structural limitations commonly associated with exfoliated samples, enabling reproducible fabrication of clean heterointerfaces and establishing a nearly ideal in-situ experimental system. Furthermore, scanning tunneling microscopy and spectroscopy (STM and STS) enable direct imaging of the seamless boundaries in Mo(W)Te2 lateral heterostructures, while uncovering their distinct real-space distributions of the local density of states. Our results establish a scalable pathway for engineering crystalline Te-based structures with controlled geometry and stacking, providing an essential step toward quantum and topological device platforms based on the transition metal ditellurides family.
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All authors Ya Deng, Zi-Yi Han, Yao Wu, Kongyang Yi, Ya-Ning Ren, Dundong Yuan, Chao Zhu, Lin He, Zheng Liu

Statistical Mechanics · Cross-listed from cs.IT

Grouped Reverse Importance Sampling for the Partition Function

We introduce and analyze several grouped variants of the method of reverse importance sampling (RIS) for estimating a partition function from samples of the Boltzmann distribution $p(x)=e^{ \betaU(x)}/Z(\beta)$. Ordinary RIS weighs each sample separately. By contrast, our proposed grouped RIS (GRIS) methods are based on assigning the samples into groups (or batches) of size $k\ge 2$ and applying a joint weight function to each group. The focal point of the research is the quest for a tractable weight function that would yield the smallest possible mean squared error (MSE). A simple identity relates the normalized MSE to the chi-squared divergence between the joint-weight distribution and the distribution of the $k$-fold sum of independent energies. Our first theoretical finding is that any weight that improves on ordinary RIS ($k=1$) must couple the group components. In other words, it must not be a product-form function across those components, as product-form weight functions always worsen the MSE. Our second, and more important, finding is that, without loss of optimality, it is sufficient to seek weight functions that depend only on the total energy, $\sum_iU(x_i)$, of the group (group-energy weight functions); for the sliding-window variants, the analogous result is open. This finding simplifies both the theoretical analysis and the application of the method substantially. For $k=2$ and $k=3$, the MSE associated with non-overlapping (NOL) groups is reduced by $20$–$65\%$ across three examples. We then propose two additional variants of GRIS, both based on sliding-window grouping (as opposed to NOL grouping). The first applies a fixed weight sliding window (FSW) across all (cyclic) shifts of the sliding window, and the second allows a variable-weight sliding window (VSW). The FSW scheme improves on the NOL one, and the VSW improves even further, as will be demonstrated numerically.
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Soft Condensed Matter

Solid-to-solid transition in dense assemblies of elongated cells

Cell shapes in confluent tissues range from nearly isotropic epithelial morphologies to highly elongated endothelial ones. In standard vertex models, tissue rigidity is controlled by a target shape index; increasing this index drives cell elongation and ultimate tissue fluidization. Here, we consider the case where cell elongation emerges autonomously by assigning an intrinsic, passive elastic preference for anisotropic shape. This distinction reverses the usual expectation: cell elongation does not fluidize the tissue, but drives a solid-to-solid transition from an ordered isotropic solid to a disordered anisotropic solid, with finite yield stress and shear rigidity on either side of the transition. These results decouple cell shape from tissue rheology and caution against inferring fluid-like mechanics from elongated cell morphologies alone.
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Mesoscale and Nanoscale Physics

Perfect Absorption in the Strong Coupling Regime via Degenerate Critical Coupling

Perfect absorption (PA) represents a fundamental limit of light-matter interaction and a means to maximize nanoscale energy conversion. While PA is now a well-established phenomenon, both the theoretical feasibility and a practical mechanism for achieving it under single-beam excitation within the strong coupling regime is unknown. Through rigorous solution of Maxwells equations for a compact photonic crystal (PhC) architecture incorporating a two-dimensional semiconductor, we present a general method based on degenerate critical coupling for single-port PA of exciton-polaritons. At the crossing of two polariton branches, we achieve near-unity absorption exceeding 99.8 % in a structure thinner than $100\,$nm. This effect is robust under realistic Gaussian beam excitation, and can be realized across different temperatures and excitonic materials by tailoring the PhC geometry. Our results establish a strategy for enabling efficient light-matter coupling, with direct implications for the development of metal-free, ultra-compact polaritonic logic devices, sensors, and energy-harvesting platforms.
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All authors Eleonora P. Kraus, Jamie M. Fitzgerald, Carlos Maciel-Escudero, Ermin Malic

Materials Science

Thermal Rectification from Size-Dependent Phonon Confinement in Nanoparticle Assemblies

Thermal insulation remains an important technological challenge across the vast number of applications, from living quarters to quantum technology. Here, we exploit the size-dependent modification of the phonon density of states arising from phonon confinement in nanoparticles to fabricate a simple phonon rectifier. The smaller of the two connected nanoparticles imposes stronger phonon confinement leading to rectifying phonon transport. This concept is extended to the macroscale by constructing two overlapping layers of differently sized nanoparticles, thereby realizing a macroscopic phonon diode. Following the localized heat deposition by laser light, the temperature profiles across a phonon-diode were measured by infrared imaging. Although the rectifying strength is moderate, the abundance of optimization possibilities makes this method promising for ultra-low volume thermal insulation at both the nano- and macroscale
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All authors Megan J. Farrington, David J. Wasserman, Eden R. Josza, Alessandro Podestà, Alessio Zaccone, Mariia Sidorova, Alexej D. Semenov, Nicola Ludwig, Marcel Di Vece

Materials Science

Preconditioning Magnetic Systems in Kohn-Sham Density Functional Theory

The convergence of the self-consistent field iterations in Kohn-Sham density functional theory can be significantly hindered by the presence of small eigenvalues in the dielectric matrix, which are often associated with electronic phase transitions in magnetic systems. In this work, we study this type of convergence issues and propose a new preconditioning scheme to mitigate them. Our preconditioning scheme is inspired by the Stoner model and based on a non-interacting susceptibility that neglects orbital variations. We demonstrate the effectiveness of our approach on a range of ferromagnetic systems, showing that it can significantly reduce the number of iterations required to achieve convergence in the vicinity of magnetic phase transitions.
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Mesoscale and Nanoscale Physics

Floquet Topological Phases and Anomalous Hall Signatures in Irradiated Two-dimensional $d_{xy}$-Wave Altermagnets

We study Floquet topological phases in two-dimensional $d_{xy}$-wave altermagnets driven by off-resonant circularly polarized light and subject to an out-of-plane magnetization induced via extrinsic exchange coupling from a proximate ferromagnet. Using a lattice Floquet formulation, we show that the system is governed by a driving parameter $\beta$ that controls the emergence of distinct gap-closing points and associated topological phases. For $|\beta|>1$, topology is dominated by anisotropic Dirac points at high symmetry points, leading to Chern phases with $|\mathcal{C}|=2$. For $|\beta|<1$, light-induced off-symmetry $G$ points appear in four families in the Brillouine zone, enabling higher Chern phases up to $|\mathcal{C}|=4$. Low-energy analysis reveals that high symmetry points host anisotropic massive Dirac fermions, while $G$ points realize generalized two-dimensional anisotropic Dirac points with fully momentum-dependent pseudospin structure, leading to distinct Berry curvature distributions. In the metallic regime, the anomalous Hall conductivity provides an experimental signature of these Floquet topological phases, exhibiting sharp features associated with Berry curvature accumulation near local gap-closing regions.
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Soft Condensed Matter

Analyzing the Gelation Transition through Fractional Viscoelasticity and the Mittag-Leffler-Prabhakar Function

The gelation transition, a process that transforms a flowable liquid into an elastic solid, occurs in a variety of systems, ranging from colloidal to polymeric. During the gelation transition, a system passes through a critical gel state characterized by scale-free power-law viscoelasticity. Interestingly, the fractional calculus provides a natural mathematical language for such power-law viscoelasticity. In this work, we develop physically constrained fractional viscoelastic models, as well as those based on the three-parameter Mittag-Leffler-Prabhakar function, for both the pre-gel and post-gel regimes, ensuring consistency with the conventional scaling relations in each regime. While the fractional pre-gel model is observed to be valid only for a restricted subset of parameter values, the Prabhakar function-based model for the relaxation modulus, which translates into a Havriliak-Negami function-based complex modulus, rigorously removes this limitation. We enforce continuity of the dynamic moduli and their derivatives across the critical gel point, which universally imposes a symmetry in the relaxation dynamics on either side of the critical gel state. Such enforcement further validates the hyperscaling relation connecting the critical exponents, making it a theoretical necessity rather than an empirical coincidence. We validate the proposed models against time- and frequency-domain experimental data. A model-agnostic, frequency-independent rheological fingerprint of the critical gel state, uniquely determined by two critical exponents, is also identified.
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Soft Condensed Matter

Solid adsorption: the missing mechanism for surfactant contact lines – a phase-field approach

We develop a thermodynamically consistent phase-field model for soluble surfactants in two-phase flows, incorporating both interfacial and solid surface adsorption. The model is derived via variational principles consistent with the second law of thermodynamics, resulting in modified free energies and boundary conditions that capture surfactant transport, adsorption, and wetting dynamics. A key contribution of this work is the inclusion of surfactant adsorption on solid walls, which leads to qualitative agreement with experimental observations: unlike prior numerical studies that predicted hydrophilic surfaces becoming more hydrophilic and hydrophobic surfaces more hydrophobic, our model shows a shift toward increased hydrophilicity across all contact angles-consistent with experimental trends. Our results establish that solid adsorption provides the missing mechanism required for predictive modelling of surfactant-laden contact line dynamics.
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All authors Parvathy K. Kannan, Kazi T. Iqbal, Diego Díaz, Ilse Mateman, Shahab Mirjalili, Gustav Amberg, Shervin Bagheri, Outi Tammisola

Soft Condensed Matter

Dynamic heterogeneity in sodium silicate melts via machine-learning potential

We present a comprehensive characterisation of dynamic heterogeneity in sodium silicate melts using molecular dynamics simulation with machine-learning potentials. By studying sodium disilicate, tetrasilicate, and hexasilicate melts across a range of temperatures, mean squared displacement and a time-correlation function computed up to the nanosecond timescale provide a detailed account of how spatial mobility disparities emerge in a realistic multicomponent oxide glass. Within these timescales, the self-part of the van Hove function for sodium displays a bimodality, demonstrating that alkali transport is mediated by discrete displacement events consistent with a hopping mechanism. This distinct hopping allows sodium ions to decouple from the sluggish relaxation of the silicate matrix. Furthermore, evaluation of the non-Gaussian parameter reveals that, although all constituent species exhibit dynamic heterogeneity, the non-Gaussian behaviour is most pronounced for oxygen atoms. This trend reflects the intermittency of structural rearrangements, where framework atoms undergo rare and stochastic events compared to the frequent displacements of mobile ions. Our findings elucidate the microscopic mechanism of ion transport and its connection to dynamic heterogeneity in silicate melts, offering a new avenue to study fundamental glassy physics in realistic vitreous materials.
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Materials Science

Lattice Reconstruction and Orbital Hybridization Suppress Magnetism in TaCo$_2$Te$_2$

Structural reconstruction in low-dimensional quantum materials can strongly modify electronic symmetry and magnetic stability through orbital hybridization. Here, we investigate the interplay between lattice reconstruction, electronic structure, and magnetic instability in the layered van der Waals compound TaCo$_2$Te$_2$ using scanning tunneling microscopy and spectroscopy (STM/STS), non-contact atomic force microscopy (nc-AFM), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT). While nc-AFM resolves a distorted hexagonal Te surface lattice, STM/STS reveal a pronounced square-like electronic symmetry that does not directly follow the atomic structure. ARPES further shows a strongly anisotropic Fermi surface and reconstructed low-energy states. Spatially resolved spectroscopy and orbital-projected DFT demonstrate that the bias-dependent STM contrast does not arise from a simple reversal between occupied and unoccupied states, but from the energy-integrated local density of states dominated by electronic states exhibiting opposite spatial contrast at selected energies. DFT calculations further show that reconstruction suppresses the magnetic instability present in the undistorted structure, stabilizing a nonmagnetic ground state through enhanced orbital hybridization. These results establish TaCo$_2$Te$_2$ as a model system in which lattice reconstruction reorganizes electronic symmetry and suppresses magnetism, highlighting structural reconstruction as a route for controlling correlated and magnetic phases in low-dimensional quantum materials.
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All authors Ulysse Chazarin, Bharat C. Bathu, Zuned Ahmed, Marta Zonno, Chiara Bigi, Francois Bertran, Adolfo O. Fumega, Orlando J. Silveira, Shawulienu Kezilebieke

Mesoscale and Nanoscale Physics

Floquet-Engineered Chern Insulator in two-dimensional $d_{x^2-y^2}$-Wave Altermagnets

We investigate Floquet-engineered topological phases in two-dimensional $d_{x^2-y^2}$-wave altermagnets irradiated by circularly polarized light in the off-resonant regime. These materials exhibit large momentum-dependent spin-splitting governed by distinctive magnetic symmetries. Using a lattice model combined with Floquet theory, we demonstrate that irradiation induces the light-tunable quantum anomalous Hall phases with the Chern numbers up to $\pm 3$. The resultant phase diagram is verified by calculating the anomalous Hall conductivity and also the edge modes inside the band gap of a nanoribbon version of the altermagnet. Our findings establish d-wave altermagnets as promising platforms for realizing nonequilibrium topological states of matter. The low-energy continuum limit of the lattice-based Floquet Hamiltonian results in a linear and higher-order-in-momentum spin-orbit couplings, and also a Zeeman-like magnetization, all arising from light-induced virtual photon processes. The resulting higher-order spin-orbit coupling generates the additional gapless Dirac points which, together with the high-symmetry gap-closings, yield enhanced Berry curvature and high Chern numbers. The light irradiation effectively breaks the static $d_{x^2-y^2}$-wave magnetic symmetry mixing in an isotropic photo-induced $s$-wave correction.
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Strongly Correlated Electrons · Cross-listed from hep-th

Central charges $C_J$ and $C_T$ in QED$_d$-GNY model and scalar QED$_d$

We compute the leading-order $1/N$ corrections to the central charges $C_J$ and $C_T$ in the conformal QED$_d$-Gross-Neveu-Yukawa (GNY) model and the scalar QED$_d$ in $d$ dimensions. The scaling dimensions of the lowest adjoint bilinear scalars are obtained to order $O(1/N)$ for general $d$. In $d=3$, the $U(1)$ Abelian gauge theory possesses a topological $U(1)$ global symmetry, and we evaluate the central charge $C_J^{\text{top}}$ of the topological symmetry current to subleading order in the $1/N$ expansion. Our interest in these theories is primarily motivated by their potential connection to the $SO(5)$ symmetric deconfined quantum critical point (DQCP). We compare the large $N$ results for the central charges $C_J$ and $C_T$ with the conformal data of the $SO(5)$ DQCP obtained from fuzzy sphere and conformal bootstrap. The large $N$ predictions of the QED$_3$-GNY model are found to be in reasonable agreement with the nonperturbative estimates for the $SO(5)$ DQCP.
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Mesoscale and Nanoscale Physics

Photon-Assisted Tunneling in Double Quantum Dot: Application of Scattering Theory

We theoretically examine the photon-assisted tunneling (PAT) in a double quantum dot (DQD) in parallel when one of the quantum dots (QDs) is irradiated by an AC field. First, we formulate the PAT in a single QD by solving the time-dependent Schrödinger equation using the scattering theory. The QD has an oscillating energy level, $\varepsilon(t)=\varepsilon_0+eV_{\mathrm{AC}}\cos\omega t$, and is connected to two leads by the tunnel coupling $\Gamma$. We show that the resonant tunneling takes place through energy levels of the polariton, $\varepsilon_0+N\hbar\omega$ ($N=0,\pm 1, \pm 2, \cdots$), when $\Gamma \ll \hbar\omega$ (PAT) and through the energy level $\varepsilon(t)$ when $\Gamma \gg \hbar\omega$ (adiabatic transport). Then, the scattering theory is applied to the PAT in the DQD in the presence of magnetic flux penetrating between the QDs. We observe the Aharonov–Bohm effect not only in the main peak ($N=0$) but also in subpeaks ($N \ne 0$), indicating coherent transport through the polariton states. Our theory is also applicable to the DQD in the three-terminal geometry. We demonstrate the phase measurement through the irradiated QD and show that the measured phase shift changes continuously from 0 to $\pi$ around both the main peak and subpeaks.
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Quantum Gases

Binary Dipolar Condensates of Dysprosium Isotopes with Tunable Spatial Order

Dipolar quantum mixtures provide a route to many-body phases in which long-range anisotropic interactions couple with density, composition and spatial order. Here we realize a new quantum-degenerate dipolar mixture of $^{162}$Dy and $^{164}$Dy in a single-species-like apparatus. The mixture combines nearly matched single-particle Hamiltonians, tunable interactions and composition parameters, and isotope-resolved characterization. Tuning the interaction balance and relative composition reorganizes the coupled condensates from a miscible state into core–shell-like, side-by-side, and exchanged core–shell-like immiscible configurations. These results establish dysprosium isotope mixtures as a compact and versatile platform for multicomponent dipolar quantum matter, ranging from impurity physics to binary supersolidity.
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All authors Shenshuang Nie, Zibin Jiang, Junrong Huang, Xiao Luo, Fucheng Qin, Kaiyue Wang, Mingyang Guo

Materials Science

Shape-Constrained Bayesian Active Learning of Self-Limiting Saturation Curves

Saturation curves, monotone responses that rise from zero to a plateau, recur across gas adsorption, enzyme kinetics, and self-limiting growth. Learning one from a few costly, noisy measurements is a common bottleneck. We present a Bayesian active-learning platform built on a penalized monotone I-spline. Non-negative weights make every posterior draw rise from zero and never fall, a survey measurement anchors the plateau in place of a flatness prior, and the input reaching any saturation level is read from the posterior by level crossing, assuming no kinetic form. Each measurement is placed where the surrogate is least certain, which beats random designs and edges a log-spaced grid of the same budget. One fixed configuration recovers five kinetically distinct regimes from twenty measurements to a saturation error of 0.037 to 0.041, below the output noise, and averages 0.045 on 250 curves from an unseen distribution. Running unconstrained Gaussian processes (GPs) and two unpenalized monotone bases through the same loop separates each ingredient's contribution. Logarithmic resolution and the roughness penalty carry the accuracy, while monotonicity guarantees a level crossing unique on every draw. The penalty keeps the surrogate the most accurate model at every noise level, and its second-order form centers the recommended input for saturation where a first-order penalty reads late (a bias of +0.32 s with 94% coverage, against +0.44 s and 64% for the matched unconstrained GP). Because the recommended input lies where the curve is nearly flat, no method can pin it down precisely, and we report it as a cost-indexed quantile with the probability of falling short.
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2606.26577 · 25 Jun · v2: substantially revised and extended, with new analyses, figures and tables, and with the Supporting Information appended. 84 pages: main text with 8 figures and 4 tables, followed by the Supporting Information (5 figures, 19 tables). Code and cached results: https://github.com/pouyna/SplineBAL

Materials Science

Topological phase transition driven by in-plane spin rotation

The intrinsic coupling between magnetism and nontrivial band topology in magnetic topological insulators makes external magnetic fields a powerful tool for manipulating topological states. However, conventional magnetic control mechanisms, such as driving magnetic phase transitions or fully reversing magnetization, typically demand large magnetic fields and lack continuous tunability. Here, we establish a symmetry framework for the reversible switching of topological states via continuous in-plane spin rotation, governed by magnetic point group constraints on the Berry curvature distribution. Using a two-dimensional kagome ferromagnetic Chern insulator as a prototype, we demonstrate that a 60{\deg}in-plane magnetization rotation reverses the sign of the Chern number, transitioning through a topologically trivial state. Crucially, micromagnetic simulations confirm that this spin-reorientation-driven switching operates under exceptionally small magnetic fields and on ultrafast timescales. This work provides a highly efficient, low-energy paradigm for the manipulation of topological states.
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All authors Xinyue Zhu, Yu Xie, Yifei Hao, Fei Gao, Yue Li, Junting Zhang

Statistical Mechanics · Cross-listed from nlin.SI

Symmetries of the Generalized Yang–Baxter Equations

The generalized Yang-Baxter equations are multi-site versions of the standard Yang-Baxter equation. When spectral parameters are included, such equations are expected to lead to integrable Hamiltonians with local interactions involving multiple degrees of freedom. In this work we characterize both the continuous and discrete symmetries of these equations required to establish an equivalence class of solutions. We find that the set of such symmetries depends on the number of sites on which the equation is supported. In several cases there are more symmetries than the standard Yang-Baxter equation, thus placing heavy constraints on the number of inequivalent solutions and the associated integrable models. As an application we show how to restrict the generic $16\times16$ ansatz to the 30-dimensional subspace invariant under a chosen discrete symmetry subgroup. An explicit $16\times 16$ solution is also written down.
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All authors Pramod Padmanabhan, Somnath Maity, Akash Sinha, Vladimir Korepin

Materials Science

Ductility Design Rules for Tungsten based Refractory High Entropy Alloys from Sparse Experimental Datasets

Tungsten-based refractory high-entropy alloys (RHEAs) are promising materials for fusion applications but often remain brittle at room temperature because of tungsten's high ductile-to-brittle transition temperature (DBTT). To identify alloying strategies that improve ductility, we compiled a curated dataset of experimentally reported tungsten-containing alloys and developed composition-based, physics-informed descriptors for machine learning. Three classifiers were evaluated using nested cross-validation, and a support vector classifier (SVC) showed the best generalization for this sparse dataset. Shapley additive explanations identified the exchange-correlation parameter, valence electron concentration, pressure field, and electronegativity mismatch as the most influential features governing ductile-brittle behavior. Synthetic compositions generated within the convex interpolation domain of the training data were evaluated and visualized on pseudo-ternary diagrams to map predicted ductility trends. The model predicts that moderate additions of Ti, Ni, and Co increase the likelihood of room-temperature ductility, whereas high Cr contents promote brittle behavior. These predictions agree with published experimental observations, including Ti-assisted ductility through solid-solution and electronic effects and embrittlement in Cr-rich refractory alloys. Agreement between DFT-derived elastic descriptors and SVC decision-function margins further supports the physical relevance of the learned classification boundary. Although the available mechanical dataset remains limited and heterogeneous, the model captures experimentally consistent trends and provides an interpretable, physics-informed framework for screening tungsten-based RHEAs for targeted simulation and experimental validation in fusion environments.
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Mesoscale and Nanoscale Physics

Photo-thermal origin of pulse laser induced orientation of crystallographic c axis in Tellurium thin films

Recent studies have shown that the orientation of crystallographic c axis of Tellurium thin films can be controlled using picosecond long laser pulses. This method provides spatially programmable control of the crystal orientation and is therefore highly attractive for practical applications in functional optical and electronic devices. Previously, it was suggested that laser-induced selective melting and recrystallization can cause the laser-induced reorientation. However, this interpretation remains inconclusive due to limited data. To clarify the mechanism, here we systematically study Te samples under different irradiation conditions. We find that the threshold fluence for inducing optical reorientation depends on the number of laser pulses. The results agrees well with a minimal kinetic model based on the Arrhenius law. Using the model developed, we investigate the condition required to control the optic axis in other two-dimensional materials, such as black phosphorus, WTe2, and SnSe. These findings provide a guide for developing functional electro-optical devices based on anisotropic materials.
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All authors Arata Mitsuzuka, Yuta Kobayashi, Takuto Hiraoka, Masashi Kawaguchi, Masamitsu Hayashi

Soft Condensed Matter · Cross-listed from astro-ph.EP

A semi-analytic model of the bouncing barrier for protoplanetary dust aggregates

Collisional bouncing limits the growth of dust aggregates in protoplanetary disks, but its dependence on aggregate size, collision velocity, and filling factor remains poorly understood. Here we develop a semi-analytic model for the sticking probability of colliding dust aggregates. We divide each aggregate collision into two phases: a compression phase and a separation phase. The compression phase is described with an elastoplastic contact model, which determines the maximum contact radius and repulsive energy after compression. The separation phase is treated as fracture of a stochastic network of interparticle bonds, whose fracture energy is evaluated using weakest-link statistics. The model naturally predicts that larger aggregates bounce more readily because larger contact regions are more likely to contain weak bonds. Comparison with distinct element method simulations shows that the model reproduces the simulated sticking–bouncing boundary. Furthermore, applying the calibrated model to moderately porous aggregates inferred from ALMA observations of protoplanetary disks, we find that the predicted bouncing barrier passes through the observationally inferred size–velocity range. Thus, our semi-analytic model provides a useful framework for predicting the collisional evolution of protoplanetary dust aggregates.
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All authors Sota Arakawa, Haruto Oshiro, Yuki Yoshida, Kiwamu Yoshii

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Nonsmooth Bloch Oscillations in Non-Hermitian Systems

Bloch oscillations (BOs) represent a paradigmatic manifestation of force-driven band dynamics in lattices, conventionally characterized by continuous quasimomentum evolution and smooth periodic trajectories. Here we show that non-Hermiticity qualitatively changes this paradigm, introducing nonsmooth BOs characterized by cusp-like real-space trajectories and abrupt momentum jumps. Reversing the force switches the dynamics between smooth and nonsmooth BOs, enabling strongly nonreciprocal dynamics. We derive a universal relation for the critical force that governs the nonsmooth-to-smooth dynamical transition in general one-dimensional lattices, which is induced by a pitchfork bifurcation in momentum space. Our work establishes a unified framework for non-Hermitian BOs and uncovers a fundamental bifurcation mechanism that can generate nonsmooth wave transport in entirely linear systems.
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Wednesday 24 June

Mesoscale and Nanoscale Physics · Cross-listed from physics.chem-ph

Large CISS Polarization from the Hierarchy Between Transport and Geometrical Spin Currents

Large spin polarization observed in chiral-induced spin selectivity (CISS) remains difficult to explain quantitatively. Experimental polarizations measured in chiral molecular systems are often substantially larger than expected from weak microscopic spin-orbit interaction in organic materials. We revisit the geometrical spin current introduced previously for electrons constrained to curved paths and propose a scale argument relevant to transport through double-stranded DNA (dsDNA). Estimation of the intrinsic geometrical spin-current scale using representative dsDNA parameters yields current magnitudes substantially larger than measured transport currents in many CISS experiments. We suggest that this hierarchy allows transport to be interpreted as weak leakage from underlying curved spin-current states. Within this picture, large CISS polarization emerges as transport selection of pre-existing spin-current branches.
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Statistical Mechanics

Comment on "Fundamental limit of phonon Tesla valve for heat rectification from first principles"

Thermal rectification is a two-terminal property: the same device must carry different heat-current magnitudes when two reservoir temperatures are interchanged. In this Comment on Ref.~\cite{WuHu2026}, we ask whether the reported ratio $\gamma=R_{\mathrm{f}}/R_{\mathrm{b}}$ can represent such a two-terminal rectification ratio within the fixed-background linearized phonon Boltzmann transport equation (BTE) used in that work. We show that, for a passive two-terminal reservoir problem, any fixed linearized BTE whose scattering operator preserves a uniform equilibrium temperature shift, and whose boundary-value problem is well posed, gives equal forward and reverse resistance magnitudes. A direction-dependent response can still occur under a prescribed gradient-weighted source–sink protocol, but such a response should be distinguished from two-terminal thermal rectification.
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Mesoscale and Nanoscale Physics

Quantum Hall effect in three-dimensional lattice induced by Wannier-Stark-Landau localization

We study the quantum Hall effect in a cubic lattice subjected to parallel electric and magnetic fields aligned along a crystal axis. The dual fields confine electrons in three dimensions with their classical orbits residing on the surface of a finite-size cylinder. In the quantum limit, the spectrum yields a three-dimensional generalization of the Hofstadter butterfly, featuring equidistant resonances near the spectral center and discrete levels near the boundaries. When the Fermi energy lies within these spectral gaps, the Hall conductance in the plane normal to the fields is quantized while other components of the conductance tensor vanish. Under open boundary conditions, this quantum Hall state exhibits topological chiral hinge modes protected by bulk Chern numbers. Our results offer a novel platform for studying the quantum Hall effect in both solid-state heterostructures and synthetic lattices.
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Soft Condensed Matter

Frustrated shapes of solid domains in fluid membrane vesicles: From rolls and folds to crumples and wrinkles

Fluid-solid composite vesicles, comprising 2D solid domains integrated into a topologically-closed fluid bilayer membrane, exhibit complex morphologies arising from the geometric frustration between spherical closure of the membrane and 2D solid elasticity. This scenario is distinct from the better studied case of multi-fluid domain vesicles. Here, we study the elastic energies and shape equilibria of a closed vesicle membrane containing a single, flexible circular solid domain using discrete finite-element (Surface Evolver) simulations, determining the key physical and mechanical parameters to govern shape selection. While we find that the 2D solid (shear) elasticity has minimal impact on the highly-under inflated morphologies, the geometrically non-linear resistance of the solid to Gaussian curvature substantially impacts the shape and elastic patterns form for inflated vesicles, by an amount that it grows with ratio of vesicle size to the elastic thickness of solid. For sufficiently large (thin) vesicles we characterize a generic sequence of ground state patterns of solid shape with increasing inflation: from cylindrical rolls and isometric folds to spatially complex patterns of crumples and wrinkles and ultimately to smooth caps. This sequence of non-isometric patterns at high-inflation is shown to be governed by the same far-from-threshold mechanics used to describe similar shape transitions in microscopic sheets on curved liquid interfaces, establishing that inflated shapes are governed by two basic mechanical scales of membrane tension. We find our predictions for highly-anisotropic shape equilibria of fluid-solid composite vesicles closely match experimentally observed shapes of giant unilamellar vesicles of phase-separated DPPC and DOPC.
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All authors Geunwoong Jeon, Anthony N. A. Prempeh, Maria M. Santore, Gregory M. Grason

Quantum Gases

Non-ergodic dynamical phase transition via a zero-mode exceptional point in a non-Markov atomic Josephson junction

Open quantum systems typically lose their initial memory due to the environmental decoherence resulting in thermalization. We demonstrate a striking breakdown of this paradigm in a head-to-tail Bose-Josephson junction, which is described by an intrinsically momentum-coupled Caldeira-Leggett model. Through exact non-Markov Langevin simulations, we discover a novel type of non-ergodic dynamical phase transitions into a running state, which has no counterpart in Markov limit. Crucially, we reveal that this transition is fundamentally governed by a zero-mode exceptional point emerging from the non-Markov friction. This topological origin is characterized by the winding of the response function. Finally, numerical quantum simulations of an equivalent driven XXZ spin chain confirm that this exceptional-point-induced signature robustly survives as a dynamical crossover against strong quantum fluctuations and the dynamical backreaction of the environment. This macroscopic robustness offers a promising platform for long-lived quantum memories in dissipative environments.
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