CMP Journal 2025-06-02
Statistics
Nature Nanotechnology: 1
Nature Physics: 2
arXiv: 60
Nature Nanotechnology
Dynamic nanodomains dictate macroscopic properties in lead halide perovskites
Original Paper | Phase transitions and critical phenomena | 2025-06-01 20:00 EDT
Milos Dubajic, James R. Neilson, Johan Klarbring, Xia Liang, Stephanie A. Bird, Kirrily C. Rule, Josie E. Auckett, Thomas A. Selby, Ganbaatar Tumen-Ulzii, Yang Lu, Young-Kwang Jung, Cullen Chosy, Zimu Wei, Yorrick Boeije, Martin v. Zimmermann, Andreas Pusch, Leilei Gu, Xuguang Jia, Qiyuan Wu, Julia C. Trowbridge, Eve M. Mozur, Arianna Minelli, Nikolaj Roth, Kieran W. P. Orr, Arman Mahboubi Soufiani, Simon Kahmann, Irina Kabakova, Jianning Ding, Tom Wu, Gavin J. Conibeer, Stephen P. Bremner, Michael P. Nielsen, Aron Walsh, Samuel D. Stranks
Lead halide perovskites have emerged as promising materials for solar energy conversion and X-ray detection owing to their remarkable optoelectronic properties. However, the microscopic origins of their superior performance remain unclear. Here we show that low-symmetry dynamic nanodomains present in the high-symmetry average cubic phases, whose characteristics are dictated by the A-site cation, govern the macroscopic behaviour. We combine X-ray diffuse scattering, inelastic neutron spectroscopy, hyperspectral photoluminescence microscopy and machine-learning-assisted molecular dynamics simulations to directly correlate local nanoscale dynamics with macroscopic optoelectronic response. Our approach reveals that methylammonium-based perovskites form densely packed, anisotropic dynamic nanodomains with out-of-phase octahedral tilting, whereas formamidinium-based systems develop sparse, isotropic, spherical nanodomains with in-phase tilting, even when crystallography reveals cubic symmetry on average. We demonstrate that these sparsely distributed isotropic nanodomains present in formamidinium-based systems reduce electronic dynamic disorder, resulting in a beneficial optoelectronic response, thereby enhancing the performance of formamidinium-based lead halide perovskite devices. By elucidating the influence of the A-site cation on local dynamic nanodomains, and consequently, on the macroscopic properties, we propose leveraging this relationship to engineer the optoelectronic response of these materials, propelling further advancements in perovskite-based photovoltaics, optoelectronics and X-ray imaging.
Phase transitions and critical phenomena, Solar cells
Nature Physics
Precision is not limited by the second law of thermodynamics
Original Paper | Quantum information | 2025-06-01 20:00 EDT
Florian Meier, Yuri Minoguchi, Simon Sundelin, Tony J. G. Apollaro, Paul Erker, Simone Gasparinetti, Marcus Huber
Physical devices operating out of equilibrium are affected by thermal fluctuations, limiting their operational precision. This issue is particularly pronounced at microscopic and quantum scales, where its mitigation requires additional entropy dissipation. Understanding this constraint is important for both fundamental physics and technological design. Clocks, for example, need a thermodynamic flux towards equilibrium to measure time, resulting in a minimum entropy dissipation per clock tick. Although classical and quantum models often show a linear relationship between precision and dissipation, the ultimate bounds on this relationship remain unclear. Here we present an autonomous quantum many-body clock model that achieves clock precision that scales exponentially with entropy dissipation. This is enabled by coherent transport in a spin chain with tailored couplings, where dissipation is confined to a single link. The result demonstrates that coherent quantum dynamics can surpass the traditional thermodynamic precision limits, potentially guiding the development of future high-precision, low-dissipation quantum devices.
Quantum information, Single photons and quantum effects
Supersolid-like sound modes in a driven quantum gas
Original Paper | Bose-Einstein condensates | 2025-06-01 20:00 EDT
Nikolas Liebster, Marius Sparn, Elinor Kath, Jelte Duchene, Helmut Strobel, Markus K. Oberthaler
Driven systems are of fundamental scientific interest, as they can exhibit properties distinct from the same system at equilibrium. In certain cases, long-lived states of driven matter can emerge with new material properties. Here we probe the excitation spectrum of an emergent patterned state in a driven superfluid and find that its response is identical to that of a one-dimensional supersolid. By preparing wave packets as well as specific collective modes and probing their dynamics, we identify two distinct sound modes associated with spontaneously broken U(1) and translational symmetries. Consistent with the hydrodynamic description of superfluid smectics, longitudinal excitations propagate with finite velocities, whereas transverse perturbations exhibit diffusive behaviour. These results demonstrate how the conceptual framework of supersolidity can be used to characterize dynamic and far-from-equilibrium states.
Bose-Einstein condensates, Quantum fluids and solids, Quantum simulation
arXiv
Motility-dependent selective transport of active matter in trap arrays: Separation methods based on trapping-detrapping and deterministic lateral displacement
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-02 20:00 EDT
Vyacheslav R. Misko, Franco Nori, Wim De Malsche
Selecting active matter based on its motility represents a challenging task, as it requires different approaches than common separation techniques intended for separation based on, e.g., size, shape, density, and flexibility. This motility-based selection is important for, e.g., selecting biological species, such as bacteria or highly motile sperm cells for medically assisted reproduction. Common separation techniques are not applicable for separating species based on motility as such species can have indistinguishable physical properties, i.e., size, shape, density, and differ only by their ability to execute self-propelled motion as, e.g., motile, and immotile sperm cells. Therefore, selecting active species based on motility requires completely different approaches. Some of these have been developed including sperm cell selection techniques, e.g., swim-up techniques, passive selection methods based on the ability of highly motile sperm cells to swim across streamlines, as well as more sophisticated techniques. Here we theoretically demonstrate via numerical simulations various efficient methods of selection and separation based on the motility of active species using arrays of traps. Two approaches are proposed: one allowed the selective escape of motile species from traps, and the other one relying on a deterministic lateral displacement (DLD)-type method. As a model system, we consider self-propelled Janus particles whose motility can be tuned. The resulted separation methods are applicable for separation of biological motile species, such as bacteria or sperm cells, as well as for Janus micro- and nanoparticles.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Chemical Physics (physics.chem-ph), Medical Physics (physics.med-ph)
20 pages, 8 figures (preliminary version; journal version contains also “Supporting Information’’ file)
Nanoscale 17, 13434 - 13446 (2025)
Long-range spin transport in asymmetric quadruple quantum dots configurations
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
David Fernández-Fernández, Johannes C. Bayer, Rolf J. Haug, Gloria Platero
We theoretically investigate long-range coherent charge transport in linear quadruple quantum dot (QQD) arrays under reduced symmetry configurations. Employing a master equation approach, we identify precise resonant conditions that enable minimal occupation of intermediate dots, thereby facilitating long-range transfer between distant sites. Our results highlight the critical role of parameter asymmetry and coherent tunneling mechanisms in achieving efficient quantum state transfer.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages, 12 figures
Density of states correlations in Lévy Rosenzweig-Porter model via supersymmetry approach
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-02 20:00 EDT
Elizaveta Safonova, Aleksey Lunkin, Mikhail Feigel’ man
We studied global density-of-states correlation function $ R(\omega)$ for Lévy-Rosenzveig-Porter random matrix ensemble\cite{BirTar_Levy-RP} in the non-ergodic extended phase. Using extension of Efetov’s supersymmetry approach ~\cite{MirFyod_non_Gauss} we calculated $ R(\omega)$ exactly in all relevant ranges of $ \omega$ . At relatively low $ \omega \leq \Gamma$ , (with $ \Gamma \gg \Delta$ being effective mini-band width) we found GUE-type oscillations with period of level spacing $ \Delta$ , decaying exponentially at the Thouless energy scale $ E_{Th} = \sqrt{\Delta \Gamma/2\pi}$ . At high energies $ \omega \gg E_{Th}$ our results coincide with those obtained in Ref.\cite{lunkin2024localdensitystatescorrelations} via cavity equation approach. Inverse of the effective mini-band width $ 1/\Gamma$ is shown to be given by the average of the local decay times over Lévy distribution.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mathematical Physics (math-ph)
23 pages, 3 pictures
Multicomponent Linear Transport in the Absence of Local Equilibrium
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-02 20:00 EDT
Yu-Jen Chiu, Eric M. Weiner, Ahmad K. Omar
The linear laws of transport phenomena are central in our description of irreversible processes in systems across the physical sciences. Linear irreversible thermodynamics allows for the identification of the underlying forces driving transport and the structure of the relevant transport coefficients for systems that are locally in equilibrium. Increasingly, linear relations are found to describe transport in systems in which a local equilibrium hypothesis is unlikely to hold. Here, we derive a mechanical theory of multicomponent transport without appealing to equilibrium notions. Our theory for the Onsager transport tensor highlights the general breakdown of the familiar Onsager reciprocal relations and Einstein relations when a local equilibrium is absent. The procedure outlined is applied to a variety of systems, including passive systems, mixtures with nonreciprocal interactions, electrolytes under an electric field, and active systems, and can be straightforwardly used to understand other transport processes. The framework further provides a basis to extend numerical approaches for computing the transport coefficients of nonequilibrium systems, as is demonstrated for a system with nonreciprocal interactions.
Statistical Mechanics (cond-mat.stat-mech)
Fully Generalized Spin Models with Strain Effects of Kitaev Spin Liquid Candidate Materials
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
Pureum Noh, Hyunggeun Lee, Myung Joon Han, Eun-Gook Moon
The $ KJ\Gamma\Gamma’$ spin model-originally derived for an ideal $ P\bar{3}1m$ symmetric geometry-has long served as a central framework for understanding candidate Kitaev materials. In realistic crystals, however, this ideal geometry is seldom realized, either at low temperatures or under external perturbations, limiting the model’s quantitative applicability. Here we introduce a fully generalized spin model, denoted $ \epsilon$ -$ KJ\Gamma\Gamma’$ , that explicitly incorporates arbitrary lattice deformations $ \epsilon$ . All spin-exchange interactions and their strain-dependent coefficients are obtained from density-functional theory (DFT) calculations and a microscopic derivation of coupling constants for materials based on $ d^5$ transition-metal ions. For $ \alpha$ -RuCl$ _3$ under a strain of $ 3%$ , new emergent exchange channels acquire magnitudes comparable to their unstrained counterparts. Building on these parameters, we investigate strain-driven quantum phase transitions between competing magnetic states-including the zigzag order and the Kitaev quantum spin liquid (KQSL)-and identify a strain-induced topological transition within the KQSL states that offers a practical diagnostic of Kitaev physics. Furthermore, our symmetry analysis of the $ \epsilon$ -$ KJ\Gamma\Gamma’$ model is applicable to both $ d^{5}$ ions, such as $ \alpha$ -RuCl$ _3$ , and $ d^{7}$ systems, including cobalt-based compounds.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Main text: 13 pages, 4 figures, 4 tables
Dynamical detection of extended nonergodic states in many-body quantum systems
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-02 20:00 EDT
David A. Zarate-Herrada, Isaías Vallejo-Fabila, Lea F. Santos, E. Jonathan Torres-Herrera
Fractal dimensions are tools for probing the structure of quantum states and identifying whether they are localized or delocalized in a given basis. These quantities are commonly extracted through finite-size scaling, which limits the analysis to relatively small system sizes. In this work, we demonstrate that the correlation fractal dimension $ D_2$ can be directly obtained from the long-time dynamics of interacting many-body quantum systems. Specifically, we show that it coincides with the exponent of the power-law decay of the time-averaged survival probability, defined as the fidelity between an initial state and its time-evolved counterpart. This dynamical approach avoids the need for scaling procedures and enables access to larger systems than those typically reachable via exact diagonalization. We test the method on various random matrix ensembles, including full random matrices, the Rosenzweig-Porter model, and power-law banded random matrices, and extend the analysis to interacting many-body systems described by the one-dimensional Aubry-André model and the disordered spin-1/2 Heisenberg chain. In the case of full random matrices, we also derive an analytical expression for the entire evolution of the time-averaged survival probability.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
12 pages, 13 figures
Band Structure Engineering of Coupled-Resonator Phononic Polyacetylene and Polyaminoborane
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
B. Manjarrez-Montañez, R. A. Méndez-Sánchez, Y. Betancur-Ocampo, A. Martínez-Argüello
A methodology for constructing a quasi-one-dimensional coupled-resonator phononic metamaterial is presented. This is achieved through the design of artificial phononic analogs of two molecular structures: trans-polyacetylene and trans-polyaminoborane. The band structure of trans-polyacetylene is analyzed in relation to the Su-Schrieffer-Heeger (SSH) model, while that of trans-polyaminoborane is examined using the $ \kappa$ -deformed Dirac equation, both within a tight-binding framework. Additionally, the obtained finite realization of the artificial trans-polyacetylene exhibits topologically protected states.
Materials Science (cond-mat.mtrl-sci)
Molecular Dynamics Prediction of the Effect of Neutron Irradiation on the Ductile-to-Brittle Transition in Fe-Ni-Cr Alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
A. Ustrzycka, H. Mousavi, F. J. Dominguez-Gutierrez, S. Stupkiewicz
This study provides a comprehensive investigation into the fracture behavior of irradiated Fe-Ni-Cr alloys, focusing on the radiation-induced ductile-to-brittle transition (DBT). Unlike the commonly studied temperature-driven DBT, this transition is driven by radiation-induced defects, which impede dislocation motion and reduce the material’s capacity for plastic deformation, ultimately leading to brittle failure. Utilizing Molecular Dynamics simulations, this work examines the interaction between radiation-induced defects, such as dislocation loops and voids, and their influence on crack propagation and energy dissipation mechanisms. The results reveal distinct roles played by these defects: voids facilitate crack growth by reducing local cohesive energy, while dislocation loops act as barriers that impede crack advancement and redirect crack paths, significantly altering crack morphology. Building on the classical approach of separating fracture energy into brittle cleavage and plastic components, this study adapts this decomposition to irradiated materials. This approach appraises the distinct roles of surface energy and plastic work across varying radiation damage levels, providing critical insights into how irradiation-induced defects govern fracture dynamics.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Interaction between shallow NV$^-$ and spin active azafullerenes on hydrogenated and fluorinated (001) diamond surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Bastien Anézo, Denis Arčon, Chris Ewels
The interaction between surface-lying nitrogen-substituted fullerenes (radical azafullerene, C$ _{59}$ N$ ^\bullet$ ) with sub-surface negative nitrogen-vacancy complexes (NV$ ^-$ ) in diamond is investigated using first principles calculations. We consider (2$ \times$ 1) reconstructed (001) oriented diamond surfaces with both H- and F-surface termination. The charge stability of NV$ ^-$ , when in close proximity to both the nearby surface and the spin active azafullerene is discussed, in the context of diamond band bending arising from surface-induced changes in electron affinity (EA). In the case of the hydrogenated surface, the system spin is quenched, yielding a negatively charged azafullerene (C$ _{59}$ N$ ^-$ ) and neutrally charged NV$ ^0$ as the most stable electronic configuration. In contrast, fluorinating the surface favours the negatively charged NV$ ^-$ , and conserves the C$ _{59}$ N$ ^\bullet$ , neutrality and stabilizes uncompensated free spins. This opposing behaviour is attributed to surface charge doping emerging from different band bending effects associated with the surface EA. This study is consistent with experimentally observed photoluminescence quenching, and shows that surface passivation by fluorination could efficiently tackle the problem of charge transfer between adsorbed molecules and shallow NV centers.
Materials Science (cond-mat.mtrl-sci)
9 pages, 6 figures, supplementary materials
Strained 2D TMD lateral heterojunctions via grayscale thermal-Scanning Probe Lithography
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
G. Zambito (1), G. Ferrando (1), M. Barelli (1), M. Ceccardi (1), F. Caglieris (2), D. Marre (1), F. Bisio (2), F. B. de Mongeot (1), M. C. Giordano (1) ((1) Dipartimento di Fisica, Università di Genova, Genova, Italy, (2) CNR-SPIN, Genova, Italy)
Nanoscale tailoring of the optoelectronic response of 2D Transition Metal Dichalcogenides semiconductor layers (TMDs) has been achieved thanks to a novel strain engineering approach based on the grayscale thermal-Scanning Probe Lithography (t-SPL). This method allows the maskless nanofabrication of locally strained 2D MoS2-Au lateral heterojunction nanoarrays that are characterized by asymmetric electrical behavior. 2D MoS2 layers are conformally transferred onto grayscale t-SPL templates characterized by periodic nanoarrays of deterministic faceted nanoridges. This peculiar morphology induces asymmetric and uniaxial strain accumulation in the 2D TMD material allowing to tailor their electrical work-function at the nanoscale level, as demonstrated by Kelvin Probe Force Microscopy (KPFM). The modulation of the electronic response has been exploited to develop periodic nanoarrays of lateral heterojunctions endowed with asymmetric electrical response by simple maskless deposition of Au nanocontacts onto the strained 2D TMD layers. The locally strained Au-MoS2 layers show asymmetric lateral heterojunctions with engineered carrier extraction functionalities, thus representing a promising platform in view of tunable ultrathin nanoelectronic, nanophotonic and sensing applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
29 Pages, 15 figures
Electrical Detection of Single-Domain Néel Vector Reorientation across the Spin-Flop Transition in Cr2O3 Crystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Wei-Cheng Liao, Haoyu Liu, Weilun Tan, Josiah Keagy, Jia-mou Chen, Jing Shi
Electrical transport measurements in heterostructures of antiferromagnetic Cr2O3 bulk crystals and a thin Pt layer exhibit sharp responses as the Néel vector of the Cr2O3 undergoes the spin-flop transition. This abrupt change can arise from several distinct mechanisms including magnetostriction, proximity-induced anomalous Hall, spin Hall anomalous Hall, and spin Hall planar Hall effects. While large Pt devices sensing multiple up/down domains can produce indistinguishable Hall signal jumps due to different initial Néel vector orientations, smaller Pt devices that sense single domains isolate the proximity-induced Hall signals. This allows direct electrical detection of Néel vector reorientation across the spin-flop transition in single domain regions. Furthermore, the single-domain state can be prepared by magnetic field cooling or magnetoelectric cooling. We demonstrate a method to control and characterize almost the three-dimensional orientation of single-domain Néel vectors by exploiting Hall measurements and cooling techniques, crucial for future antiferromagnetic spintronic applications.
Materials Science (cond-mat.mtrl-sci)
Relaxation pathways and emergence of domains in square artificial spin ice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Matteo Menniti, Naëmi Leo, Pedro Villalba-González, Matteo Pancaldi, and Paolo Vavassori
Multi-domain states of square artificial spin ice show a range of different morphologies ranging from simple stripe-like domains to more organically shaped coral domains. To model the relevant dynamics leading to the emergence of such diverse domain structures, simplified descriptions of the switching behavior of individual nanomagnets are necessary. In this work, we employ kinetic Monte Carlo simulations of the demagnetization of square artificial spin ice toward its ground state, and compare how the choice of transition barriers affect the emergence of mesoscale domains. We find that the commonly used mean-field barrier model (informed by equilibrium energetics only) results in propagation of ground-state string avalanches. In contrast, taking into account chiral barrier splitting enabled by state-dependent local torques supports the emergence of complex-shaped coral domains and their successful relaxation towards the ground state in later relaxation stages. Our results highlight that intrinsic contributions to switching barriers, in addition to the effect of extrinsic defects often attributed to nanofabrication irregularities, can subtly shift favored transition pathways and result in different emergent mesoscale features. Future kinetic Monte Carlo models that describe the evolution of artificial spin systems should thus account for these effects.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
11 pages, 6 figures
Exploring Domain Wall Pinning in Ferroelectrics via Automated High Throughput AFM
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Kamyar Barakati, Yu Liu, Hiroshi Funakubo, Sergei V. Kalinin
Domain-wall dynamics in ferroelectric materials are strongly position-dependent since each polar interface is locked into a unique local microstructure. This necessitates spatially resolved studies of the wall-pinning using scanning-probe microscopy techniques. The pinning centers and preexisting domain walls are usually sparse within image plane, precluding the use of dense hyperspectral imaging modes and requiring time-consuming human experimentation. Here, a large area epitaxial PbTiO$ _3$ film on cubic KTaO$ _3$ were investigated to quantify the electric field driven dynamics of the polar-strain domain structures using ML-controlled automated Piezoresponse Force Microscopy. Analysis of 1500 switching events reveals that domain wall displacement depends not only on field parameters but also on the local ferroelectric-ferroelastic configuration. For example, twin boundaries in polydomains regions like a$ _1^-$ /$ c^+$ $ \parallel$ a$ _2^-$ /$ c^-$ stay pinned up to a certain level of bias magnitude and change only marginally as the bias increases from 20V to 30V, whereas single variant boundaries like a$ _2^+$ /$ c^+$ $ \parallel$ a$ _2^-$ /$ c^-$ stack are already activated at 20V. These statistics on the possible ferroelectric and ferroelastic wall orientations, together with the automated, high-throughput AFM workflow, can be distilled into a predictive map that links domain configurations to pulse parameters. This microstructure-specific rule set forms the foundation for designing ferroelectric memories.
Materials Science (cond-mat.mtrl-sci), Computer Vision and Pattern Recognition (cs.CV), Machine Learning (cs.LG), Applied Physics (physics.app-ph)
17 pages, 6 figures
Cross-Modal Characterization of Thin Film MoS$_2$ Using Generative Models
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Isaiah A. Moses, Chen Chen, Joan M. Redwing, Wesley F. Reinhart
The growth and characterization of materials using empirical optimization typically requires a significant amount of expert time, experience, and resources. Several complementary characterization methods are routinely performed to determine the quality and properties of a grown sample. Machine learning (ML) can support the conventional approaches by using historical data to guide and provide speed and efficiency to the growth and characterization of materials. Specifically, ML can provide quantitative information from characterization data that is typically obtained from a different modality. In this study, we have investigated the feasibility of projecting the quantitative metric from microscopy measurements, such as atomic force microscopy (AFM), using data obtained from spectroscopy measurements, like Raman spectroscopy. Generative models were also trained to generate the full and specific features of the Raman and photoluminescence spectra from each other and the AFM images of the thin film MoS$ _2$ . The results are promising and have provided a foundational guide for the use of ML for the cross-modal characterization of materials for their accelerated, efficient, and cost-effective discovery.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG), Applied Physics (physics.app-ph)
36 pages, 10 figures, 10 tables
Line and Planar Defects with Zero Formation Free Energy: Applications of the Phase Rule toward Ripening-Immune Microstructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Extended one- and two-dimensional defects in crystalline materials are usually metastable. The thermodynamic ground state of the material is presumed to be defect-free. Here, we investigate the conditions under which extended defects, such as grain boundaries, can exist in a multicomponent alloy when the latter reaches the thermodynamic ground state allowed by the Gibbs phase rule. We treat all extended defects as low-dimensional phases on the same footing as the conventional bulk phases. Thermodynamic analysis shows that, in the ground state, the formation free energies of all extended defects must be zero, and the system must follow a generalized phase rule. The latter predicts that only a finite number of symmetry-related defect types can coexist in the material in the ground state. Guided by the phase rule, we discuss finite-size polycrystalline and/or polyphase microstructures that are fully immune to coarsening and their possible transformations.
Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
Symmetry-Breaking Magneto-Optical Effects in Altermagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Jiuyu Sun, Yongping Du, Erjun Kan
The recently discovered altermagnets (AMs), hosting momentum-dependent spin splitting and vanishing net magnetization, have attracted intensive attention for their promising application in novel spintronics. However, limited by facility and material constraints, experimentally distinguishing them from conventional antiferromagnets (AFMs) remains a challenge, which hinders the high-throughput screening for AM candidates. Here, we predict strain-mediated magneto-optical responses in AMs, which can serve as a universal and experimentally accessible strategy for efficient identification of AMs. Symmetry analysis reveals that uniaxial strain can selectively breaks rotation or mirror symmetries in AMs while preserving $ PT$ symmetry in AFMs, thereby activating distinct linear magneto-optical responses (e.g., optical absorption and Kerr rotation) unique to AMs. First-principles calculations across prototypical systems – including semiconducting V$ _2$ Se$ _2$ O monolayer and metallic CrSb bulk – show that the strain-induced optical signatures are significant enough for conventional optical measurements. Our work establishes a rapid, non-invasive characterization methodology for altermagnetism across material platforms, accelerating its exploration for spin-based technologies.
Materials Science (cond-mat.mtrl-sci)
Instantons and topological order in two-leg electron ladders: A universality class
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
S.-R. Eric Yang, Hyun Cheol Lee, Hoang-Anh Le, In-Hwan Lee
Our numerical study of the disordered Hubbard model with nearest-neighbor hopping shows that a two-leg electron ladder has a finite topological entanglement entropy in the regime where the density of states exhibits an exponentially decaying gap. The value of the topological entanglement entropy suggests that two-leg ladders belong to the same universality class as graphene zigzag nanoribbons, despite several structural differences. A Shankar-Witten-type bosonization Lagrangian with disorder captures several features of the numerically obtained results for disordered two-leg ladders. Additionally, we propose a Lagrangian in which the fusion of two semions residing on different chains generates a fermion (instanton). We apply this Lagrangian within the framework of the pinned charge-density-wave model and compute the relevant Green’s function using the bosonization method. This approach predicts a linear density of states at a critical disorder strength. Below this threshold, a soft gap emerges, which is in qualitative agreement with our numerical results.
Strongly Correlated Electrons (cond-mat.str-el)
Phys. Rev. B 111, 205144 (2025)
Quantum anomalous Hall effects and Hall crystals at fractional filling of helical trilayer graphene
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
Sen Niu, Jason Alicea, D. N. Sheng, Yang Peng
Helical trilayer graphene realizes a versatile moiré system in which anomalous Hall effects have been recently observed at integer and fractional fillings. Focusing on helical trilayers near the magic angle and under a substrate potential, we demonstrate that an isolated higher Chern band with Chern number $ |C_{band}|=2$ emerges, enabling the exploration of many-body states beyond the conventional Landau level paradigm. We use exact diagonalization to predict a rich phase diagram of gapped states unattainable in a single $ |C_{band}|=1$ band. At filling $ \nu=2/3$ , we identify a quantum Hall crystal with integer Hall conductance $ |\sigma_{H}|=e^2/h$ coexisting with a $ \sqrt{3}\times \sqrt{3}$ charge density wave order. At $ \nu=1/2$ , we find a quantum Hall pseudospin ferromagnet featuring extensive ground state degeneracy, Hall conductance $ |\sigma_{H}|=e^2/h$ , and $ 2\times 2$ charge order. Finally, at $ \nu=1/3$ we find a translation-symmetric fractional Chern insulator with $ |\sigma_{H}|=2e^2/3h$ . By incorporating spin and valley degrees of freedom, we identify an optimal filling regime $ \nu_{\rm{total}}=3+\nu$ , where three flavors are fully filled, leaving the fourth at partial filling $ \nu$ . Notably, inter-flavor interactions renormalize the bandwidth and stabilize all the gapped phases even in realistic parameter regimes away from the chiral limit.
Strongly Correlated Electrons (cond-mat.str-el)
Zener tunnelling in biased bilayer graphene via analytic continuation of semiclassical theory
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Harley Scammell, Oleg P. Sushkov
Employing a semiclassical method based on analytic continuation, we compute the electron-hole pair production rate in biased bilayer graphene subject to an in-plane electric field. This approach, originally due to Zwaan, bypasses the need for exact solutions at turning points, which are generally unavailable beyond linear or quadratic band structures. Applying this technique to biased bilayer graphene reveals non-standard features of the asymptotic wavefunctions, in particular the necessity of retaining decaying components even in classically allowed regions. By providing a fully analytic solution, this work complements and clarifies earlier results based on hybrid analytical-numerical treatments, and importantly establishes the absolute normalisation of the pair production rate – and hence of the tunnelling current.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The understanding of the penetration and clusterization of 1-alkanol in bilayer membrane: An open outlook based on atomistic molecular dynamics simulation
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-02 20:00 EDT
1-alkanols are well known to have anesthetic and penetration properties, though the mode of operation remains enigmatic. We perform extensive atomistic molecular dynamics simulation to study the penetration of 1-alkanols of different chain lengths in the dioleoyl-phosphatidylcholine (DOPC) bilayer model membrane. Our simulations show that the depth of penetration of 1-alkanol increases with chain length, n, and the deuterium order of the DOPC tail increases with the chain length of the acyl-chain of the 1-alkanol. We find a cut-off value for the length of the acyl-chain of 1-alkanol, n = 12, where 1-alkanol with a chain length greater than the cut-off value takes longer to penetrate the membrane. Our simulation study also demonstrates that the membrane exhibits clusters of 1-alkanols with acyl chains longer than the cut-off value, whereas 1-alkanols with acyl-chain shorter than the cut-off value are distributed homogeneously in the membrane and penetrate the membrane in a shorter time than longer-acyl-chain 1-alkanols. These findings add to our understanding of the anomalies in anesthetic molecule partitioning in the cell membrane and may have implications for general anesthesia.
Soft Condensed Matter (cond-mat.soft)
9 pages, 9 Figures in the main text and 2 Figures in Supplementary Information
Photostriction-tunable Polarization and Structural Dynamics in Interlayer Sliding Ferroelectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Kun Yang, Jianxin Yu, Jia Zhang, Sheng Meng, Jin Zhang
Two-dimensional ferroelectrics with robust polarization offer promising opportunities for non-volatile memory, field-effect transistors, and optoelectronic devices. However, the impact of lattice deformation on polarization and photoinduced structural response remains poorly understood. Here, we employ first-principles calculations to demonstrate photodoping-induced lattice expansion in rhombohedrally stacked bilayer MoS2, revealing a strong coupling between photodoping carrier and lattice structure. We identify a pronounced photostrictive response in sliding ferroelectrics, wherein electron-hole excitation leads to substantial in-plane expansion, increased interlayer spacing, and enhanced ferroelectric polarization. This strain-induced modulation drives significant bandgap renormalization. The photostriction-tunable polarization and structural dynamics arise from the strong electromechanical coupling inherent to the non-centrosymmetric rhombohedral stacking. The findings provide critical insights into the nonthermal lattice expansion governing sliding ferroelectrics at atomic-scale timescales, while simultaneously laying the groundwork for next-generation electronic and memory technologies by leveraging lattice-tunable polarization switching.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
4 figures
Evidence for energy-dependent scattering dominating thermoelectricity in heavy fermion systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
Daiki Goto, Kentaro Kuga, Kiyohisa Tanaka, Tsunehiro Takeuchi, Masaharu Matsunami
In the field of thermoelectric materials and devices, improving energy conversion efficiency remains a long-standing challenge. As a promising approach to address this issue, tuning the electron-scattering mechanisms beyond the ordinary constant relaxation time approximation (CRTA) has been proposed. However, direct experimental evidence for an energy-dependent scattering reflected in the Seebeck coefficient is still lacking. Here we demonstrate using angle-resolved photoemission spectroscopy that the relaxation time of heavy fermion quasiparticles is highly dependent on the energy near the Fermi level. The observed energy dependence of the relaxation time is due to the coherent Kondo scattering, describing the sign of the Seebeck coefficient reasonably well, which cannot be deduced from CRTA. Our findings provide not only deeper insight into the understanding of thermoelectricity in correlated materials, but also new perspectives on possible orbital-selective engineering of thermoelectric materials.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Bose-Einstein Condensation, Fluctuations and Spontaneous Symmetry Breaking
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-02 20:00 EDT
A. Crisanti, A. Sarracino, M. Zannetti
The realisation of Bose-Einstein condensation under grand-canonical conditions has provided the experimental evidence for the simultaneous occurrence of macroscopic fluctuations and phase coherence of the condensate. The observation of these two features, against a consolidated tradition which wants the fluctuations to be pathological (grand-canonical catastrophe) and incompatible with spontaneous symmetry braking, calls for a comprehensive rethinking of the approach to the problem. In this paper we consider the uniform ideal gas in a box and we present an alternative conceptual framework. We show that the usually-employed Bogoliubov quasi-average construction fails to reproduce the broken-symmetry state. The observed features are accounted for by a different pattern of spontaneous symmetry breaking, characterised by condensation of fluctuations and long-range correlations of the order parameter.
Statistical Mechanics (cond-mat.stat-mech), Quantum Gases (cond-mat.quant-gas)
6 pages
Probing quasiparticle excitations in a doped Mott insulator via Friedel oscillations
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
Anurag Banerjee, Emile Pangburn, Catherine Pépin, Cristina Bena
In this work, we investigate impurity-induced Friedel oscillations in the doped two-dimensional Hubbard model, focusing on the role of holon and doublon excitations. We show that weak impurities, due to the non-fermionic nature of the underlying quasiparticles, induce Friedel oscillations whose behavior is consistent with an effective non-interacting theory for these quasiparticles, and whose wavevector reflects the violation of Luttinger’s theorem. At larger impurity strength, the system transitions to a phase-separated state composed of coexisting Mott-insulating (half-filled) and hole-rich regions. Within the composite operator framework, this phase separation arises from a competition between the kinetic energy of holons and the tendency to form tightly bound holon-doublon pairs. Our results offer new insights into the nature of charge carriers and the emergent electronic phases in the doped Mott regime.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
NbTiN Nanowire Resonators for Spin-Photon Coupling on Solid Neon
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Y. Tian, I. Grytsenko, A. Jennings, J. Wang, H. Ikegami, X. Zhou, S. Tamate, H. Terai, H. Kutsuma, D. Jin, M. Benito, E. Kawakami
Electrons floating on a solid neon exhibit long charge coherence times, making them attractive for hybrid quantum systems. When combined with high-quality, high-impedance superconducting resonators and a local magnetic field gradient, this platform enables strong charge-photon and spin-charge coupling – key ingredients for scalable spin qubit architectures. In this work, we fabricated NbTiN superconducting nanowire resonators and measured internal quality factors around $ 10^5$ . We successfully deposited several hundred-nanometer-thick layers of solid neon, followed by gradual electron loading. The presence of neon and electrons was confirmed via resonance frequency shifts without degradation of the resonator’s quality factor. These results demonstrate that NbTiN superconducting nanowire resonators are compatible with electrons-on-neon systems and suitable for future qubit experiments. We further performed a theoretical analysis of optimized micro-magnet configurations, showing that spin qubit gate fidelities exceeding 99.99% for single-qubit and 99.9% for two-qubit operations are achievable using natural neon at the charge sweet spot.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Universal Phase Transitions of Matter Induced in Optically Driven Cavities
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Optical cavities have been widely applied to manipulate the properties of solid state materials inside it. We propose that in systems embedded within optical cavities driven by incident pump light, the pump induces generic phase transitions into new non-equilibrium steady states. This effect arises from the ponderomotive potential, the effective static potential exerted by the pump on the low energy degrees of freedom, which exhibits a universal step-like structure that pushes the matter degrees of freedom in the direction that red-shifts the cavity photon modes. For a two dimensional electron liquid in a driven cavity, this step-like potential pushes the electron density to jump to a smaller value so that a hybrid cavity photon mode is red shifted to slightly below the pump frequency. Similarly, for a disordered superconductor in such a driven cavity, this potential acts on the superconducting order parameter and causes a first order phase transition to a new steady state with a smaller gap. By realistic electromagnetic modeling of the cavity, we construct the non-equilibrium phase diagrams for experimentally relevant devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
5 pages, 3 figures
Revisiting the Topological Nature of TaIrTe4, SrSi2, and Cu2XY3: An ab-initio Investigation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Prakash Pandey, Sudhir K. Pandey
Several topological electronic materials have been theoretically predicted, leading to a comprehensive catalog systematically characterized by their band crossings. Researchers have attempted to experimentally verify the topological nature of some materials from the present catalogs, but not all efforts have yielded positive results. Here, we introduce a possible reason for the discrepancies between theoretical and experimental results. In this direction, firstly we have revisited the nature of the well-known topological materials TaIrTe$ _4$ and SrSi$ _2$ using \textit{state-of-the-art ab-initio} calculations, and found additional Weyl points in both materials that were missing in previously reported studies. Then we have verified the recently predicted topological states of the \textit{Imm2}-phase of Cu$ _2$ XY$ _3$ (X=Si, Ge, Sn & Y=S, Se, Te). Contrary to previously reported results, we did not find any Weyl points or nodal arcs in Cu$ _2$ SnTe$ _3$ . Notably, our theoretical results reveal that Cu$ _2$ SiTe$ _3$ , Cu$ _2$ GeTe$ _3$ and Cu$ _2$ GeSe$ _3$ each host four small nodal rings, eight Weyl points, and eight nodal arcs, respectively, which differ from previous studies. Considering Cu$ _2$ SnS$ _3$ as an example, we have also investigated the robustness of the topological phase against local strain. Our study provides insights into the inconsistencies between theoretical predictions and experimental results, and demonstrates how the topological phase is sensitive to changes in lattice parameters, atomic positions, and exchange-correlation functionals.
Materials Science (cond-mat.mtrl-sci)
Fe contribution to the magnetic anisotropy of $L{1_0}$-ordered FePt thin films studied by angle-dependent x-ray magnetic circular dichroism
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Goro Shibata, Keisuke Ikeda, Takeshi Seki, Shoya Sakamoto, Yosuke Nonaka, Zhendong Chi, Yuxuan Wan, Masahiro Suzuki, Tsuneharu Koide, Hiroki Wadati, Koki Takanashi, Atsushi Fujimori
Among magnetic thin films with perpendicular magnetic anisotropy (PMA), $ L1_0$ -ordered FePt has attracted significant attention because of its exceptionally strong PMA. However, the microscopic origin of its strong PMA has not been elucidated experimentally. We have investigated the contribution of the Fe $ 3d$ electrons to its magnetic anisotropy energy by angle-dependent x-ray magnetic circular dichroism at the Fe $ L_{2,3}$ edge. By this technique, one can deduce the magnetic dipole moment $ m_\text{T}$ , which represents the anisotropic spatial distribution of spin-polarized electrons, and the orbital moment anisotropy (OMA) of Fe $ 3d$ electrons. Detected finite $ m_\text{T}$ indicates that the spin-polarized Fe $ 3d$ electrons are distributed preferentially in the out-of-plane direction of the films. This $ m_\text{T}$ of Fe overwhelms the positive contribution of OMA to PMA, and reduces the PMA of $ L1_0$ -ordered FePt thin films, consistent with a previous first-principles calculation. The present result implies that a large positive contribution of the non-magnetic element Pt rather than Fe governs the PMA of $ L1_0$ -ordered FePt thin films.
Materials Science (cond-mat.mtrl-sci)
14 pages, 4 figures, 2 supplementary figures
Quantum Point Contact with Local Two-body Loss
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-06-02 20:00 EDT
Motivated by recent advances in ultracold atomic gas experiments, we investigate a two-terminal mesoscopic system in which two-body loss occurs locally at the center of a one-dimensional chain. By means of the self-consistent Born approximation in the Keldysh formalism, we uncover mesoscopic current formulas that are experimentally relevant and applicable to the weak dissipation regime. Although these formulas are analogous to those for systems with one-body loss, it turns out that the channel transmittance and loss probability depend on the nonequilibrium occupation at the lossy site. We demonstrate that this occupation dependence leads to a weaker suppression of currents in the presence of two-body loss compared to one-body loss, in agreement with a recent experimental observation.
Quantum Gases (cond-mat.quant-gas)
Thinning algorithms for the Monte Carlo simulation of kinetic Ising models
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-02 20:00 EDT
The thinning method for numerical generation of the nonhomogeneous Poisson process (NHPP) arrival times has been adapted to accelerate Monte Carlo simulations of the kinetic Ising models (KIMs) with the Glauber spin-flip dynamics. The performance of the suggested algorithms has been illustrated by simulation of the decay of metastable states in stationary KIMs and of hysteresis in KIMs in a periodic external field. The thinning has been implemented by means of piecewise constant majorizing functions which exceed or are equal to NHPP rate. It has been shown that in favorable cases the use of thinning makes possible the simulations of hysteresis at frequencies in tens nanohertz and the decay of metastable states with lifetimes by many orders exceeding those in previous simulations. Good agreement of simulated results with low-temperature analytic theories has been established. Though the algorithm acceleration has been shown to enhance with lowering temperature, the hysteresis has been simulated at moderately low temperatures of practical interest estimated to cover the range from below the room temperature up to temperatures used in hyperthermia applications.
Statistical Mechanics (cond-mat.stat-mech)
16 pages, 12 figures
50 years of spin glass theory
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-02 20:00 EDT
David Sherrington, Scott Kirkpatrick
In 1975, two papers were published that together sparked major new directions, conceptual, mathematical and practically applicable, in several previously disparate fields of science. In this short review, we expose key aspects of their thinking, implementations and implications, along with a selection of further crucial and consequential developments. These papers were Theory of spin glasses' by this http URL and this http URL (EA)[1] and Solvable Model of a Spin-Glass’, by this http URL and this http URL (SK)[2], both concerned with trying to understand recent experiments that suggested a new phase of matter.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
Very short review
Magnetic Circular Dichroism at the Oxygen K edge in Microcrystals of Spinels Grown on Ru(0001)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
A. Mandziak, V. Sosa, P. Nita, L. Martín-García, J. E. Prieto, M. Foerster, M. A. Niño, L. Aballe, C. Granados-Miralles, A. Quesada, C. Tejera-Centeno, S. Gallego, J. de la Figuera
We have measured the circular magnetic dichroism in the x-ray absorption at the K-edge of oxygen in microcrystals of different spinel oxides. The microcrystals are islands of micrometric size and nanometric thickness, grown on Ru(0001) substrates using high-temperature oxygen-assisted molecular beam epitaxy. The domains observed in the oxygen K-edge dichroism have the same distribution and orientation as those observed in x-ray magnetic circular dichroism at the L$ _{3}$ edge of the octahedral cations. Integrating the area from a single domain, x-ray magnetic circular dichroic spectra of oxygen were measured and, by the application of the K-edge sum rule, non vanishing orbital magnetic moments aligned with the octahedral cations were found. Density functional theory calculations, which did not show any orbital moment at the oxygen anions, indicate that the energy ranges where oxygen dichroism is observed correspond to those with significant hybridization with the cations d bands. They also show a correlation between the magnitude of the measured value of the oxygen orbital moment and the theoretical one for the cations, and demonstrate that this trend is preserved in the presence of Fe excess in the samples. Our experimental XMCD suggest, following the DFT calculations, that the origin of the oxygen magnetic moment lies in the hybridization of the oxygen unoccupied p-derived bands with the cation bands, mostly with the d-derived ones.
Materials Science (cond-mat.mtrl-sci)
8 pages, 3 figures
Frustrated vacancy ordering creates novel quantum properties in Kutinaite, $\mathrm{Ag}{6}\mathrm{Cu}{14.4}\mathrm{As}_7$
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-02 20:00 EDT
Kim-Khuong Huynh, Rasmus Baden Stubkjær, Ventrapati Pavankumar, Emilie Skytte Vosegaard, Karl Omer Rimon Juul, Kasper Rasmussen Borup, Yong P. Chen, Bo Brummerstedt Iversen
Ideal crystals are fully ordered, but real-world crystals always contain defects breaking translational symmetry. Random defects in crystals have important implications and they e.g. provide the foundation for semiconductor-based electronic devices. Structurally correlated defects introduce an additional level of complexity, which may lead to novel materials properties, but rationalization of relations between correlated disorder and the emergent material properties are very rare. Here we report that the defect structure of the mineral Kutinaite, Ag6Cu14.4As7, exhibits unprecedented metallic diamagnetism, a hallmark of non-trivial electronic states that require delicate symmetrical protection. Using a combination of X-ray scattering methodologies, simulations, and physical property measurements, we deduced and verified subtle frustrated vacancy ordering of the Cu sublattice when cooling crystals below ~300 K. The vacancy frustration in Kutinaite leads to unique quantum properties, and our study calls for a reconsideration of the role of vacancies as quasi-chemical species in crystals.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
39 pages, combined main text and supplementary information, five figures in the main text, 14 figures in SI
Decoupling Local Electrostatic Potential and Temperature-Driven Atomistic Forming Mechanisms in TaOx/HfO2-Based ReRAMs using Reactive Molecular Dynamics Simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Simanta Lahkar, Valeria Bragaglia, Behnaz Bagheri, Donato Francesco Falcone, Matteo Galetta, Marilyne Sousa, Aida Todri-Sanial
Resistive random access memories (ReRAMs) with a bilayer TaOx/HfO2 stack structure have been shown to possess uniquely promising resistive switching characteristics. However, the key atomistic forming mechanisms and the physical processes that govern the behavior of this kind of device remain to be clarified. Here, we present a detailed analysis of the physical mechanisms underlying its forming at the atomistic level through molecular dynamics (MD) simulations using an extended charge equilibration scheme to describe the effects of applied voltage with the charge transfer ionic potential formalism. The displacement of the tantalum ions was found to be the highest, followed by that of the hafnium ions, in response to a sufficiently high applied voltage across the electrodes, whereas the oxygen ions had a relatively minor voltage-driven response. This led to the formation of a tantalum-depleted, oxygen-rich zone near the positive top electrode acting as the anode and the clustering of oxygen vacancies that nucleated into the filament near the negative bottom electrode, or the cathode. This process resulted in partial shielding of the bulk dielectric from the applied voltage. We found a minimum threshold voltage was required to initiate vacancy clustering to form the filament. Filament growth during forming is attributed to a localized mechanism, driven by thermally activated generation of oxygen vacancy defects, which get stabilized by the local electric fields near the edge of the nucleated filament at the cathode.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Computational Physics (physics.comp-ph)
Crystal Growth & Physical Property Characterization of Mixed Topological Insulator BiSbTe$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Dinesh Kumar (Banasthali), Kapil Kumar (CSIR-NPL), N. K. Karn (CSIR-NPL), Ganesh Gurjar (Ramajas - DU), V.P.S. Awana (CSIR-NPL), Sudesh (Banasthali)
This article reports the synthesis of a single crystalline mixed topological insulator (TI) BiSbTe$ _3$ and its detailed structural and magneto-transport properties. The single crystalline samples of BiSbTe$ _3$ are grown by the melt-growth process and characterized by X-ray diffraction (XRD), Energy dispersive X-ray analysis (EDAX) and Raman spectroscopy. The single crystal XRD peaks dictated the growth direction along the c-axis. The Raman spectrum elucidated the characteristic peaks of the mixed topological insulator. The broadening of Raman peaks exhibited the formation of Te-Bi-Te and Te-Sb-Te bonds and associated vibrational modes. The single crystals are characterized by magneto-transport measurements down to 2 K and up to 14 Tesla transverse magnetic field. The residual resistance ratio (R200 K/R0 K) is found to be 3.64, which endorses the metallic nature of the synthesized crystal. The relative resistance turns out to be higher for the mixed TI than the pure TIs i.e., Bi$ _2$ Te$ _3$ or Sb$ _2$ Te$ _3$ . The lower Debye temperature (82.64 K) of BiSbTe$ _3$ connotes the presence of effective electron-phonon interaction at quite low temperatures in comparison to pure TI, which explains the observed suppression in magnetoresistance (MR) for the mixed TI. At 2 K, an MR of 150 percent is observed for BiSbTe$ _3$ , which is suppressed in contrast to the pure TIs i.e., Bi$ _2$ Te$ _3$ or Sb$ _2$ Te$ _3$ . Though the MR% is suppressed significantly, its non-saturating linear behavior indicates the topological nature of the studied mixed TI. The modified Hikami-Larkin-Nagaoka (HLN) equation analysis of magneto-conductivity of mixed TI revealed that the conductivity has not only a surface states driven 2D component but also contributions from the bulk charge carriers and quantum scattering.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
18 Pages Text + Figs Accepted JMSE
First-Passage-Time Asymmetry for Biased Run-and-Tumble Processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-02 20:00 EDT
Yonathan Sarmiento, Benjamin Walter, Debraj Das, Samvit Mahapatra, Édgar Roldán, Rosemary J. Harris
We explore first-passage phenomenology for biased active processes with a renewal-type structure, focusing in particular on paradigmatic run-and-tumble models in both discrete and continuous state spaces. In general, we show there is no symmetry between distributions of first-passage times to symmetric barriers positioned in and against the bias direction; however, we give conditions for such a duality to be restored asymptotically (in the limit of a large barrier distance) and highlight connections to the Gallavotti-Cohen fluctuation relation and the method of images. Our general trajectory arguments are supported by exact analytical calculations of first-passage-time distributions for asymmetric run-and-tumble processes escaping from an interval of arbitrary width, and these calculations are confirmed with high accuracy via extensive numerics. Furthermore, we quantify the degree of violation of first-passage duality using Kullback-Leibler divergence and signal-to-noise ratios associated with the first-passage times to the two barriers. We reveal an intriguing dependence of such measures of first-passage asymmetry on the underlying tumbling dynamics which may inspire inference techniques based on first-passage-time statistics in active systems.
Statistical Mechanics (cond-mat.stat-mech)
45 pages, 11 figures
Localized atomic vibrations caused by point impurity in long chains of noble gas atoms adsorbed in outer grooves of carbon nanobundle
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
E.V. Manzhelii, S.B. Feodosyev
The characteristics of discrete vibrational levels caused by a point three-parameter substitutional impurity in long linear chain of inert gas atoms adsorbed in groove on the surface of carbon nanobundle are studied. The impurity atom differs from the atoms of the chain in the following parameters: the mass, the parameter of interaction with neighboring atoms and the parameter of interaction with the substrate. Analytical expressions for the frequencies of the localized vibrations and the intensities of these vibrations are obtained. The conditions for the existence of localized vibrations both below and above the band of the quasi-continuous spectrum of the adsorbed chain are also obtained.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 2 figures
Dynamical thermal near-field routing with the non-reciprocal Weyl semi-metal Co$_3$Sn$_2$S$_2$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
We demonstrate theoretically the non-reciprocal heating dynamics of two nanoparticles in the vicinity of a substrate all made of the ferromagnetic Weyl semi-metal Co$ _3$ Sn$ _2$ S$ _2$ . We show that the thermal routing effect is due to a spin-spin coupling mechanism between the nanoparticle resonances and the non-reciprocal surface modes of the substrate. Our numerical results indicate that the non-reciprocal heating effect is on the order of 22.5% of the applied temperature differences. This strong rounting effect paves the way for first experimental realizations employing Weyl semi-metals and applications in nanoscale thermal management.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Strain-induced manipulation of non-collinear antiferromagnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Mithuss Tharmalingam, Feodor Svetlanov Konomaev, Kjetil M. D. Hals
In recent years, there has been growing interest in harnessing non-collinear antiferromagnets (NCAFMs) for applications in antiferromagnetic spintronics. A key requirement for their practical use is the ability to control the spin order in a reliable and tunable manner. In this work, we investigate how the spin order in kagome antiferromagnets – an important class of NCAFMs – can be manipulated via strain. Starting from a microscopic spin Hamiltonian, we derive an effective action for the kagome antiferromagnet that captures the coupling between the spin order and the system’s strain tensor. At the microscopic level, this coupling arises from strain-induced modifications of the Dzyaloshinskii-Moriya and exchange interactions. Using this effective description, we explore two strain-driven phenomena: (1) strain-induced switching of the antiferromagnetic spin order and (2) the piezomagnetic response. We numerically show that strain facilitates thermally assisted switching between spin configurations of opposite chirality. Specifically, we find that uniform tensile and compressive strain govern both the average switching time and the preferred switching direction between chiral states. Furthermore, we demonstrate that strain induces a net magnetization and provide an experimentally testable prediction of this effect for a typical NCAFM. Our results provide a theoretical framework for modeling strain-induced manipulation of kagome antiferromagnets, underscoring strain as a promising route for functional control of NCAFMs.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
10 pages, 5 figures
Accelerated ultrafast demagnetization of an interlayer-exchange-coupled Co/Mn/Co trilayer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Jendrik Gördes, Ivar Kumberg, Chowdhury S. Awsaf, Marcel Walter, Tauqir Shinwari, Sangeeta Thakur, Sangeeta Sharma, Christian Schüßler-Langeheine, Niko Pontius, Wolfgang Kuch
We investigate the ultrafast magnetization dynamics of an interlayer-exchange-coupled Co/Mn/Co trilayer system after excitation with an ultrafast optical pump. We probe element- and time-resolved ferromagnetic order by X-ray magnetic circular dichroism in resonant reflectivity. We observe an accelerated Co demagnetization time in the case of weak total parallel interlayer coupling at 9.5 ML Mn thickness for antiparallel alignment of both Co layers compared to parallel alignment as well as for parallel alignment in the case of strong parallel interlayer coupling at 11 ML of Mn. From ab initio time-dependent density functional theory calculations, we conclude that optically induced intersite spin transfer of spin-polarized electrons from Co into Mn acts as a decay channel to enhance and accelerate ultrafast demagnetization. This spin transfer can only take place in case of a collinear Mn spin structure. We argue that this is the case for antiparallel alignment of both Co layers at 9.5 ML Mn thickness and parallel alignment in case of 11 ML of Mn. Our results point out that an antiferromagnetic spacer layer and its spin structure have a significant effect on the magnetization dynamics of adjacent ferromagnetic layers. Our findings provide further insight into fundamental mechanisms of ultrafast demagnetization and may lead to improve dynamics in multilayered systems for faster optical switching of magnetic order.
Materials Science (cond-mat.mtrl-sci)
Quantum-Ready Microwave Detection with Scalable Graphene Bolometers in the Strong Localization Regime
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Yu-Cheng Chang (1), Federico Chianese (2), Naveen Shetty (2), Johanna Huhtasaari (2), Aditya Jayaraman (2), Joonas T. Peltonen (1), Samuel Lara-Avila (2), Bayan Karimi (1 and 3), Andrey Danilov (2), Jukka P. Pekola (1), Sergey Kubatkin (2 and 4) ((1) Pico group, QTF Centre of Excellence, Department of Applied Physics, Aalto University, Finland, (2) Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden, (3) Pritzker School of Molecular Engineering, University of Chicago, USA, (4) InstituteQ, the Finnish Quantum Institute, Aalto University, Finland)
Exploiting quantum interference of charge carriers, epitaxial graphene grown on silicon carbide emerges as a game-changing platform for ultra-sensitive bolometric sensing, featuring an intrinsic resistive thermometer response unmatched by any other graphene variant. By achieving low and uniform carrier densities, we have accessed a new regime of strong charge localization that dramatically reduces thermal conductance, significantly enhancing bolometer performance. Here we present scalable graphene-based bolometers engineered for detecting GHz-range photons, a frequency domain essential for superconducting quantum processors. Our devices deliver a state-of-the-art noise equivalent power of 40 zW$ /\sqrt{\rm Hz}$ at $ T=40$ mK, enabled by the steep temperature dependence of thermal conductance, $ G_{\rm th}\sim T^4$ for $ T<100$ mK. These results establish epitaxial graphene bolometers as versatile and low-back-action detectors, unlocking new possibilities for next-generation quantum processors and pioneering investigations into the thermodynamics and thermalization pathways of strongly entangled quantum systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Instrumentation and Detectors (physics.ins-det)
Hydrogen defects and band alignment in metal-organic frameworks
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Band alignment, namely the prediction of band-edge positions of semiconductors and insulators in aqueous solutions, is an important problem in physics and chemistry. Such a prediction is especially challenging for complex materials. Here we present an approach to align band structure of metal-organic frameworks (MOFs) on an absolute energy scale which can be used for direct comparison with experiments. Hydrogen defects are used as probes into the chemical bonding of the covalently bonded hybrid materials. An effective defect energy level, defined as the average of the charge-state transition levels of the defects at the linker and at the secondary building unit, is identified as a charge neutrality level to align band structures. This level captures subtle chemical details at both the organic and inorganic building blocks and provides results that are in agreement with experiments in a wide range of different MOFs. We also compare with results obtained from using other approaches involving surface calculations and average pore-center electrostatic potentials.
Materials Science (cond-mat.mtrl-sci)
13 pages, 12 figures, 2 tables
Detecting the axion field with waveguide apparatus
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
André H. Gomes, Winder A. Moura-Melo
We demonstrate that a conventional hollow conductor waveguide filled with a material exhibiting the coexistence of chiral magnetic and anomalous quantum Hall effects supports the propagation of transverse electromagnetic modes within its interior. This simple setup provides an optically feasible and direct method to probe the simultaneous presence of these phenomena, potentially enabling the detection of the axion field in the condensed matter realm.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), High Energy Physics - Phenomenology (hep-ph), Optics (physics.optics)
Comments are welcome!
Weak localization as probe of spin-orbit-induced spin-split bands in bilayer graphene proximity coupled to WSe$_2$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
E. Icking, F. Wörtche, A.W. Cummings, A. Wörtche, K. Watanabe, T. Taniguchi, C. Volk, B. Beschoten, C. Stampfer
Proximity coupling of bilayer graphene (BLG) to transition metal dichalcogenides (TMDs) offers a promising route to engineer gate-tunable spin-orbit coupling (SOC) while preserving BLG’s exceptional electronic properties. This tunability arises from the layer-asymmetric electronic structure of gapped BLG, where SOC acts predominantly on the layer in contact with the TMD. Here, we present high-quality BLG/WSe$ _2$ devices with a proximity-induced SOC gap and excellent electrostatic control. Operating in a quasi-ballistic regime, our double-gated heterostructures allow to form gate-defined p-n-p cavities and show clear weak anti-localization (WAL) features consistent with Rashba-type SOC. At lower hole densities, a transition to weak localization (WL) is observed, signaling transport through a single spin-split valence band. These findings - in agreement with calculations - provide direct spectroscopic evidence of proximity-induced spin-split band in BLG and underscore the potential of BLG/TMD heterostructures for spintronics and spin-based quantum technologies.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
7 pages, 4 figures
Nematic ordering in active fluids driven by substrate deformations: Mechanisms and patterning regimes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-02 20:00 EDT
Varun Venkatesh, Amin Doostmohammadi
The interplay between active matter and its environment is central to understanding emergent behavior in biological and synthetic systems. Here, we show that coupling active nematic flows to small-amplitude deformations of a compliant substrate can fundamentally reorganize the system’s dynamics. Using a model that combines active nematohydrodynamics with substrate mechanics, we find that contractile active nematics-normally disordered in flat geometries-undergo a sharp transition to long-range orientational order when the environment is deformable. This environmentally induced ordering is robust and enables distinct patterning regimes, with wrinkle morphologies reflecting the nature of the active stresses. Our results reveal a generic mechanism by which mechanical feedback from soft environments can lead to ordering in active systems.
Soft Condensed Matter (cond-mat.soft)
6 pages, 4 figures
Structural Stability of Sulfur Depleted MoS2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Ygor M. Jaques, Cristiano F. Woellner, Lucas M. Sassi, Marcelo L. Pereira Jr, Luiz A. Ribeiro Jr, Pulickel M. Ajayan, Douglas S. Galvão
Transition metal dichalcogenides (TMDs), particularly monolayer MoS2, have received increased attention in materials science and have been exploited in diverse applications from photonics to catalysis. Defects in TMDs play a crucial role in modulating their properties, and understanding defect-induced dynamics is of great importance. This study investigates the dynamics of sulfur depletion in defective monolayer MoS2, which yields stable MoS monolayers. Various defect sizes, temperature regimes, and substrate effects were investigated. Through comprehensive classical molecular (ReaxFF) molecular dynamics (MD) and ab initio MD (AIMD) simulations, we elucidate the dynamics of sulfur vacancy formation in MoS2 lattices. After removing all sulfur atoms from the top layer, several sulfur atoms from the bottom layer spontaneously migrate to the top layer as a response to increase structural stability, thus creating a MoSx alloy. These findings deepen our understanding of defect dynamics in TMDs, offering valuable insights into the controlled engineering of their properties for nanotechnology applications.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
19 pages
Magnetoimpedance properties of CoNbZr, multilayer CoNbZr/Au and multilayer NiFe/Au thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Indujan Sivanesarajah, Leon Abelmann, Uwe Hartmann
Thin-film magnetic sensors using the giant magnetoimpedance (GMI) effect show great promise for sensitive low-field magnetic measurements. Optimising sensor performance requires a thorough understanding of the properties of various soft magnetic materials. This study examines the electric, magnetic, and GMI properties of sputtered single-layer amorphous CoNbZr, multilayer amorphous CoNbZr/Au, and crystalline NiFe/Au thin films. GMI measurements reveal distinct ferromagnetic resonance (FMR) frequencies: 1.4 GHz for CoNbZr, 0.7 GHz for CoNbZr/Au, and 0.5 GHz for NiFe/Au. Au interlayers improve the GMI response, increasing the GMI ratio by 50% and reducing FMR frequency compared to single-layer CoNbZr. The highest GMI ratio of 300% occurs in a 20 $ \mu$ m x 5000 $ \mu$ m CoNbZr/Au strip at 1.8 GHz under 2 mT, while NiFe/Au exhibits 280% at 4 mT. These differences are linked to variations in in-plane demagnetising factors and saturation magnetisations, emphasising the role of material and geometry in GMI sensor performance.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Finite-time scaling on low-dimensional map bifurcations
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-02 20:00 EDT
Daniel A. Martin, Qian-Yuan Tang, Dante R. Chialvo
Recent work has introduced the concept of finite-time scaling to characterize bifurcation diagrams at finite times in deterministic discrete dynamical systems, drawing an analogy with finite-size scaling used to study critical behavior in finite systems. In this work, we extend the finite-time scaling approach in several key directions. First, we present numerical results for 1D maps exhibiting period-doubling bifurcations and discontinuous transitions, analyzing selected paradigmatic examples. We then define two observables, the finite-time susceptibility and the finite-time Lyapunov exponent, that also display consistent scaling near bifurcation points. The method is further generalized to special cases of 2D maps including the 2D Chialvo map, capturing its bifurcation between a fixed point and a periodic orbit, while accounting for discontinuities and asymmetric periodic orbits. These results underscore fundamental connections between temporal and spatial observables in complex systems, suggesting new avenues for studying complex dynamical behavior.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Adaptation and Self-Organizing Systems (nlin.AO), Neurons and Cognition (q-bio.NC)
Emergent Dynamics of Active Systems on Curved Environments
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-02 20:00 EDT
Euan D. Mackay, Giulia Janzen, D. A. Matoz Fernandez, Rastko Sknepnek
Curvature plays a central role in the proper function of many biological processes. With active matter being a standard framework for understanding many aspects of the physics of life, it is natural to ask what effect curvature has on the collective behaviour of active matter. In this paper, we use the classical theory of surfaces to explore the active motion of self-propelled agents confined to move on a smooth curved two-dimensional surface embedded in Euclidean space. Even without interactions and alignment, the motion is non-trivially affected by the presence of curvature, leading to effects akin, e.g.\ to gravitational lensing and tidal forces. Such effects can lead to intermittent trapping of particles and profoundly affect their flocking behaviour.
Soft Condensed Matter (cond-mat.soft)
Polariton-mediated light emission induced by electric current flow in nanostructured polyaniline
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Jerzy J. Langer, Ewelina Frackowiak, Katarzyna Ratajczak
We present here a new mechanism of light emission induced by the electric current in polyaniline micro- and nanostructures. This process involves the formation of excitons, exciton-polaritons and finally an exciton-polariton condensate, leading to laser-like emission.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
16 pages
Spin-dependent transport through edge states in 2D semi-Dirac materials with Rashba spin-orbit coupling and band inversion
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-02 20:00 EDT
Marta García-Olmos, Yuriko Baba, Alexander López, Mario Amado, Rafael A. Molina
We investigate the bulk-boundary correspondence in two-dimensional type-I semi-Dirac materials with band inversion and Rashba spin-orbit coupling. Employing a dimensional reduction framework, we identify the Zak phase along the quadratically dispersing direction as a topological invariant that captures the presence of edge states. In the non-trivial topological regime, systems with finite width exhibit energy-dependent edge states that are topologically protected only at specific momenta. At kx equal to zero, symmetry-protected edge states emerge, analogous to the Rashba-free case. At finite kx, the interplay of spin-orbit coupling and band structure gives rise to spin-dependent edge states, localized on specific edges based on its spin and particle-hole character. We compute spin-resolved conductance through these edge channels and observe robust, tunable oscillations attributable to spin precession induced by the effective Rashba magnetic field. These results reveal how spin-orbit interactions enrich the edge physics of semi-Dirac systems and provide a platform for spintronic control in anisotropic topological materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
First principles computations of the Stark shift of a defect-bound exciton: the case of the T center in silicon
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Louis Alaerts, Yihuang Xiong, Sinéad M. Griffin, Geoffroy Hautier
The T center in silicon has recently drawn a lot of attention for its potential in quantum information science. The sensitivity of the zero-phonon line (ZPL) to electrical field was recently investigated by a combination of different experimental methods but there is still no first principles study on the Stark shift of the T center. Dealing with the defect-bound exciton nature of the excited state is particularly challenging using density functional theory because of the large spatial delocalization associated with the wavefunction. Here, we tackle this issue by performing a convergence study over the supercell size. We obtain an exciton binding energy of 28.5meV, in good agreement with experimental results. We then calculate the Stark shift through the dipole moment change of the ZPL transition of the T center using the modern theory of polarization formalism and find a modest linear coefficient of $ \Delta \mu$ =0.79D along X and $ \Delta \mu$ =0.03D along Y. We discuss our results in light of the recent experimental measurements of the Stark shift. Our analysis suggests that bound-exciton defects could be particularly sensitive to local field effect as a result of their large spatial extent.
Materials Science (cond-mat.mtrl-sci)
11 pages, 9 figures
Emergent boundary supersymmetry in a one dimensional superconductor
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
Parameshwar R. Pasnoori, Patrick Azaria, Colin Rylands, Natan Andrei
The interplay between bulk properties and boundary conditions in one-dimensional quantum systems, gives rise to many intriguing phenomena. These include the emergence of zero energy modes which are of significant interest to a variety of fields. In this work we investigate the presence of such zero modes in cases where the boundary conditions are dynamical and arise due to the coupling to some quantum degrees of freedom. In particular, we study a one-dimensional spin-singlet superconductor, modeled by the Gross-Neveu field theory, coupled to spin $ \frac{1}{2}$ magnetic impurities at its boundaries via a spin-exchange interaction. We solve the model exactly for arbitrary values of the bulk and the impurity coupling strengths using nested coordinate Bethe ansatz and show that the system exhibits a rich boundary phase structure. For a range of couplings, the low energy degrees of freedom form irreducible representations of the supersymmetric $ spl(2,1)\otimes spl(2,1)$ algebra which become degenerate at a specific point, indicating the emergence of supersymmetry in the low energy boundary degrees of freedom. We show that at the supersymmetric point there exist exact zero energy modes that map one ground state with the other. We express these in terms of the generators of the algebra.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con), Mathematical Physics (math-ph)
Accurate grain boundary plane distributions for textured microstructures from stereological analysis of orthogonal two-dimensional electron backscatter diffraction orientation maps
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Martin Folwarczny, Ao Li, Rushvi Shah, Aaron Chote, Alexandra C. Austin, Yimin Zhu, Gregory S. Rohrer, Michael A. Jackson, Souhardh Kotakadi, Katharina Marquardt
We present a method for obtaining qualitatively accurate grain boundary plane distributions (GBPD) for textured microstructures using a stereological calculation applied to two-dimensional electron backscatter diffraction (EBSD) orientation maps. Stereology, applied to 2D EBSD orientation maps, is currently the fastest method of obtaining GBPDs. Existing stereological methods are not directly applicable to textured microstructures because of the biased viewing perspectives for different grain boundary types supplied from a single planar orientation map. The method presented in this work successfully removes part of this bias by combining data from three orthogonal EBSD orientation maps for stereology. This is shown here to produce qualitatively correct GBPDs for heavily textured synthetic microstructures with hexagonal and tetragonal crystal symmetries. Synthetic microstructures were generated to compare the stereological GBPD to a known ground truth, as the true GBPD could be obtained from a triangular mesh of the full grain boundary network in 3D. The triangle mesh data contained all five macroscopic parameters to fully describe the grain boundary structure. It was observed that our stereological method overestimated the GBPD anisotropy. However, qualitative analysis of the GBPD remains useful. Furthermore, it was found that combining data from three orthogonal sections gives reliable results when sectioning the texture’s primary axes.
Materials Science (cond-mat.mtrl-sci)
Ultrafast electron dynamics upon above band-gap excitation in epitaxial LaFeO$_3$(001) thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
Friederike Elisa Wührl, Antonia Rieche, Anne Oelschläger, Kathrin Dörr, Wolf Widdra
Strong electron correlations in perovskite oxides give rise to rich and often unexpected electronic phenomena. In this study, we present a comprehensive surface-science investigation of epitaxial thin films of the charge-transfer insulator LaFeO$ 3$ (001). The characterization includes low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), and photoemission spectroscopy. We map both the occupied and unoccupied electronic states using two-photon photoemission (2PPE) spectroscopy. Furthermore, we probe electron dynamics through an ultraviolet-ultraviolet (UV-UV) pump-probe experiment, exciting electrons from hybridized O~$ 2p$ /Fe $ 3d$ states to Fe minority-spin states above the band gap. Our results reveal three distinct unoccupied states, which we assign to Fe $ t{2g\downarrow}$ , Fe $ e_{g\downarrow}$ , and La $ 5d$ orbitals. Notably, the conduction band minimum exhibits a biexponential decay with time constants of 39,fs and 1100,fs, suggesting the presence of two independent decay pathways.
Materials Science (cond-mat.mtrl-sci)
Closed-form survival probabilities for biased random walks at arbitrary step number
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-02 20:00 EDT
Debendro Mookerjee, Sarah Kostinski
We present a closed-form expression for the survival probability of a biased random walker to first reach a target site on a 1D lattice. The expression holds for any step number $ N$ and is computationally faster than non-closed-form results in the literature. Because our result is exact even in the intermediate step number range, it serves as a tool to study convergence to the large $ N$ limit. We also obtain a closed-form expression for the probability of last passage. In contrast to predictions of the large $ N$ approximation, the new expression reveals a critical value of the bias beyond which the tail of the last-passage probability decays monotonically.
Statistical Mechanics (cond-mat.stat-mech), Data Analysis, Statistics and Probability (physics.data-an)
Cryogenic scanning photocurrent spectroscopy for materials responses to structured optical fields
New Submission | Other Condensed Matter (cond-mat.other) | 2025-06-02 20:00 EDT
Duxing Hao, Chun-I Lu, Ziqi Sun, Yu-Chen Chang, Wen-Hao Chang, Ye-Ru Chen, Akiyoshi Park, Beining Rao, Siyuan Qiu, Yann-Wen Lan, Ting-Hua Lu, Nai-Chang Yeh
Circular dichroism spectroscopy is known to provide important insights into the interplay of different degrees of freedom in quantum materials, and yet spectroscopic study of the optoelectronic responses of quantum materials to structured optical fields, such as light with finite spin and orbital angular momentum, has not yet been widely explored, particularly at cryogenic temperature. Here we demonstrate the design and application of a novel instrument that integrates scanning spectroscopic photocurrent measurements with structured light of controlled spin and orbital angular momentum. For structured photons with wavelengths between 500 nm to 700 nm, this instrument can perform spatially resolved photocurrent measurements of two-dimensional materials or thin crystals under magnetic fields up to $ \pm$ 14 Tesla, at temperatures from 300 K down to 3 K, with either spin angular momentum $ \pm \hbar$ ororbital angular momentum $ \pm \ell \hbar$ (where $ \ell$ =1,2,3… is the topological charge), and over a (35 $ \times$ 25) $ \mu m^2$ area with ~ 1 $ \mu m$ spatial resolution. These capabilities of the instrument are exemplified by magneto-photocurrent spectroscopic measurements of monolayer 2H-$ MoS_2$ field-effect transistors, which not only reveal the excitonic spectra but also demonstrate monotonically increasing photocurrents with increasing |$ \ell $ | as well as excitonic Zeeman splitting and an enhanced Landé g-factor due to the enhanced formation of intervalley dark excitons under magnetic field. These studies thus demonstrate the versatility of the scanning photocurrent spectrometry for investigating excitonic physics, optical selection rules, and optoelectronic responses of novel quantum materials and engineered quantum devices to structured light.
Other Condensed Matter (cond-mat.other), Instrumentation and Detectors (physics.ins-det)
Study of the structural and electronic properties of the Heusler Co2FeGe alloy by DFT approach
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-02 20:00 EDT
A. Jamraoui, Y. Selmani, A. Jabar, L. Bahmad
In this work we reported the structural and electronic properties of the Heusler compound Co2FeGe using the AKAI-KKR code under the GGA approximation. We established that this material presents not only magnetic character but also has a metallic behavior. Our calculations have been conducted using the DFT method in the framework of the AKAI-KKR code. This study enabled us to define certain characteristics and initial parameters for creating a model of the system. The method used allowed us to apply fundamental concepts to the studied system in the form of modeling. The main results, of the studied Heusler compound Co2FeGe are: i) this material is magnetic; ii) The band structure of the material predicts a metallic character; iii) the origin of magnetism comes mainly from the transition metals Co and Fe atoms. These results, assure that the studied quaternary Heusler Co2FeGe stands for a strong candidate for different spintronics applications.
Materials Science (cond-mat.mtrl-sci)
Nematicity in iron pnictides: phase competition and emergent symmetry
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-02 20:00 EDT
Yiming Wang, Changle Liu, Shan Wu, Jianda Wu, Qimiao Si, Rong Yu
The phase diagram of iron-based superconductors contains a host of electronic orders, which are intimately connected with their superconductivity. Here we analyze the fluctuations of one type of nematic order in another. Our analysis leads to an emergent U(1) symmetry at a first-order transition between a nematic phase and a $ C_4$ -symmetric charge-ordered phase. We characterize the continuous symmetry in terms of a certain hidden Lie algebra that links the different orders. This emergent symmetry leads to a Goldstone mode at the transition and causes softening of excitations in the nematic and charge sectors near the transition. The underlying physics bears a resemblance to the anisotropic XZ spin model, with the nematic order and charge $ C_4$ order parameters playing the roles of the $ x$ and $ z$ components of the magnetization vector, respectively. We provide the experimental evidence in support of the proposed effects, and discuss the general implications of our results for the physics of iron-based superconductors and other correlated systems.
Strongly Correlated Electrons (cond-mat.str-el)
6+11 pages, 3+2 figures
Active Gaussian Network Model: a non-equilibrium description of protein fluctuations and allosteric behavior
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-02 20:00 EDT
Giulio Costantini, Lorenzo Caprini, Umberto Marini Bettolo Marconi, Fabio Cecconi
Understanding the link between structure and function in proteins is fundamental in molecular biology and proteomics. A central question in this context is whether allostery - where the binding of a molecule at one site affects the activity of a distant site - emerges as a further manifestation of the intricate interplay between structure, function, and intrinsic dynamics. This study explores how allosteric regulation is modified when intrinsic protein dynamics operate under out-of-equilibrium conditions. To this purpose, we introduce a simple nonequilibrium model of protein dynamics, inspired by active matter systems, by generalizing the widely employed Gaussian Network Model (GNM) to incorporate non-thermal effects. Our approach underscores the advantage of framing allostery as a causal process by using, as a benchmark system, the second PDZ domain of the human phosphatase hPT1E that mediates protein-protein interactions. We employ causal indicators, such as response functions and transfer entropy, to identify the network of PDZ2 residues through which the allosteric signal propagates across the protein structure. These indicators reveal specific regions that align well with experimental observations. Furthermore, our results suggest that deviations from purely thermal fluctuations can significantly influence allosteric communication by introducing distinct timescales and memory effects. This influence is particularly relevant when the allosteric response unfolds on timescales incompatible with relaxation to equilibrium. Accordingly, non-thermal fluctuations may become essential for accurately describing protein responses to ligand binding and developing a comprehensive understanding of allosteric regulation.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)