CMP Journal 2025-07-22
Statistics
Nature Materials: 2
Physical Review Letters: 7
arXiv: 104
Nature Materials
Atomic-scale frustrated Josephson coupling and multicondensate visualization in FeSe
Original Paper | Scanning probe microscopy | 2025-07-21 20:00 EDT
Nileema Sharma, Matthew Toole, James McKenzie, Sheng Ran, Xiaolong Liu
In a Josephson junction involving multiband superconductors, competition between interband and interjunction Josephson couplings gives rise to frustration and spatial disjunction of superfluid densities among superconducting condensates1,2,3,4,5,6,7. Such frustrated coupling manifests as the quantum interference of Josephson currents from different tunnelling channels and becomes tunable if channel transparency can be varied5,6,7,8. To explore these unconventional effects in the prototypical s±-wave superconductor FeSe (ref. 9), we use atomic-resolution scanned Josephson tunnelling microscopy10,11,12,13 for condensate-resolved imaging and junction tuning–capabilities unattainable in macroscopic Josephson devices with fixed characteristics. We quantitatively demonstrate frustrated Josephson tunnelling by examining two tunnelling inequalities. The relative transparency of two parallel tunnelling pathways is found tunable, revealing a tendency towards a 0-π transition with decreasing scanned Josephson tunnelling microscopy junction resistance. The simultaneous visualization of both superconducting condensates reveals anticorrelated superfluid modulations, highlighting the role of interband scattering. Our study establishes scanned Josephson tunnelling microscopy as a powerful tool enabling new research frontiers of multicondensate superconductivity.
Scanning probe microscopy, Superconducting properties and materials
An amorphous Li-V-O-F cathode with tetrahedral coordination and O-O formal redox at low voltage
Original Paper | Batteries | 2025-07-21 20:00 EDT
Kun Zhang, Tonghuan Yang, Tao Chen, Yali Yang, Zewen Jiang, Chuan Gao, Yuxuan Zuo, Wukun Xiao, Dingguo Xia
The ever-increasing demand for lithium-ion batteries has necessitated the development of high-performance cathode materials. However, previous studies have predominantly focused on crystal cathodes comprising the octahedral coordination of metal atoms and a well-ordered layered topology. This omits other cathode materials with other structures or coordination that could potentially surpass conventional counterparts in terms of performance. Here, using X-ray diffraction, resonant inelastic X-ray scattering and X-ray absorption near-edge spectra experiments, we investigated an amorphous Li-V-O-F cathode (a-LVOF) with tetrahedral coordination and elucidated an O-O formal redox mechanism at a moderate voltage of 4.1 V, without a conventional octahedral Li-O-Li configuration. The electrochemically amorphized material fosters randomly distributed VO4 units and scattered dangling oxygen bonds, which facilitated O-O binding. Moreover, a-LVOF demonstrates a high capacity of 230 mAh g-1. Our findings reveal a low-voltage O-O formal redox mechanism in an amorphized cathode material.
Batteries, Electrochemistry
Physical Review Letters
Phase Transitions in an Expanding Medium: Hot Remnants
Research article | Gauge-gravity dualities | 2025-07-21 06:00 EDT
Romuald A. Janik, Matti Järvinen, and Jacob Sonnenschein
We analyze the dynamics of a first order confinement-deconfinement phase transition in an expanding medium using an effective boundary description fitted to the holographic Witten model. We observe and analyze hot plasma remnants, which do not cool down or nucleate bubbles despite the expansion of the system. The appearance of the hot remnants, the dynamics of their shrinking, and subsequent dissolution and further heating up is very robust and persists in such diverse scenarios as boost-invariant expansion with a flat Minkowski metric and cosmological expansion in a Friedmann-Robertson-Walker spacetime.
Phys. Rev. Lett. 135, 041601 (2025)
Gauge-gravity dualities, Phase transitions, Relativistic hydrodynamics
Search for ${P}{c\overline{c}s}(4459{)}^{0}$ and ${P}{c\overline{c}s}(4338{)}^{0}$ in $\mathrm{\Upsilon }(1S,2S)$ Inclusive Decays at Belle
Research article | Branching fraction | 2025-07-21 06:00 EDT
I. Adachi et al. (The Belle and Belle II Collaborations)
Using data samples of 102 million $\mathrm{\Upsilon }(1S)$ events and 158 million $\mathrm{\Upsilon }(2S)$ events collected by the Belle detector at the KEKB asymmetric-energy ${e}^{+}{e}^{- }$ collider, we search for $[udsc\overline{c}]$ pentaquark states decaying to $J/\psi \mathrm{\Lambda }$. Using the first observations of $\mathrm{\Upsilon }(1S,2S)$ inclusive decays to $J/\psi \mathrm{\Lambda }$, we find evidence of the ${P}{c\overline{c}s}(4459{)}^{0}$ state with a local significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the ${P}{c\overline{c}s}(4459{)}^{0}$ to be $(4471.7\pm{}4.8\pm{}0.6)\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $(22\pm{}13\pm{}3)\text{ }\text{ }\mathrm{MeV}$, respectively. The branching fractions for ${P}{c\overline{c}s}(4459{)}^{0}$ production are measured to be $\mathcal{B}[\mathrm{\Upsilon }(1S)\rightarrow {P}{c\overline{c}s}(4459{)}^{0}/{\overline{P}}{c\overline{c}s}(4459{)}^{0}+\mathrm{anything}]=(3.5\pm{}2.0\pm{}0.2)\times{}{10}^{- 6}$ and $\mathcal{B}[\mathrm{\Upsilon }(2S)\rightarrow {P}{c\overline{c}s}(4459{)}^{0}/\phantom{\rule{0ex}{0ex}}{\overline{P}}_{c\overline{c}s}(4459{)}^{0}+\mathrm{anything}]=(2.9\pm{}1.7\pm{}0.4)\times{}{10}^{- 6}$. The inclusive branching fractions of $\mathrm{\Upsilon }(1S,2S)\rightarrow J/\psi \mathrm{\Lambda }/\overline{\mathrm{\Lambda }}$ are measured to be $\mathcal{B}[\mathrm{\Upsilon }(1S)\rightarrow J/\psi \mathrm{\Lambda }/\overline{\mathrm{\Lambda }}+\mathrm{anything}]=(36.9\pm{}5.3\pm{}2.4)\times{}{10}^{- 6}$ and $\mathcal{B}[\mathrm{\Upsilon }(2S)\rightarrow J/\psi \mathrm{\Lambda }/\overline{\mathrm{\Lambda }}+\mathrm{anything}]=(22.3\pm{}5.7\pm{}3.1)\times{}{10}^{- 6}$. We measure the visible cross section $\sigma ({e}^{+}{e}^{- }\rightarrow J/\psi \mathrm{\Lambda }/\overline{\mathrm{\Lambda }}+\mathrm{anything})=(90\pm{}14\pm{}6)\text{ }\text{ }\mathrm{fb}$ for the continuum production at $\sqrt{s}=10.52\text{ }\text{ }\mathrm{GeV}$. In all cases, the first uncertainties are statistical and the second are systematic.
Phys. Rev. Lett. 135, 041901 (2025)
Branching fraction, Hadron production, Hadronic decays, Multiquark bound states, Quark model
Double Spin Resonance for Traceable Ultrasensitive Atomic Spin Sensor
Research article | Atomic & molecular collisions | 2025-07-21 06:00 EDT
Xiaofei Huang, Weiyi Wang, Yanhui Hu, Yong-Chun Liu, Jiancheng Fang, and Kai Wei
We report an ultrasensitive atomic spin sensor employing double spin resonance, achieving a spin signal enhancement of 2600 and a sensitivity of $0.57\text{ }\text{ }\mathrm{fT}/\sqrt{\mathrm{Hz}}$ under nonzero magnetic field measurements. Furthermore, we establish an in situ alkali-noble-gas spin sensor by tracing the measured spin precession frequency to the nuclear spins gyromagnetic ratio constant with high accuracy. The dominant systematic uncertainty induced by Fermi-contact interactions during the trace process has been suppressed by more than 2 orders of magnitude via pulsed train sequences. This Letter paves the way for achieving both ultrahigh sensitivity and traceability, offering promising opportunities for exploring new physics beyond the standard model and advancing quantum metrology in complex environments.
Phys. Rev. Lett. 135, 043001 (2025)
Atomic & molecular collisions, Coherent control, Dark matter, Light-matter interaction, Optical pumping, Quantum measurements, Atomic ensemble, Atoms
Superlubric Motion of Wavelike Domain Walls in Sliding Ferroelectrics
Research article | Ferroelectric domains | 2025-07-21 06:00 EDT
Changming Ke, Fucai Liu, and Shi Liu
Polarization reversal in sliding ferroelectrics relies on symmetry-breaking domain walls and the tensorial nature of Born effective charges.
Phys. Rev. Lett. 135, 046201 (2025)
Ferroelectric domains, Ferroelectricity, Hexagonal boron nitride, Molecular dynamics
Intervalley Coherent Order in Rhombohedral Tetralayer Graphene on ${\mathrm{MoS}}_{2}$
Research article | Flat bands | 2025-07-21 06:00 EDT
Wei-Yu Liao, Wen-Xiao Wang, Shihao Zhang, Yang Zhang, Ling-Hui Tong, Wenjia Zhang, Hao Cai, Yuan Tian, Yuanyuan Hu, Li Zhang, Lijie Zhang, Zhihui Qin, and Long-Jing Yin
Multilayer rhombohedral graphene (RG) has recently emerged as a new, structurally simple flat-band system, which facilitates the exploration of interaction-driven correlation states with highly ordered electron arrangements. Despite a variety of many-body order behaviors observed in RG by transport measurements, the direct microscopic visualization of such correlated phases in real space is still lacking. Here, we show the discovery of a robust intervalley coherent order—a long-predicted ground state in RG—at 77 K in tetralayer RG placed on ${\mathrm{MoS}}_{2}$ via imaging atomic-scale spatial reconstruction of wave functions for correlated states. This state is visualized in $\sim 60%$ and $\sim 70%$ filled flat bands, where clear spectroscopic signatures of electronic correlations are observed, manifesting as a $\sqrt{3}\times{}\sqrt{3}$ reconstructed supercell on the graphene lattice. Surprisingly, such a $\sqrt{3}\times{}\sqrt{3}$ pattern is absent in hexagonal-boron-nitride-supported RG under the same experimental conditions. These findings, together with our Hartree-Fock mean-field calculations, suggest a spin-orbit proximity-induced robust intervalley coherent phase of interacting electrons in tetralayer RG. Our results provide microscopic insights into the correlated phases in RG multilayers and highlight the significant potential for realizing highly accessible collective phenomena through van der Waals proximity.
Phys. Rev. Lett. 135, 046202 (2025)
Flat bands, Local density of states, Graphene, Scanning tunneling microscopy, Scanning tunneling spectroscopy
Disorder-Induced Slow Relaxation of Phonon Polarization
Research article | Acoustic phonons | 2025-07-21 06:00 EDT
Yuta Suzuki and Shuichi Murakami
The role of the polarization degree of freedom in lattice dynamics in solids has been underlined recently. We theoretically discover a relaxation mechanism for both linear and circular polarizations of acoustic phonons. In the absence of scattering, the polarization exhibits oscillatory behavior. This behavior leads to a counterintuitive result: unlike linear momentum, more frequent scattering events cause slower polarization relaxation due to motional narrowing. We validate this mechanism using the quantum kinetic equation. We derive the relaxation rates of polarizations analytically for isotropic elastic bodies and numerically for a cubic crystal. Remarkably, we reveal that linear polarizations relax more slowly than circular ones. Our findings provide a pathway to prolong the lifetime of phonon angular momentum by designing disorder. This improvement has the potential to advance thermal management in disordered materials, facilitate phononic information transport, and strengthen spin-phonon coupling in spintronic devices.
Phys. Rev. Lett. 135, 046301 (2025)
Acoustic phonons, Crystal defects, Lattice dynamics, Lifetimes & widths, Point defects, Quantum kinetic theory, Crystalline systems
Linear Scaling Causal Discovery from High-Dimensional Time Series by Dynamical Community Detection
Research article | Community structure | 2025-07-21 06:00 EDT
Matteo Allione, Vittorio Del Tatto, and Alessandro Laio
A new statistical test identifies groups of variables that are mutually coupled and can be represented in a causal graph as single, aggregated nodes, which allows the extraction of hierarchical structures from observational data.
Phys. Rev. Lett. 135, 047401 (2025)
Community structure, Directed networks, Network inference, Time series analysis
arXiv
Integral fractional viscoelastic models in SPH: LAOS simulations versus experimental data
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Luca Santelli, Adolfo Vázquez-Quesada, Aizzati Burgoa, Aitor Arriaga, Ritardo Hernandez, Marco Ellero
The rheological behaviour of a polymer was investigated by performing numerical simulations in complex flow and comparing them to experiments. For our simulations, we employed a Smoothed Particle Hydrodynamics scheme, utilizing an integral fractional model based on the K-BKZ framework. The results are compared with experiments performed on melt-state isotactic polypropylene under medium and large amplitude oscillatory shear.
The numerical results are in good agreement with the experimental data, and the model is able to capture and predict both the linear and the non-linear viscoelastic behaviours of the polymer melt. Results show that equipping SPH with an integral fractional model is promising approach for the simulation of complex polymeric materials under realistic conditions.
Soft Condensed Matter (cond-mat.soft)
Siamese Neural Network for Label-Efficient Critical Phenomena Prediction in 3D Percolation Models
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-22 20:00 EDT
Shanshan Wang, Dian Xu, Jianmin Shen, Feng Gao, Wei Li, Weibing Deng
Percolation theory serves as a cornerstone for studying phase transitions and critical phenomena, with broad implications in statistical physics, materials science, and complex networks. However, most machine learning frameworks for percolation analysis have focused on two-dimensional systems, oversimplifying the spatial correlations and morphological complexity of real-world three-dimensional materials. To bridge this gap and improve label efficiency and scalability in 3D systems, we propose a Siamese Neural Network (SNN) that leverages features of the largest cluster as discriminative input. Our method achieves high predictive accuracy for both site and bond percolation thresholds and critical exponents in three dimensions, with sub-1% error margins using significantly fewer labeled samples than traditional approaches. This work establishes a robust and data-efficient framework for modeling high-dimensional critical phenomena, with potential applications in materials discovery and complex network analysis.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG)
14 pages, 9 figures
A comparative numerical study of stochastic Hamiltonian Camassa-Holm equations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Darryl D. Holm, Maneesh Kumar Singh, Oliver D. Street
We introduce a stochastic perturbation of the Camassa-Holm equation such that, unlike previous formulations, energy is conserved by the stochastic flow. We compare this to a complementary approach which preserves Casimirs of the Poisson bracket. Through an energy preserving numerical implementation of the model, we study the influence of noise on the well-known ‘peakon’ formation behaviour of the solution. The energy conserving stochastic approach generates an ensemble of solutions which are spread around the deterministic Camassa-Holm solution, whereas the Casimir conserving alternative develops peakons which may propagate away from the deterministic solution more dramatically.
Statistical Mechanics (cond-mat.stat-mech), Exactly Solvable and Integrable Systems (nlin.SI)
Comments welcome
The fracture toughness of molybdenum at different grain sizes under and since brittle-ductile transition: computer modeling and experiment
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
K.M. Borysovska, N.M. Marchenko, Yu. Koval, Yu.N. Podrezov, S.A. Firstov
The sharp growth of the fracture toughness after brittle-ductile transition happens at grain sizes approximately equal to the plastic zone size. Here we analyze the influence of the grain boundary on the evolution of the ensemble of dislocations near the crack tip using dislocation dynamics method. We show evidence that for large grain sizes, the size has little effect on the ensemble of dislocations and the fracture toughness, but when dislocations reach the grain boundary, distribution of dislocations changes, which leads to increase of the fracture toughness.
Materials Science (cond-mat.mtrl-sci)
19 pages, 11 figures
High-$T_{\rm c}$ Ag$_x$BC and Cu$_x$BC superconductors accessible via topochemical reactions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
Daviti Gochitashvili, Charlsey R. Tomassetti, Elena R. Margine, Aleksey N. Kolmogorov
Hole-doping of covalent materials has long served as a blueprint for designing conventional high-$ T_{\rm c}$ superconductors, but thermodynamic constraints severely limit the space of realizable compounds. Our {\it ab initio} results indicate that metastable Ag$ _x$ BC and Cu$ _x$ BC phases can be accessed via standard topochemical ion exchange reactions starting from Li$ _x$ BC precursors. Unlike all known stoichiometric layered metal borocarbides, the predicted AgBC and CuBC derivatives, comprising honeycomb layers bridged by dumbbells, are metallic rather than semiconducting. Anisotropic Migdal-Eliashberg analysis reveals that the intrinsically hole-doped AgBC possesses a unique combination of electronic and vibrational features to exhibit two-gap superconductivity above 50 K.
Superconductivity (cond-mat.supr-con)
Interplay of orbital and spin magnetization in trigonal tellurium
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Zhenqi Hua, Chang Niu, Sandeep Joy, Pukun Tan, Gang Shi, Haoyang Liu, Jiaxing Guo, David Graf, Peide Ye, Cyprian Lewandowski, Peng Xiong
Orbital effects, despite their fundamental significance and potential to engender novel physical phenomena and enable new applications, have long been underexplored compared to their spin counterparts. Recently, surging interest in the orbital degree of freedom has led to the discovery of a plethora of orbital-related effects, underscoring the need for a deeper understanding of their roles in quantum materials. Here, we report first experimental signatures of orbital magnetization in trigonal Tellurium, an elemental semiconductor with a unique helical crystal structure that serves as a natural platform for investigating orbital effects. Detailed angular dependent linear and nonlinear magnetotransport measurements, supported by theoretical Boltzmann transport analysis, reveal the coexistence of current-induced spin polarization and orbital magnetization. By disentangling the interplay between spin and orbital degrees of freedom, this work establishes a general framework for understanding orbital magnetization in chiral crystals and beyond, paving the way for its utilization in orbitronics and spintronics.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The physics and mathematics of living and dying matter
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Tanniemola B. Liverpool, Kristian K. Müller-Nedebock, Xichen Chao, Chang Yuan
We introduce and study a class of active matter models in which we keep track of fuel (stored energy) consumption. They are by construction, thermodynamically consistent. Using these models it is possible for us to observe and follow how active behaviour develops and also how it dissipates as the energy runs out. It is also straightforward to define, calculate and keep track of macroscopic thermodynamic quantities.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
5 pages, 4 figures
Fermion quantum criticality far from equilibrium
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Rohan Mittal, Tom Zander, Johannes Lang, Sebastian Diehl
Driving a quantum system out of equilibrium while preserving its subtle quantum mechanical correlations on large scales presents a major challenge, both fundamentally and for technological applications. At its core, this challenge is pinpointed by the question of how quantum effects can persist at asymptotic scales, analogous to quantum critical points in equilibrium. In this work, we construct such a scenario using fermions as building blocks. These fermions undergo an absorbing-to-absorbing state transition between two topologically distinct and quantum-correlated dark states. Starting from a microscopic, interacting Lindbladian, we derive an effective Lindblad-Keldysh field theory in which critical fermions couple to a bosonic bath with hydrodynamic fluctuations associated with particle number conservation. A key feature of this field theory is an emergent symmetry that protects the purity of the fermions’ state even in the presence of the thermal bath. We quantitatively characterise the critical point using a leading-order expansion around the upper critical dimension, thereby establishing the first non-equilibrium universality class of fermions. The symmetry protection mechanism, which exhibits parallels to the problem of directed percolation, suggests a pathway toward a broader class of robust, universal quantum phenomena in fermionic systems.
Statistical Mechanics (cond-mat.stat-mech)
42 pages, 13 figures
Martini 3 application for the design of bistable nanomachines
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Alexander D. Muratov, Vladik A. Avetisov
During our previous modeling using all-atom molecular dynamics, we have identified several foldamers whose nanoscale behavior resembles that of classic bistable machines, namely the Euler archs and Duffing oscillators. However, time limitations of the all-atom molecular dynamics prevent us from performing a full-scale investigation of long-time behavior and prompt us to develop a coarse-grained model. In this work, we summarize our recent research on developing such models using the most widely available method called Martini.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Soft Condensed Matter (cond-mat.soft), Chaotic Dynamics (nlin.CD), Computational Physics (physics.comp-ph)
9 pages, 5 figures, 1 table
Surface Charge Relaxation Controls the Lifetime of Out-of-Equilibrium Colloidal Crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Laura Jansen, Thijs ter Rele, Marjolein Dijkstra
Interactions between charged colloidal particles are profoundly influenced by charge regulation and charge renormalization, rendering the effective potential highly sensitive to local particle density. In this work, we investigate how a dynamically evolving, density-dependent Yukawa interaction affects the stability of out-of-equilibrium colloidal structures. Motivated by a series of experiments where unexpectedly long-lived colloidal crystals have suggested the presence of like-charged attractions, we systematically explore the role of charge regulation and charge renormalization. Using Poisson-Boltzmann cell theory, we compute the effective colloidal charge and screening length as a function of packing fraction. These results are subsequently incorporated into Brownian dynamics simulations that dynamically resolve the evolving colloid charge as a function of time and local density. In the case of slow relaxation dynamics, our results show that incorporating these charging effects significantly prolongs the lifetimes of out-of-equilibrium colloidal crystals, providing an explanation for the experimental observation of long-lived crystals. These findings demonstrate that the interplay of surface charge dynamics and colloidal interactions can give rise to complex and rich nonequilibrium behavior in charged colloidal suspensions, opening new pathways for tuning colloidal stability through electrostatic feedback mechanisms.
Soft Condensed Matter (cond-mat.soft)
14 pages, 5 figures (supplementary: 9 pages, 5 figures)
Supercurrent tuning of the Josephson coupling energy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Maxwell Wisne, Venkat Chandrasekhar
The ability to non-dissipatively tune the Josephson coupling energy of Josephson junctions is a useful tool in frequency-tunable qubits. This is typically done by threading magnetic flux through two junctions connected in a loop, a geometry that exposes the qubit to magnetic environmental noise. In this paper, we show that by biasing a junction with supercurrent from a separate pair of superconducting leads coupled to the device, the Josephson energy can be tuned without the need for a flux loop. Our multiterminal device may enable the realization of a frequency-tunable qubit with greatly reduced susceptibility to flux noise.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 pages, 3 figures
Chiral-induced circularly polarized light emission from a single-molecule junction
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
In the present work we theoretically analyze electroluminescence occurring in a biased single-molecule junction with a chiral bridge imitated by a helical chain. We show that optical transitions between electron states of the chiral linker may result in the emission of circular polarized light whose handedness depends on both direction of propagation and the polarity of the bias voltage provided that the coupling between the bridge sites is sufficiently strong. The mechanism controlling this specific light emission does not depend on the magnetic moments and spin-orbit interactions. It rather relies on the chiral properties of the bridge molecule and on the distribution of the bias voltage between the electrodes in the junction.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 4 figures
Dynamic annihilation pathways of magnetic skyrmions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
The investigation of magnetic solitons often relies on numerical modeling to determine key features such as stability, annihilation, nucleation, and motion. However, as soliton sizes approach atomic length scales, the accuracy of these predictions become increasingly sensitive to the details of the numerical model. Here, we study the annihilation of two-dimensional magnetic skyrmions using a pseudospectral approach and compare its performance to that of conventional micromagnetic simulations. A central distinction between the models lies in their treatment of the exchange interaction, which governs the magnon dispersion relation and plays a crucial role to balance the uniaxial anisotropy to stabilise skyrmions. We demonstrate that both the choice of model and spatial discretisation significantly influence the skyrmion dynamics and the magnetic field required for annihilation. The pseudospectral model provides a consistent description across length scales and captures complex behaviours such as skyrmion breathing on its path to annihilation. Our results have direct implications in the state-of-the-art modeling of skyrmions and other two-dimensional textures and will impact the modeling of three-dimensional textures such as hopfions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Phonon Weyl points and chiral edge modes with unconventional Fermi arcs in NbSi$_{2}$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
NbSi$ _{2}$ crystallizes in the P6$ _{2}$ 22 symmetry, featuring chiral chains of Si atoms. The absence of inversion symmetry, combined with its chiral structure, gives arise to unique physical properties. The breaking of inversion symmetry leads to the emergence of Weyl points, while the chiral structure enables the formation of chiral edge modes. As a result, NbSi$ _{2}$ serves as an ideal platform for exploring the interplay between phonon Weyl points and chiral phonon edge modes. For example, we identify the presence of a structure consisting of three Weyl points with a Chern number of $ \mathcal{C} = +1$ around the $ \bar{\text{K}}$ point. These nodes form unconventional Fermi arcs connecting the $ \bar{\Gamma}$ or $ \bar{\text{K}}$ points, which mimic an effective Chern number of $ \mathcal{C} = -2$ .
Materials Science (cond-mat.mtrl-sci)
10 pages, 6 figures
Segregation and Ordering of Light Interstitials (B, C, H, and N) in Cr-Ni Alloys: Implications for Grain Boundary Stability in Superalloy Design
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Tyler D. Doležal, Rodrigo Freitas, Ju Li
The segregation and ordering behavior of light interstitials (B, C, and N) in Cr30-Ni is examined, as these elements are critical for grain boundary stability and high-temperature mechanical performance in Ni-based superalloys. Using Monte Carlo simulations, we identify the chemical and structural preferences of these interstitials in both bulk and grain boundary (GB) environments, aligning with experimental segregation and precipitation trends. Boron strongly prefers GBs over the bulk, where it enhances GB cohesion and stabilizes the GB structure. Uniquely, boron induces a structural transformation at higher concentrations, hinting at the formation of serrated GBs where boron content is high, which improves high-temperature mechanical performance. Carbon and nitrogen form carbide and nitride motifs and exhibit limited GB solubility, reinforcing their precipitation tendencies. In support of ongoing hydrogen embrittlement mitigation strategies, we also examined hydrogen behavior. Hydrogen demonstrated chemical stability in the Cr-Ni GB zone, suggesting it may preferentially migrate inward along Cr- and Ni-rich GBs while avoiding Mo-enriched regions, further supporting Mo’s role in mitigating embrittlement. These findings suggest that Mo-containing borides may serve as effective barriers against hydrogen-induced degradation by inhibiting H ingress and stabilizing GB cohesion. By elucidating the chemical and structural preferences of these light interstitials, this work provides a robust computational framework for guiding superalloy design toward improved high-temperature grain boundary stability, resistance to hydrogen embrittlement, and controlled chemical ordering.
Materials Science (cond-mat.mtrl-sci)
Acta Materialia, 296, 01 September 2025, 121221
Atomistic Simulations of Short-range Ordering with Light Interstitials in Inconel Superalloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Tyler D. Dolžal, Emre Tekoglu, Jong-Soo Bae, Gi-Dong Sim, Rodrigo Freitas, Ju Li
This study employed hybrid Monte Carlo Molecular Dynamics simulations to investigate the short-range ordering behavior of Ni-based superalloys doped with boron or carbon. The simulations revealed that both boron and carbon dissociated from their host Ti atoms to achieve energetically favored ordering with Cr, Mo, and Nb. Boron clusters formed as B2, surrounded by Mo, Nb, and Cr, while carbon preferentially clustered with Cr to form a Cr23C6 local motif and with Nb to form Nb2C. Distinct preferences for interstitial sites were observed, with boron favoring tetrahedral sites and carbon occupying octahedral sites. In the presence of a vacancy, B2 shifted from the tetrahedral site to the vacancy, where it remained coordinated with Mo, Nb, and Cr. Similarly, carbon utilized vacancies to form Nb2C clusters. Excess energy calculations showed that B and C exhibited strong thermodynamic stability within their short-range ordered configurations. However, under Ti-rich conditions, C was more likely to segregate into TiC, despite preexisting ordering with Cr. This shift in stability suggests that increased Ti availability would alter carbide formation pathways, drawing C away from Cr-rich networks and promoting the development of TiC. Such redistribution may disrupt the continuity of Cr-based carbide networks, which play a critical role in stabilizing grain boundaries and impeding crack propagation. These effects further underscore the impact of interstitial-induced ordering on phase stability and microstructural evolution. This work provides an atomistic perspective on how boron- and carbon-induced ordering influences microstructure and mechanical properties. These findings highlight the critical role of interstitial-induced short-range ordering and demonstrate that this mechanism can be leveraged as a design principle to fine-tune alloy microstructures for specific engineering applications.
Materials Science (cond-mat.mtrl-sci)
Computational Materials Science, Vol 253, May 2025, 113858
New metastable ice phases via supercooled water
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Hiroki Kobayashi, Kazuki Komatsu, Kenji Mochizuki, Hayate Ito, Koichi Momma, Shinichi Machida, Takanori Hattori, Kunio Hirata, Yoshiaki Kawano, Saori Maki-Yonekura, Kiyofumi Takaba, Koji Yonekura, Qianli Xue, Misaki Sato, Hiroyuki Kagi
Water exhibits rich polymorphism, where more than 20 crystalline phases have been experimentally reported. Five of them are metastable and form at low temperatures by either heating amorphous ice or degassing clathrate hydrates. However, such metastable phases rarely crystallise directly from liquid water, making it challenging to study metastable phase relations at relatively high temperatures. Here, we report that high-pressure metastable phases of ice, including two unknown phases named ices XXI and XXII, crystallise directly from liquid water in a deeply supercooled region around the homogeneous nucleation temperature. The key is to use emulsified water to stabilise supercooled water in laboratory timescales. Ices XXI and XXII are obtained by isothermal compression of emulsified water at 295 K and 250 K, respectively. Our powder x-ray and neutron diffraction analyses combined with molecular dynamics (MD) simulations revealed the surprisingly complex structures of these new phases with Z = 152 (ice XXI) and 304 (ice XXII). Ice XXI is topologically identical to ‘ice T2’ previously predicted by MD simulations, and our experimental structural model can be used as a benchmark for its structures in simulations, which depend on the force fields. On cooling, ice XXI transforms into an orientationally ordered counterpart named ice XXIII. Our results revealed the “hidden” structural complexity of water underlying the phase diagram, as implied by previous computational works. Further efforts at unveiling such metastable phase relations will bridge the large gaps between computational and experimental phase diagrams of water.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Phonon density of states of magnetite (\ce{Fe3O4}) nanoparticles via molecular dynamics simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Pablo Galaviz, Kyle A. Portwin, Dehong Yu, Kirrily C. Rule, David L. Cortie, Zhenxiang Cheng
This study presents a comprehensive computational investigation of magnetite nanoparticles, systematically evaluating a range of force fields against experimental results. We analyze the influence of particle size, temperature, and surface-adsorbed water molecules on the structural and dynamic properties of the nanoparticles. We performed classical molecular dynamics of nanoparticles and bulk magnetite and utilized density functional theory calculations for bulk magnetite for comparison. Our results reveal that nanoparticle size and the presence of adsorbed water molecules have a pronounced impact on the density of states. Specifically, as the nanoparticle size is decreased, phonon modes exhibit significant broadening and softening, which is attributable to reduced phonon lifetimes resulting from enhanced boundary scattering. The incorporation of water further broadens the density of states and extends the spectra to higher energy regions. Temperature variations result in a slight broadening and softening of the phonon density of states, particularly in the oxygen-dominated region, which is attributed to phonon anharmonicity.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
39 pages, 19 figures
Critical angles and one-dimensional moiré physics in twisted rectangular lattices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Dongdong An, Tao Zhang, Qiaoling Xu, Hailing Guo, Majeed Ur Rehman, Dante M. Kennes, Angel Rubio, Lei Wang, Lede Xian
Engineering moiré superlattices in van der Waals heterostructures provides fundamental control over emergent electronic, structural, and optical properties allowing to affect topological and correlated phenomena. This control is achieved through imposed periodic modulation of potentials and targeted modifications of symmetries. For twisted bilayers of van der Waals materials with rectangular lattices, such as PdSe2, this work shows that one-dimensional (1D) moiré patterns emerge universally. This emergence is driven by a series of critical twist angles (CAs). We investigate the geometric origins of these unique 1D moiré patterns and develop a universal mathematical framework to predict the CAs in twisted rectangular lattices. Through a density functional theory (DFT) description of the electronic properties of twisted bilayer PdSe2, we further reveal directionally localized flat band structures, localized charge densities and strong spin-orbit coupling along the dispersive direction which points to the emergence of an effectively 1D strongly spin-orbit coupled electronic systems. This establishes twisted rectangular systems as a unique platform for engineering low-symmetry moiré patterns, low-dimensional strongly correlated and topological physics, and spatially selective quantum phases beyond the isotropic paradigms of hexagonal moiré materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 3 figures
A new collective mode in an iron-based superconductor with electronic nematicity
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
Haruki Matsumoto, Silvia Neri, Tomoki Kobayashi, Atsutaka Maeda, Dirk Manske, Ryo Shimano
Elucidation of the symmetry and structure of order parameter(OP) is a fundamental subject in the study of superconductors. Recently, a growing number of superconducting materials have been identified that suggest additional spontaneous symmetry breakings besides the primal breaking of U(1) gauge symmetry, including time-reversal, chiral, and rotational symmetries. Observation of collective modes in those exotic superconductors is particularly important, as they provide the fingerprints of the superconducting OP. Here we investigate the collective modes in an iron-based superconductor, FeSe, a striking example of superconductivity emergent in an electronic nematic phase where the rotational symmetry of electronic degree of freedom is spontaneously broken. By using terahertz nonlinear spectroscopy technique, we discovered a collective mode resonance located substantially below the superconducting gap energy, distinct from the amplitude Higgs mode. Comparison with theoretical calculations demonstrates that the observed mode is attributed to a collective fluctuation between the s+d-wave-like ground state and the subleading pairing channel, which corresponds to the so-called Bardasis-Schrieffer mode but also resembles an intraband Leggett mode. Our result corroborates the multicomponent pairing channels in FeSe activated in the lower space group symmetry in the electronic nematic phase.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Light-Induced Giant Enhancement of the Nonlinear Hall Effect in Two-Dimensional Electron Gases at KTaO3 (111) Interfaces
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Hui Zhang, Daming Tian, Xiaobing Chen, Weijian Qi, Lu Chen, Min Li, Yetong Bai, Jine Zhang, Furong Han, Huaiwen Yang, Yuansha Chen, Yunzhong Chen, Jing Wu, Yongbing Xu, Fengxia Hu, Baogen Shen, Jirong Sun, Weisheng Zhao
The nonlinear Hall effect (NLHE), an emergent phenomenon in noncentrosymmetric systems, enables the generation of a transverse voltage without an external magnetic field through a second-order electrical response. However, achieving a sizable NLHE signal remains a critical challenge for its application in frequency-doubling and rectifying devices. Here, we report a light-induced giant enhancement of the NLHE in the two-dimensional electron gas (2DEG) at the CaZrO3/KTaO3 (111) interface. Under light illumination, the second harmonic Hall voltage (V2{\omega} y) increases substantially and undergoes a sign reversal. Correspondingly,the second-order transverse conductivity increases by nearly five orders of magnitude, reaching 2.4 um V-1 omega-1, while also reversing its sign. Scaling analysis indicates that skew scattering is the dominant mechanism underlying the NLHE and is highly tunable via optical gating. Photoexcitation pumps electrons from in-gap states into the higher-lying Ta 5d conduction band, generating high-mobility photocarriers that significantly increase the cubic transport scattering time, thereby driving a dramatic enhancement of {\sigma}(2) yxx. First-principles calculations further reveal that the Berry curvature distribution on the Fermi surface strongly depends on band filling. As the Fermi level approaches a band crossing in the Ta 5d subband near the M point, the Berry curvature triple undergoes a sign change, accounting for the experimentally observed sign reversal of the nonlinear Hall response. Our work offers a new strategy to optically boost and tune the nonlinear Hall effect in oxide 2DEG systems, paving the way for applications in light-controlled rectification and nonlinear electronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Abrupt transitions in the optimization of diffusion with distributed resetting
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Pedro Julián-Salgado, Leonardo Dagdug, Denis Boyer
Brownian diffusion subject to stochastic resetting to a fixed position has been widely studied for applications to random search processes. In an unbounded domain, the mean first passage time at a target site can be minimized for a convenient choice of the resetting rate. Here we study this optimization problem in one dimension when resetting occurs to random positions, chosen from a distribution with compact support that does not include the target. Depending on the shape of this distribution, the optimal resetting rate either varies smoothly with the mean distance to the target, as in single-site resetting, or exhibits a discontinuity caused by the presence of a second local minimum in the mean first passage time. These two regimes are separated by a critical line containing a singular point that we characterize through a Ginzburg-Landau theory. To quantify how useful a given resetting position is for a search process, we calculate the distribution of the last resetting position before absorption. The discontinuous transition above separates two markedly different optimal strategies: one with a small resetting rate where the last path before absorption starts from a rather distant but likely position, while the other strategy has a large resetting rate, favoring last paths starting from not-so-likely points but which are closer to the target.
Statistical Mechanics (cond-mat.stat-mech)
11 pages, 5 Figures
Tunable exchange bias in Y$_3$Fe$5$O${12}$ film on Gd$_3$Ga$5$O${12}$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Umesh Thuwal, Sumanta Maity, Ruksana Pervin, Rohit Medwal, Joseph Vimal Vas, Yasuhiro Fukuma, Herve Courtois, Clemens B. Winkelmann, Anjan Kumar Gupta
Ferrimagnetic Y$ _3$ Fe$ _5$ O$ _{12}$ grown on the (001) surface of paramagnetic Gd$ _3$ Ga$ _5$ O$ _{12}$ experiences an exchange bias field, which has been attributed to the magnetism of an interface layer between the two materials. We report here that when grown using sputtering and with lower post-annealing temperatures than in previous works, the blocking temperature of the interface magnetic layer is lowered to about 7 K, while still displaying a strong exchange bias. This exchange bias is then found to be tunable between its two extreme values by carefully varying the field cooling protocol. This is attributed to a slow and complex dynamics of the spins of the interface-layer when it is warmed up close to its blocking (or melting) temperature, which is reminiscent of a spin glass.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages (5 figures) + 2 page suppl-info (6 figures)
Possible Orthorhombic Phase of Ta$_2$O$_5$ under High Pressures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Yan Gong, HuiMin Tang, Yong Yang, Yoshiyuki Kawazoe
A potential orthorhombic phase of Ta$ _2$ O$ _5$ , designated as Y-Ta$ _2$ O$ _5$ , is predicted under high-pressure conditions through density functional theory (DFT) calculations combined with structural search algorithms. This phase, consisting of four formula units per unit cell ($ Z = 4$ ), exhibits the highest known Ta-O coordination numbers. Y-Ta$ _2$ O$ _5$ is found to be the most energetically favorable form of Ta$ _2$ O$ _5$ in the pressure range of approximately 70 GPa to at least 200 GPa. Both standard DFT-GGA and higher-accuracy GW calculations reveal that Y-Ta$ _2$ O$ _5$ is a wide bandgap semiconductor with a direct bandgap. Additionally, nuclear quantum effects (NQEs) introduce nontrivial corrections to external pressure at fixed volumes, underscoring their significance in high-pressure phase stability analyses.
Materials Science (cond-mat.mtrl-sci)
30 Pages, 4 Figures, 2 Tables
Anisotropic Anderson localization in higher-dimensional nonreciprocal lattices
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-22 20:00 EDT
Nonreciprocity breaks the symmetry between forward and backward propagation, giving rise to a range of peculiar wave phenomena. In this work, we investigate Anderson localization in higher-dimensional nonreciprocal lattices. Focusing on the two-dimensional Hatano-Nelson model, we uncover anisotropic hybrid modes (HMs) that exhibit skin localization along one direction and Anderson localization along the other. We determine the Anderson transition along different directions via the transfer matrix approach and finite-size scaling of Lyapunov exponents. This allows us to map out mobility edges that separate HMs from normal skin modes and Anderson localized modes (ALMs), revealing an ALM-HM-ALM reentrant transition. Our analysis extends to arbitrary dimensions, and we demonstrate the existence of skin-Anderson transitions on the infinite-dimensional nonreciprocal Bethe lattice using the forward-scattering approximation.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
6 pages, 3 figures
Symmetry-breaking strain drives significant reduction in lattice thermal conductivity: A case study of boron arsenide
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Kaile Chen, Xin Jin, Xiaolong Yang
Recent research has revealed that cubic boron arsenide (BAs) exhibits a non-monotonic pressure dependence of lattice thermal conductivity ($ \kappa_{\rm L}$ ) under isotropic strain. Here, through rigorous first-principles calculations, we unveil that uniaxial tensile strain induces a monotonic reduction in the $ \kappa_{\rm L}$ of BAs – a striking contrast to the isotropic scenario. The results show that applying uniaxial (100) strain leads to the lifting of phonon band degeneracy, accompanied by an overall softening of the phonon spectrum. These modifications significantly increase phonon-phonon scattering channels by facilitating the fulfillment of selection rules, resulting in a concurrent increase in both three- and four-phonon scattering rates. Consequently, $ \kappa_{\rm L}$ exhibits a dramatic suppression of nearly 80% under large tension at room temperature. Meanwhile, we unexpectedly observe that the uniaxial strain suppresses $ \kappa_{\rm L}$ much more strongly in the direction perpendicular to the strain than along the stretching direction. This work establishes the fundamental understanding of the thermal conductivity behavior of BAs under uniaxial strain and opens a promising avenue for manipulating solid-state heat transport by tuning crystal symmetry.
Materials Science (cond-mat.mtrl-sci)
Metal-Insulator transition and Charge Transport Mechanisms in SnSe$_2$ Field-Effect Transistor
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Aarti Lakhara, Lars Thole, Rolf J. Haug, P. A. Bhobe
We report an observation of metal-insulator transition in a thin film of SnSe$ _2$ . The room-temperature carrier concentration of SnSe$ _2$ film was increased by electrostatic doping to 1.14$ \times$ 10$ ^{13}$ cm$ ^{-2}$ . A crossover from insulating phase to metallic state was clearly observed. The low-temperature charge transport mechanism is governed by two-dimensional (2D) variable-range hopping. This mechanism is influenced by band bending and gap states introduced by selenium vacancies. At low temperatures, the mobility is primarily limited by charged impurities, while at higher temperatures, it follows a power-law dependence, $ \mu = T^{-\gamma}$ , indicating a dominance of electron-phonon scattering. The application of a gate field shifts the Fermi level toward the conduction band, and at sufficiently high temperatures, this drives the system into a metallic state. Our findings offer insights into the charge transport mechanisms in SnSe$ _2$ FET, this understanding will allow for the optimization of other 2D materials for advanced electronic device applications.
Materials Science (cond-mat.mtrl-sci)
5 pages, 5 figures, supplementary text
Multiply quantized vortex spectroscopy in a quantum fluid of light
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-22 20:00 EDT
Killian Guerrero, Kevin Falque, Elisabeth Giacobino, Alberto Bramati, Maxime J Jacquet
The formation of quantized vortices is a unifying feature of quantum mechanical systems, making it a premier means for fundamental and comparative studies of different quantum fluids. Being excited states of motion, vortices are normally unstable towards relaxation into lower energy states. However, here we exploit the driven-dissipative nature of polaritonic fluids of light to create stationary, multiply charged vortices. We measure the spectrum of collective excitations and observe negative energy modes at the core and positive energy modes at large radii. Their coexistence at the same frequency normally causes the dynamical instability, but here intrinsic losses stabilize the system, allowing for phase pinning by the pump on macroscopic scales. We observe common features of quantized vortices in quantum fluids and other rotating geometries like astrophysical compact objects, opening the way to the study of universal amplification phenomena.
Quantum Gases (cond-mat.quant-gas), General Relativity and Quantum Cosmology (gr-qc), Quantum Physics (quant-ph)
12 pages, 7 figs, comments are welcome!
The Anisotropy of Thermal Activation Energy of 2H-NbS$_2$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
Yang Wang, Pengjian Tan, Mingxi Chi, Boxi Wei, Anchun Ji, Jian Wang, He Wang
We investigate the anisotropic flux dynamics in 2H-NbS$ _2$ single crystals through temperature-dependent resistance measurements under in-plane ($ H \parallel ab$ plane) and out-of-plane ($ H \perp ab$ plane) magnetic fields. Analysis of thermally activated flux flow (TAFF) resistance in the superconducting mixed state reveals stark contrasts in thermal activation energy ($ U_0$ ) scaling and field dependence. For $ H \perp ab$ , $ U_0(0.1 \mathrm{T}) = (1228.76 \pm 53.64)$ K follows the Arrhenius relation with a power-law field decay ($ U_0\propto H^{-\alpha}$ ). In contrast, under $ H \parallel ab$ , $ U_0(0.5 \mathrm{T}) = (7205.58 \pm 619.65)$ K aligns with the modified TAFF theory, where the scaling exponent $ q = 2$ potentially reflects two-dimensional vortex behavior in the TAFF region, and the field dependence of $ U_0$ follows parabolic relation $ H^{\gamma}\left[1 - \frac{H}{H^{\ast}}\right]^2$ . These results establish 2H-NbS$ _2$ as a model system for probing the anisotropy of flux dynamics in layered superconductors.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
16 pages, 4 figures
Low Temp. Phys. 51, 856 (2025)
The physical consequences of sperm gigantism
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Jasmin Imran Alsous, Brato Chakrabarti, Bryce Palmer, Michael J. Shelley
The male fruit fly produces ~1.8 mm long sperm, thousands of which can be stored until mating in a ~200 micron sac, the seminal vesicle. While the evolutionary pressures driving such extreme sperm (flagellar) lengths have long been investigated, the physical consequences of their gigantism are unstudied. Through high-resolution three-dimensional reconstructions of in vivo sperm morphologies and rapid live imaging, we discovered that stored sperm are organized into a dense and highly aligned state. The packed flagella exhibit system-wide collective ‘material’ flows, with persistent and slow-moving topological defects; individual sperm, despite their extraordinary lengths, propagate rapidly through the flagellar material, moving in either direction along material director lines. To understand how these collective behaviors arise from the constituents’ nonequilibrium dynamics, we conceptualize the motion of individual sperm as topologically confined to a reptation-like tube formed by its neighbors. Therein, sperm propagate through observed amplitude-constrained and internally driven flagellar bending waves, pushing off counter-propagating neighbors. From this conception, we derive a continuum theory that produces an extensile material stress that can sustain an aligned flagellar material. Experimental perturbations and simulations of active elastic filaments verify our theoretical predictions. Our findings suggest that active stresses in the flagellar material maintain the sperm in an unentangled, hence functional state, in both sexes, and establish giant sperm in their native habitat as a novel and physiologically relevant active matter system.
Soft Condensed Matter (cond-mat.soft)
Swift heavy ion track formation in SiC films under high-temperature irradiation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
The resistance of bulk silicon carbide (SiC) to impacts of swift heavy ions (SHI) decelerating at room temperature in the electronic stopping regime is well known. However, the effect of the SiC film thickness on the formation and structure of SHI tracks over a wide range of irradiation temperatures remains unexplored. To address this disadvantage, we utilize a model sensitive to irradiation temperature that describes all stages of ion track formation: from material excitation, considering the emission of excited electrons from the film surface (MC code TREKIS-3), to the reaction of the material’s atomic system to the excitation (classical molecular dynamics). We observed the formation of two different types of nanostructures on the surface of SiC films with thicknesses ranging from 10 nm to 100 nm when irradiated with 710 MeV Bi ions: craters and hills. The type of nanostructure formed depended on the irradiation temperature. The transition irradiation temperature ($ T_{tr}$ ) from hills to craters grows with the film thickness and follows an empirical relation $ T_{tr}=T_{tr}^{cr} \left(1-\left(1+\left(L/L_{cr} \right)^2 \right)^{-\frac{1}{2}} \right)$ with $ T_{tr}^{cr}=1534$ K and $ L_{cr}=2.8$ nm. That means such a transition should occur in bulk SiC at the irradiation temperature of $ \approx 1534$ K.
Materials Science (cond-mat.mtrl-sci)
Investigation on high-order planar Hall effect in trigonal PtBi$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Fangqi Cai, Mingxi Chi, Yingjie Hu, Heyao Liu, Yangyang Chen, Chao Jing, Wei Ren, He Wang
The trigonal PtBi$ _2$ (t-PtBi$ _2$ ) as a Weyl semimetal possessing triply degenerate points in its electronic bands near the Fermi level endows it with rich electronic properties. Previous studies have already measured the planar Hall effect (PHE) and in-plane anisotropic magnetoresistance (AMR) of t-PtBi$ _2$ . We noticed that their experimental results exhibited high-order features in both the PHE and AMR, yet these features were not systematically investigated. In our work, we conducted more systematic measurements and analyses of the PHE and AMR in t-PtBi$ _2$ . Both PHE and AMR show high-order features under low temperatures and strong magnetic fields, and these features share a similar temperature and magnetic field dependence with the turn-on behavior of resistance and temperature curves, indicating a common physical origin for them. We further summarize the critical conditions for the emergence of high-order PHE in t-PtBi$ _2$ , which will help to understand the origin of high-order features. In addition, we performed computational simulations on the AMR of t-PtBi$ _2$ , and the results were consistent with the experiments, indicating the high-order features are the result of the combined contribution of the Fermi surface anisotropy and the scaling behavior of magnetoresistance. Our findings will contribute to a deeper understanding of the origins of high-order features in non-magnetic topological materials.
Materials Science (cond-mat.mtrl-sci)
18 pages, 4 figures,
Appl. Phys. Lett. 126, 233101 (2025)
Supersolidity in Optically Trapped Polariton Condensates
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
P. N. Kozhevin, A. D. Liubomirov, R. V. Cherbunin, M. A. Chukeev, I. Yu. Chestnov, A. V. Kavokin, A. V. Nalitov
Superfluids under specific conditions can exhibit spontaneous breaking of continuous translation symmetries and form exotic spatially ordered states of matter known as supersolids. Despite its early theoretical prediction, it took over half-a-centrury to experimentally demonstrate the supersolid phase in ultracold atomic Bose-Einstein condensates, forming due to long-range interatomic interactions. Here we propose as a promising new platform for supersolidity exciton-polariton superfluids, confined in annular optically induced traps. The supersolid phase emerges due to effective attractive interactions, mediated by the normal excitonic component of the system. Experimental demonstration of spontaneously formed spatially ordered phase is in agreement with detailed mean-field theoretical analysis and numerical simulation. The spontaneous character of the observed supersolid transition is further evidenced by the formation of specific zero-energy Nambu-Goldstone modes in the collective excitation spectrum.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas)
16 pages, 8 figures
Spin orientation – a subtle interplay between strain and multipole Coulomb interactions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Subhra Sen Gupta, Shinjini Paul, Suman Mandal, D. D. Sarma, Priya Mahadevan
We address the technologically important issue of the spin orientation on a correlated magnetic surface and how to manipulate it. We consider a prototypical strongly correlated system, NiO, and show that a single particle approach with anisotropic hoppings, or even a many-electron model with a scalar Hubbard $ U$ and Hund’s $ J$ fails to explain the strain driven spin reorientation transition (SRT). We set up a model treating both anisotropic single particle effects and orbital-dependent, full multipole electron-electron interaction effects at the same footing. Within this model, predictive power to explain the observed SRT is regained and the results indicate the novel possibility of using an electric field to control SRT in magnetic films grown on piezoelectric substrates.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
5 pages, 3 figures and Supplementary Material included
Floquet composite Dirac semimetals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Hong Wu, Jia-Ji Zhu, Jian Li, Xue-Min Yang, Jiang-Shan Chen, Mu Zhou
Dirac semimetals are classified into types I, II, and III based on the topological charge of their Dirac points. If a three-dimensional (3D) system can be sliced into a family of $ k_z$ -dependent normal and topological insulators, type I Dirac points separate a 2D normal insulator from a 2D first-order topological insulator, while type II (III) Dirac points separate a 2D normal (first-order) insulator from a 2D second-order topological insulator. To investigate the effects arising from the interplay of distinct Dirac points, one may wonder whether these Dirac points can coexist in single system. Here, we propose a scheme to induce composite Dirac semimetals in a Floquet four-band system with time-reversal and space-inversion symmetries. A general description is established to characterize Dirac semimetals in Floquet systems. The results show that Dirac semimetals hosting coexisting type I, II, and III Dirac points can be induced by delta-function or harmonic driving. Our results provide a promising new avenue for exploring novel Dirac semimetals.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages and 5 figures
Intrinsic pressure as a convenient mechanical framework for dry active matter
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Zihao Sun, Longfei Li, Chuyun Wang, Jing Wang, Huaicheng Chen, Gao Wang, Liyu Liu, Fangfu Ye, Mingcheng Yang
The identification of local pressure in active matter systems remains a subject of considerable debate. Through theoretical calculations and extensive simulations of various active systems, we demonstrate that intrinsic pressure (defined in the same way as in passive systems) is an ideal candidate for local pressure of dry active matter, while the self-propelling forces on the active particles are considered as effective external forces originating from the environment. Such a framework is universal and especially convenient for analyzing mechanics of dry active systems, and it recovers the conventional scenario of mechanical equilibrium well-known in passive systems. Thus, our work is of fundamental importance to further explore mechanics and thermodynamics of complex active systems.
Soft Condensed Matter (cond-mat.soft)
8 pages,4 figures
Low Speed Oblique Impact Behavior On Granular Media Across Gravitational Conditions; The role of cohesion
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Seungju Yeo, Rachel Glade, Alice Quillen, Hesam Askari
Analyses of impact provide rich insights from the evolution of granular bodies to their structural properties of the surface and subsurface layers of celestial bodies. Although chemical cohesive bonding has been observed in asteroid samples, and low-speed impact has been a subject of many studies, our understanding of the role of cohesion in these dynamics is limited, especially at small gravities such as those observed on asteroid surfaces. In this work, we use numerical discrete element method (DEM) and analytical dynamic resistive force theory (DRFT) modeling to examine the effect of cohesion on the outcome of the impact into loose granular media and explore scaling laws that predict impact behavior in the presence of cohesion under various gravitational conditions and cohesive strengths. We find that the effect of cohesion on the impact behavior becomes more significant in smaller gravitational acceleration, raising the need to scale the cohesion coefficient with gravity. We find that due to an insufficient understanding of confounding between cohesion and friction-induced quasi-static and inertial resistance, the outcomes of the DEM simulation models are incongruent with a suggested analytic model using Froude and Bond number scaling based on an additive contribution of frictional and inertial forces. Our study suggests that new dimensionless parameters and scaling are required to accurately capture the role of cohesion, given its ties to frictional behavior between the grain particles at different gravities.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Space Physics (physics.space-ph)
Designing Two-Dimensional Octuple-Atomic-Layer M$_2$A$_2$Z$_4$ as Promising Photocatalysts for Overall Water Splitting
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Dingyanyan Zhou, Yujin Ji, Mir F. Mousavi, Youyong Li
Two-dimensional (2D) materials have emerged as promising candidates as photocatalytic materials due to their large surface areas and tunable electronic properties. In this work, we systematically design and screen a series of octuple-atomic-layer M$ _2$ A$ _2$ Z$ _4$ monolayers (M = Al, Ga, In; A = Si, Ge, Sn; Z = N, P, As) using first-principles calculations. 108 structures are constructed by intercalation approach, followed by a comprehensive evaluation of their thermodynamic and dynamic stability, band gaps, and band edge alignments to assess their potential for photocatalytic overall water splitting. Among them, eight candidates meet the criteria for overall water splitting under acidic condition (pH = 0), and Al$ _2$ Si$ _2$ N$ _4$ and Al$ _2$ Ge$ _2$ N$ _4$ , further exhibit suitable band edge positions for photocatalysis under both acidic and neutral environments (pH = 0 and 7). Al$ _2$ Si$ _2$ N$ _4$ and Al$ _2$ Ge$ _2$ N$ _4$ also show pronounced visible-light absorption and structural stability in aqueous conditions. Importantly, the introduction of N vacancies on the surfaces of Al$ _2$ Si$ _2$ N$ _4$ and Al$ _2$ Ge$ _2$ N$ _4$ significantly enhances their catalytic activity for both hydrogen reduction and water oxidation reactions, further supporting their potential as photocatalysts for overall water splitting. Our study provides theoretical insights for the rational design of efficient and stable 2D photocatalysts for overall water splitting.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Reconciling Translational Invariance and Hierarchy
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Tensor networks are not only numerical tools for describing ground states of quantum many-body systems, but also conceptual aids for understanding their entanglement structures. The proper way to understand tensor networks themselves is through explicit examples of solvable ground states that they describe exactly. In fact, this has historically been how tensor networks for gapped ground states, such as the matrix product state (MPS) and the projected entangled paired state, emerged as an elegant analytical framework from numerical techniques like the density matrix renormalization group. However, for gapless ground states, generically described by the multiscale entanglement renormalization ansatz (MERA), a corresponding exactly solvable model has so far been missing. This is because the hierarchical structure of MERA intrinsically breaks the translational invariance. We identify a condition for MERA to be compatible with translational invariance by examining equivalent networks of rank-3 tensors. The condition is satisfied by the previously constructed hierarchical tensor network for the Motzkin and Fredkin chains, which can be considered a non-unitary generalization to the MERA. The hierarchical TN description is complemented by a translationally invariant MPS alternative, which is used to derive the power-law decay of the correlation function and critical exponents.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph), Quantum Physics (quant-ph)
Superconducting order parameter manifested in quasicrystals
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
Sougata Biswas, Debika Debnath, Paramita Dutta
Recent discovery of the superconducting ground state in Quasicrystals (QCs) has opened up an exciting new avenue for superconductivity based on QCs. However, theoretical studies to date have largely focused on a limited subset of quasiperiodic structures. In this work, we broaden the scope by theoretically investigating the behavior of the superconducting order parameter (OP) across a wide class of aperiodic systems, including both generalized Fibonacci and non-Fibonacci QCs based on the attractive Hubbard model. We begin with a one-dimensional toy model, and for the generality of our findings, we extend our analysis to two-dimensional QCs. Remarkably, despite the increased dimensionality, the qualitative features of the OP remain largely preserved. By systematically analyzing models generated through various growth rules, we elucidate the influence of quasiperiodicity on the OP amplitudes. We study the evolution of the OP with respect to the temperature, strength of the interaction, and nearest-neighbor hopping amplitude. Our numerical analysis identifies the most favorable QC structure and parameter regime that supports enhanced onsite pairing amplitudes. Additionally, we provide a comparative analysis of the superconducting transition temperatures across the range of quasiperiodic configurations. To gain further insight into these systems, we compute key thermodynamic quantities: the entropy and electronic specific heat, and examine their dependence on the underlying structural sequences. This analysis enables us to determine which QC structures are most conducive to Cooper pair formation.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
19 pages, 16 figures; Comments are welcome
Temperature Dependent Mechanical and Structural Properties of Uniaxially Strained Planar Graphene
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Sané Erasmus, Charalampos Skokos, George Kalosakas
Using molecular dynamics simulations in a planar graphene sheet, we investigate the temperature dependence of its mechanical behavior under uniaxial tensile stress applied either along the armchair or the zigzag direction. Stress-strain curves are calculated for different temperatures and the corresponding dependence of various elastic parameters, like the Young modulus, the third-order elastic modulus, the tensile strength and failure strain, is presented. Fracture stress and strain, as well as the Young modulus, decrease almost linearly with temperature. The distributions of bond lengths and bond angles at different strains and temperatures are also discussed and approximate analytical expressions are presented. The latter describe accurately the numerically obtained distributions.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Chaotic Dynamics (nlin.CD), Applied Physics (physics.app-ph), Computational Physics (physics.comp-ph)
18 pages, 11 figures
Anomalous temperature dependence of local magnetic fields in altermagnetic MnTe
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Thomas J. Hicken (1), Oliver Amin (2), Alfred Dal Din (2), J. Hugo Dil (3 and 4), Dominik Kriegner (5), Hubertus Luetkens (1), Helena Reichlová (5), Zaher Salman (1), Klára Uhlířová (6), Peter Wadley (2), Juraj Krempaský (3), Jonas A. Krieger (1) ((1) PSI Center for Neutron and Muon Sciences, Villigen, Switzerland, (2) School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, (3) Photon Science Division, Paul Scherrer Institut, Villigen, Switzerland, (4) Institut de Physique, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, (5) Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic, (6) Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic)
Altermagnets are a novel type of magnetic system that has a spin-polarised electric band structure in the absence of a net magnetic moment, leading to exciting prospects in potential device applications. Hexagonal MnTe, a prototypical altermagnet, has arguably shown the most properties consistent with theoretical predictions, including an anomalous Hall effect despite no net magnetisation, and strong altermagnet-induced spin splitting in the electronic band structure. Here we present muon-spin spectroscopy measurements of a single crystal of MnTe. Below room temperature we observe pronounced anomalies in the muon-spin depolarisation, as well as the onset of a second, non-proportional internal field in the absence of an applied field. These findings point to a change in the magnetic structure around $ T\simeq250$ K, which coincides with other changes in reported properties, such as transport.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Spiral renormalization group flow and universal entanglement spectrum of the non-Hermitian 5-state Potts model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Vic Vander Linden, Boris De Vos, Kevin Vervoort, Frank Verstraete, Atsushi Ueda
The quantum $ 5$ -state Potts model is known to possess a perturbative description using complex conformal field theory (CCFT), the analytic continuation of ``theory space” to a complex plane. To study the corresponding complex fixed point on the lattice, the model must be deformed by an additional non-Hermitian term due to its complex coefficient $ \lambda$ . Although the variational principle breaks down in this case, we demonstrate that tensor network algorithms are still capable of simulating these non-Hermitian theories. We access system sizes up to $ L = 28$ , which enable the observation of the theoretically predicted spiral flow of the running couplings. Moreover, we reconstruct the full boundary CCFT spectrum through the entanglement Hamiltonian encoded in the ground state. Our work demonstrates how tensor networks are the correct approach to capturing the approximate conformal invariance of weakly first-order phase transitions.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
12 pages, 14 figures
Classical theory of electron-ion correlations at electrochemical interfaces: Closing the circuit from double-layer charging to ion adsorption
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Nils Bruch, Michael Eikerling, Tobias Binninger
The electric double layer (EDL) that forms at the interface between metals and ionic solutions is at the heart of various energy technologies. Recent experimental data have challenged our traditional understanding of the EDL charging behavior, which is based on mean-field Gouy-Chapman-Stern-type (GCS) models. In this article, we present a classical theory for the EDL, derived from first-principles statistical mechanics, that accounts for electron-ion correlation effects using the method of image charges and systematically extends beyond the mean-field level. Such electron-ion correlations introduce an additional interaction between the metal surface and electrolyte ions, significantly altering the EDL structure. Our theory, valid in the limit of dilute electrolyte solutions and weakly charged metal surfaces, achieves quantitative agreement with experimental capacitance data across a wide range of electrode materials and electrolyte solvents, and thus resolves long-standing questions on the origin of discrepancies to GCS predictions. Thereby, the framework conceptually unifies the processes of double-layer charging and ion adsorption (electrosorption), which are typically considered as distinct phenomena, but are shown to be manifestations of the same fundamental electrostatic principles.
Statistical Mechanics (cond-mat.stat-mech)
Fluctuation-induced Hall-like lateral forces in a chiral-gain environment
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Daigo Oue, Mário G. Silveirinha
Here, we demonstrate that vacuum fluctuations can induce lateral forces on a small particle positioned near a translation-invariant uniform non-Hermitian substrate with chiral gain. This type of non-Hermitian response can be engineered by biasing a low-symmetry conductor with a static electric field and is rooted in the quantum geometry of the material through the Berry curvature dipole. The chiral-gain material acts as an active medium for a particular circular polarisation handedness, while serving as a passive, dissipative medium for the other polarisation handedness. Owing to the nonreciprocity and gain characteristics, momentum is continuously exchanged in a preferred direction parallel to the surface between the test particle and the surrounding electromagnetic field, giving rise to lateral forces. Interestingly, the force can be viewed as a fluctuation-induced drag linked to the nonlinear Hall current. Indeed, although the gain is driven by an electric current, the resulting force acts perpendicular to the bias – unlike conventional current-drag effects. This effect stems from the skewed propagation characteristics of surface modes and gain-momentum locking. Our theory reveals a Hall-like asymmetry in the field correlations and establishes a novel link between quantum geometry and fluctuation-induced phenomena, offering new possibilities for nanoscale control via tailored electromagnetic environments.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics), Quantum Physics (quant-ph)
Enhanced phonon-drag by nanoscale design of homoepitaxial \hbox{$β$-Ga$_2$O$_3$}
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
J. Boy, R. Mitdank, A. Popp, Z. Galazka, S.F. Fischer
Phonon drag may be harnessed for thermoelectric generators and devices. Here, we demonstrate the geometric control of the phonon-drag contribution to the thermopower. In nanometer-thin electrically conducting $ \beta$ -Ga$ 2$ O$ 3$ films homoepitaxially-grown on insulating substrates it is enhanced from -0,4 mV/K to up to -3 mV/K at 100 K by choice of the film thickness. Analysis of the temperature-dependent Seebeck coefficients reveal that a crossover from three-dimensional to quasi-two-dimensional electron-phonon interaction occurs for film thicknesses below 75~nm. The ratio of phonon-phonon to electron-phonon relaxation times in these confined structures is $ 10$ times larger than that of bulk. Generally the phonon drag can be tuned depending on the relations between the phonon-drag interaction length $ \lambda\text{PD}$ , the phonon mean free path $ \lambda$ and the film thickness $ d$ . Phonon drag can be enhanced for $ \lambda\text{PD}\gg\lambda>d$ .
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
14 pages, 4 figures
The effect of fiber plasticity on domain formation in soft biological composites – Part II: An imperfection analysis
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Dimitris Iordanidis, Fernanda F. Fontenele, Konstantinos Poulios, Michalis Agoras, Nikolaos Bouklas
The main objective of this work is to numerically investigate the effect of geometric imperfections on the macroscopic response and domain formation in soft biological composites that exhibit plasticity in the stiff (fiber) this http URL work builds on the corresponding bifurcation analysis in Part I of this study for simple laminates with perfectly flat layers under plane strain, nonmonotonic loading conditions, aligned with the layer direction. The post-bifurcation solution obtained in Part I for these materials corresponds physically to the formation of twin lamellar domains perpendicular to the loading axis, which is consistent with the chevron like deformation patterns that develop in tendons under cyclic loading. As biological materials are highly imperfect, and specifically tendons exhibit a high degree of so called crimp in the collagen fibers, in this study the effect of imperfections to the response is explored. For all composites with small initial imperfections that have been considered, the results of this work have been found to be in complete agreement with the corresponding analytical results of Part I, and, domains have been found to emerge at a macroscopically compressive state. However, as the imperfection amplitude is increased and becomes of the order to the layer width, or greater, domains begin to develop at macroscopically tensile stresses, which is in agreement with the fact that the loading of soft biological materials such as tendons and ligaments is tensile in nature. Thus, the findings of this work suggest strongly that plasticity and geometric imperfections of collagen fibers may play a key role on the onset and evolution of domains in actual soft biological composites.
Soft Condensed Matter (cond-mat.soft)
Analysis of Hopf solitons as generalized fold maps
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Yuta Nozaki, Darian Hall, Ivan I. Smalyukh, Yuya Koda
The Hopf index, a topological invariant that quantifies the linking of preimage fibers, is fundamental to the structure and stability of hopfions. In this work, we propose a new mathematical framework for modeling hopfions with high Hopf index, drawing on the language of singularity theory and the topology of differentiable maps. At the core of our approach is the notion of a generalized Hopf map of order $ n$ , whose structure is captured via fold maps and their Stein factorizations. We demonstrate that this theoretical construction not only aligns closely with recent experimental observations of high-Hopf-index hopfions, but also offers a precise classification of the possible configurations of fiber pairs associated to distinct points. Our results thus establish a robust bridge between the geometry of singular maps and the experimentally observed topology of complex field configurations of hopfions in materials and other physical systems.
Soft Condensed Matter (cond-mat.soft), Geometric Topology (math.GT)
14 pages, 18 figures
Size-Dependent Lattice Pseudosymmetry for Frustrated Decahedral Nanoparticles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Oliver Lin, Zhiheng Lyu, Hsu-Chih Ni, Xiaokang Wang, Yetong Jia, Chu-Yun Hwang, Lehan Yao, Jian-Min Zuo, Qian Chen
Geometric frustration is a widespread phenomenon in physics, materials science, and biology, occurring when the geometry of a system prevents local interactions from being all accommodated. The resulting manifold of nearly degenerate configurations can lead to complex collective behaviors and emergent pseudosymmetry in diverse systems such as frustrated magnets, mechanical metamaterials, and protein assemblies. In synthetic multi-twinned nanomaterials, similar pseudosymmetric features have also been observed and manifest as intrinsic lattice strain. Despite extensive interest in the stability of these nanostructures, a fundamental understanding remains limited due to the lack of detailed structural characterization across varying sizes and geometries. In this work, we apply four-dimensional scanning transmission electron microscopy strain mapping over a total of 23 decahedral nanoparticles with edge lengths, d, between 20 and 55 nm. From maps of full 2D strain tensor at nanometer spatial resolution, we reveal the prevalence of heterogeneity in different modes of lattice distortions, which homogenizes and restores symmetry with increasing size. Knowing the particle crystallography, we reveal distinctive spatial patterns of local lattice phase transformation between face-centered cubic and body-centered tetragonal symmetries, with a contrast between particles below and above d of 35 nm. The results suggest a cross-over size of the internal structure occurs, as particles shape transition from modified-Wulff shape favored at nanoscale to faceted, pentagonal bipyramidal shape. Ultimately, our 4D-STEM mapping provides new insight to long-standing mysteries of this historic system and can be widely applicable to study nanocrystalline solids and material phase transformation that are important in catalysis, metallurgy, electronic devices, and energy storage materials.
Materials Science (cond-mat.mtrl-sci)
Broad-band THz emission by Spin-to-Charge Conversion in Topological Material – Ferromagnet Heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Xingyue Han, Xiong Yao, Tilak Ram Thapaliya, Genaro Bierhance, Chihun In, Zhuoliang Ni, Amilcar Bedoya-Pinto, Sunxiang Huang, Claudia Felser, Stuart S. P. Parkin, Tobias Kampfrath, Seongshik Oh, Liang Wu
Terahertz spintronic devices combine ultrafast operation with low power consumption, making them strong candidates for next-generation memory technologies. In this study, we use time-domain terahertz emission spectroscopy to investigate spin-to-charge conversion (SCC) in bilayer heterostructures comprising topological insulators (TIs) or Weyl semimetals (WSMs) with ferromagnetic metals (FMs). SCC is studied in TI materials \ce{Bi2Se3}, Pb-doped \ce{Bi2Se3}, and (Bi$ _{1-x}$ Sb$ _x$ )$ _2$ Te$ _3$ , and the WSM NbP. Our results reveal that the dependence of SCC on TI thickness varies with interface quality, indicating that thickness dependence alone is not a reliable criterion for distinguishing between inverse spin Hall effect and the inverse Rashba–Edelstein effect mechanisms. We find efficient SCC in TIs depends on both \textit{in-situ} growth to prevent surface oxidation and proper composition. In NbP$ \vert$ FM bilayers, we observe THz emission with efficiency and bandwidth comparable to that of TIs, highlighting the broader potential of topological materials. Finally, broadband spectral measurements demonstrate that both TIs and WSMs can generate THz pulses with frequencies extending up to 8,THz. These findings underscore the promise of topological materials as efficient platforms for ultrafast, broadband spintronic applications.
Materials Science (cond-mat.mtrl-sci)
A minimal model with stochastically broken reciprocity
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
We introduce a minimal model consisting of a two-body system with stochastically broken reciprocity (i.e., random violation of Newton’s third law) and then investigate its statistical behaviors, including correlation functions, time evolution of probability distribution functions, energy gain, and entropy production. The effective temperature of this two-body system immersed in a thermal bath is derived. Furthermore, we heuristically present an extremely minimal model where the relative motion adheres to the same rules as in classical mechanics, while the effect of stochastically broken reciprocity only manifests in the fluctuating motion of the center of mass.
Statistical Mechanics (cond-mat.stat-mech), Classical Physics (physics.class-ph)
7 pages, 1 figure
Interference and short-range correlation in fermionic Hubbard gases
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-22 20:00 EDT
Yan-Song Zhu, Hou-Ji Shao, Yu-Xuan Wang, De-Zhi Zhu, Hao-Nan Sun, Si-Yuan Chen, Chi Zhang, Xing-Can Yao, Yu-Ao Chen, Jian-Wei Pan
The interference patterns of ultracold atoms, observed after ballistic expansion from optical lattices, encode essential information about strongly correlated lattice systems, including phase coherence and non-local correlations. While the interference of lattice bosons has been extensively investigated, quantitative studies of the lattice fermion interference remain challenging. Here, we report the observation and quantitative characterization of interference patterns in low-temperature, homogeneous fermionic Hubbard gases. We develop a novel method to extract first-order correlations from interference patterns, which directly reflect the short-range phase coherence of lattice fermions. Mapping the nearest-neighbor correlations as a function of lattice filling and interaction strength, we observe a crossover from a metal to a Mott insulator. Moreover, at half filling, the measured correlations agree well with quantum Monte Carlo calculations and remain finite in the regime of strong repulsion, revealing virtual tunneling processes driven by quantum fluctuations.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Probing the band structure of the strongly correlated antiferromagnet NiPS3 across its phase transition
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Benjamin Pestka, Biplab Bhattacharyya, Milosz Rybak, Jeff Strasdas, Adam K. Budniak, Adi Harchol, Marcus Liebmann, Niklas Leuth, Honey Boban, Vitaliy Feyer, Iulia Cojocariu, Daniel Baranowski, Simone Mearini, Lutz Waldecker, Bernd Beschoten, Christoph Stampfer, Yaron Amouyal, Lukasz Plucinski, Efrat Lifshitz, Krzysztof Wohlfeld, Magdalena Birowska, Markus Morgenstern
NiPS3 is an exfoliable van-der-Waals intralayer antiferromagnet with zigzag-type spin arrangement. It is distinct from other TMPS3 (TM: transition metal) materials by optical excitations into a strongly correlated state that is tied to the magnetic properties. However, the related, fundamental band structure across the antiferromagnetic phase transition has not been probed yet. Here, we use angular-resolved photoelectron spectroscopy with {\mu}m resolution in combination with DFT+U calculations for that purpose. We identify a characteristic band shift across TN. It is attributed to bands of mixed Ni and S character related to the superexchange interaction of Ni 3t2g orbitals. Moreover, we find a structure above the valence band maximum with little angular dispersion that could not be reproduced by the calculations. The discrepancy suggests the influence of many-body interactions beyond the DFT+U approximations in striking contrast to the results on MnPS3 and FePS3, where these calculations were sufficient for an adequate description.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Finite-temperature properties of the Frenkel-Kontorova model: Relation to tribological systems and fluid rheology
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Shubham Agarwal, Martin H. Müser
The Frenkel-Kontorova model is a simple yet generic framework for the description of tribological phenomena and processes, including dry solid friction and the motion of adsorbed layers. As revealed in this work, it also reproduces qualitatively various features of complex liquids, such as, power-law sub-diffusion between the ballistic and the diffusive regimes as well as a cross-over from a non-Arrhenius to an Arrhenius dependence of the diffusion coefficient near the temperature, where the specific heat assumes its maximum. The study of these and related thermal and kinetic properties highlights several misconceptions prevalent in the literature. Most notably, shear thinning with a shear-thinning exponent close to zero can be the natural consequence from enforced basin hopping: the energy drops caused by shear-induced instabilities dictate the friction-velocity dependence at medium shear rates rather than the way how shear forces reduce the free energy barriers for directed motion. Thus, even if the rheology is described by semi-empirical theories such as the Eyring model, any agreement with experimental data, whether past, present, or future, may be purely coincidental.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
16 pages, 20 figures, 51 references
Potential barriers are nearly-ideal quantum thermoelectrics at finite power output
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Chaimae Chrirou, Abderrahim El Allati, Robert S Whitney
Quantum thermodynamics defines the ideal quantum thermoelectric, with maximum possible efficiency at finite power output. However, such an ideal thermoelectric is challenging to implement experimentally. Instead, here we consider two types of thermoelectrics regularly implemented in experiments: (i) finite-height potential barriers or quantum point contacts, and (ii) double-barrier structures or single-level quantum dots. We model them with Landauer scattering theory as (i) step transmissions and (ii) Lorentzian transmissions. We optimize their thermodynamic efficiency for any given power output, when they are used as thermoelectric heat-engines or refrigerators. The Lorentzian’s efficiency is excellent at vanishing power, but we find that it is poor at the finite powers of practical interest. In contrast, the step transmission is remarkably close to ideal efficiency (typically within 15%) at all power outputs. The step transmission is also close to ideal in the presence of phonons and other heat-leaks, for which the Lorentzian performs very poorly. Thus, a simple nanoscale thermoelectric - made with a potential barrier or quantum point contact - is almost as efficient as an ideal thermoelectric.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
11 pages, 6 figures
Lifshitz Quantum Mechanics and Anisotropic Josephson Junction
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
We consider quantum mechanics in spacetime with time anisotropy. Such Lifshitz quantum mechanics is characterized by a kinetic term with fractional derivatives. We show that, contrary to popular belief, local conservation of probability is respected when the probability current is properly identified. As an application we consider a Josephson Junction with an anisotropic insulating layer. We show that anisotropy affects the tunneling rate and can greatly enhance the working of Josephson Junction.
Superconductivity (cond-mat.supr-con), High Energy Physics - Theory (hep-th), Quantum Physics (quant-ph)
9 pages, 2 figures
Quantum Capacitance and Electronic Properties of a Hexagonal Boron Nitride based FET Gas Sensor
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
We present a comprehensive theoretical investigation of gas sensing in monolayer hexagonal boron nitride (h-BN) based field-effect transistors (FET) using the non-equilibrium Green function formalism and Landauer-Büttiker approach. Moving beyond conventional density functional theory analyses, our framework captures the full device level response by incorporating field-dependent quantum transport and temperature effects. We model the impact of NO, H$ _2$ S, HF and CO$ _2$ gases on the band structure and density of states (DOS), carrier concentration, quantum capacitance and I-V characteristics. The results indicate that CO$ _2$ followed by NO induce strongest perturbations via mid-gap states and band edge shifts, leading to the appearance of asymmetric Van-Hove singularities with enhanced carrier modulation and quantum capacitance. It is observed that HF induce moderate perturbation while H$ _2$ S induce weakest response for all temperature and biasing condition. It is found that an applied vertical electric field narrows the band gap via the Stark effect, further boosting mobility and tunability. Temperature influences sensing response by enhancing charge transfer at moderate levels and causing desorption at higher temperatures. We found that CO$ _2$ consistently show the highest sensitivity and selectivity followed by NO and HF, while H$ _2$ S display the weakest response. This study offers a comprehensive framework to engineer h-BN based FET sensors by harnessing intrinsic band modulation and quantum capacitance for molecule discrimination and temperature optimization.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages 7 figures
Sustained Amplification of Coherent Spin Waves by Parametric Pumping with Surface Acoustic Waves
New Submission | Other Condensed Matter (cond-mat.other) | 2025-07-22 20:00 EDT
Carson Rivard, Albrecht Jander, Pallavi Dhagat
Parametric amplification offers a route to overcoming intrinsic damping in spin-wave systems, a key challenge in the development of magnonic signal processing and computing technologies. Here we demonstrate the sustained amplification of coherent forward volume magnetostatic spin waves in a yttrium-iron-garnet thin film using a traveling surface acoustic wave as a nonstationary pump. A gain of up to 6 dB is achieved under continuous pumping below the threshold for parametric instability. The interaction generates an idler wave at a distinct frequency, consistent with three-wave mixing governed by energy and momentum conservation. This approach enables stable, frequency- and wavevector-selective spin-wave gain using practical pump power levels, establishing acoustic wave pumping as a viable mechanism for realizing active components in integrated magnonic circuits.
Other Condensed Matter (cond-mat.other), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Interfacial Stability in Tensionless Phase-Separated Quorum-Sensing Systems
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Zihao Sun, Longfei Li, Fangfu Ye, Mingcheng Yang
Interfacial phenomena of motility-induced phase separation of active particles challenge our conventional understanding of phase coexistence. Despite the ubiquity of nonmechanical communication couplings among real active particles, most works on active interface have concentrated on active Brownian systems with steric interparticle interactions. Here, we study the interfacial behavior of phase-separated active particles interacting solely via quorum-sensing communications using both theory and simulations. Strikingly, we find that the quorum-sensing active system exhibits vanishing mechanical surface tension but nonzero effective capillary surface tension. We further demonstrate that the mechanical equilibrium of the tensionless interface is sustained by polarization force at the interface; while its dynamics is governed by the surface stiffness, which arises from tangential particle flux induced by local interfacial deformation. Our work reveals the fundamental distinction between mechanical and capillary surface tensions in active matter and paves the way for future exploration of active interface phenomena.
Soft Condensed Matter (cond-mat.soft)
7pages,3 figures
Neutron reflectometry on superspreading and non-superspreading trisiloxane surfactants
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Joshua Reed, Séforah Carolina Marques Silva, Philipp Gutfreund, Joachim Venzmer, Tatiana Gambaryan-Roisman, Emanuel Schneck
Certain trisiloxane surfactants have the remarkable property of being able to superspread: Small volumes of water rapidly wet large areas of hydrophobic surfaces. The molecular properties of the surfactants which govern this technologically relevant effect are still under debate. To gain a deeper understanding, the surfactant behaviour during the spreading process needs to be studied at molecular length scales. Here, we present neutron reflectivity analyses of two trisiloxane surfactants of similar chemical structure, of which only one exhibits superspreading properties. We present an approach to determining the composition of the adsorbed surfactant layer in spread surfactant films at the solid-liquid interface, accounting for contributions from attenuated back-reflections of the neutron beam in films with thicknesses in the range of several tens to hundreds of micrometers. Differences between superspreading and non-superspreading surfactants with regard to their volume fraction profiles at the solid/liquid interface obtained in the self-consistent analysis of the reflectivity curves are in agreement with a simple explanation of the difference in spreading behaviour based on thermodynamics.
Soft Condensed Matter (cond-mat.soft)
Anomalous Power Factor Enhancement and Local Structural Transition in Ni-Doped TiCoSb
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Suman Mahakal, Pallabi Sardar, Diptasikha Das, Subrata Jana, Swapnava Mukherjee, Biplab Ghosh, Shamima Hussain, Santanu K. Maiti, Kartick Malik
We report a significant enhancement (~269%) in the power factor (PF) and a local structural transition in Ni-doped TiCoSb samples (TiCo_{1-x}Ni_xSb, (x= 0.0, 0.01, 0.02, 0.03, 0.04, and 0.06). First-principles calculations reveal that even minute Ni doping induces a substantial shift in the Fermi level (EF) and alters the density of states (DOS). Structural analysis via Rietveld refinement of X-ray diffraction (XRD) data shows anomalous behavior at x = 0.02, supported by Williamson-Hall and modified methods. X-ray absorption spectroscopy (XAS) at the Ti and Co K-edges further confirms a pronounced local structural change at this composition. These structural transitions are consistent with temperature-dependent resistivity (\rho(T)) and thermopower (S(T)) data, which reflect changes in EF and disorder. Analysis of Lorentz number and scattering parameters reinforces the observed modifications in the electronic structure. The simultaneous enhancement of S and electrical conductivity at x = 0.02 is attributed to the disorder-to-order transition, leading to the marked rise in PF.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main article (15 pages, 13 figures), Supplemental article (15 pages, 9 figures), Comments are welcome
General scaling behavior of superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
V.R. Shaginyan, A.Z. Msezane, S.A. Artamonov
The physics of high-$ T_c$ superconductors, which has been a major topic in condensed matter physics for more than thirty years, reveals some features of conventional superconductors. We analyze the scaling of the condensation energy $ E_{\Delta}$ divided by $ \gamma$ , $ E_{\Delta}/\gamma\simeq N(0)\Delta_1^2/\gamma$ , that equally applicable to both conventional and unconventional high-$ T_c$ superconductors. Here $ N(0)$ is the density of states, $ \Delta_1$ is the maximum value of the superconducting gap and $ \gamma$ is the Sommerfeld coefficient. Basing on this observation, we analyze experimental facts that reveal the general scaling properties of both high-$ T_c$ and ordinary superconductors, and theoretically explain that the Homes’ law $ \rho_{s0}= (1/2\pi\lambda_D)^2= T_c\sigma(T_c)$ is applicable to the both types of superconductors. Here $ \rho_{s0}$ is the superconducting electron density, $ \lambda_D$ is the zero-$ T$ penetration depth, $ \sigma$ is the normal state conductivity, $ T$ is temperature and $ T_c$ is the temperature of superconduction phase transition. For the first time, we also explain the reason of violation of the Homes’ law. Our theoretical results agree well with experimental facts.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 5 figures
Entropy Production from Density Field Theories for interacting particles systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Antonin Brossollet, Giulio Biroli
Entropy production quantifies the breaking of time-reversal symmetry in non-equilibrium systems. Here, we develop a direct method to obtain closed, tractable expressions for entropy production in a broad class of dynamical density functional theories, from Dean’s exact stochastic equation for microscopic densities to coarse-grained fluctuating-hydrodynamics models with density-dependent mobility. The method employs an Onsager-Machlup path-integral formulation. Our results reproduce particle-level calculations and matches recent Doi-Peliti treatments, confirming that the irregular noise structure of Dean’s equation poses no obstacle when handled consistently. We further extend the framework to active mixtures with non-reciprocal interactions and to run-and-tumble or active-Brownian suspensions, generalizations that require a careful treatment of the spurious-drift. Our method furnishes a practical route to quantify irreversibility in density functional field theories and paves the way for systematic studies of entropy production in multi-field active fluids that couple density, momentum and orientation.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
23 pages
The Order-disorder Transition in Incompressible Polar Active Fluids with an Easy Axis
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Leiming Chen, Chiu Fan Lee, John Toner
Dry active matter in an anisotropic medium is of experimental relevance, and the interplay between anisotropy and the dynamics of the active matter remains under-explored. Here, we derive the hydrodynamic equations of a generic dry polar active fluid that preferentially flows along a particular axis induced by the anisotropy of the medium. We then study its critical behavior at the order-disorder transition in which the symmetry between forward" and back” along the special axis is spontaneously broken. We obtain the critical static and dynamic exponents, mean velocity, and two point correlation functions exactly in three dimensions, and to two-loop level in two dimensions, by mapping our class of systems to the equilibrium Ising model with dipolar interactions.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
26 pages, 2 figures
Revisiting the magnetic ground states of RECo$_5$ permanent magnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
F. de Almeida Passos, G. J. Nilsen, R. Dankelman, M. Thijs, G. Balakrishnan, S. Kumar, A. Thamizhavel, J. Larrea Jiménez
In light of recent improvements in the theory of rare earth magnets, as well as the availability of improved neutron powder diffraction data on these materials, we revisit the magnetic single-ion properties of SmCo$ _5$ and the magnetic structures of YCo$ _5$ and NdCo$ _5$ . From neutron diffraction patterns in a wide range of temperatures between 3 K and 800 K, we obtain the thermal coefficient expansion and the magnetic moment values for the latter two materials. For SmCo$ _5$ , we fit existing neutron spectroscopy data with a model recently used for NdCo$ _5$ to obtain the crystal field parameters, which are essential to determine the low-lying energy scales that set the Hamiltonian. Our results may trigger new experimental and theoretical studies towards a new route for the realization of permanent magnets.
Strongly Correlated Electrons (cond-mat.str-el)
Quantum Mechanical Study of the Electronic Structure and Thermoelectric Properties of Heusler Alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Heusler alloys were discovered in 1903, and materials with half-metallic characteristics have drawn more attention from researchers since the advances in semiconductor industry. Heusler alloys have found application as spin-filters, tunnel junctions or giant magnetoresistance (GMR) devices in technological applications. In this work, the electronic structures, phonon dispersion, thermal properties, and electrical conductivities of PdMnSn and six novel alloys (AuCrSn, AuMnGe, Au2MnSn, Cu2NiGe, Pd2NiGe and Pt2CoSn) along with their magnetic moments are studied using ab initio calculations to understand the roots of half-metallicity in these alloys of Heusler family. From the phonon dispersion, the thermodynamic stability of the alloys in their respective phases is assessed. Phonon modes were also used to further understand the electrical transport in the crystals of these seven alloys. This study evaluates the relationship between materials’ electrical conductivity and minority-spin bandgap in the band structure, and it provides suggestions for selecting constituent elements when designing new half-metallic Heusler alloys of C1b and L21 structures.
Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
Energy Underprediction from Symmetry in Machine-Learning Interatomic Potentials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Wei Nong, Ruiming Zhu, Zekun Ren, Martin Hoffmann Petersen, Shuya Yamazaki, Nikita Kazeev, Andrey Ustyuzhanin, Gang Wu, Shuo-Wang Yang, Kedar Hippalgaonkar
Machine learning interatomic potentials (MLIAPs) have emerged as powerful tools for accelerating materials simulations with near-density functional theory (DFT) accuracy. However, despite significant advances, we identify a critical yet overlooked issue undermining their reliability: a systematic energy underprediction. This problem becomes starkly evident in large-scale thermodynamic stability assessments. By performing over 12 million calculations using nine MLIAPs for over 150,000 inorganic crystals in the Materials Project, we demonstrate that most frontier models consistently underpredict energy above hull (Ehull), a key metric for thermodynamic stability, total energy, and formation energy, despite the fact that over 90% of test structures (DFT-relaxed) are in the training data. The mean absolute errors (MAE) for Ehull exceed ~30 meV/atom even by the best model, directly challenging claims of achieving ``DFT accuracy’’ for property predictions central to materials discovery, especially related to (meta-)stability. Crucially, we trace this underprediction to insufficient handling of symmetry degrees of freedom (DOF), constituting both lattice symmetry and Wyckoff site symmetries for the space group. MLIAPs exhibit pronounced errors (MAE for Ehull $ >$ ~40 meV/atom) in structures with high symmetry DOF, where subtle atomic displacements significantly impact energy landscapes. Further analysis also indicates that the MLIAPs show severe energy underprediction for a large proportion of near-hull materials. We argue for improvements on symmetry-aware models such as explicit DOF encoding or symmetry-regularized loss functions, and more robust MLIAPs for predicting crystal properties where the preservation and breaking of symmetry are pivotal.
Materials Science (cond-mat.mtrl-sci)
15 pages, 3 figures, supplementary information included
Light-induced ultrafast magnetization dynamics in van der Waals antiferromagnetic CrSBr
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Ali Kefayati, Branislav Nikolic, Yafei Ren
The magnetization dynamics driven by the femtosecond laser pulse of antiferromagnet van der Waals semiconductor CrSBr is studied within time-dependent density functional theory. We investigate the effect of laser fluence as well as the excitation frequency on the ultrafast dynamics of spins. In low fluence, the local magnetic moment of Cr increases when the laser frequency is below the band gap, whereas it decreases when the laser frequency is below the band gap. In high fluence, we find strong demagnetization independent of excitation frequency. We find that the ultrafast demagnetization in CrSBr is dominated by intralayer and interlayer optical intersite spin transfer, and spin flip via the spin-orbit coupling plays a minor role. Our results reveal hole excitation in the low-fluence regime and electron excitation in the high-fluence regime. Further, we investigate the effect of the external static magnetic field on the dynamics. We demonstrate even and odd high harmonic generation in the local magnetic moments and electric current, respectively. The external magnetic field results in an out-of-plane charge current via the inverse spin Hall effect as well as odd harmonics in the local magnetic moment dynamics as a result of breaking the time-reversal symmetry.
Materials Science (cond-mat.mtrl-sci)
7 pages, 4 figures
Observation of Self-Bound Droplets of Ultracold Dipolar Molecules
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-22 20:00 EDT
Siwei Zhang, Weijun Yuan, Niccolò Bigagli, Haneul Kwak, Tijs Karman, Ian Stevenson, Sebastian Will
Ultracold gases of dipolar molecules have long been envisioned as a platform for the realization of novel quantum phases. Recent advances in collisional shielding, protecting molecules from inelastic losses, have enabled the creation of degenerate Fermi gases and, more recently, Bose-Einstein condensation of dipolar molecules. However, the observation of quantum phases in ultracold molecular gases that are driven by dipole-dipole interactions has so far remained elusive. In this work, we report the formation of self-bound droplets and droplet arrays in an ultracold gas of strongly dipolar sodium-cesium molecules. Starting from a molecular Bose-Einstein condensate (BEC), microwave dressing fields are used to induce dipole-dipole interactions with controllable strength and anisotropy. By varying the speed at which interactions are induced, covering a dynamic range of four orders of magnitude, we prepare droplets under equilibrium and non-equilibrium conditions, observing a transition from robust one-dimensional (1D) arrays to fluctuating two-dimensional (2D) structures. The droplets exhibit densities up to 100 times higher than the initial BEC, reaching the strongly interacting regime, and suggesting the possibility of a quantum-liquid or crystalline state. This work establishes ultracold molecules as a system for the exploration of strongly dipolar quantum matter and opens the door to the realization of self-organized crystal phases and dipolar spin liquids in optical lattices.
Quantum Gases (cond-mat.quant-gas), Atomic and Molecular Clusters (physics.atm-clus), Atomic Physics (physics.atom-ph), Quantum Physics (quant-ph)
16 pages, 11 figures
Engineering Spin Splitting in Antiferromagnets by Superatoms with Internal Degree of Freedom
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Fengxian Ma, Zeying Zhang, Zhen Gao, Xiaobei Wan, Yandong Ma, Yalong Jiao, Shengyuan A. Yang
Superatoms, stable atomic clusters acting as building blocks for new materials, offer unique opportunities due to their rich properties and potential for 2D material assembly. While extensive research has focused on their similarities to ordinary atoms, the role of their internal degrees of freedom (IDOF) remains largely unexplored. Concurrently, compensated antiferromagnets (AFMs) with intrinsic spin-split band structures have emerged as a promising class of materials for spintronics, yet their experimental realization, particularly in two dimensions, is limited. Here, we bridge these two fields by proposing a novel strategy to achieve spin-split AFMs using superatoms with IDOFs. We establish our core concept using a simple model, demonstrating how superatom IDOFs can be leveraged to engineer system symmetry and induce spin splitting in AFM states. We concretely illustrate this strategy by first-principles calculations on a Mo-decorated carborophene sheets, constructed from closo-carborane superatoms. We show that the distinct IDOFs of carborane isomers (electric-dipole-like and nematic) are critical in determining the symmetry of the resulting 2D superatomic crystal and, consequently, the spin splitting pattern of its AFM states. Our findings underscore the profound significance of superatom IDOFs-a feature absent in ordinary atoms-and introduce a new paradigm for engineering spin splitting in AFM lattices. This work opens novel avenues for the design of advanced spintronic and quantum materials based on superatoms.
Materials Science (cond-mat.mtrl-sci)
Description using equilibrium temperature in the canonical ensemble within the framework of the Tsallis statistics with the conventional expectation value
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
We studied the thermodynamic quantities and the probability distribution, expressing the probability distribution as a function of the energy, in the canonical ensemble within the framework of the Tsallis statistics, which is characterized by the entropic parameter $ q$ , with the conventional expectation value. We treat the power-law-like distribution. The equilibrium temperature, which is often called the physical temperature, is employed to describe the probability distribution. The Tsallis statistics represented by the equilibrium temperature was applied to $ N$ harmonic oscillators, where $ N$ is the number of the oscillators. The expressions of the energy, the Tsallis entropy, and the heat capacity were obtained. The expressions of these quantities and the expression of the probability distribution were obtained when the differences between adjacent energy levels are the same. These quantities and the distributions were numerically calculated. The $ q$ dependences of the energy, the Rényi entropy, and the heat capacity are weak. In contrast, the Tsallis entropy depends on $ q$ . The probability distribution as a function of the energy depends on $ N$ and $ q$ .
Statistical Mechanics (cond-mat.stat-mech)
15 pages, 18 figures
Spin Faraday pattern formation in a circular spin-orbit coupled Bose-Einstein condensate with stripe phase
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-22 20:00 EDT
Shixiang Chen, Hongguang Liang, Juan Wang, Yan Li
We investigate the spin Faraday pattern formation in a periodically driven, pancake-shaped spin-orbit-coupled (SOC) Bose-Einstein condensate (BEC) prepared with stripe phase. By modulating atomic interactions using $ in$ -$ phase$ and $ out$ -$ of$ -$ phase$ protocols, we observe collective excitation modes with distinct rotational symmetries (L-fold). Crucially, at the critical modulation frequency, $ out$ -$ of$ -$ phase$ modulation destabilizes the L = 6 pattern, whereas $ in$ -$ phase$ modulation not only preserves high symmetry but also excites higher-order modes (L $ \ge $ 6). Unlike conventional binary BECs, Faraday patterns emerge here without initial noise due to SOC-induced symmetry breaking, with all patterns exhibiting supersolid characteristics. Furthermore, we demonstrate control over pattern symmetry, radial nodes, and pattern radius by tuning the modulation frequency, providing a new approach for manipulating quantum fluid dynamics. This work establishes a platform for exploring supersolidity and nonlinear excitations in SOC systems with stripe phase.
Quantum Gases (cond-mat.quant-gas), Atomic Physics (physics.atom-ph)
When quenched and annealed pinning transitions coincide? A directed walk near a corrugated wall in disorders of various types
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
We study the pinning transition in a (1+1)-dimensional model of a fluctuating interface interacting with a corrugated impenetrable wall. The interface is described by the $ N$ -step directed 1D random walk on a discrete half-line $ m \ge 0$ , and the interaction with the wall is modeled by a quenched site-dependent short-ranged random potential $ u_j$ ($ j=1,…,N$ ) located at $ m=0$ , with distribution $ Q(u_j)$ . By computing the first two moments, $ \la G_N \ra$ and $ \la G_N^2 \ra$ , of the partition function $ G_N$ averaged over the disorder, we show that the pinning transition for $ \la G_N^2 \ra$ may or may not coincide with that of $ \la G_N \ra$ , depending on the details of the disorder distribution $ Q(u_j)$ . This result reconciles opposite viewpoints on whether the pinning transition points in models with annealed and quenched disorder coincide or not.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn), Mathematical Physics (math-ph)
19 pages, 2 figures, 4 tables
High pressure and temperature thermoelasticity of hcp osmium from ab initio quasi-harmonic theory
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
We present a systematic ab initio study of the thermoelastic properties of hcp osmium as functions of temperature and pressure within the quasi-harmonic approximation (QHA). The precision of the Zero Static Internal Stress Approximation (ZSISA) and of the volume-constrained ZSISA (V-ZSISA) are rigorously assessed. For osmium, we find negligible deviations between ZSISA and a full free energy minimization (FFEM) approach. Also, the V-ZSISA approximation influences the results very little, as we found already in beryllium, despite the markedly different behavior of the c/a ratio with temperature in the two metals. Our QHA-derived ECs show excellent agreement with available experimental data in the temperature range of 5-301 K, outperforming the results obtained from the quasi-static approximation (QSA). Additionally, we report the pressure-dependent QHA ECs at 5 K, 301 K, and 1000 K, spanning pressures from 0 to 150 kbar.
Materials Science (cond-mat.mtrl-sci)
9 pages, 11 figures, 2 tables
Physical Review B 112, 024103 (2025)
Elucidating the origin of long-range ferromagnetic order in Fe$_3$GeTe$_2$ by low-energy magnon excitation studies
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Birte Beier, Erik Walendy, Jan Arneth, Eva Brücher, Reinhard K. Kremer, Rüdiger Klingeler
We report a detailed high-field/high-frequency ferromagnetic resonance (HF-FMR) study of low-energy magnon excitations in the van der Waals ferromagnet Fe$ 3$ GeTe$ 2$ . At 2 K, the field dependence of the magnon branches is well described by a semiclassical domain-based model, from which we extract key microscopic parameters including the anisotropy gap $ \Delta = 170\pm 4$ GHz, the anisotropy field $ B{\rm A} = 5.85\pm 0.08$ T, and the effective $ g$ -factor $ g{\rm ab}\simeq g_{\rm c} = 2.07(4)$ . Furthermore the uniaxial anisotropy constant was determined to be $ K = (10.5\pm 0.23) \times 10^{-6}$ erg/cm$ ^3$ . Anisotropic short-range magnetic order persists above $ T_{\rm C}$ up to approximately 270 K, as evidenced by a finite anisotropy gap and anisotropic shifts in the FMR resonance fields. Both results clearly show the presence of anisotropic local magnetic fields well above $ T_{\rm C}$ . Our findings underscore the crucial role of magneto-crystalline anisotropy in driving long-range magnetic order in Fe$ _3$ GeTe$ _2$ .
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Pressure-Induced Low-Spin State Destabilization and Piezo-Chromic Effect in an Iron(II) Spin Crossover Complex with Pyrazol-Pyridine-Triazolate Coordination Core
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Hanlin Yu, Maksym Seredyuk, Nan Ma, Katerina Znoviak, Nikita Liedienov, M. Carmen Muñoz, Iván da Silva, Francisco-Javier Valverde Muñoz, Ricardo-Guillermo Torres Ramírez, Elzbieta Trzop, Wei Xu, Quanjun Li, Bingbing Liu, Georgiy Levchenko, J. Antonio Real
Rapidly developing science and technology demand new materials with versatile and promising properties for practical applications. In this context, pseudo-octahedral iron(II) spin crossover (SCO) complexes are particularly appealing - not only for their fundamental scientific interest but also for their potential as key components in the development of multifunctional switchable molecular materials and novel technological applications. This work presents the synthesis and structure of a new mononuclear SCO complex [FeII(L)2]0\astnMeOH (n = 2, 0) where L is the asymmetrically substituted tridentate ligand [4-trifluoromethylphenyl-(1H-1,2,4-triazol-5-yl)-6-(1H-pyrazol-1-yl)pyridine]. Due to high trigonal distortion, the solvated form (n = 2) remains high spin (HS) at all temperatures. In contrast, the more regular Oh geometry of the unsolvated form, 4CF3, favors a complete spin transition (ST) at room temperature, which has been investigated, in the pressure interval 0-0.64 GPa, by means of its magnetic and optical properties. Contrary to intuition and experience, the increase of pressure on 4CF3 denotes a radically abnormal behavior of this ST, involving: i) decrease of the characteristic temperatures, ii) increase of the high-spin molar fraction in the temperature range where the low-spin state is stable at ambient pressure; iii) increase of the thermal hysteresis width; and iv) above certain threshold pressure, full stabilization of the high-spin state. All these observations have been explained in the framework of a thermodynamic that model based on the elastic interactions.
Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft)
42 pages, 1 scheme, 21 figures, 7 tables
Efficient ultrafast photoacoustic transduction on Tantalum thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Konstantinos Kaleris, Emmanouel Kaniolakis-Kaloudis, Evaggelos Kaselouris, Kyriaki Kosma, Emmanouil Gagaoudakis, Vassilis Binas, Stelios Petrakis, Vasilis Dimitriou, Makis Bakarezos, Michael Tatarakis, Nektarios A. Papadogiannis
Nano-acoustic strain generation in thin metallic films via ultrafast laser excitation is widely used in material science, imaging and medical applications. Recently, it was shown that transition metals, such as Titanium, exhibit enhanced photoacoustic transduction properties compared to noble metals, such as Silver. This work presents experimental results and simulations that demonstrate that among transition metals Tantalum exhibits superior photoacoustic properties. Experiments of nano-acoustic strain generation by femtosecond laser pulses focused on thin Tantalum films deposited on Silicon substrates are presented. The nano-acoustic strains are measured via pump-probe transient reflectivity that captures the Brillouin oscillations produced by photon-phonon interactions. The observed Brillouin oscillations are correlated to the photoacoustic transduction efficiency of the Tantalum thin film and compared to the performance of Titanium thin films, clearly demonstrating the superior photoacoustic transduction efficiency of Tantalum. The findings are supported by computational results on the laser-induced strains and their propagation in these thin metal film/substrate systems using a Two-Temperature Model in combination with thermo-mechanical Finite Element Analysis. Finally, the role of the metal transducer-substrate acoustic impedance matching is discussed and the possibility to generate appropriately modulated acoustic pulse trains inside the crystalline substrate structures for the development of crystalline undulators used for {\gamma}-ray generation is presented.
Materials Science (cond-mat.mtrl-sci), Accelerator Physics (physics.acc-ph), Applied Physics (physics.app-ph), Optics (physics.optics)
23 pages, 6 figures
Appl. Phys. A 129, 527 (2023)
Simphony: A full tight-binding package for lattice vibrations and topological phonon analysis
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Francesc Ballester, Ion Errea, Maia G. Vergniory
Simphony is an open-source software package designed for the topological analysis of lattice vibrations based on Wannier tight-binding models. Its primary function is to classify the topology of novel materials by computing bulk and slab phonon band structures, extracting phonon surface spectra, and providing analysis tools such as Wilson loop calculations and Weyl node detection. The workflow is analogous to that of established electronic topology codes like Wannier90 and WannierTools. It also incorporates long-range polar interactions during the wannierization process, making Simphony one of the first tools capable of diagnosing topology in polar insulators.
Materials Science (cond-mat.mtrl-sci)
34 pages, 5 figures, source code available at this https URL
Anomalous charge density wave in two-dimensional altermagnet WO
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Zi-Hao Ding, Zhen-Feng Ouyang, Ze-Feng Gao, Wei Ji, Kai Liu, Peng-Jie Guo, Zhong-Yi Lu
Recently, the study of novel physical properties arising from the combination of altermagnetism and other matter phases has attracted widespread attention, such as the integration of altermagnetism and topology. However, research on the combination of altermagnetism and charge density waves remains relatively sparse. In this letter, based on symmetry analysis and first-principles calculations, we demonstrate for the first time that altermagnetism and charge density waves can coexist in a two-dimensional material and predict monolayer WO to be such a material. Moreover, our calculations reveal that the altermagnetic order in monolayer WO stabilizes the $ \sqrt{2}\times\sqrt{2}$ charge density wave. Further, the $ \sqrt{2}\times\sqrt{2}$ charge density wave is not driven by Fermi-surface nesting but rather by strong electron-phonon coupling. More importantly, the $ \sqrt{2}\times\sqrt{2}$ charge density wave in monolayer WO leads to an anomalous transition from semimetal to metal. Therefore, we realize an anomalous charge density wave phase in altermagnetic WO. Considering the strong electron-phonon coupling and good metallic properties in the altermagnetic charge density wave state, our work may provide new insights into the realization of nontrivial altermagnetic superconductivity.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 4 figures
Data-driven Discovery of Novel High-performance Quaternary Chalcogenide Photovoltaics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Nikhil Singh, Mohammad Ubaid, Pabitra Kumar Nayak, Jiangang He, Dibyajyoti Ghosh, Chris Wolverton, Koushik Pal
Photovoltaic materials facilitate the conversion of sunlight into electricity by harnessing the interaction between light and matter, offering an eco-friendly and cost-efficient energy solution. Combining data-driven approaches with static and time-dependent density functional theories and nonadiabatic molecular dynamics simulations, we predict 14 high-performance photoabsorber materials from a family of known quaternary semiconductors. Among these, we investigate four compounds - SrCuGdSe3, SrCuDyTe3, BaCuLaSe3, and BaCuLaTe3 in greater detail. Hybrid density functional theory calculations including spin-orbit coupling reveal that SrCuGdSe3, SrCuDyTe3, BaCuLaSe3 and BaCuLaTe3 possess direct band gaps of 1.65, 1.79, 1.05, and 1.01 eV, respectively. These band gap values lie close to an optimal range ideal for visible-light absorption. Consequently, the calculated optical absorption coefficient and spectroscopic limited maximum efficiency for these compounds become comparable or larger than crystalline silicon, GaAs, and methylammonium lead iodide. Calculated exciton binding energies for these compounds are relatively small (30-32 meV), signifying easy separation of the electron-hole pairs, and hence enhanced power conversion efficiencies. Investigations of photoexcited carrier dynamics reveal a relatively long carrier lifetime (~ 30-40 ns), suggesting suppressed nonradiative recombination and enhanced photo-conversion efficiencies. We further determined the defect formation energies in these compounds, which showed that despite the likely formation of cation vacancies and interstitial defects, midgap states remain absent making these defects non-detrimental to carrier recombination. Our theoretical predictions invite experimental verification and encourage further investigations of these and similar compounds in this quaternary semiconductor family.
Materials Science (cond-mat.mtrl-sci)
Modeling and Design of Integrated Iontronic Circuits Based on Ionic Bipolar Junction Transistors
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Soichiro Tottori, Rohit Karnik
Biological systems rely on ions and molecules as information carriers rather than electrons, motivating the development of devices that interface with biochemical systems for sensing, information processing, and actuation via spatiotemporal control of ions and molecules. Iontronics aims to achieve this vision by constructing devices composed of ion-conducting materials such as polyelectrolyte hydrogels, but advancing beyond simple single-stage circuit configurations that operate under steady-state conditions is a challenge. Here, we propose and model more complex ionic circuits, namely bistable flip-flop and ring oscillators, consisting of multiple ionic bipolar junction transistors (IBJTs). We begin by modeling and characterizing single IBJTs using both a simplified one-dimensional Nernst-Planck model and a more-detailed two-dimensional Poisson-Nernst-Planck model, elucidating the effects of geometry, size, and fixed charge on the IBJT performance and response time. The one- and two-dimensional models exhibit good agreement, indicating negligible transverse inhomogeneities. Additionally, these models show that reducing the base width improves current amplification, a behavior analogous to electronic BJTs. Building on this understanding, by using the IBJTs as voltage inverters and buffers, we design and model more complex ionic circuits that dynamically change their states in response to ionic signals. Specifically, we demonstrate that the ionic flip-flop retains one-bit memory and that the ring oscillator achieves autonomous periodic self-oscillation without an external clock. Our work provides a foundation for designing dynamic iontronic circuitry using ionic conductors, enabling biochemical signal processing and logic operations based on ionic transport.
Soft Condensed Matter (cond-mat.soft), Applied Physics (physics.app-ph)
Effect of Co partitioning to the γ matrix on the microstructural stablity of a Ti-rich Ni-Base Superalloy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Sudeepta Mukherjee, Hemant Kumar, B.S. Murty, Satyam Suwas, Surendra Kumar Makineni
The microstructural stability and mechanical properties of superalloys at high temperatures are significantly influenced by the composition and nature of the solutes they contain. Most of the alloys with high solvus temperature have higher gamma prime coarsening resistance, while the larger lattice misfit is attributed to higher gamma prime coarsening rate. In this work, we explore the influence of Co on the microstructure evolution, thermophysical/mechanical properties and gamma prime precipitate coarsening kinetics in a Ti-rich Ni-Co-Cr-Al-Ti based alloy. More specifically, we focus on the effect of partitioning of Co into the gamma matrix on the redistribution of other solutes across the interface. We observe a significant increase in the coarsening resistance and a twofold increase in the activation energy with the increase in the Co composition from 10at.%Co to 30at.%Co, even though the gamma prime solvus reduces by 75C. As otherwise, a higher solvus, usually, indicates better microstructural stability at high temperatures. We employed a combined experimental and theoretical approach by atom probe tomography (APT) and CALPHAD simulations to probe the critical role of Co partitioning to gamma matrix on the solute transport in the gamma matrix and flux across the gamma/gamma prime interfaces, which is found to control the overall gamma prime coarsening behavior in the alloy. The observed behavior was rationlised by the proposition of a simplistic unified coarsening rate expression that successfully decouples thermodynamic and kinetic contributions. Additionally, we also observe that the gamma prime volume fraction dominates over the gamma prime precipitate size on the 0.2% yield strength (YS) of the alloys.
Materials Science (cond-mat.mtrl-sci)
$\mathbb{Z}_2$ topological trion insulator
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Trions, charged quasiparticles formed by binding an exciton to an excess charge carrier, dominate the optical response of doped transition metal dichalcogenides (TMDs), and the study of the transport properties of trions in TMDs may have application in developing high-speed excitonic and optoelectronic devices. However, an important building block for low-dissipation optoelectronic devices that provides dissipationless transport channels for trions has remained elusive. Here, we propose the concept of a $ \mathbb{Z}_2$ topological trion insulator that features helical dissipationless edge states for trions. This is realized for intralayer trions, which inherit the valley-orbit coupling of intralayer excitons in TMDs subject to a moiré periodic potential. We find that under certain circumstances, the moiré trion band becomes topological, characterized by the $ \mathbb{Z}_2$ topological number. We further provide two specific material realizations of this $ \mathbb{Z}_2$ topological insulator: a doped monolayer TMD placed on top of a twisted hBN substrate, and a generic twisted TMD heterobilayer. We also examine the effect of charge screening and find that the $ \mathbb{Z}_2$ topological trion insulator remains robust. Our work paves the way toward realizing dissipationless excitonic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Harnessing higher-dimensional fluctuations in an information engine
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Antonio Patrón Castro, John Bechhoefer, David A. Sivak
We study the optimal performance of an information engine consisting of an overdamped Brownian bead confined in a controllable, $ d$ -dimensional harmonic trap and additionally subjected to gravity. The trap’s center is updated dynamically via a feedback protocol designed such that no external work is done by the trap on the bead, while maximizing the extraction of gravitational potential energy and achieving directed motion. We show that performance strikingly improves when thermal fluctuations in directions perpendicular to gravity are harnessed. This improvement arises from feedback cooling of these transverse degrees of freedom, along which all heat is extracted; comparable performance can be achieved even without vertical measurements. This engine design modularizes the functions of harnessing fluctuations and storing free energy, drawing a close analogy to the Szilard engine.
Statistical Mechanics (cond-mat.stat-mech)
13 pages, 5 figures
Magnetic Phase Diagrams of Antiferromagnet DyB12 with Jahn-Teller Lattice Instability and Electron Phase Separation
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
A.N. Azarevich, A.V. Bogach, K.M. Krasikov, V.V. Voronov, S.Yu. Gavrilkin, A.Yu. Tsvetkov, S. Gabani, K. Flachbart, N.E. Sluchanko
The origin of charge transport and magnetization anisotropy was studied in DyB12, an antiferromagnetic (AF) metal with Neel temperature TN = 16.3 K that exhibits both cooperative Jahn-Teller distortions of the fcc crystal structure and nanoscale electronic instabilities (dynamic charge stripes). Based on the results obtained the magnetic field (H) vs temperature (T) phase diagrams have been constructed. Moreover, from angle dependent magnetoresistance and magnetization measurements the butterfly-type patterns of the H-phi magnetic phase diagram in the (110) plane were created, which include a number of different magnetic phases separated from each other by radial and circular boundaries. Several positive and negative contributions to magnetoresistance were separated and analyzed, providing arguments in favor of the important role of the spin density wave 5d-component in the magnetic structure of AF state. We argue that charge fluctuations in stripes are responsible for the suppression of the Ruderman-Kittel-Kasuya-Yoshida (RKKY) indirect exchange between the nearest neighbored Dy3+ ions located along the same 110 directions, as these dynamic charge stripes produce the magnetic phase diversity and the butterfly-type anisotropy in DyB12.
Strongly Correlated Electrons (cond-mat.str-el)
19 pages, 15 figures
Spin-orbit crossover and the origin of magnetic torque in kagome metals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Mathias S. Scheurer, Harley D. Scammell
Recent experiments on the kagome metal Cs$ 3$ Sb$ 5$ reveal a curious phase transition-like feature: a nematic magnetic torque response that abruptly sets in at $ T\tau \approx 130$ ~K, above the known charge density wave transition at $ T\text{CDW} \approx 100$ ~K. Counterintuitively, elastoresistance measurements–a standard probe of nematicity–show no corresponding signal, ruling out a nematic phase transition and placing strong constraints on possible explanations. Beyond nematicity, the torque is paramagnetic for in-plane magnetic field, while above a critical out-of-plane field, an in-plane magnetisation appears, accompanied by hysteresis. We show that this combination of features cannot be accounted for by charge density waves or intraband magnetic order. Instead, we propose that interband ordering–via a symmetry-allowed interband spin-orbit coupling and a time-reversal and spatial symmetry-breaking interband order parameter–together with a background strain field, consistent with typical experimental conditions, provides a natural explanation; in our picture, the behaviour at $ T_\tau$ is understood as a crossover in the symmetry-allowed interband spin-orbit coupling strength. Our theory accounts for the nematic magnetic torque, hysteresis, and the transition-like onset at $ T_\tau$ , while also making testable predictions, including strain-induced magnetisation. In doing so, it challenges the prevailing view of the normal state.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Skyrmion Hall effect and shape deformation of current-driven bilayer skyrmions in synthetic antiferromagnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Mu-Kun Lee, Javier A. Vélez, Rubén M. Otxoa, Masahito Mochizuki
The commonly believed absence of skyrmion Hall effect for topologically trivial magnetic skyrmions is reconsidered for bilayer skyrmions in synthetic antiferromagnets driven by spin-transfer and spin-orbit torques. Using a general Lagrangian formalism, we show that Bloch-type bilayer skyrmions acquire a finite Hall angle when driven by spin-orbit torque, while Néel-type skyrmions do not, in agreement with micromagnetic simulations. Both types of skyrmions exhibit current-induced elliptical deformation with minor and major axes aligned longitudinally and transversely to their velocity, respectively. A linear relation between velocity and longitudinal radius is derived with a coefficient proportional to the strength of spin-orbit torque. These effects are critical for antiferromagnetic skyrmion-based applications such as skyrmion racetrack memory. The Lagrange equations also reproduce the linear Hall angle-helicity relation reported by Msiska et al., Phys. Rev. Appl. 17, 064015 (2022). An intuitive explanation of the skyrmion Hall effect for arbitrary helicity based on the antiferromagnetic exchange torque is also provided.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 5 figures
Effectiveness of Hybrid Optimization Method for Quantum Annealing Machines
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Shuta Kikuchi, Nozomu Togawa, Shu Tanaka
To enhance the performance of quantum annealing machines, several methods have been proposed to reduce the number of spins by fixing spin values through preprocessing. We proposed a hybrid optimization method that combines a simulated annealing (SA)-based non-quantum-type Ising machine with a quantum annealing machine. However, its applicability remains unclear. Therefore, we evaluated the performance of the hybrid method on large-size Ising models and analyzed its characteristics. The results indicate that the hybrid method improves upon solutions obtained by the preprocessing SA, even if the Ising models cannot be embedded in the quantum annealing machine. We analyzed the method from three perspectives: preprocessing, spin-fixed sub-Ising model generation method, and the accuracy of the quantum annealing machine. From the viewpoint of the minimum energy gap, we found that solving the sub-Ising model with a quantum annealing machine results in a higher solution accuracy than solving the original Ising model. Additionally, we demonstrated that the number of fixed spins and the accuracy of the quantum annealing machine affect the dependency of the solution accuracy on the sub-Ising model size.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
15 pages, 11 figures
Towards Understanding Prolate 4$f$ Monomers: Numerical Predictions and Experimental Validation of Electronic Properties and Slow Relaxation in a Muffin-shaped Er$^\mathrm{III}$ Complex
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
J. Arneth, C. Pachl, G. Greif, B. Beier, P. W. Roesky, K. Fink, R. Klingeler
We report the synthesis, crystal structure and magnetic properties of the triply-capped, slightly distorted trigonal-prismatic complex [Er(PPTMP)$ _2$ (H$ _2$ O)][OTf]$ 3$ (PPTMP = (4-(6-(1,10-phenanthrolin-2-yl)pyridin-2-yl)-1H-1,2,3-triazol-1-yl)methyl pivalate) ($ \mathbf{1}$ ). Complex $ \mathbf{1}$ is shown to exhibit field-induced slow relaxation of the magnetisation at $ B = 0.1,\mathrm{T}$ via two distinct relaxation paths. Using tunable high-frequency/high-field electron paramagnetic resonance spectroscopy, we experimentally determine the effective $ g$ -factors and zero field splittings of the two energetically lowest Kramers doublets (KD). Our data reveal that the triply-capped, slightly distorted trigonal-prismatic ligand field favours an $ m \simeq \pm 9/2$ magnetic ground state, while the main contribution to the first excited KD at $ \Delta{1 \rightarrow 2} = 780(5),\mathrm{GHz}$ is suggested to be $ m \simeq \pm 5/2$ . The ground state $ g$ -tensor has generally axial form but hosts significant transversal components, which we conclude to be the source of SMM-silent behaviour in zero field. Our findings are backed up by ab-initio spin-orbit configuration interaction calculations showing excellent agreement with the experimental data.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 10 figures
Interplay of Zeeman Splitting and Tunnel Coupling in Coherent Spin Qubit Shuttling
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Ssu-Chih Lin, Paul Steinacker, MengKe Feng, Ajit Dash, Santiago Serrano, Wee Han Lim, Kohei M. Itoh, Fay E. Hudson, Tuomo Tanttu, Andre Saraiva, Arne Laucht, Andrew S. Dzurak, Hsi-Sheng Goan, Chih Hwan Yang
Spin shuttling offers a promising approach for developing scalable silicon-based quantum processors by addressing the connectivity limitations of quantum dots (QDs). In this work, we demonstrate high-fidelity bucket-brigade (BB) spin shuttling in a silicon MOS device, utilizing Pauli Spin Blockade (PSB) readout. We achieve an average shuttling fidelity of \SI{99.8}{\percent}. The residual shuttling error is highly sensitive to the ratio between interdot tunnel coupling and Zeeman splitting, with tuning of these parameters enabling up to a twenty-fold variation in error rate. An appropriate four-level Hamiltonian model supports our findings. These results provide valuable insights for optimizing high-performance spin shuttling systems in future quantum architectures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Vortices in dipolar condensates of interlayer excitons
New Submission | Other Condensed Matter (cond-mat.other) | 2025-07-22 20:00 EDT
Sara Conti, Andrey Chaves, Luis A. Pena Ardila, David Neilson, Milorad V. Milosevic
Recently observed signatures of Bose-Einstein condensation and superfluidity of dipolar excitons have drawn enormous attention to excitonic semiconductor bilayers. In superfluids, stabilization and observation of vortex matter is usually a decisive proof of coherent condensation order. However to date, the vortex behavior in a 2D excitonic system with aligned dipole-like interactions that are long-range and everywhere repulsive has not been addressed. We here provide a theoretical description of the vortex characteristics, interaction, and lattices in a dipolar exciton superfluid, solving the corresponding Gross-Pitaevskii equation, while varying the exciton dipole moments and the exciton density - both tunable in the experiment, by interlayer separation and gating, respectively. We draw particular attention to the appearance of a maximum in the density redistribution around the edge of each vortex, in the phase-space region where the dipole interactions are particularly strong, and where a transition to an incompressible exciton supersolid is expected.
Other Condensed Matter (cond-mat.other)
Discrete time crystal and perfect many-body tunneling in a periodically driven Heisenberg spin chain
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
We investigate the non-equilibrium dynamics of a Heisenberg spin-1/2 chain driven by a periodic magnetic field. Based on its instantaneous integrability and inherent symmetry, we analytically study the magnetization and many-body tunneling (MBT). Both of them exhibit periodicity distinct from the driving period. The magnetization is shown to be independent of the initial state and robust against perturbations, signaling the formation of discrete time crystal (DTC) order. The DTC phase is found to be continuously tunable through magnetic field. The system exhibits perfect MBT, manifested as exactly vanishing Loschmidt echo (LE) thus divergent LE rate function at half period of the DTC. Remarkably, the perfect MBT is independent of the system size, and can be traced to an effective gap closure induced by quantum geometric effects. Furthermore, the Loschmidt echo spectra entropy shows logarithmic-dependence on system size, consistent with non-thermal nature of the DTC phase. We propose a protocol using ultracold atoms for experimental realization of the DTC and MBT.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Gases (cond-mat.quant-gas)
6 pages, 3 figures - Supplementary Material 4 pages
Non-perturbative macroscopic theory of interfaces with discontinuous dielectric constant
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Y. M. Beltukov, A. V. Rodina, A. Alekseev, Al. L. Efros
Discontinuity of dielectric constants at the interface is a common feature of all nanostructures and semiconductor heterostructures. It gives rise to a divergence of the self-interaction potential acting on a charge near the interface, and it presents an obstruction to a perturbative description. In several limiting cases, this problem can be avoided by zeroing out the carrier wave function at the interface. In this paper, we developed a non-perturbative theory which gives a self-consistent description of carrier propagation through an interface with dielectric discontinuity. It is based on conservation of the current density propagating through the interface, and it is formulated in terms of general boundary conditions (GBC) for the wave function at the interface with a single phenomenological parameter W. For these GBC, we find exact solutions of the Schrödinger equation near the interface and the carrier energy spectrum including resonances. Using these results, we describe the photo effect at the semiconductor/vacuum interface and the electron energy spectrum in the interface quantum well, as well as the dependence of these two phenomena on the interface parameter W.
Materials Science (cond-mat.mtrl-sci)
Ab-initio exploration of Gd monolayer interfaced with WSe$_2$: from electronic and magnetic properties to the anomalous Hall effect
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Lyes Mesbahi (1), Omar Messaoudi (1), Hamid Bouzar (1), Samir Lounis (2) ((1) Laboratoire de Physique et Chimie Quantique (LPCQ), Mouloud Mammeri University of Tizi-Ouzou, 15000 Tizi-Ouzou, Algeria, (2) Institute of Physics, Martin-Luther-University Halle-Wittenberg, 06099 Halle (Saale), Germany)
Heterostructures involving transition metal dichalcogenides (TMDs) have attracted significant research interest due to the richness and versatility of the underlying physical phenomena. In this work, we investigate a heterostructure consisting of a rare-earth material, specifically a Gd monolayer, interfaced with WSe$ _2$ . We explore its electronic structure, magnetic properties, and transport behavior, with particular emphasis on the emergence of the anomalous Hall effect (AHE). Both Gd and W are heavy elements, providing strong spin-orbit coupling (SOC), which plays a crucial role in triggering the AHE. The combination of strong SOC and inversion symmetry breaking leads to pronounced asymmetries between the $ \Gamma-K$ and $ \Gamma-K^\prime$ directions in the Brillouin zone. Our calculations reveal a substantial anomalous Hall conductivity (AHC) at the ferromagnetic interface, primarily originating from numerous avoided crossings involving the d-states of both Gd and W near the Fermi level. Moreover, we demonstrate that the AHC is highly tunable, either by adjusting the in-plane lattice constant or by reducing the separation between Gd and WSe$ _2$ .
Materials Science (cond-mat.mtrl-sci)
Layer-selective Cooper pairing in an alternately stacked transition metal dichalcogenide
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
Haojie Guo, Sandra Sajan, Irián Sánchez-Ramírez, Tarushi Agarwal, Alejandro Blanco Peces, Chandan Patra, Maia G. Vergniory, Rafael M. Fernandes, Ravi Prakash Singh, Fernando de Juan, Maria N. Gastiasoro, Miguel M. Ugeda
Multigap superconductivity emerges when superconducting gaps form on distinct Fermi surfaces. Arising from locally overlapping atomic orbitals, multiple superconducting bands introduce a new internal degree of freedom in the material that, however, escapes external control due to their coexistence in real space in the known multigap superconductors. Here, we show that the layered superconductor 4Hb-TaSSe - composed of alternating trigonal (H) and octahedral (T) polymorph layers - is a multigap superconductor, featuring two weakly coupled superconducting condensates with distinct properties, spatially separated in alternating layers. Using high-resolution quasiparticle tunneling and Andreev reflection spectroscopy in the two polymorph layers, we identify two superconducting gaps that vary in size and internal structure. The intrinsic Cooper pairing in each polymorph is corroborated by the temperatures and magnetic fields at which the gaps open up, which differ in each polymorph layer and show opposing resilience to these parameters. This behavior enables selective external actuation upon the condensates. Our theoretical model based on ab-initio calculations reproduces key features of the observed superconducting gaps in the presence of finite interlayer hybridization and explains the unusually high critical field observed in the T-layer. Our results establish TMD polymorphs as platforms for engineering tunable multigap superconductors, offering new opportunities in layered superconducting device architectures.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Interaction-induced nematic Dirac semimetal from quadratic band touching: A constrained-path quantum Monte Carlo study
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-22 20:00 EDT
Zi Hong Liu, Hongyu Lu, Zi Yang Meng, Lukas Janssen
Electronic systems with quadratic band touchings, commonly found in two- and three-dimensional materials such as Bernal-stacked bilayer graphene, kagome metals, HgTe, and pyrochlore iridates, have attracted significant interest concerning the role of interactions in shaping their electronic properties. However, even in the simplest model of spinless fermions on a two-dimensional checkerboard lattice, the quantum phase diagram as a function of nearest-neighbor interaction remains under debate. We employ constrained-path quantum Monte Carlo simulations (CP-QMC) simulations to investigate the problem using a two-dimensional torus geometry. We cross-validate our results on small lattices by comparing them with density-matrix renormalization group calculations, finding quantitative agreement. In particular, we implement an improved optimization scheme within the CP-QMC simulations, enabling the identification of a bond-nematic Dirac semimetal phase that was found in tensor-network studies on cylindrical geometries, but remains inaccessible to Hartree-Fock mean-field methods. The CP-QMC approach makes it possible to establish the emergence of this phase in a geometry that preserves lattice rotational symmetry and permits extrapolation to the thermodynamic limit. Our results show that the quantum phase diagram of spinless fermions on the checkerboard lattice with nearest-neighbor repulsion features three interaction-induced phases at half filling: a quantum anomalous Hall insulator at weak coupling, a bond-nematic Dirac semimetal at intermediate coupling, and a site-nematic insulator at strong coupling.
Strongly Correlated Electrons (cond-mat.str-el)
12 pages, 13 figures
Giant Reversible Piezoelectricity from Symmetry-Governed Stochastic Dipole Hopping
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Denan Li, Haofei Ni, Yi Zhang, Shi Liu
Organic–inorganic hybrid perovskites with giant piezoelectric responses, exemplified by TMCM-CdCl$ 3$ , represent a promising platform for flexible and environmentally friendly electromechanical materials. However, the microscopic origin of such exceptional performance in this weakly polar system has remained elusive. Here, using deep-learning-assisted large-scale molecular dynamics simulations, we resolve this paradox by reproducing the experimentally measured piezoelectric coefficient $ d{33} \approx 220$ ~pC/N, and demonstrating that the giant response arises from the collective contribution of multiple intrinsic components, particularly the shear component $ d_{15}$ . This effect does not stem from conventional polarization rotation or phase switching, but instead originates from stochastic 120$ ^\circ$ in-plane rotational hopping of a small fraction of organic cations. This discrete hopping mechanism is governed by the local C$ 3$ -symmetric halogen-bonding network between the host framework and the guest cation. The Arrhenius-type temperature dependence of $ d{15}$ further confirms the role of thermally activated dipole hopping. This work provides a clear pathway to enhance piezoelectric performance of hybrid materials through rational engineering of host–guest interactions.
Materials Science (cond-mat.mtrl-sci)
16 pages, 4 figures
Using stochastic thermodynamics with internal variables to capture orientational spreading in cell populations undergoing cyclic stretch
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-22 20:00 EDT
Rohan Abeyaratne, Sanjay Dharmaravan, Giuseppe Saccomandi, Giuseppe Tomassetti
We revisit the modeling framework introduced in [N. Loy and L. Preziosi: Bull. Math. Bio., 85, 2023] to describe the dynamics of cell orientation under cyclic stretch. We propose a reformulation based on the principles of Stochastic Thermodynamics with Internal Variables introduced in [T. Leadbetter, P. Purohit, and C. Reina: PNAS Nexus, 2, 2023]. This approach allows us to describe not only the evolution of the orientation distribution, but also the observed spreading phenomenon. The insight provided by our model reveals an interesting phenomenon, which we call two-stage reorientation: when cells begin aligned with an energy maximum, their orientations spread before concentrating at the energy minimum. This theoretical prediction suggests a new experiment to test this modeling framework.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft), Mathematical Physics (math-ph), Probability (math.PR)
Evaluation of hydrogen diffusion and trapping in ferritic steels containing (Ti,Cr)C particles using electrochemical permeation and thermal desorption spectroscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Hydrogen diffusion and trapping in ferritic steels containing (Ti,Cr)C particles was investigated using electrochemical permeation (EP) and thermal desorption spectroscopy (TDS). The trapping parameters for the test materials were evaluated by fitting the measurements with a finite element model based on the McNabb-Foster equations using least-squares optimisation. The measurements showed that hydrogen diffusion in ferrite is slowed significantly by the presence of fine (<5 nm) (Ti,Cr)C particles; coarser particles had little or no effect. The TDS measurements were consistent with hydrogen traps with a high energy barrier. The uniqueness of the hydrogen trapping parameters obtained using the fitting procedure was evaluated. It was found that the system was overdetermined; the measurements could be fitted with multiple combinations of trapping parameters. Consequently, it was not possible to determine the individual trapping parameters using this procedure. Trapping parameters were also evaluated from TDS measurements by applying Kissinger’s equation. Using this procedure a trap binding energy of 0.24 eV was calculated for all materials, albeit with a high degree of uncertainty.
Materials Science (cond-mat.mtrl-sci)
Fully atomic layer deposited transparent carrier selective contacts for bifacial Cd-free Cu2ZnSnSe4 thin-film solar cells
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Rosa Almache-Hernándeza, Gerard Masmitjà, Benjamín Pusay, Eloi Ros, Kunal J. Tiwari, Pedro Vidal-Fuentes, Victor Izquierdo-Roca, Edgardo Saucedo, Cristóbal Voz, Joaquim Puigdollers, Pablo Ortega
Thin-film solar cells based on kesterite (Cu2ZnSnSe4) material are a promising alternative for photovoltaic devices due to their composition consisting of earth abundant elements, ease of production at a relatively low temperatures and excellent optical absorption properties. Additionally, this absorber compound allows a tuneable bandgap energy in the 1 to 1.5 eV window range, which makes it an attractive candidate either as a top or a bottom solar cell in tandem technologies combined with transparent carrier-selective contacts. However, conventional kesterite devices use a toxic CdS layer as an electron-selective contact, resulting in the difficultto-dispose chemical waste. This work explores the use of a stack of ZnO and Al-doped ZnO (AZO) films deposited by ALD to replace the CdS-based contacts in kesterite devices. The inclusion of a polyethylenimine (PEI) interlayer as dipole to enhance the overall electrical contact performance is also discussed. The transparent back contact is formed by an ALD V2Ox thin layer over a FTO conductive electrode. Fabricated kesterite solar cells exhibit remarkable photocurrent density values of 35 mAcm-2, open-circuit voltage around 260 mV and efficiencies up to 3.5% using front illumination. The aforementioned photovoltaic parameters yield to 5.3 mAcm-2, 160 mV and 0.3% respectively under back illumination, demonstrating the bifaciality of the proposed structure.
Materials Science (cond-mat.mtrl-sci)
32 pages, 10 figures
Relationship between Structure and Dynamics of an Icosahedral Quasicrystal using Unsupervised Machine Learning
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-22 20:00 EDT
Edwin A. Bedolla-Montiel, Susana Marín-Aguilar, Marjolein Dijkstra
We present a comprehensive study of the structure, formation, and dynamics of a one-component model system that self-assembles into an icosahedral quasicrystal (IQC). Using molecular dynamics simulations combined with unsupervised machine learning techniques, we identify and characterize the unique structural motifs of IQCs, including icosahedral and dodecahedral arrangements, and quantify the evolution of local environments during the IQC formation process. Our analysis reveals that the formation of the IQC is driven by the emergence of distinct local clusters that serve as precursors to the fully developed quasicrystalline phase. Additionally, we examine the dynamics of the system across a range of temperatures, identifying transitions from vibrationally restricted motion to activated diffusion, and uncovering signatures of dynamic heterogeneity inherent to the quasicrystalline state. To directly connect structure and dynamics, we use a machine-learning-based order parameter to quantify the presence of distinct local environments across temperatures. We find that regions with high structural order, as captured by specific machine-learned classes, correlate with suppressed self-diffusion and minimal dynamical heterogeneity, consistent with phason-like motion within the IQC. In contrast, regions with lower structural order exhibit enhanced collective motion and increased dynamical heterogeneity. These results establish a quantitative framework for understanding the coupling between structural organization and dynamical processes in quasicrystals, providing new insights into the mechanisms governing IQC stability and dynamics.
Soft Condensed Matter (cond-mat.soft)
13 pages, 12 figures
Enhanced Superconductivity and Vortex Dynamics in One-Dimensional TaS2 Nanowires
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-22 20:00 EDT
Mathew Pollard, Visakha Ho, Clarissa Wisner, Eric Bohannan, Yew San Hor
We report the synthesis of high-quality 2H-TaS2 nanowires via a controlled two-step conversion process from TaS3 precursors, achieving robust superconductivity with a transition temperature Tc ~ 3.6 K which is significantly higher than bulk 2H-TaS2 (Tc ~ 0.8 K). Structural and compositional analyses confirm phase purity and preserved 1D morphology, while magnetotransport measurements reveal an enhanced upper critical field {\mu}oHc2 (2 K) ~ 5 T, far exceeding the bulk value ({\mu}oHc2 (0) ~ 1.17 T), attributed to dimensional confinement and suppression of charge density wave order. Magnetic characterization demonstrates complex vortex dynamics, including flux jumps and a second magnetization peak, indicative of strong pinning and crossover from elastic to plastic vortex regimes. These findings establish TaS2 nanowires as a versatile platform for studying superconductivity in reduced dimensions and exploiting confinement-driven quantum phenomena for advanced applications.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
17 pages, 4 figures and 38 references
Charge density wave in intermetallic oxides R$_5$Pb$_3$O (R = La and Ce)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-22 20:00 EDT
Rafaela F. S. Penacchio, Siham Mohamed, Haley A. Harms, Lin-Lin Wang, Sergey L. Bud’ko, Paul. C Canfield, Tyler J. Slade
The R$ _5$ Pb$ _3$ O family was discovered decades ago, but has remained largely unexplored. Here, we report single crystal growth and basic characterization for the La and Ce members of this family. At room temperature, these compounds adopt a tetragonal structure (I4/mcm), where R and Pb atoms form linear chains along the c-axis. We identify a second-order structural phase transition at 260 K and 145 K for R = La and Ce, respectively. Single crystal X-ray diffraction reveals a lattice modulation below the transition temperature, resulting in R-Pb pairs in the z direction. The broken symmetry in the low-temperature phases results in a primitive structure with space group P4/ncc. Transport and diffraction measurements, in agreement with density functional theory calculations, support that the R$ _5$ Pb$ _3$ O (R = La and Ce) series hosts an electron-phonon coupling driven charge density wave (CDW) at low temperatures. The CDW ordering temperature is suppressed by more than 100 K by the La to Ce substitution, suggesting high pressure-sensitivity. Therefore, this family offers the potential for investigating competing orders in oxides, with heavier rare-earth members still to be explored.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Optimized Fabrication Procedure for High-Quality Graphene-based Moiré Superlattice Devices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-22 20:00 EDT
Shuwen Sun, Pablo Jarillo-Herrero
Moiré superlattices constitute a versatile platform to investigate emergent phenomena arising from the interplay of strong correlations and topology, while offering flexible in situ tunability. However, the fabrication of such moiré superlattices is challenging. It is difficult to achieve highly uniform devices with a precise twist angle because of the unintentional introduction of heterostrain, twist angle disorder, and angle/lattice relaxation during the nanofabrication process. This article introduces an optimized, experience-informed protocol for fabricating high-quality graphene-based moiré superlattice devices, focusing on a modified dry transfer technique. The transfer process is performed in a highly tunable, custom-built transfer setup that enables precise position, angle, and temperature control. By combining rigorous flake selection criteria, pre-cleaned bubble-free bottom gates, and graphene laser ablation, the moiré superlattice is constructed by deliberately overlaying twisted graphene flakes at a submicron speed at room temperature. Through precise control of the transfer process, the resulting graphene moiré superlattice devices exhibit high uniformity and desired twist angles. This optimized protocol addresses existing challenges in the fabrication of graphene-based moiré superlattice devices and paves the way for further advances in the rapidly evolving field of moiré materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
28 pages, 8 figures; for associated video demonstration, see this https URL
Journal of Visualized Experiments (221), e68230 (2025)