CMP Journal 2026-08-17
Statistics
Nature: 3
Nature Materials: 1
Nature Nanotechnology: 1
Nature Reviews Physics: 1
arXiv: 53
Nature
Positional isomerisation of pyridine via nitrogen transposition
Original Paper | Synthetic chemistry methodology | 2026-08-16 20:00 EDT
Wonjun Choi, Hyewon Ju, Jiyong Park, Sungwoo Hong
Positional isomers of pyridines often display distinct biological activities1,2 yet their direct interconversion remains largely inaccessible, so each isomer is typically prepared through an independent synthesis. Here we report a general strategy for pyridine positional isomerization enabled by controlled reorganization of the heteroaromatic core through sequential nitrogen insertion and deletion. N-atom transposition allows predictable translocation of preinstalled substituents without altering substituent identity. The method is broadly applicable to mono-, di-, and multisubstituted pyridines and operates across structurally complex molecular environments, providing direct access to positional isomers. This work establishes positional isomerization as a practical synthetic transformation, defining pyridine substitution patterns as mutable variables in retrosynthetic design.
Synthetic chemistry methodology
Programmable remodelling of carbon-nitrogen connectivity in amines
Original Paper | Synthetic chemistry methodology | 2026-08-16 20:00 EDT
James D. Robinson, François Richard, Kohl A. Ratkovich, Joseph M. Phelps, Matthew J. Gaunt
Tertiary amines are ubiquitous motifs in biologically active molecules, where they play central roles in molecular recognition and function1,2. Among these, tertiary benzylamines are particularly prominent in discovery chemistry as readily assembled starting points for lead generation from abundant building blocks3,4, with favourable physicochemical and binding properties. However, despite their accessibility, the core C-N connectivity of these frameworks remains effectively locked5,6, confining diversification to benzylamine derivatives and preventing direct access to structurally distinct aryl-alkylamine architectures. Overcoming this limitation requires direct and selective reconfiguration of C-N connectivity within fully elaborated amine scaffolds. Here we show that tertiary benzylamines can be transformed from static scaffolds into programmable platforms for molecular diversification through catalytic remodeling of their C-N bonds7-9. N-alkylation with a bifunctional electrophile generates a quaternary ammonium intermediate that encodes palladium-catalyzed disassembly and reconfiguration of C-N connectivity. This concept is first exemplified through one-carbon homologation of tertiary benzylamines and, more significantly, establishes a general strategy for programmable insertion of modular units–ranging from single carbon atoms to complex molecular fragments, including hydrocarbon chains, heterocycles and aryl groups–directly across the C-N bond on fully elaborated amine scaffolds. This capability opens a route to programmable diversification of amine frameworks, enabling systematic exploration of amine connectivity and molecular architecture.
Synthetic chemistry methodology
Defect passivation and optical management of triple-junction solar cells
Original Paper | Devices for energy harvesting | 2026-08-16 20:00 EDT
Ye Xu, Zhijie Wang, Chen Deng, Lianlian Qi, Yi Mo, Qianqian Wang, Danni Yu, Yao Wang, Yifan Chen, Yiqin Tian, Pengcheng Zhao, Ming Luo, Dongrui Jiang, Haiyun Li, Xiaobing Ding, Rui Xia, Dongdong Yan, Pengcheng Ge, Delei Xin, Huifeng Yao, Shangqian Zhu, Kaihu Xian, Chengyue Zhou, Guangtao Yang, Li Yin, Yingguo Yang, Anurag Krishna, Wallace C. H. Choy, Pietro P. Altermatt, Jianlu Wang, Zhigang Xie, Xueling Zhang, Junhao Chu, Hong Zhang, Jifan Gao, Yifeng Chen
Perovskite/perovskite/silicon-based triple-junction solar cells are a promising low-cost route to surpass the Shockley-Queisser efficiency limit of single-junction photovoltaics, but their performance is constrained by non-radiative losses in wide-bandgap perovskites and sub-optimal light management across the multilayer stack1-3. Here, we introduce a passivating molecule, 4F-POEABr, which strongly suppresses surface-defect-mediated recombination of WBG perovskite films. The ammonium attached and electron-deficient structure of 4F-POEABr provides combined chemical and field-effect passivation, enabling a quasi-Fermi-level splitting of 1.53 eV and an open-circuit voltage of 1.413 V in the WBG sub-cell. In parallel, systematic interference management is used to optimize the current density of the current-limited middle sub-cell, yielding a gain of 0.5 mA cm⁻2 via a tailored tin oxide/indium zinc oxide bilayer structure. As a result, the triple-junction devices achieve certified steady-state power conversion efficiencies of 32.22% for a 1.046 cm2 aperture area and 26.97% for a 15.62 cm2 aperture area, with negligible hysteresis. Robust interconnection layers and engineered perovskite interfaces further enhance operational stability and reduce device-to-device variation. This work demonstrates a synergistic strategy for pushing perovskite/silicon triple-junction solar cells toward their theoretical efficiency limits, enabling scalable, high-performance photovoltaic technologies.
Devices for energy harvesting, Solar cells
Nature Materials
An aberration-corrected bionic eye for full-colour vision and event-driven motion detection
Original Paper | Electronic devices | 2026-08-16 20:00 EDT
Zhenghao Long, Kaichen Wang, Shaoshuai He, Xiaofei Sun, Zilong Ye, Jianye Li, Ke Shen, Xiao Qiu, Yucheng Ding, Feng Xue, Yu Zhou, Shivam Kumar, Swapnadeep Poddar, Xichao Tan, Yunlong Zi, Zhiyong Fan
Vision sensors are central to machine vision and intelligence. However, conventional planar devices rely on multielement optics and external processors to correct optical aberrations. This approach constrains miniaturization, reduces power efficiency and generally limits the field of view. Curved sensors can provide compact, aberration-corrected imaging, but their resolution has been below practicable levels. Here we present a bioinspired bionic eye system based on a hemispherical tandem artificial retina. This high curvature image sensor achieves a pixel density of 1,905 ppi with 367,500 total pixels, providing full-colour imaging across 300-800 nm and an aberration-corrected field of view exceeding 160°. Furthermore, the tandem design enables in-sensor, event-driven motion detection. Compared with frame-based imaging, this approach reduces the demand for bandwidth by over 99.95% and achieves a motion recognition accuracy of 98.6%. This work addresses the resolution bottleneck of hemispherical sensors and highlights their promise as compact, multifunctional vision applications.
Electronic devices, Nanowires
Nature Nanotechnology
Hydration layer mediates near-frictionless sieving of monovalent ions
Original Paper | Nanofluidics | 2026-08-16 20:00 EDT
Jinlei Yang, Bin Tu, Yawei Liu, Sai Xu, Kaihang Zhang, Shixian Xin, Han Xie, Zhouwen Cao, Shuting Xu, Yue Ying, Zhifei Sun, Munan Fang, Xiaopeng Zhang, Xinghua Shi, Lianshan Li, Zhiyong Tang
Achieving simultaneous high selectivity and permeability for monovalent cation separation remains challenging due to energy-intensive dehydration requirements in current rigid nanopores. Here we develop a hydration-layer-mediated sieving strategy by anchoring hydrated ions at the pore rim of a covalent organic framework monolayer to form dynamic angstrom-scale hydrapores. Ion transport is regulated via attraction and repulsion between bound and migrating ions, arising from the merging and squeezing of hydration layers, enabling precise discrimination without full dehydration. Under a concentration gradient (∆C = 1 M), the membrane exhibits selectivity of 148 for K+/Li+ and 42 for Na+/Li+ with a K+ permeance of 2 × 104 mol m-2 h-1, three orders of magnitude higher than those of state-of-the-art membranes. A low activation energy of 5.5 kcal mol-1 indicates near-frictionless transport, offering a new paradigm for monovalent cation separation.
Nanofluidics, Structural properties
Nature Reviews Physics
van der Waals Josephson junctions for quantum science and technology
Review Paper | Electronic properties and materials | 2026-08-16 20:00 EDT
Joydip Sarkar, Ayshi Mukherjee, Amit Basu, Ritajit Kundu, Arijit Kundu, Mandar M. Deshmukh
Josephson junctions (JJs) made out of van der Waals (vdW) materials offer a unique route to explore novel functionalities in superconducting devices such as emergent phases, anisotropic order parameters and crystalline tunnel barriers that remain inaccessible in conventional JJs. Over the past decade, vdW JJs have advanced rapidly, driven by new fabrication techniques and a diverse vdW materials library that enables the integration of materials with vastly disparate properties for scientific exploration. Beyond material diversity, vdW crystalline materials offer new control over device symmetries, enabling the realization of Hamiltonians unique to 2D systems. Furthermore, the long relaxation times of excitations in 2D heterostructures open possibilities for creating quantum sensors, with the 2D material itself acting as an efficient bus for transmitting excitations to the active sensing element. The use of vdW materials has also opened up the opportunity to explore the effect of moiré structures and topology, which could lead to potential applications in quantum computation and ultra-sensitive hybrid sensors. Although opportunities abound with vdW JJs, the challenge of scalability must be surmounted for translation into real-world devices. In this Review, we synthesize current developments in this field and offer a forward-looking roadmap.
Electronic properties and materials, Superconducting properties and materials
arXiv
Comment on: Microscopic signatures of an imaginary charge density wave in a kagome metal
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Ilija K. Nikolov, Adrien Rosuel, Vesna F. Mitrović
In this Comment, exact diagonalization and quantitative analysis show that the reported signatures of loop currents in Ref. [arXiv:2605.05101; this https URL] can instead be explained by crystalline mosaicity and pre-transitional CDW fluctuations. Specifically: (i) the NQR linewidth tracks a standard Curie-Weiss (CW) law with no anomalies; (ii) the Zp-NQR asymmetric lineshapes stem from an angular mosaic spread, reproducing the spin-transition-dependent skewness; and (iii) the reported emergent field ($ h_{\rm loc}$ ) arises from particular fitting constraints and attributing the angular distribution to an internal field rather than mosaicity. Consequently, the data in Ref. [arXiv:2605.05101; this https URL] remain insufficient to establish TRSB due to loop currents or a phase transition at $ T^\ast \sim$ 120 K.
Strongly Correlated Electrons (cond-mat.str-el)
comment on arXiv:2605.05101
On first-order thermodynamic equilibrium conditions for fluid-fluid and solid-phase interfaces
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-08-17 20:00 EDT
Nicodemo Di Pasquale, Thomas Hudson
Starting from the constrained variational formulation of Larché and Cahn for solids in contact with fluids, a unified thermodynamic framework for such systems is developed. Both bulk and interfacial equilibrium conditions arise as stationarity conditions of a single thermodynamic functional. While earlier theory neglects a full treatment of interfacial contributions and therefore cannot describe systems in which surface effects are significant, the present formulation incorporates interfacial thermodynamics directly into the variational principle. The framework is introduced first for fluid-fluid systems to establish the underlying mathematical structure, and is then extended to solid-fluid interfaces. Within this setting, classical equilibrium relations for heterogeneous systems emerge naturally from different classes of admissible variations, providing a common theoretical basis for bulk, interfacial, and configurational thermodynamics.
Statistical Mechanics (cond-mat.stat-mech), Materials Science (cond-mat.mtrl-sci)
55 pages, 1 figure
Far-from-equilibrium topological phase transition in one dimension
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-08-17 20:00 EDT
Ze-Min Huang, Gustav John, Sebastian Diehl
We uncover a mechanism for far-from-equilibrium topological phase transitions, via a one-dimensional compact phase model evolving deterministically from random initial conditions. It rests on topology and symmetry rather than on phenomenological postulates: phase compactness permits vortices, and a homogeneous fixed point suppresses their nucleation, with the fixed point itself implied by phase-shift symmetry. The competition between vortex-induced disordering and relaxation toward homogeneity drives a continuous nonequilibrium transition, whose universality class we identify as directed percolation (DP). We demonstrate this by constructing the corresponding effective field theory and numerically confirming DP critical scaling through dynamical-scaling analysis.
Statistical Mechanics (cond-mat.stat-mech), Quantum Gases (cond-mat.quant-gas)
6+2 pages, 6 figures
Far-from-equilibrium scaling of non-abelian Goldstone modes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-08-17 20:00 EDT
Carl Philipp Zelle, Gustav John, Orla Supple, Romain Daviet, Sebastian Diehl
We identify a broad class of nonthermal phases generated by the interplay of continuous symmetry breaking and weak nonequilibrium driving. Extending Kardar-Parisi-Zhang (KPZ) physics beyond the single $ SO(2)$ chronon associated with periodically broken time translations, we construct nonequilibrium nonlinear sigma models for $ SO(2)\times O(N)$ symmetry, describing non-Abelian time crystals with coexisting temporal and internal order. This symmetry structure arises naturally in driven quantum materials, active matter, and optically induced periodic states. For rotating and oscillating phases, we derive the Goldstone theories and show that chronon-$ O(N)$ couplings remain finite deep in the ordered regime. One-loop renormalization group analysis reveals a KPZ-like dimensional structure: in $ d=1,2$ , arbitrarily weak nonequilibrium perturbations destabilize the equilibrium fixed point and generate strongly coupled nonthermal fixed points, realizing emergent equilibrium breaking. By contrast, for $ d > 2$ , weak perturbations are irrelevant and effective equilibrium is restored. A central result is unconventional weak dynamic scaling in the rotating phase: strongly coupled Goldstone sectors acquire distinct universal dynamical exponents despite belonging to the same order parameter. We characterize this scaling analytically and corroborate it through direct simulations in $ 1+1$ dimensions. In the oscillating phase, we recover and extend weak-scaling regimes known from drifting polymers. Finally, compactness and topological defects ultimately destroy long-range order but leave experimentally accessible nonthermal scaling windows. Together, these results extend KPZ universality to non-Abelian symmetry breaking.
Statistical Mechanics (cond-mat.stat-mech)
Thickness-dependent secondary-electron emission from suspended MoS$_2$ membranes in the helium ion microscope
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Cyan Kim, David Lister, Philip Jackle, Karen L. Kavanagh
Secondary-electron (SE) emission in the helium ion microscope (HIM) becomes sensitive to membrane thickness when the sample is thin enough for He-ion transmission and when the SEs emitted from the bottom surface are collected. We correlated the total SE intensity of suspended, nanometer-thick MoS$ _2$ flakes on lacey carbon with thickness measured independently by electron energy-loss spectroscopy. The response peaks at 40-55 nm, with an apparent back-to-front SE signal ratio reaching 4.7. The peaked, thickness-dependent component is attributed primarily to SE emission at the bottom surface of the flake, rather than to transmitted ions striking instrument surfaces. Applying SRIM ionization profiles, an asymmetric SE-escape model with a longer escape depth on the exit side reproduces the response. We find an effective exit-side escape depth of approximately 10 nm, five times the assumed 2 nm entrance value, suggesting that deposited energy reaches the exit surface far more efficiently than the entrance surface or that the SRIM model’s energy deposition profile is shifted by an effect such as channeling. The correlation provides a rapid thickness screen for suspended membranes and a route to testing low-energy ion-solid interaction models in thin materials.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
6 pages, 3 figures. Submitted to Applied Physics Letters. Supplementary material included as an ancillary file
Complete Suppression of Thermomagnetic Instabilities in Nb Superconducting Films by Combined Metallic Layers and Ion Irradiation
New Submission | Superconductivity (cond-mat.supr-con) | 2026-08-17 20:00 EDT
D. Carmo, A. M. H. de Andrade, R. Giulian, A. A. M. Oliveira, W. A. Ortiz, F. Colauto
Thermomagnetic instabilities in superconducting films can trigger flux avalanches that disrupt the critical state and impair the performance of superconducting devices. Here we investigate the stabilization of Nb thin films subjected to a perpendicular magnetic field by two complementary approaches: the addition of normal-metal overlayers and Ar ion irradiation. Magnetization measurements and magneto-optical imaging show that the metallic layers suppress the onset of avalanches at low applied fields, whereas ion irradiation reduces the high-field portion of the instability region by shifting the upper threshold for avalanche activity to lower fields. When combined in the same sample, these two partial stabilization effects lead to complete suppression of thermomagnetic instabilities. In particular, a Nb film coated with a 1(\mu)m-thick Cu layer after irradiation at a fluence of (5\times10^{16})ions/cm(^2) exhibits smooth magnetization curves and avalanche-free flux penetration. This combined treatment restores stable critical-state behavior and provides a practical route for stabilizing Nb superconducting films in thin-film superconducting technologies.
Superconductivity (cond-mat.supr-con)
Stochastic twinning in confined volumes of Mg: Insights from in-situ micromechanical testing and atomistic simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Hexin Wang, Fatim Zahra Mouhib, Chunhua Tian, Sang-Hyeok Lee, Henry Ovri, Julien Guénolé, Sandra Korte-Kerzel, Talal Al-Samman, Zhuocheng Xie
Tensile twinning plays a central role in accommodating
Materials Science (cond-mat.mtrl-sci)
Benchmarking the flow of epithelial cell monolayer with self-aligning deformable active membranes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Marcos Pasa, Carine P. Beatrici, François Graner, Leonardo G. Brunnet, Emanuel F. Teixeira
Collective cell migration emerges from the interplay between motility, deformability and mechanical interactions, yet incorporating these ingredients into computationally efficient tissue models remains challenging. Here, we benchmark self-aligning deformable active membranes in a confined-flow geometry that mimics epithelial monolayer migration around a circular obstacle. In this model, cells are represented as deformable, adhesive membranes whose self-propulsion direction relaxes towards their velocity. By systematically varying the self-alignment timescale, cell-cell adhesion and inlet forcing, we characterize the resulting flows through collective alignment, relative density, neighbor rearrangements and spatial velocity fields. The model captures a broad spectrum of tissue behaviors, ranging from disordered, liquid-like flows to highly aligned, solid-like states. Compared with a related multiparticle model, self-aligning active membranes achieve stronger collective alignment, exhibit a more systematic density response and access states closer to both limits of the solid-liquid spectrum. We further show that increasing the target shape index promotes cell elongation and accelerates tissue flow, directly linking cell-scale deformability to tissue-scale transport. Finally, we compare simulated velocity profiles with experimental measurements from in vitro migrating MDCK epithelial cell monolayers and find qualitative agreement across multiple horizontal and vertical transects around the obstacle. These results establish self-aligning deformable active membranes as a versatile framework for connecting cell mechanics, shape adaptation and self-alignment to collective tissue migration in confined geometries.
Soft Condensed Matter (cond-mat.soft)
16 pages, 14 figures
Ion-Pairing Enhancement under Osmotic Stress: Disentangling the Effects of Ion and Water Activities
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Jay Prakash Singh, Viatcheslav Freger
The dependence of ion pairing on osmotic stress may strongly affect the performance of ionic materials and membranes whose interior is often osmotically stresses, yet quantitative understanding of this dependence and, specifically, the effects of water and ion activities is limited. Motivated by this gap, we analyze the enhancement of ion pairing with osmotic pressure for concentrated aqueous KCl, NaCl, and LiCl solutions using molecular dynamics simulations. Based on rigorous thermodynamic relations, we separate the contributions of ion non-ideality to the pairing constant, varying with osmotic pressure, from other effects including water release and type of ion-pair. Our analysis reveals that ion non-ideality indirectly generates a stronger effect on pairing than the direct one of water release. However, its effect is moderated and may even be reversed for more hydrated pairs by a similarly large and opposite effect of ion-pair non-ideality assigned to varying dielectric properties of the solution and water restructuring upon pairing. The interplay between these contributions, including large and pair type-specific hydration effects on the cost of pairing, explains the observed opposing trends: pairing decreases with osmotic pressure for more hydrated solvent-separated pair types while increasing for contact pairs. The trend becomes more pronounced for more hydrated smaller cations, but was fairly independent of the water model used. The results further suggest that dielectric effects enhanced in ionic materials-and, as a result, larger variations of ion-pair non-ideality, compared with aqueous solutions, should have a more significant impact on pairing than water release.
Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph)
From suspensions to porous multilayers: microstructure formation and particle packing in drying colloidal films
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Drying particle suspensions is widely used to assemble particles and to fabricate porous functional layers for various applications, in which microstructural properties critically influence the overall device performance. Understanding the mechanisms governing drying-induced microstructure formation is therefore essential for predictive control of the resulting structures. In this work, we numerically investigate the evolution of microstructures during the drying of particle suspension films, with a particular focus on the role of particle-particle interactions. For weakly interacting particles, the particles assemble into hexagonal structures at the interface, and upon drying, trigger subsequent layer-by-layer assembly. We present a simple theoretical model to predict the time evolution of the layer thickness, validated against our simulation results. With strong particle interactions, the particles aggregate and form a network-like structure during drying, leading to a porous deposit. The porosity of the structure follows a power-law relationship with a dimensionless adhesion parameter that characterizes the particle-particle interaction force relative to the capillary force. By systematically varying the adhesion parameter, three packing regimes of the final structure are identified: hexagonal close packing, random close packing, and adhesive packing. Overall, our results demonstrate that particle-particle interactions play a decisive role in determining the final porous structure, providing practical guidance for tailoring functional layers through controlled manipulation of particle interactions.
Soft Condensed Matter (cond-mat.soft)
10 pages, 6 figures
Rapid Kirigami Simulation using the Bar & Hinge Approach
New Submission | Other Condensed Matter (cond-mat.other) | 2026-08-17 20:00 EDT
Raj Pradip Khawale, Elaheh Mehdizadeh, John Brigham, Evgueni T. Filipov
Kirigami, the art of cutting sheets, offers unique characteristics such as shape morphing, stretchability, and adaptability, with applications in deployable and reconfigurable structures. While Finite Element (FE) approaches are widely used to analyze kirigami structures, they are computationally intensive and prone to convergence issues. On the other hand, existing simplified and theoretical models for evaluating kirigami are typically restricted to specific designs and analytical scenarios. This paper proposes a generalized, computationally efficient reduced-order model based on the bar and hinge approach for analyzing any kirigami system. The model represents the entire kirigami structure using truss bars, bending hinges, and torsional springs, capturing both the deformation and internal forces of the system. We derive stiffness expressions for kirigami structures that experience stretching and out-of-plane bending deformations, as well as for structures that experience only in-plane stretching and rotations. The accuracy and robustness of the model are validated through comparisons with FE analysis and experimental data on both single-cut kirigami designs and more complex designs with multiple cuts. Our results demonstrate less than 5% difference in deformation predictions and achieve at least a tenfold computational speedup compared to FE simulations. Additionally, we demonstrate the model’s capabilities through simulating complex scenarios, including kirigami-skinned crawlers, high-throughput property-space exploration, and in-plane kirigami-inspired metamaterials. These examples demonstrate computational capabilities that enable large-deformation structural simulations and high-throughput design exploration beyond the practical limits of conventional FE methods.
Other Condensed Matter (cond-mat.other), Computational Engineering, Finance, and Science (cs.CE)
23 pages, 11 figures, journal paper
Systematic extinctions in inelastic neutron scattering from molecular spin clusters
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Inelastic neutron scattering on a single crystal resolves how the intensity of a magnetic transition of a molecular spin cluster varies with the momentum-transfer vector $ \mathbf{Q}$ . The point group fixes that dependence completely when a single symmetry species mediates the transition and the local spin operators contain only one occurrence of that species. Functions for such universal $ \mathbf{Q}$ dependences have been tabulated. As we show here, even when these conditions are not fulfilled, the point group still fixes, at a given geometry, momentum transfers at which the intensity vanishes for every Hamiltonian that has the symmetry of the cluster. We call such momentum transfers extinctions and derive an equation whose every zero is an extinction, built from the symmetry species of the two levels and from the positions and scattering amplitudes of the magnetic sites. The extinctions follow in closed form in two cases: when each orbit of symmetry-equivalent sites contributes a single occurrence of the mediating species, and when the site phases recur under a subgroup up to one common factor.
Strongly Correlated Electrons (cond-mat.str-el)
16 pages, 9 figures
Multiscale Correlation of Morphological, Chemical, and Optical Properties in p-Type Porous Silicon
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Arturo Ramírez-Porras, Isaac Prado-Bermúdez
We report a systematic study of the correlations among electrochemical processing conditions and the morphological, chemical, and optical properties of porous silicon (pSi). Twenty pSi samples were fabricated from boron-doped (100) crystalline silicon by varying current density, etching time, and hydrofluoric-acid concentration. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and photoluminescence were used to characterize the resulting structures. The two-dimensional porosity varied only moderately, whereas porous-layer thickness increased with etching time and current density. The silicon oxide to silicon hydride ratio showed comparatively small variations. Corrected photoluminescence spectra were fitted with a four-component quantum-wire/quantum-dot model including localized surface-state transitions. The extracted quantum-wire and quantum-dot dimensions decreased systematically with increasing current density, while the photoluminescence maximum under 375 nm excitation showed no clear monotonic dependence on processing conditions. The results demonstrate that no single descriptor adequately captures the multiscale behavior of porous silicon.
Materials Science (cond-mat.mtrl-sci)
10 pages, 6 figures, 1 table
Strong photoresponse of edge two-dimensional electrons in a magnetic field
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-08-17 20:00 EDT
Sergey A. Mikhailov, Wladislaw Michailow
Electrons in two-dimensional electron gases in the presence of an out-of-plane magnetic field propagate along the edge with a high velocity of the order of the Fermi velocity. Under microwave and terahertz radiation, photon absorption by these electrons provides a pathway to realising sensitive radiation detection. Here, we develop a detailed quantum theory of the photocurrent generated in such a system by an incident electromagnetic wave and propose an experimental geometry for observing the predicted phenomenon. By using suitably arranged radiation confinement structures, a strong photocurrent generation efficiency can be obtained. We also demonstrate that the resulting photoresponse in III-V semiconductor structures can be orders of magnitude higher than that measured in graphene.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph), Optics (physics.optics), Quantum Physics (quant-ph)
28 pages, 7 figures
Physical Review B 113, 245301 (2026)
SPEAR: Structure Property Explainability with Attention Regularization
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Aditya Raghavan, Utkarsh Pratiush, Dalton A. Pearl, Jade Holliman Jr, Katharine Page, Philip D Rack, Sergei V Kalinin
Machine learning is increasingly used to learn structure property relationships from spectroscopic and diffraction data, yet its adoption in materials discovery is often limited by poor interpretability of model predictions. Although attention mechanisms are frequently treated as inherently explainable, unregularized attention can yield unstable, fragmented, or intensity driven attribution patterns that obscure the physical origin of these relationships. Here we introduce SPEAR (Structure Property Explainability with Attention Regularization), a framework that constrains attention distributions during training to improve their stability, selectivity, and physical interpretability. SPEAR augments attention based regression with a learnable temperature that controls attention concentration and a smoothness penalty that enforces coherence across neighboring spectral positions, treating attention as a learnable explanatory object rather than a post hoc visualization. Using synthetic spectral benchmarks with known generative structure, we show that attention regularization produces smooth, contiguous attribution profiles aligned with causal features while preserving predictive accuracy. Applied to experimental X ray diffraction data from a combinatorial rare earth zirconate thin film library, the regularized model selectively emphasizes physically relevant diffraction features and decouples feature importance from raw peak intensity. The reflection it identified prompted a reassessment of our earlier structural analysis, revealing a correlation between the 220 peak position, the tetragonal distortion that accommodates cation size disorder, and the local thermal conductivity. Attention regularization therefore provides a principled training constraint for explainable structure property regression, yielding mechanistically meaningful explanations without sacrificing predictive performance.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Realizing record-high transverse thermoelectric figure of merit at room temperature in artificially tilted multilayers based on high power factor NiFe alloy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Yebin Lee, Fuyuki Ando, Takamasa Hirai, Keisuke Hirata, Kota Hasegawa, Ken-ichi Uchida
Transverse thermoelectric conversion using artificially tilted multilayers (ATMLs) offers a versatile device architecture that circumvents the structural limitations of conventional longitudinal thermoelectrics. However, achieving competitive room-temperature thermoelectric performance without an external magnetic field remains a critical challenge. Here, we report a record-high transverse thermoelectric figure of merit $ z_{yx}T$ of 0.36 in Ni$ _{50}$ Fe$ _{50}$ /Bi$ _{0.2}$ Sb$ _{1.8}$ Te$ _{3}$ -based ATML at room temperature without an external magnetic field. Leveraging the longitudinal high power factor in a Ni$ _{50}$ Fe$ _{50}$ alloy and the sharp contrast in electrical and thermal transport properties between $ n$ -type Ni$ _{50}$ Fe$ _{50}$ and $ p$ -type Bi$ _{0.2}$ Sb$ {1.8}$ Te$ {3}$ , we engineer an anisotropic structure that simultaneously exploits high electrical conductivity, large transverse thermopower, and low thermal conductivity to maximize $ z{yx}T$ in ATML. Through the direct measurements of these thermoelectric transport parameters, we obtained $ z{yx}T$ of 0.36 in Ni$ _{50}$ Fe$ _{50}$ /Bi$ _{0.2}$ Sb$ _{1.8}$ Te$ _{3}$ -based ATML, which is in excellent agreement with the analytical prediction of 0.36 owing to the low interfacial electrical and thermal resistances at the Ni$ _{50}$ Fe$ _{50}$ /Bi$ _{0.2}$ Sb$ _{1.8}$ Te$ _{3}$ junctions. These results pave the way for the practical implementation of transverse thermoelectric materials around room temperature.
Materials Science (cond-mat.mtrl-sci)
7 pages, 5 figures
Autferroics-based true random number generators with enhanced performance
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Jun-Jie Zhang, Shuai Dong, Boris I. Yakobson
Physical entropy-driven true random number generators are essential for emerging probabilistic computing paradigms, but conventional implementations based on magnetic tunneling junctions have reached their performance plateaus limited by inherent tradeoffs and weak tunability. Here, autferroics, a sister branch of multiferroics, is proposed to construct true random number generators. Benefiting from its unique energy landscape due to strong seesaw-type magnetoelectricity, the performance of true random number generation can be significantly enhanced in autferroic tunneling junctions, verified by passing standard statistical tests. Furthermore, autferroics-based random number generators can exhibit multi-field tunability and intrinsic multi-state randomness, opening an avenue for efficient hardware realization of the complex-number arithmetic and simulation of probability distributions of quantum mixed states within stochastic circuits.
Materials Science (cond-mat.mtrl-sci)
Posterior Inference of Hamiltonian Parameters from RIXS Spectroscopy
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Samuel Klein, Thomas M. Linker, Louis Conreux, Daniel Ratner, Apurva Mehta, Makoto Tachibana, Jiemin Li, Jonathan Pelliciari, Valentina Bisogni, Wei He, Xiangpeng Luo, Mark P. M. Dean, Marton K. Lajer, Michael Kagan, Joshua J. Turner, Yongqiang Cheng, Sean Gasiorowski
We present the first application of simulation-based inference to resonant inelastic X-ray scattering spectroscopy. Using truncated marginal neural ratio estimation to efficiently restrict the prior and conditional flow matching as the joint density estimator, we infer full posteriors with a modest simulation budget for two Ni$ ^{2+}$ compounds—NiPS$ _3$ as a representative covalent case and K$ _2$ NiF$ _4$ as a more atomic one. We demonstrate that a vision transformer encoder whose tokenization matches the physical layout of the RIXS map yields better-covered and sharper posteriors than generic image encoders. Applying the validated method to experimental NiPS$ _3$ and K$ _2$ NiF$ _4$ data, we recover a joint posterior that reveals parameter correlations invisible to point estimators, and a posterior predictive distribution that closely matches the observed spectrum. The amortized posterior unlocks a class of analyses not previously available to the field such as nuisance-marginalized uncertainty quantification, multi-measurement posterior fusion and active experimental design.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Data Analysis, Statistics and Probability (physics.data-an), Machine Learning (stat.ML)
Small-world structure of quantum computer hardware
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-08-17 20:00 EDT
S. J. da Silva Junior, D. L. Shepelyansky, J. Lages
We show that the network of quantum register states of a quantum computer (QC), coupled through residual two-body interactions between qubits, exhibits small-world properties analogous to those of complex networks found in human society. The most probable Erdős number between any two states is about 9, comparable to the six degrees of separation reported by Milgram for social networks. Using the $ \mathring{A}$ berg criterion, which retains only interactions exceeding the local energy spacing, we construct an effective ($ \mathring{A}$ berg) network and show that, above a critical coupling strength, this network percolates into a giant component spanning nearly the whole quantum register space. This percolation transition closely matches the onset of quantum chaos and dynamical thermalization established previously via costly exact diagonalization, while our approach extends the accessible system size up to $ n_q=30$ qubits.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Anomalous Orbital Reconstruction Controlled by Interorbital Correlations and Hund’s Coupling
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Yu Ni, Lvjin Wang, Jinfeng Wang, Yunkun Niu, Zhaoming Fu, Yun Song
The microscopic origin of anomalous orbital polarization in a class of low-dimensional correlated oxides remains unresolved due to the competition among crystal-field effects, electronic correlations, and orbital-dependent dimensionality. Using dynamical mean-field theory, we investigate a two orbital Hubbard model with orbital-dependent dimensionality and reveal the mechanism for anomalous orbital polarization through orbital reconstruction beyond the bare crystal-field picture. We identify interorbital Coulomb interaction-induced charge competition as a key microscopic mechanism responsible for the orbital redistribution, which leads first to an orbital-polarized correlated metal and subsequently to an orbital-polarized Mott insulator. We further find that Hund’s coupling acts as a filling-dependent regulator of orbital reconstruction. It weakens the correlation-induced orbital redistribution at quarter filling by competing with interorbital charge fluctuations, while at half filling it completely suppresses the orbital-polarized state by stabilizing high-spin orbital-balanced configurations. These results provide a unified picture of correlation driven orbital reconstruction and highlight the relevance of interorbital interactions and Hund’s coupling for understanding orbital phenomena in low-dimensional transition-metal oxides.
Strongly Correlated Electrons (cond-mat.str-el)
12 pages, 10 figures
Thermal effect on the anomaly-induced electromechanical response in gapped graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-08-17 20:00 EDT
Mechanical deformation of gapped graphene can act on Dirac quasiparticles as an emergent gauge field. When this deformation field couples to the same current as the electromagnetic field, the parity anomaly produces a mixed electromechanical Chern-Simons response: a phonon electric field drives a transverse electrical current, and a phonon magnetic field binds charge. Previous zero-temperature results predict a sharp change in the response when the chemical potential crosses the band edge. We show that finite temperature replaces this sharp feature by a universal smooth crossover controlled only by the ratios of temperature, gap, and chemical potential. The response remains almost quantized in the insulating regime, is rounded over a gate window of order temperature near the band edge, and approaches the doped Berry-curvature result with a controlled Sommerfeld correction. We apply the result to two experimentally useful drives: a traveling flexural wave, which produces a transverse second-harmonic current, and a dynamic phonon mixed with a static ripple, which produces a fundamental-frequency signal. The same gate-temperature line shape controls both signals. This gives a direct way to separate the anomaly-induced current from ordinary electromechanical backgrounds and to extract the effective gap and electronic temperature in graphene devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
7 pages, 5 figures
Single-impurity polarons in hard-core lattice bosons at low and intermediate fillings
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-08-17 20:00 EDT
We investigate a single mobile impurity in a two-dimensional hard-core Bose–Hubbard bath at low and intermediate fillings and determine how polaronic dressing evolves with bath filling for impurity–bath couplings ranging from weak to strong and ultimately to the two-component hard-core limit. Using large-scale, sign-problem-free worm-algorithm quantum Monte Carlo simulations, we extract momentum-space quasiparticle properties from the impurity Green’s function and resolve the accompanying real-space bath rearrangement from an imaginary-time-averaged impurity-centered correlator. We also vary the impurity hopping $ t_{\rm imp}$ to assess how reduced mobility modifies dressing in the strong-coupling regime. For the fillings accessible at each coupling, the impurity remains a dressed quasiparticle whose ground-state energy, effective mass, and residue vary smoothly with filling $ n_{\rm b}$ . In real space, increasing $ n_{\rm b}$ strengthens the short-range depletion while shifting the dominant response toward the impurity. In the two-component hard-core limit $ U_{\rm ib}/t_{\rm b}!\to!\infty$ , the large-distance recovery of the cumulative density deformation exhibits only weak filling dependence over the range considered here, whereas short-range core indicators continue to evolve. Our results quantitatively characterize strongly dressed polarons in a correlated, compressible lattice bath and resolve how filling and impurity mobility modify the near-core response and spatial extent of the dressing cloud.
Quantum Gases (cond-mat.quant-gas)
10 pages
Testing the Reptation Picture: Topological Constraint from Monomer Dynamics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Xiaofei Tian, Qinhang Liu, Zhi-Chao Yan, Liang Gao, Tongfei Shi, Jizhong Chen
The reptation model postulates that entangled polymers slide within a fractal tube. Here we employ a model-independent relation between the zero-displacement probability and the mean-square displacement that applies to time-dependent fractal structures, enabling direct measurement of the fractal dimension $ d_\mathrm{f}$ of the geometry experienced by monomer motion. For two-dimensional obstacle arrays and in the slip-link model, $ d_\mathrm{f}$ agrees with the reptation prediction $ d_\mathrm{f}=1/\nu$ (where $ \nu$ is the Flory exponent). In polymer melts, however, we find $ d_\mathrm{f} \approx 2.6$ — a value close to the fractal dimension of percolation clusters, not the reptation value $ d_\mathrm{f}=2$ . This contrasts sharply with the reptation picture, in which a Rouse chain slides in a fractal structure with $ d_\mathrm{f}=2$ , spectral dimension $ d_\mathrm{s}=1$ , and walk dimension $ d_\mathrm{w}=4$ ; our results point instead to a percolation-like scenario, characterized by $ d_\mathrm{f}\approx 2.6$ , $ d_\mathrm{s}\approx 1.3$ , and $ d_\mathrm{w}\approx 4$ — revealing a dynamically emergent, finite-size fractal geometry distinct from the static tube.
Soft Condensed Matter (cond-mat.soft)
Periodicity-driven revision of the phase diagram of the generalized Baxter-Wu model with asymmetric complex couplings
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Yuting Wang, Ye Ling, Haihong Li, Yuhai Liu
The conventional self-dual lines of the generalized Baxter-Wu (GBW) model with asymmetric complex couplings are known to be $ \sinh(2K)=\pm \cos(2\phi)$ , where $ K$ and $ \phi$ are the real and imaginary parts of the coupling. We demonstrate that these lines are incomplete: the periodicity of the partition function, encoded in the cosine factor of the bundled Boltzmann weight, generates additional self-dual lines $ \sinh(2K)=\pm \sin(2\phi)$ . Guided by the complete set of self-dual candidates, we perform Monte Carlo simulations using brute-force reweighting (Metropolis) and the Wang-Landau methods. Simulations indicate that the self-dual lines at the partition-function minima $ \phi_{\mathcal{Z}{\min}}=(2n+1)\pi/8$ constitute a critical threshold. They are genuine critical boundaries for $ |K| \ge \frac{1}{2}\operatorname{arsinh}(\cos(\pi/4)) \approx 0.32924$ , while for smaller $ |K|$ they are not. At $ \phi{\mathcal{Z}{\min}}$ , the sign problem is most severe and finite-size scaling corrections are largest; the local peak observed below the phase boundary in the temperature scan is thus a finite-size artifact, not a genuine new phase. We further clarify the capability and limitations of the average sign and its derivatives for detecting phase transitions. In particular, the negative peak of the average sign at $ \phi{\mathcal{Z}_{\min}}$ does not correspond to a genuine phase transition. We also evaluate the Wang-Landau method, which, despite formally circumventing the sign problem, still faces the exponential barrier.
Strongly Correlated Electrons (cond-mat.str-el)
13pages,7figures
Observation of in-plane anomalous Nernst effect
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Tadashi Yoneda, Shinichi Nishihaya, Markus Kriener, Haruto Kaminakamura, Ming-Chun Jiang, Naohiro Tezuka, Yoshiya Murakami, Ryotaro Arita, Hiroaki Ishizuka, Masaki Uchida
The Nernst effect, which enables the conversion of a heat current into a transverse voltage under magnetic field or spin magnetization, holds significant promise for energy harvesting and thermal management in future electronics. However, the conventional Nernst effect is fundamentally constrained by the orthogonality requirement that the applied field or spontaneous magnetization must be perpendicular to the plane defined by the temperature gradient and the induced voltage. Here we report that symmetry-tailored ultrathin films of a prototypical ferromagnetic oxide exhibit anomalous Nernst effect arising from intrinsic coupling to spontaneous in-plane spin magnetization. Systematic magnetothermoelectric measurements under spherical rotations of the magnetic field reveal that a pronounced Nernst signal, comparable in magnitude to the out-of-plane response, emerges robustly associated with out-of-plane orbital magnetization. Our findings demonstrate that the anomalous Nernst effect is no longer limited by the orthogonality condition, opening new opportunities for more flexible designs of magnetothermoelectric materials and devices.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
27 pages, 5 figures
Quantum Geometric Kondo Cloud
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
A magnetic impurity embedded in a metal is collectively screened by Fermi-surface quasiparticles into a many-body spin-singlet ground state, forming a Kondo cloud of size $ \xi_{\rm K}\sim\hbar v_F/(k_B T_{\rm K})$ . This kinematic picture collapses in flat bands, where $ v_F=0$ and the hierarchy of dispersive energy shells is absent. Here we show that the missing organizing principle is quantum geometry. A magnetic impurity coupled to an isolated flat band selects a single active bath mode: a coherent superposition of flat-band Bloch states weighted by the hybridization factor $ v(\mathbf{k})$ , while all orthogonal flat-band modes remain dark. The resulting flat-band Kondo problem is a quantum geometric molecule, with an algebraic Kondo scale set by the total projected hybridization strength rather than a logarithmic-renormalization scale. In real space, the impurity-bath spin correlation defines a quantum geometric Kondo cloud. Its cloud-size tensor admits a gauge-invariant decomposition into a hybridization-weighted quantum metric, a dressed Berry-connection covariance, and a positive hybridization-gradient term, yielding the lower bound $ \xi_{\rm K}^2\geq \sum_{\mathbf{k}}\rho(\mathbf{k}){\rm Tr},g(\mathbf{k})$ , where $ \rho(\mathbf{k})=|v(\mathbf{k})|^2/\sum_{\mathbf{k}}|v(\mathbf{k})|^2$ . Our result reveals that, in flat bands, Kondo screening is governed by the quantum geometry and interference structure of the impurity-selected Bloch wave packet, rather than Fermi-surface kinematics.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
7 pages, 3 figures
Superconductivity in strongly overdoped cuprates: beyond the single-band model
New Submission | Superconductivity (cond-mat.supr-con) | 2026-08-17 20:00 EDT
Ruichao Chen, Linda Sederholm, Yannick Klein, Ludovic Delbes, Benoît Baptiste, Paraskevas Parisiades, Emmanuel Maisonhaute, Davide Delmonte, Edmondo Gilioli, Maarit Karppinen, Ronald I. Smith, David A. Keen, Yann Le Godec, Andrea Gauzzi
In order to explain the observation of an extended superconducting region in several overdoped cuprates, which contrasts the dome scenario, by means of neutron and synchrotron x-ray powder diffraction we study the crystal structure of YBa$ _2$ Cu$ _3$ O$ {y}$ , where strong oxygen overdoping up to $ y = 7.4$ is achieved under high-pressure. A bond valence sum analysis indicates that 1/5 of the extra holes created by the excess oxygen are transferred to the CuO$ 2$ planes, thus increasing the hole density up to $ p=0.27$ hole/Cu, where superconductivity is expected to vanish according to the dome scenario. Instead, our data confirm a previous observation [Okai, Ono and Mitsuhashi, Physica C: Superconductivity {\bf 366}, 164 (2002)] that the superconducting critical temperature, $ T_c$ , remains constant with $ y$ . Our data analysis accounts for this discrepancy in terms of the much shorter bond between the apical oxygen and the planar Cu ion, which suggests that the extra holes occupy the $ a_1$ -symmetry states formed by $ d{3z^2-r^2}$ orbitals, instead of the usual $ b_1$ -symmetry Zhang-Rice singlet states formed by $ d{x^2-y^2}$ orbitals. Suitable spectroscopic measurements on single crystals may support such a two-band scenario, which would require a totally different theoretical approach to explain superconductivity in cuprates.
Superconductivity (cond-mat.supr-con)
12 pages, 7 figures
Contact Formation and Viscoelastic Detachment in Non-Circular Soft Adhesive Contacts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Adhesive contact measurements on soft polymers are commonly interpreted using Johnson-Kendall-Roberts (JKR) theory, which is formulated for circular contacts. Here, we examine contact formation and detachment in non-circular soft adhesive contacts using PDMS crossed-cylinder experiments. The crossing angle was varied from 30 to 90 degrees, producing contacts from highly elongated ellipses to nearly circular geometries while keeping the material pair fixed. During loading, the contact aspect ratio b/a rapidly approached an angle-dependent plateau, indicating approximately self-similar growth. This motivates use of the area-equivalent radius c=sqrt(a\astb) and geometric-mean curvature radius Reff=sqrt(R1\astR2). The loading branches follow a JKR-type linearization and yield a nearly angle- and preload-independent work of adhesion, W_load=24 mJ/m^2. Johnson-Greenwood elliptical-contact fits give comparable values. In contrast, unloading and pull-off are strongly history dependent. The unloading branches require a substantially larger effective separation energy, W_unload,eff, which increases with preload and decreasing crossing angle. A reduced viscoelastic model based on the same area-equivalent description captures the principal unloading response over 50-80 degrees using a single shared parameter set across angles and preloads. These results show that contact formation is governed primarily by area-equivalent scaling, whereas detachment is governed by geometry- and history-dependent dissipative separation.
Soft Condensed Matter (cond-mat.soft)
Accurate and efficient calculation of atomic forces in solids with non-self-consistent hybrid functionals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Damian Contant, Maria Hellgren
Hybrid functionals are routinely employed self-consistently within the generalized Kohn-Sham framework. The evaluation of the nonlocal Fock exchange operator makes hybrid functional calculations computationally expensive, in particular with plane-wave basis sets. Here, we investigate the advantages of non-self-consistent hybrid functional calculations, focusing on the evaluation of atomic forces. The analytical force terms that arise due to non-self-consistency are computed using density functional perturbation theory (DFPT), as implemented within the Quantum ESPRESSO distribution. A non-self-consistent hybrid force calculation thus consists of self-consistent DFPT calculations with a local or semi-local functional and a single evaluation of the Fock exchange operator. The overall computational cost is, thereby, reduced in general, especially for solids that require a dense Brillouin-zone sampling. Moreover, results for structural parameters are barely affected by self-consistency, and vibrational frequencies are typically agreeing within 0.5%, thus making non-self-consistent calculations an interesting alternative.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
13 pages, 3 figures, 7 tables
Electrostatic Phenomenology Benchmarks for Machine-Learned Interatomic Potentials in Electrochemistry: Beyond the Energy-Force Metric
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Barbara Sumić, Ria Vasdev, Sudheesh Kumar Ethirajan, Jing Yang, Clotilde S. Cucinotta, Richard G. Hennig, Karsten Reuter, Stefan Ringe, Mira Todorova, Christoph Freysoldt, Jörg Neugebauer
Accurate treatment of long-range interactions in machine learning interatomic potentials (MLIPs) is essential for electrochemical simulations. However, aggregate energy and force errors alone are insufficient to establish an MLIP’s physical accuracy since they do not detect qualitative inconsistencies in the model such as the prediction of image-charge attraction, dielectric screening, or charge transfer. We introduce a benchmark suite EPhEct (Electrostatic Phenomena for Electrochemistry) of focused test cases designed to evaluate MLIPs on electrochemically relevant physical phenomena. The tests probe for image-charge attraction at a metal electrode, the splitting between longitudinal and transverse optical phonons as a probe of ionic and electronic screening, the dipole moment of interfacial water, and Fermi-level pinning during ion discharge. These tests establish a qualitative diagnostic routine complementary to aggregate energy-force metrics.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph), Computational Physics (physics.comp-ph)
Simplified Silicon Nitride Nanomembrane Circuits for van der Waals Integration
New Submission | Superconductivity (cond-mat.supr-con) | 2026-08-17 20:00 EDT
Tommaso Confalone, Vasilisa Gerega, Flavia Lo Sardo, Shreya Kumbhakar, Davide Massarotti, Francesco Tafuri, Shigeyuki Ishida, Hiroshi Eisaki, Kornelius Nielsch, Golam Haider, Nicola Poccia
Two-dimensional (2D) materials and van der Waals (vdW) heterostructures provide an exceptional platform for engineering quantum devices, yet realizing their potential requires electrical integration without compromising the pristine properties of atomically thin crystals through conventional nanofabrication. Transferable circuitry addresses this challenge by decoupling circuit fabrication from device assembly, enabling electrical contacting without directly processing the active material. Here, we introduce SiN$ _x$ nanomembrane (NMB) circuits realized through a simplified top-down strategy that reduces fabrication complexity, processing steps and specialized tools required by our previous bottom-up approach. As a stringent benchmark of material preservation, we electrically integrate a four-unit-cell-thick, optimally doped Bi$ _2$ Sr$ _{2-x}$ La$ _x$ CuO$ _{6+\delta}$ (Bi2201) flake and observe a superconducting transition at T$ _c^{inf}$ ~32K, close to the T$ _c^{onset}$ ~34K measured by susceptibility in the parent crystals. The preservation of superconductivity demonstrates electrical integration of fragile layered materials without direct exposure to conventional cleanroom procedures, providing a versatile platform for integrating increasingly complicated vdW heterostructures, moiré materials, and hybrid quantum architectures.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Topological phases and quantum criticality from $SU(2)$ Chern-Simons-matter theories
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Yunchao Hao, Yingcheng Li, Kangle Li, Liujun Zou
Motivated by recent numerical studies where various $ SU(2)$ Chern-Simons-matter theories emerge, we analytically study topological phases and quantum criticality in two-dimensional systems described by such theories. First, we classify $ SU(2)_k$ topological orders in all lattice spin systems with a $ p4\times SO(3)$ symmetry, where $ k$ is an arbitrary nonzero integer. We find that for each odd $ k$ , the topological order can emerge in systems with an arbitrary Lieb-Schultz-Mattis (LSM) anomaly, and the symmetry cannot permute anyons. If the system has a nontrivial (respectively, trivial) LSM anomaly, then there is exactly one (respectively, nine) symmetry-enriched topological (SET) phases. On the other hand, $ SU(2)_k$ topological order with any even $ k$ can only emerge in systems with a trivial LSM anomaly. If $ k\notin{6, 10, 14, \cdots}$ , the symmetry cannot permute anyons, and there are 16 SET phases. If $ k\in{6, 10, 14, \cdots}$ , there are 4 different ways how the symmetry can permute anyons, and there are 64 SET phases. Next, we analyze the $ SU(2)_k$ Chern-Simons theories coupled to $ N_f$ flavors of gapless matter fields that can be either bosonic or fermionic. For both types of theories, we consider a joint large-$ N_f$ and large-$ k$ limit with $ N_f/k$ fixed, and compute the scaling dimensions of the bilinear operators of the bosons or fermions to the order of $ 1/N_f$ . These results sharpen our understanding of these emergent exotic topological phases and quantum criticality, and provide useful guidance to explore them further.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Gases (cond-mat.quant-gas), High Energy Physics - Theory (hep-th)
Probing intrinsic magnetic phases in low-dimensional nearly twin-free NiPS$_3$ single crystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Yeochan An, Heejun Yang, Sung Jin Park, Giung Park, Woonghee Cho, Pyeongjae Park, Seokhwan Yun, Yoshimitsu Kohama, Je-Geun Park
We report the intrinsic thermal and magnetic properties of the low-dimensional van der Waals (vdW) antiferromagnet NiPS$ 3$ and explore its emergent magnetic phases by controlling crystallographic twinning. Using nearly twin-free crystals, we resolve intrinsic properties that are typically obscured by multidomain effects in bulk samples. Magnetization results reveal a highly anisotropic, sharp spin-flop transition, confirming the high domain purity of our crystals. Furthermore, high-precision thermodynamic and transport data reveal a broad fluctuation regime around the Néel temperature ($ T{\mathrm{N}}$ = 157.5 K), with a heat capacity anomaly and a concurrent suppression of thermal conductivity. Field-dependent thermal transport shows a small but distinct contribution from spin-lattice coupling, as evidenced by the dip at the spin-flop transition. We develop a theoretical model to explain these properties reported in this paper, with good agreement between experiment and theory. Our work establishes a definitive baseline for bulk properties of NiPS$ _3$ and demonstrates the feasibility of resolving intrinsic anisotropies by addressing crystallographic twinning in vdW magnets.
Materials Science (cond-mat.mtrl-sci)
Accepted by Advanced Functional Materials; 27 pages, 6 main figures, 8 supporting figures
Microscopic investigation of spin dynamics in the single-chain magnet Sr4Mn2CoO9
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
G. Roy, S. Ghosh, M. Kumar, E. Kushwaha, J. Sannigrahi, V. Caignaert, W. Prellier, D. T. Adroja, D. Voneshen, V. Hardy, T. Basu
One-dimensional single-chain magnets offer a unique platform for studying the interplay of crystal-field effects, exchange interactions, and lattice dynamics. Here, we investigate spin excitations in Sr4Mn2CoO9 using inelastic neutron scattering (INS) and theoretical modelling. INS reveals two low-energy magnetic excitations at 4 and 7 meV from Mn-Co-Mn spin chains, alongside higher-energy crystal-electric-field (CEF) excitations from two crystallographically inequivalent Co2+ sites. Interestingly, these spin excitations persist at room temperature, demonstrating dynamic magnetic correlations in the absence of long-range order. Furthermore, the crystal-field modelling, based on Stevens operator formalism, reproduces well the CEF spectra, establishing Ising-like Kramers ground-state doublets with strong uniaxial magnetic anisotropy for both Co2+ ions. In addition, the spin wave simulation using SpinW reproduces the spin excitation spectrum and reveals microscopic exchange interactions in two non-interacting Mn-Co-Mn spin chains. Finally, machine-learning lattice-dynamics calculations confirm the phonon spectrum and spin-phonon coupling. By projecting the exchange Hamiltonian onto CEF ground-state doublets, we estimate exchange-induced splittings matching the observed excitations. Thus, our results elucidate low-energy spin dynamics arising from combined crystal-field anisotropy and exchange interactions, with the persistent low-energy excitation providing a microscopic pathway for thermally activated spin relaxation. Furthermore, this work delivers a unified microscopic understanding of the interplay between crystal-field effects, magnetic exchange, and lattice dynamics in Sr4Mn2CoO9, advancing insights into spin dynamics in low-dimensional transition-metal oxides.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
12 pages manuscript with 7 Figures
Disorder signatures emerging at millikelvin temperatures in Si/SiGe field-effect stacks
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-08-17 20:00 EDT
Lino Visser, Alberto Mistroni, Yuji Yamamoto, Fabian Fidorra, Oksana Fursenko, Steffen Marschmeyer, Marvin H. Zoellner, Giovanni Capellini, Dominique Bougeard, Vincent Mourik, Marco Lisker, Felix Reichmann
The performance and scalability of electron spin qubits based on gate-defined quantum-dots in undoped Si/SiGe field-effect stacks remain constrained by disorder originating from the gate stack. Its coupling to the quantum well can be reduced by increasing the Si quantum well depth, while electrostatic charge history, for example through interface-trap filling, can further modify the effective disorder landscape. Although such disorder is commonly benchmarked through mobility measurements using magnetotransport and Hall bar devices, dedicated investigations at millikelvin temperatures relevant for quantum-dot operation remain limited. Here, we use temperature-dependent magnetotransport on Hall bar shaped field-effect transistors to investigate how mobility-based disorder signatures depend on quantum-well depth and charge history from (1.5\mathrm{K}) down to the millikelvin regime. We show that magnetotransport characterization at (1.5\mathrm{K}) captures the dominant mobility improvement associated with reduced dielectric-interface coupling, but can underestimate disorder differences that emerge at millikelvin temperatures, particularly in the low-density regime. Our results therefore highlight that millikelvin magnetotransport characterization of Hall bar devices can provide additional insight for optimizing Si/SiGe field-effect stacks, particularly in the context of gate-defined quantum dot spin qubits.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages (6 main, 9 supplementary), 13 figures (3 main, 10 supplementary)
Dispersive-phonon-driven room-temperature Ni1+-Ni2+ polaron hopping in spin-charge coupled rutile niobate
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Gourab Roy, Mohit Kumar, Sayan Ghosh, Ekta Kushwaha, Manh Duc Le, Devashibhai T. Adroja, Tathamay Basu
Understanding how lattice dynamics mediate polaron hopping is essential for designing multifunctional correlated oxides. Here, we demonstrate room-temperature dispersive phonon excitations and elucidate the Ni1+-Ni2+ polaron-hopping mechanism and the presence of rare spin-charge-phonon coupling even in a magnetically short-range-ordered state in rutile niobate, a rare room-temperature magnetodielectric system. We reveal room-temperature dispersive phonon excitations using inelastic neutron scattering (INS), complemented by machine-learning-based phonon calculations, to establish the microscopic origin of the polaron-hopping mechanism. Experimental evidence of dispersive phonon-driven polaron hopping is scarce. INS measurements show significant dispersive phonon excitations at 21, 33, and 47 meV, implying collective lattice dynamics that enable delocalized polaron propagation via coupled charge-spin-phonon interactions. Dispersive phonons couple to charge carriers and promote correlated NiO6 lattice distortions, facilitating delocalized polaron hopping. Low-energy magnetic excitations at 4 and 8 meV indicate the presence of local short-range magnetic correlations or spin-orbit-coupling-induced anisotropy in deformed NiO6 octahedra, which are thoroughly discussed. Machine-learning phonon calculations replicate the experimentally observed phonon excitations and demonstrate lattice instability, which is compatible with dynamic local distortions caused by polaron production. These findings provide microscopic evidence for a coupled charge-spin-phonon mechanism that mediates polaron hopping in rutile oxide systems.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
11 pages manuscript with 5 figures
Wave Transport in Fourier Quasicrystals Revealed by Water Waves
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Angélique Campaniello, Lior Alon, Rémi Carminati, Emmanuel Fort, Marcel Filoche
Fourier quasicrystals are aperiodic structures whose diffraction spectrum consists not of a dense set of Bragg peaks, as in ordinary quasicrystals, but of isolated ones scattered across a discrete, nonperiodic set. This sparse reciprocal-space structure should leave wave transport largely undisturbed except at a few selected wavevectors. We put this prediction to the test using surface water waves scattering off a two-dimensional Fourier quasicrystal. Full-field measurements reveal three distinct transport regimes as the incident wavevector increases: transparency, selective scattering, and strong scattering. By reconstructing the structure factor from the measured wavefields, we directly relate these regimes to the underlying reciprocal-space structure. Our results establish Fourier quasicrystals as a physical platform in which wave transport can be controlled through the organization of diffraction peaks in reciprocal space.
Soft Condensed Matter (cond-mat.soft)
7 pages, 7 figures
Generalizing the multidimensional thermodynamic uncertainty relation to combinations of arbitrary counting variables
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-08-17 20:00 EDT
Niklas Buschmann, Udo Seifert, Alexander M. Maier
Uncertainty relations provide lower bounds for otherwise hidden quantities of a partially accessible Markov network like the mean entropy production rate and the total dynamical activity. The thermodynamic uncertainty relation (TUR) is arguably the most prominent one and involves the precision of a fluctuating net current. One of its major generalizations is the multidimensional TUR (MTUR), which yields a tighter bound by using covariances of a set of observed net currents. We generalize this latter bound to time-dependently driven processes with arbitrary initial state and arbitrary measurement duration. Furthermore, this bound can be used with a set of fluctuating counting observables each of which can be time-antisymmetric, time-symmetric or time-asymmetric, i.e., a net current, a traffic or a flow. We can even allow for coarse-grained observations in which each counting observable could consist of multiple indiscernable observed transitions of the underlying system. Thus, we generalize the MTUR, extensions of the TUR for time-dependent processes based on one current, and an estimator based on one flux or on one traffic in a unifying way. We illustrate this general uncertainty relation with simple examples.
Statistical Mechanics (cond-mat.stat-mech)
Efficient simulation of second-order phase transitions in quantum anharmonic materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Andrea Baldanza, Lorenzo Monacelli
When a crystal undergoes a second-order structural phase transition, such as in ferroelectrics, Peierls, and charge-density waves, the diverging fluctuations of the order parameter lead to the break- down of the standard phonon quasiparticle picture. Simulating these highly anharmonic regimes is notoriously challenging, as methods such as molecular dynamics suffer from a critical slowdown near the transition point, while the harmonic approximation fails dramatically at saddle points of the energy landscape stabilized by quantum or thermal ionic fluctuations. This work introduces a new approach, based on the variational free-energy principle, to predict critical long-range behavior and dynamical spectra in strongly anharmonic systems, even when quantum ionic fluctuations dominate. The proposed framework builds upon the stochastic self- consistent harmonic approximation but reduces its computational scaling with the number of atoms, N, from O(N^6) to O(N^2) and the memory requirement from O(N^4) to O(N). We benchmark the method on the prototypical lead-free metal-halide perovskite CsSnI3, a promising candidate for photovoltaic engineering, simulating its phase stability and Raman spectrum near the phase transition, where the breakdown of the quasiparticle picture becomes evident. We demonstrate the effectiveness of the method by computing the full free-energy Hessian and the critical temperature in a supercell with 1080 atoms. Such simulations would have required tens of thousands of years with the legacy approach; it is now feasible in a few hours on consumer hardware.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
18 pages, 13 figures
Pressure-driven structural phase transition unlocks multifunctionality in KMgX (X = P, As, Sb, and Bi) compounds: A first-principles study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Chetna Saini, Neha Sadanandan, Tashi Nautiyal, Hongbin Zhang, Vikrant Chaudhary, Hem C. Kandpal
The search for materials with multifunctional properties has attracted significant attention due to their potential applications in various energy-related devices. Pressure-induced phase transitions provide an effective strategy for accessing different structural phases of a material without altering its chemical composition, thereby enabling the tuning of its physical properties and expanding its functional applications. In this work, we investigate the previously unexplored orthorhombic (Pnma) phase of the KMgX (X = P, As, Sb, and Bi) family using first-principles calculations and identify a pressure-induced structural transition from a tetragonal to orthorhombic phase. Stability of the pressure-accessible orthorhombic structure is rigorously confirmed by equation of state analysis together with phonon, elastic, and formation-enthalpy calculations, establishing its viability for further investigation. Optical properties calculated within the $ G_0W_0$ -Bethe-Salpeter equation (BSE) framework, incorporating quasiparticle corrections and excitonic effects, exhibit direct dipole-allowed transitions at the $ \Gamma$ point and strong visible-light absorption with coefficients approaching $ 10^5\text{cm}^{-1}$ . Consequently, KMgAs and KMgSb achieve spectroscopic limited maximum efficiencies (SLME) of $ 27.12%$ and $ 26.40%$ , respectively, at a thin-film thickness of $ 0.6\mu\text{m}$ . Furthermore, thermoelectric transport calculations predict (zT) values of 0.65 and 0.58 at $ 900~\text{K}$ for p-type and n-type KMgSb, respectively, demonstrating its potential for both legs of thermoelectric devices. These values are likely conservative, as the Slack model tends to overestimate thermal conductivity. Overall, the pressure-accessible orthorhombic phase of the KMgX family emerges as a stable multifunctional semiconductor with coupled photovoltaic and thermoelectric energy-conversion capabilities.
Materials Science (cond-mat.mtrl-sci)
Orbital Hall Effect in Weyl Semimetals from quantum geometric band interference
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Chiara Pacella, Maximilian Ünzelmann, Ahmed Osman, Tim Figgemeier, Friedrich Reinert, Angel Rubio, Domenico Di Sante
Orbital angular momentum (OAM) transport in solids, prominently manifested in the orbital Hall effect, has emerged as a fundamental phenomenon that can decisively exceed its spin-based counterparts. However, the microscopic mechanisms governing OAM dynamics remain only partially understood. In particular, the role of band geometry in orbital transport is still largely unresolved. Here we address this question in the TaAs family of Weyl semimetals, TaAs, TaP, NbAs, and NbP, whose well-established topology and associated OAM textures make them an ideal platform in this context. Using ab initio density functional theory, complemented by a minimal Weyl model based on adiabatic perturbation theory, we establish — both numerically and analytically — a direct link between OAM transport, band geometry, and topological electronic structure.
Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
5 pages, 4 figures
Tuning crystal-fields by He-irradiation and orbital Widom line in SrVO$_3$ films
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Matthias Pickem, Karsten Held, Jan M. Tomczak
Helium-ion irradiation of epitaxial SrVO$ _3$ /SrTiO$ _3$ films causes a metal-insulator transition, so far attributed to a Mott localization driven by a reduced kinetic energy. Using density-functional theory plus dynamical mean-field theory, we show that the driving mechanism is instead the crystal-field splitting generated by the irradiation-induced tetragonal expansion, not the interaction-to-bandwidth ratio. The resulting $ c$ -axis vs. temperature phase diagram mirrors that of the one-band Hubbard model, but its critical end-point spawns an orbital Widom line, rooted in an anomalous compressibility of orbital, rather than charge occupation. At an effectively quarter filling, superexchange-like processes favor orbital over magnetic long-range order. Our results semi-quantitatively reproduce the fluence-dependent spectral gaps and transition thresholds reported experimentally, establishing ion implantation as a route to chemically expand correlated materials.
Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 10 figures
Unraveling the Roles of Shallow, Deep and Auger Trapping in Charge Carrier Recombination in Triple-Cation Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Jitendra Kumar, Thomas Kirchartz, Alexandr Marunchenko, Alexander Kiligaridis, Shraddha M. Rao, Shivam Singh, Ankur Yadav, Monojit Bag, Yana Vaynzof, Ivan G. Scheblykin
Understanding charge-carrier recombination in metal halide perovskites is essential for accurately identifying the factors limiting solar cell efficiency, yet it remains challenging due to the interplay of multiple competing processes. Here, we combine time-resolved photoluminescence and excitation dependent photoluminescence quantum yield measurements over a wide range of fluences and repetition rates to investigate recombination dynamics in triple-cation perovskite thin films. By jointly analyzing these multidimensional datasets, we develop a unified model that quantitatively reproduces both photoluminescence decays and absolute quantum yields across all excitation conditions. Our results reveal the coexistence of deep and shallow traps, as well as a second-order nonradiative recombination pathway attributed to Auger-assisted trapping. Importantly, this mechanism dominates under one-sun illumination, making it a critical limiting factor for photovoltaic performance. These findings provide a comprehensive framework for understanding recombination in perovskites and highlight the importance of higher-order defect-mediated processes in determining their efficiency.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
Floquet Superlattices and Edge States in Graphene Nanoribbons
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-08-17 20:00 EDT
Siam Sarower, Jonathon Dvorscak, Nancy P. Sandler, Mahmoud M. Asmar
Structured light provides a route to imprint spatially patterned Floquet potentials onto quantum materials. As a particular example, we study a zigzag graphene nanoribbon driven by two coherent tilted beams, whose interference creates a periodic polarization pattern that gives rise to a photo-induced superlattice. The matching between the periodicity of the optical field and the nanoribbon width leads to two regimes in the quasienergy spectrum: matched profiles preserve degenerate edge branches, while mismatched profiles yield a boundary-induced gap that survives in wide ribbons. We propose a two-edge model that captures this splitting through residual hybridization and the boundary-sampled optical field. The quasienergy gap reverses between valleys, leading to a valley-selective boundary response. Our results establish light-induced superlattices as a flexible method for valley selectivity in finite-size Dirac-like materials through tunable edge-state quasienergy splitting.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 9 figures
Surface Roughness and Filler Restructuring in Magneto-Active Elastomers: Magnetically Hard versus Magnetically Soft Particles
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-08-17 20:00 EDT
Júlio P. A. Santos, Mehdi Hasanzade, Chaitanya Doifode, Raphael Kriegl, Alexander Kovalev, Mikhail Shamonin, Stanislav N. Gorb, Sofia Kantorovich
Magneto-active elastomers (MAEs) – composites of magnetic nano-/micro-particles embedded in a soft polymer matrix – are promising for soft robotics, as their shape and mechanical properties can be controlled by an applied magnetic field. Most MAEs are filled with magnetically soft (MS) micro-particles, such as carbonyl iron powder (CIP). We employ molecular dynamics to study the differences between thin MAE layers with MS and magnetically hard (MH) filler particles having the same saturation magnetization. We find that both MH and MS elastomers converge to the same high-field state – a labyrinth of bundled, field-aligned chains – but do so through distinct pathways: MH MAEs break their zero-field chains, which lie parallel to the MAE layer plane (in-plane), and rotate them into alignment with an external magnetic field, whereas MS MAEs gradually build up field-aligned chains from neighboring particles. We show that the MS model reproduces the magnetization curves and surface roughness of CIP-based MAEs for magnetic fields close to saturation, while maintaining the observed qualitative features at lower field strengths. The mismatch between simulation and experimental results at low fields suggests the need for a MS model that accounts for the multi-domain nature of carbonyl iron microparticles.
Soft Condensed Matter (cond-mat.soft)
A Fixed Universal Determinant is Variationally Complete for Continuum Fermions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Giuseppe Carleo, Riccardo Rossi
How many Slater determinants does an accurate variational description of interacting fermions require? Exact expansions in a finite basis need combinatorially many, and state-of-the-art fermionic neural quantum states stack growing numbers of them. We prove that, in the norms that govern variational calculations, at most two are needed, independently of the number of particles and of the target accuracy. A single universal Slater determinant-specified in advance, independent of both the system and the state-multiplied by a smooth bosonic wave function approximates any fermionic wave function in up to three spatial dimensions in the first-order Sobolev norm, which controls the variational energy. Reaching the second-order Sobolev norm-for Coulomb interactions, the domain of the Hamiltonian, which bounds the variance of the local energy at the core of variational Monte Carlo-requires at most one additional fixed determinant, and only in three dimensions. Antisymmetry therefore costs at most two universal determinants and no expressiveness: generalized Slater-Jastrow neural quantum states are variationally complete.
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph), Quantum Physics (quant-ph)
4 pages, 2 figures
Linear response across interaction regimes in two-dimensional ferromagnets
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-08-17 20:00 EDT
Aaron Müller, Pavel E. Dolgirev, Oleksii Malyshev, Eugene Demler
Recent discoveries of two-dimensional (2D) ferromagnets have stimulated intense interest in understanding and controlling their spin transport properties. A central microscopic feature of these systems is that exchange-driven magnon–magnon interactions are strongly momentum dependent: low-momentum magnons interact weakly, while high-momentum ones can scatter strongly and exhibit collective hydrodynamic behavior. Understanding transport in such systems therefore requires a microscopic description capable of capturing ballistic and hydrodynamic regimes on equal footing. The natural framework is the quantum Boltzmann equation (QBE), whose solution is notoriously difficult because of the multidimensional collision integrals. Here, we develop a method based on an efficient representation of distribution functions as sums of Gaussians, which renders the collision integrals tractable. This approach enables accurate solution of the linearized QBE and computation of momentum- and frequency-resolved linear response in 2D ferromagnets across a broad range of temperatures and magnetic fields. In particular, we resolve a temperature-driven crossover from a ballistic regime dominated by weakly interacting low-momentum magnons to a collective hydrodynamic regime governed by strongly interacting high-momentum modes. Applying this method to monolayer CrCl$ _3$ , we obtain good agreement with recent nitrogen-vacancy-center dephasing experiments that reported anomalous magnetic noise consistent with magnon sound. More broadly, our work establishes a general framework for computing momentum- and frequency-resolved linear response in interacting 2D quantum systems describable within quantum Boltzmann kinetics.
Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el)
19 pages, 6 figures
Universal Signature of Hundness and Its Quantification
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Dongwook Kim, Ina Park, Bo Gyu Jang, Ji Hoon Shim
Hund’s coupling $ J$ induces fundamentally different correlation effects from Hubbard $ U$ . This leads to a violation of the Brinkman–Rice scenario and the emergence of a Janus-faced phase owing to its low-energy effectiveness, in which band renormalization is confined below a characteristic energy scale. We propose a quantitative framework to capture low-energy effectiveness through two correlation factors: $ z_L$ for low-energy quasiparticle renormalization and $ z_H$ for high-energy charge fluctuations, newly introduced in this study. The discrepancy between $ z_L$ and $ z_H$ reflects the Hund character of the correlation. By establishing a one-to-one correspondence between correlation factors and the spin and charge susceptibilities, we identify the spin-degree-of-freedom effectiveness as the microscopic origin of low-energy effectiveness. Our framework, validated across multiorbital models and real materials, provides a universal and quantitative measure of Hundness.
Strongly Correlated Electrons (cond-mat.str-el)
5 pages, 3 figures in main, 6 figures in supplementary material
Quasi-periodicity enforces Berry phase discontinuity in crystals
New Submission | Other Condensed Matter (cond-mat.other) | 2026-08-17 20:00 EDT
The Berry phase of an isolated electronic state is evaluated for different integration paths in reciprocal space, thanks to Riemann-Bloch states providing a consistent description in the whole Brillouin zone.
The relationship with the bounded position operator is investigated for the open-path Berry phase and with different form factors of the constituent Gaussian type atomic orbitals (GTOs).
When the Berry phase is evaluated over a closed loop in reciprocal space, a regularisation procedure in the complex plane is adopted and additional \textit{quasi}-symmetries are exploited here for the first time in order to rationalise the occurrence of non-analytical jumps as a function of the winding number or of the GTO broadening.
Other Condensed Matter (cond-mat.other)
Universal Thermodynamic Interatomic Potentials for Crystalline Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-08-17 20:00 EDT
Juno Nam, Bowen Deng, Xiaochen Du, Luis Barroso-Luque, Benjamin Kurt Miller, Rafael Gómez-Bombarelli
Free energies govern solid-state phase stability, yet computational materials discovery still relies largely on ground-state energies because free energy calculations require ensemble averages. We introduce the thermodynamic interatomic potential (TIP), which extends an interatomic potential from its static energy to a thermodynamically consistent Gibbs free energy model, with thermodynamic responses following from temperature and pressure by automatic differentiation. We implement TIP[UMA] using the universal potential UMA, train it on free energies from quasi-harmonic to molecular dynamics fidelity, and calibrate it to higher-resolution calculations or experiment. From a single evaluation, it returns the equation of state of a crystal and locates phase transitions among competing branches, including dynamically stabilized phases. Fine-tuning extends the model to alloy solubility limits and miscibility gaps. TIP makes the free energy as accessible as the potential energy, opening finite-temperature phase stability to high-throughput discovery.
Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech), Artificial Intelligence (cs.AI), Machine Learning (cs.LG), Chemical Physics (physics.chem-ph)
Chiral spin liquid and chiral antiferromagnetism in half-filled moiré Hubbard model: possible applications to twisted bilayer TMDs
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-08-17 20:00 EDT
Twisted transition metal dichalcogenides offer an exceptionally tunable moiré platform for studying correlation physics beyond conventional condensed matter systems. In particular, the intriguing interplay between the displacement field and the twist angle remains to be fully resolved. In this paper, we use large-scale density matrix renormalization group simulations to study the minimal moiré Hubbard model on a triangular lattice at half-filling, where the displacement field effect is captured by a spin-dependent staggered flux. We find that the displacement field significantly enriches the triangular Hubbard phase diagram in several qualitative ways. It rapidly destabilizes the chiral spin liquid phase beyond a narrow weak-field regime, induces pronounced chiral correlations in the strong-coupling $ 120^\circ$ -antiferromagnetic phase, and stabilizes incommensurate spin-density wave phases at weaker coupling. We further find signatures of a continuous transition between the chiral spin liquid and chiral antiferromagnetic phases at a finite displacement field, potentially driven by spinon condensation. Our results uncover rich displacement-field-driven many-body physics and provide useful guidance for future experiments in moiré superlattice systems.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
12 pages, 7 figures
Universal aspects of bulk density of states in non-Hermitian lattices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-08-17 20:00 EDT
Mykhailo Pavliuk, Askar Iliasov, Emil J. Bergholtz, Tomáš Bzdušek
Non-Hermitian lattice Hamiltonians generally exhibit strong boundary sensitivity, with periodic and open boundary conditions producing distinct density of states (DOS) in the complex-energy plane. This has led to the view that extended non-Hermitian systems lack a unique bulk DOS, with different prescriptions representing inequivalent bulk physics. Here, we show that this apparent ambiguity is largely illusory. For any finite-range tight-binding Hamiltonian, we establish a universal bulk structure: all DOS definitions arising as thermodynamic limits of finite systems share identical multipole moments and generate identical bulk dynamics at finite times and for observables measured far from boundaries. This universality is intimately tied to the thermodynamic Green’s functions, which we show to be independent of the boundary condition for large enough complex frequencies. Among all equivalent descriptions, we identify the Brown measure - obtained via Hermitization and resolvent analysis - as a canonical and convenient representative of the bulk DOS, defined directly from the infinite-volume Hamiltonian. We further show that point-gap topology imposes additional universal constraints: boundary-dependent Green’s functions are forced to coincide throughout topologically trivial point gaps. This, in particular, provides a systematic criterion, valid in arbitrary dimension, for determining where and how eigenvalues of different boundary truncations can accumulate in the complex plane, and precisely delineates the regime in which the DOS ambiguity retains physical significance.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
17 pages, 8 figures
Skyrmion Fractional Chern Insulator: An Intrinsically Multiband Route to Fractionalization in Rhombohedral Graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-08-17 20:00 EDT
Julian May-Mann, Tixuan Tan, Patrick J. Ledwith, Zhengyan Darius Shi, Trithep Devakul
We propose an unconventional microscopic origin for the fractional quantum anomalous Hall (FQAH) effect in rhombohedral graphene moiré superlattices: skyrmion fractionalization. We view the state at filling $ \nu<1$ as a metal of skyrmion vacancies, charge $ +e$ objects formed by removing layer-pseudospin skyrmions from the interaction-generated skyrmion lattice Chern insulator at $ \nu=1$ . These vacancies are intrinsically multiband degrees of freedom, absent in single Chern band-projected studies. Building on a recently proposed ideal limit, we first develop an effective field theory showing that skyrmion vacancies can themselves fractionalize, thereby inducing charge fractionalization. Focusing on $ \nu=\frac{2}{3}$ , we then construct explicit variational trial wavefunctions for the resulting skyrmion fractional Chern insulator and provide numerical evidence, together with general arguments, showing that this process is energetically favored. Our results establish a realistic route to the FQAH that does not rely on a partially filled Chern band, but instead arises from fractionalization of collective pseudospin textures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)