CMP Journal 2025-08-01
Statistics
Nature Materials: 3
Nature Nanotechnology: 2
Physical Review Letters: 3
Physical Review X: 2
Review of Modern Physics: 1
arXiv: 69
Nature Materials
Memsensing by surface ion migration within Debye length
Original Paper | Nanoscience and technology | 2025-07-31 20:00 EDT
Ruihan Guo, Qixin Feng, Ke Ma, Gi-Hyeok Lee, Moniruzzaman Jamal, Xiao Zhao, Karen C. Bustillo, Jiawei Wan, Duncan S. Ritchie, Linbo Shan, Yuhang Cai, Jiachen Li, Jack Shen, Kaichen Dong, Ru Huang, Yimao Cai, Feng Wang, Miquel Salmeron, Haimei Zheng, Matthew Sherburne, Mary Scott, Wanli Yang, Mark Asta, Kechao Tang, Junqiao Wu
Integration between electronics and biology is often facilitated by iontronics, where ion migration in aqueous media governs sensing and memory. However, the Debye screening effect limits electric fields to the Debye length, the distance over which mobile ions screen electrostatic interactions, necessitating external voltages that constrain the operation speed and device design. Here we report a high-speed in-memory sensor based on vanadium dioxide (VO2) that operates without an external voltage by leveraging built-in electric fields within the Debye length. When VO2 contacts a low-work-function metal (for example, indium) in a salt solution, electrochemical reactions generate indium ions that migrate into the VO2 surface under the native electric field, inducing a surface insulator-to-metal phase transition of VO2. The VO2 conductance increase rate reflects the salt concentration, enabling in-memory sensing, or memsensing of the solution. The memsensor mimics Caenorhabditis elegans chemosensory plasticity to guide a miniature boat for adaptive chemotaxis, illustrating low-power aquatic neurorobotics with fewer memory units.
Nanoscience and technology, Sensors and biosensors
Defect repairing in lead bromide perovskite single crystals with biasing and bromine for X-ray photon-counting detectors
Original Paper | Electronic devices | 2025-07-31 20:00 EDT
Mingze Li, Shaojie Wang, Allen Wood, Jason D. Yeager, Sergei P. Stepanoff, Jackson C. Adler, Zhifang Shi, Jian Wang, Zhijun Li, Douglas E. Wolfe, Jinsong Huang
The benign defect nature of iodide perovskites has gained strong momentum in understanding and application in perovskite devices; however, the understanding of defects in bromide perovskites remains elusive. Here we demonstrate that the biasing of lead bromide perovskite crystals, which has been broadly deemed as detrimental to device performance, can efficiently repair bulk point defects in them. The biasing results in a significant bromide-vacancy reduction, starting from the cathode side and progressing to the anode side across the whole crystal. The vacancies can diffuse back after several weeks of storage. By introducing bromine in crystal growth, we permanently reduce the bromide-vacancy concentration by ~1,000 times, enhancing charge transport and stability in formamidinium lead bromide crystals. The optimized formamidinium lead bromide detector exhibited a very high detection performance including an energy resolution of 0.7% under 137Cs 662-keV γ-rays measured under room-temperature, high-performance iodine K-edge X-ray detection at low agent concentrations and dramatically improved radiation hardness.
Electronic devices, Sensors and biosensors
Albumin-recruiting lipid nanoparticle potentiates the safety and efficacy of mRNA vaccines by avoiding liver accumulation
Original Paper | Drug delivery | 2025-07-31 20:00 EDT
Yunxuan Feng, Wanbo Tai, Pei Huang, Shaolong Qi, Xinyang Yu, Mengfei Li, Mengyao Li, Miya Zhang, Fangfang Cao, Xiaomin Gao, Kai Yang, Bing Bai, Jiaqi Lei, Meiqi Cheng, Yongcan Li, Gong Cheng, Xiaoyuan Chen, Guocan Yu
The advent of mRNA vaccines represents a breakthrough in the realm of cancer therapy and the prevention of infectious disease. Nevertheless, traditional lipid nanoparticle (LNP)-based mRNA vaccines can accumulate in the liver post-intramuscular injection, posing a risk of hepatotoxicity and reducing efficacy. Here we develop an albumin-recruiting LNP system with high lymphatic drainage and no accumulation in hepatic tissue to potentiate the efficacy and safety of mRNA vaccines. We construct a library of ionizable lipids with albumin-binding capacity as alternatives to traditional polyethylene-glycol-conjugated lipid. We identify an Evans blue-modified lipid-based LNP (EB-LNP) formulation that shows high in vivo expression, albumin-facilitated transport through intramuscular lymphatic vessels to the lymph nodes, high internalization by dendritic cells and low penetration into intramuscular blood vessels, thereby avoiding liver accumulation. EB-LNP-based mRNA vaccines demonstrate excellent antitumour and antiviral efficacy, resulting in strong cellular and humoral immune responses, including the robust activation of cytotoxic T lymphocytes and production of neutralizing antibodies post-vaccination. Overall, this system shows promise as an effective and minimally toxic platform for the development of mRNA vaccines with high efficacy and safety.
Drug delivery, Preclinical research
Nature Nanotechnology
A roadmap for next-generation nanomotors
Review Paper | Biomaterials | 2025-07-31 20:00 EDT
Shuqin Chen, Donglei Emma Fan, Peer Fischer, Ambarish Ghosh, Kerstin Göpfrich, Ramin Golestanian, Henry Hess, Xing Ma, Bradley J. Nelson, Tania Patiño Padial, Jinyao Tang, Katherine Villa, Wei Wang, Li Zhang, Ayusman Sen, Samuel Sánchez
Since their discovery in 2004, there has been remarkable progress in research on nanomotors, from the elucidation of different propulsion mechanisms to the study of their collective behaviour, culminating in investigations into their applications in biomedicine and environmental remediation. This Perspective reviews this evolution in nanomotor research and discusses the key challenges ahead, including the need for developing advanced characterization techniques, precise motion control, materials innovation, theory and modelling, and translationally feasible in vivo biomedical applications. These challenges highlight the current limitations of synthetic nanomotors and point to exciting future opportunities to revolutionize theranostics and create ‘living’ hybrid systems. We introduce the concept of ‘systems materials’ to encompass interacting functional materials across length scales from molecular to macro. Thus, this Perspective aims to inspire future generations of researchers to advance both fundamental understanding and practical breakthroughs, thereby engineering a paradigm shift in nanomotor research.
Biomaterials, Biomedical engineering, Electrocatalysis, Nanoparticles, Nanotechnology in cancer
An information ratchet improves selectivity in molecular recognition under non-equilibrium conditions
Original Paper | Supramolecular chemistry | 2025-07-31 20:00 EDT
Benjamin M. W. Roberts, Erica Del Grosso, Emanuele Penocchio, Francesco Ricci, Leonard J. Prins
Molecular recognition is essential for controlling chemical processes, passing molecular instructions to elicit responses including structure formation, signalling and replication. Usually, the selectivity of molecular recognition is under thermodynamic control; however, when a higher fidelity is required, nature improves recognition selectivity by an error correction mechanism under an energy-dissipating kinetic-control regime. Here, exploiting DNA hybridization as a model, we present an abiotic example of an information ratchet mechanism that increases selectivity for the ‘correct’ duplex from 2:1 at equilibrium to 6:1 under energy-dissipating conditions. Structural asymmetry in the DNA strands introduces kinetic asymmetry in the reaction network, enabling enrichment under non-equilibrium conditions. We quantify the free-energy cost associated with enhanced selectivity using Shannon entropy formalism, finding that an increase in information of 0.33 bits is associated with at least 3.0 kJ mol-1 of free energy. Moreover, the minimalistic structures of our error reduction system demonstrates that biomachinery is not necessary to increase molecular recognition fidelities above the thermodynamically expected values, thereby pointing a way towards solving Eigen’s paradox.
Supramolecular chemistry, Theoretical chemistry
Physical Review Letters
Observation of Anomalous Information Scrambling in a Rydberg Atom Array
Research article | Information scrambling | 2025-07-31 06:00 EDT
Xinhui Liang, Zongpei Yue, Yu-Xin Chao, Zhen-Xing Hua, Yige Lin, Meng Khoon Tey, and Li You
Evidence that quantum information can get scrambled unconventionally in a chain of atoms could improve our understanding of quantum many-body dynamics.
Phys. Rev. Lett. 135, 050201 (2025)
Information scrambling, Quantum correlations in quantum information, Rydberg atoms & molecules, Trapped atoms, Correlation function measurements
Direct Constraints on Strongly Interacting Dark Matter from the James Webb Space Telescope
Research article | Dark matter direct detection | 2025-07-31 06:00 EDT
Peizhi Du, Rouven Essig, Bernard J. Rauscher, and Hailin Xu
Researchers have analyzed “blank” calibration images, seeking signs of dark matter moving through the telescope.
Phys. Rev. Lett. 135, 051002 (2025)
Dark matter direct detection, Particle dark matter
Dissipation Bounds the Coherence of Stochastic Limit Cycles
Research article | Nonequilibrium statistical mechanics | 2025-07-31 06:00 EDT
Davide Santolin and Gianmaria Falasco
Overdamped stochastic systems maintained far from equilibrium can display sustained oscillations with fluctuations that decrease with the system size. The correlation time of such noisy limit cycles expressed in units of the cycle period is upper-bounded by the entropy produced per oscillation. We prove this constraint for first-order nonlinear systems in arbitrary dimensions perturbed by weak, uncorrelated Gaussian noise. We then extend the result to important examples of more general stochastic dynamics, including electronic and chemical clocks, illustrating the practical relevance of the dissipation-coherence bound for electronic computing and thermodynamic inference.
Phys. Rev. Lett. 135, 057101 (2025)
Nonequilibrium statistical mechanics, Stochastic thermodynamics
Physical Review X
Lattice Vibrational Hierarchy and Mean-Free-Path Filtering in ${\mathrm{Bi}}{6}{\mathrm{Cu}}{2}{\mathrm{Se}}{4}{\mathrm{O}}{6}$ Superlattice Thermoelectrics
Research article | Thermoelectrics | 2025-07-31 06:00 EDT
Shulin Bai, Haonan Shi, Yi Wen, Yixuan Hu, Junqing Zheng, Yongxin Qin, Lizhong Su, Shibo Liu, Dongrui Liu, Tian Gao, Tao Hong, Xiang Gao, Fangyuan Zhu, Bingchao Qin, and Li-Dong Zhao
Bi₆Cu₂Se₄O₆ emerges as a promising air-stable n-type thermoelectric oxide, with unique lattice dynamics–like bismuth rattling and copper vibrations–offering new ways to enhance heat-to-electricity conversion.
Phys. Rev. X 15, 031033 (2025)
Thermoelectrics
Bootstrapping the Quantum Hall Problem
Research article | Composite fermions | 2025-07-31 06:00 EDT
Qiang Gao, Ryan A. Lanzetta, Patrick Ledwith, Jie Wang, and Eslam Khalaf
Relying on bootstrap methods from high-energy physics provides a way to study strongly interacting electrons in quantum Hall systems without constructing complex wave functions, revealing new insights into both gapped and gapless phases.
Phys. Rev. X 15, 031034 (2025)
Composite fermions, Fractional quantum Hall effect, Landau levels, Quantum many-body systems, Strongly correlated systems, Two-dimensional electron system, Density matrix methods, Numerical techniques, Symmetries in condensed matter
Review of Modern Physics
Photoinduced nonequilibrium states in Mott insulators
Research article | Light-matter interaction | 2025-07-31 06:00 EDT
Yuta Murakami, Denis Golež, Martin Eckstein, and Philipp Werner
The interplay between nonequilibrium physics and strong electronic correlations offers a unique platform for manipulating material properties, exploring novel optical responses, and uncovering quantum metastable phases. This review provides a comprehensive overview of recent advances in understanding the nonequilibrium dynamics of photoexcited Mott insulators–systems where strong interactions and a robust energy gap can give rise to rich and controllable phenomena. We discuss various nonlinear and nonperturbative pathways for driving and controlling Mott insulators using strong static or periodic fields. Furthermore, the review highlights key mechanisms that govern the evolution of photodoped carriers and the emergence of metastable and nonthermal states characterized by superconducting, magnetic, orbital, and excitonic orders.
Rev. Mod. Phys. 97, 035001 (2025)
Light-matter interaction, Photoinduced effect, Mott insulators, Nonequilibrium systems, Strongly correlated systems
arXiv
Spin-Polaron Mediated Superconductivity in Doped Chern Antiferromagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
Xuepeng Wang, J. F. Mendez-Valderrama, Johannes S. Hofmann, Debanjan Chowdhury
The study of interacting topological bands with a tunable bandwidth offers a unique platform to study the interplay of intertwined orders and emergent non-electronic excitations. Here we design a time-reversal symmetric and sign-problem-free electronic model with tunable Chern bands carrying valley-contrasting Chern number, interacting via competing (anti-)ferromagnetic interactions. Using numerically exact quantum Monte-Carlo computations, we analyze the many-body phase-diagram as a function of temperature and band filling fractions over a wide range of electronic bandwidth, interaction anisotropy, and an Ising spin-orbit coupling. At a commensurate filling of the Chern bands, the ground state hosts intra-valley ferromagnetic coherence and inter-valley antiferomagnetism, thus realizing an insulating Chern antiferromagnet (CAF). Upon doping, the ground-state develops superconductivity, but where the low-energy charged quasiparticles are composite objects – electrons dressed by multiple spin-flip excitations. These spin-polaron (or skyrmion) excitations persist in the presence of a weak spin-orbit coupling. In a companion article, we address the emergent symmetries and low-energy field-theoretic aspects of the problem and reveal the proximity to a deconfined quantum critical point. We end by providing a general outlook towards building microscopic connections with models of interacting moiré materials, including twisted bilayer graphene, where many of the ingredients considered here are naturally present.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Superconductivity (cond-mat.supr-con)
11 pages, 10 figures
Exciton Berryology
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Henry Davenport, Johannes Knolle, Frank Schindler
In translationally invariant semiconductors that host exciton bound states, one can define an infinite number of possible exciton Berry connections. These correspond to the different ways in which a many-body exciton state, at fixed total momentum, can be decomposed into free electron and hole Bloch states that are entangled by an exciton envelope wave function. Inspired by the modern theory of polarization, we define an exciton projected position operator whose eigenvalues single out two unique choices of exciton Berry phase and associated Berry connection - one for electrons, and one for holes. We clarify the physical meaning of these exciton Berry phases and provide a discrete Wilson loop formulation that allows for their numerical calculation without a smooth gauge. As a corollary, we obtain a gauge-invariant expression for the exciton polarisation at a given total momentum, i.e. the mean separation of the electron and hole within the exciton wave function. In the presence of crystalline inversion symmetry, the electron and hole exciton Berry phases are quantized to the same value and we derive how this value can be expressed in terms of inversion eigenvalues of the many-body exciton state. We then consider crystalline $ C_2 \mathcal{T}$ symmetry, for which no symmetry eigenvalues are available as it is anti-unitary, and confirm that the exciton Berry phase remains quantized and still diagnoses topologically distinct exciton bands. Our theory thereby generalizes the notion of shift excitons, whose exciton Wannier states are displaced from those of the non-interacting bands by a quantized amount, beyond symmetry indicators.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Tensor Network Representations for Intrinsically Mixed-State Topological Orders
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
Bader Aldossari, Sergey Blinov, Zhu-Xi Luo
Tensor networks are an efficient platform to represent interesting quantum states of matter as well as to compute physical observables and information-theoretic quantities. We present a general protocol to construct fixed-point tensor network representations for intrinsically mixed-state topological phases, which exhibit nontrivial topological phenomena and do not have pure-state counterparts. The method exploits the power of anyon condensation in Choi states and is applicable to the cases where the target states arise from pure-state topological phases subject to strong decoherence/disorders in the Abelian sectors. Representative examples include $ m^a e^b$ decoherence of $ \mathbb{Z}_N$ toric code, decohered non-Abelian $ S_3$ quantum double as well as pure $ Z$ /$ X$ decoherence of arbitrary CSS codes. An example of chiral topological phases which cannot arise from local commuting projector models are also presented.
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph), Quantum Physics (quant-ph)
15 pages, 10 figures
Higher-order Topological States in Chiral Split Magnons of Honeycomb Altermagnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Xuan Guo, Meng-Han Zhang, Dao-Xin Yao
We theoretically explore higher-order topological magnons in collinear altermagnets, encompassing a dimensional hierarchy ranging from localized corner modes to propagating hinge excitations. By employing antiferromagnetic interlayer coupling in bosonic Bogoliubov-de Gennes (BdG) Hamiltonian, our work reveals anisotropic surface states and spatially distributed hinge modes within AA-type stacking configurations. We track the adiabatic evolution of Wannier centers to identify the bulk-polarization with second-order topological magnon insulator (SOTMI), where various magnon spectra demonstrate symmetry-protected band structure beyond conventional topology. Harnessing the stability and propagative properties of hinge modes, our study offers a potential platform for magnonic quantum information processing in altermagnetic systems that performs energy-efficient logic operation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 pages, 3 figures
Quantum confinement effect in Sb thin films
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Anuradha Wijesinghe, Yongxi Ou, Anjali Rathore, Chandima Edirisinghe, Pradip Adhikari, An-Hsi Chen, Dustin Gilbert, Anthony Richardella, Nitin Samarth, Joon Sue Lee
Antimony (Sb), an element with strong spin-orbit coupling, is predicted to undergo a topological phase transition from a topological semimetal to a topological insulator as its dimensionality approaches the two-dimensional limit, driven by the quantum confinement effect. In this study, we investigate this transition in Sb thin films grown by molecular beam epitaxy, employing electrical transport measurements and angle-resolved photoemission spectroscopy (ARPES). Electrical transport measurements revealed signatures of a modified electronic band structure, including a Hall response with multiple carrier types, a decreasing carrier concentration, and a transition in the curvature of the longitudinal resistance from quadratic to linear with decreasing film thickness. Temperature-dependent magnetoresistance further showed weak antilocalization below 16 K, indicating strong spin-orbit coupling and suggesting the presence of non-trivial topological states. Analysis of the WAL characteristics revealed a single coherent conducting channel and a thickness-dependent change in the phase decoherence mechanism. Complementary ARPES measurements confirmed that reducing the film thickness lifts the conduction band at the M-point, consistent with the emergence of a band gap. These findings support theoretical predictions of a thickness-dependent band structure evolution driven by the quantum confinement effect, providing a foundation for further exploration of topological phase transitions in Sb as well as Bi1-xSbx. The realization of an elemental topological material with simplified stoichiometry and semiconductor compatibility presents a promising avenue for next-generation hybrid systems and applications in spintronics and quantum technologies.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
19 pages, 10 figures
Exceptional Andreev spectrum and supercurrent in p-wave non-Hermitian Josephson junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
We investigate the spectrum of Andreev bound states and supercurrent in a $ p$ -wave non-Hermitian Josephson junction (NHJJ) in one dimension. The studied NHJJ is composed of two topological $ p$ -wave superconductors connected by a non-Hermitian dissipative junction. Starting from the effective non-Hermitian Bogoliubov-de Gennes bulk Hamiltonian, we find that a pair of exceptional points emerge in the complex spectrum of Andreev quasi-bound states. The two exceptional points locate symmetrically with respect to phase difference $ \phi=\pi$ at zero real energy. Their separation is tunable by the non-Hermitian dissipation strength. By analyzing the non-Hermitian scattering process at the junction, we explicitly demonstrate the loss of quasiparticles through the decay of scattering amplitude probabilities. Furthermore, we obtain the supercurrent directly by the inelastic Andreev reflection amplitudes, which provides a more intuitive interpretation of transport properties in NHJJs. The supercurrent varies continuously as a function of $ \phi$ across the exceptional points. No enhancement of critical current is observed. We also generalize our analysis to mixed $ s$ -$ p$ wave NHJJ.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures
Exploring Many-Body Quantum Geometry Beyond the Quantum Metric with Correlation Functions: A Time-Dependent Perspective
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
The quantum geometric tensor and quantum Fisher information have recently been shown to provide a unified geometric description of the linear response of many-body systems. However, a similar geometric description of higher-order perturbative phenomena including nonlinear response in generic quantum systems is lacking. In this work, we develop a general framework for the time-dependent quantum geometry of many-body systems by treating external perturbing fields as coordinates on the space of density matrices. We use the Bures distance between the initial and time-evolved density matrix to define geometric quantities through a perturbative expansion. To lowest order, we derive a time-dependent generalization of the Bures metric related to the spectral density of linear response functions, unifying previous results for the quantum metric in various limits and providing a geometric interpretation of Fermi’s golden rule. At next order in the expansion, we define a time-dependent Bures-Levi-Civita connection for general many-body systems. We show that the connection is the sum of one contribution that is related to a second-order nonlinear response function, and a second contribution that captures the higher geometric structure of first-order perturbation theory. We show that in the quasistatic, zero-temperature limit for noninteracting fermions, this Bures connection reduces to the known expression for band-theoretic Christoffel symbols. Our work provides a systematic framework to explore many-body quantum geometry beyond the quantum metric and highlights how higher-order correlation functions can probe this geometry.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
28+epsilon pages
A Perturbative Approach to Symmetric Mass Generation
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
The Landau paradigm has been a powerful framework for understanding phase transitions involving spontaneous symmetry breaking. In contrast, phase transitions between two symmetric phases, where neither phase breaks any symmetry, remain less explored. One intriguing class of such transitions involves “symmetric mass generation” (SMG), where interactions drive a transition from a gapless symmetric phase to a gapped symmetric phase. In this work, we develop a controlled perturbative approach to study a class of such transitions, based on an $ \epsilon$ -expansion around the critical dimension where the SMG-inducing-interaction becomes marginal. Applying this method to two distinct models, we identify a single-parameter-tuned transition in each case, which we conjecture captures the universal critical behavior of the SMG transition in these models. We compute universal quantities associated with these transitions.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Lattice (hep-lat), High Energy Physics - Theory (hep-th)
6 + 27 pages, 8 figures
Quantitative Nonlinear Optical Polarimetry with High Spatial Resolution
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Albert Suceava, Sankalpa Hazra, Jadupati Nag, John Hayden, Safdar Imam, Zhiwen Liu, Abishek Iyer, Mercouri Kanatzidis, Susan Trolier-McKinstry, Jon-Paul Maria, Venkatraman Gopalan
Nonlinear optical microscopy such as in the optical second-harmonic generation (SHG) modality has become a popular tool today for probing materials in the physical and biological sciences. While imaging and spectroscopy are widely used in the microscopy mode, nonlinear polarimetry, which can shed light on materials’ symmetry and microstructure, is relatively underdeveloped. This is partly because quantitative analytical modeling of the optical SHG response for anisotropic crystals and films largely assumes low-numerical aperture (NA) focusing of light, where the plane-wave approximation is sufficient. Tight focusing provides unique benefits in revealing out-of-plane polarization responses, which cannot be detected by near-plane-wave illumination at normal incidence. Here, we outline a method for quantitatively analyzing SHG polarimetry measurements obtained under high-NA focusing within a microscope geometry. Experiments and simulations of a variety of standard samples, from single crystals to thin films, are in good agreement, including measured and simulated spatial SHG maps of ferroelectric domains. A solution to the inverse problem is demonstrated, where the spatial distribution of an SHG tensor with unknown tensor coefficient magnitudes is determined by experimentally measured polarimetry. The ability to extract the out-of-plane component of the nonlinear polarization in normal incidence is demonstrated, which can be valuable for high-resolution polarimetry of 2D materials, thin films, heterostructures, and uniaxial crystals with a strong out-of-plane response.
Copyright 2025 Optica Publishing Group. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved. this https URL
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
22 pages, 8 figures, supplemental document included
Optica 12, 1153-1166 (2025)
Realizing Nonreciprocal Linear Dichroism and Emission from Simple Media
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Thomas J. Ugras, Daniel J. Gracias, Oriol Arteaga, Richard D. Robinson
Reciprocity, the principle that a system response is identical in the forward path compared to the backward path, is a fundamental concept across physics, from electrical circuits and optics to acoustics and heat conduction. Nonreciprocity arises when this symmetry is broken, enabling directional-dependent behavior. In photonics, nonreciprocity allows control over the propagation of electromagnetic waves, essential for isolators and circulators. But achieving optical nonreciprocity typically requires complex metamaterials, exotic media, or strong external fields. Because of this, researchers have historically overlooked the possibility that readily available materials could support nonreciprocal optical behavior, assuming that conventional systems lack the ability to produce nonreciprocal behavior. In this work, we challenge that assumption by revisiting the light-matter interactions of chiroptic and linearly anisotropic media. Through Stokes-Mueller formalism we derive a simple analytical expression that predicts a pathway to nonreciprocal absorption and emission of orthogonal linear polarizations. We test this idea experimentally using solution-processed films of CdS, CdSe, and CdTe magic-size clusters that possess commensurate circular dichroism (CD) and linear dichroism (LD)values and find that they can support this effect, engineering films that exhibit nonreciprocal absorption and emission of linearly polarized light. Based on the derived expressions and experiments, several design rules are presented. Our findings reveal that nonreciprocal linear dichroism and emission can be achieved in readily processable, macroscopically symmetric materials by harnessing chiral-linear optical interference. This work opens new opportunities for scalable, polarization-based photonic control for direction-dependent optical routing, optical logic, and polarization-multiplexed information encoding.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
Local Inversion Symmetry Breaking and Thermodynamic Evidence for Ferrimagnetism in Fe3GaTe2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Sang-Eon Lee, Yue Li, Yeonkyu Lee, W. Kice Brown, PeiYu Cai, Jinyoung Yun, Chanyoung Lee, Alex Moon, Lingrui Mei, Jaeyong Kim, Yan Xin, Julie A. Borchers, Thomas W. Heitmann, Matthias Frontzek, William D. Ratcliff, Gregory T. McCandless, Julia Y. Chan, Elton J. G. Santos, Jeehoon Kim, Charudatta M. Phatak, Vadym Kulichenko, Luis Balicas
The layered compound Fe3GaTe2 is attracting attention due to its high Curie temperature, low dimensionality, and the presence of topological spin textures above room temperature, making Fe$ _3$ GaTe$ _2$ a good candidate for applications in spintronics. Here, we show, through transmission electron microscopy (TEM) techniques, that Fe$ _3$ GaTe$ _2$ single crystals break local inversion symmetry while maintaining global inversion symmetry according to X-ray diffraction. Coupled to the observation of Néel skyrmions via Lorentz-TEM, our structural analysis provides a convincing explanation for their presence in centrosymmetric materials. Magnetization measurements as a function of the temperature displays a sharp first-order thermodynamic phase-transition leading to a reduction in the magnetic moment. This implies that the ground state of Fe$ _3$ GaTe$ _2$ is globally ferrimagnetic and not a glassy magnetic state composed of ferrimagnetic, and ferromagnetic domains as previously claimed. Neutron diffraction studies indicate that the ferromagnetic to ferrimagnetic transition upon reducing the external magnetic field is associated with a change in the magnetic configuration/coupling between Fe1 and Fe2 moments. We observe a clear correlation between the hysteresis observed in both the skyrmion density and the magnetization of Fe$ _3$ GaTe$ _2$ . This indicates that its topological spin textures are affected by the development of ferrimagnetism upon cooling. Observation, via magnetic force microscopy, of magnetic bubbles at the magnetic phase boundary suggests skyrmions stabilized by the competition among magnetic phases and distinct exchange interactions. Our study provides an explanation for the observation of Néel skyrmions in centrosymmetric systems, while exposing a correlation between the distinct magnetic phases of Fe$ _3$ GaTe$ _2$ and topological spin textures.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
57 pages, 6 figures, and appended Supporting Information file
ACS Nano (2025)
Temperature overshooting in the Mpemba effect of frictional active matter
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-01 20:00 EDT
Alexander P. Antonov, Hartmut Löwen
The traditional Mpemba effect refers to an anomalous cooling phenomenon when an initial hotter system cools down faster than an initial warm system. Such counterintuitive behavior has been confirmed and explored across phase transitions in condensed matter systems and also for colloidal particles exposed to a double-well potential. Here we predict a frictional Mpemba effect for a macroscopic body moving actively on a surface governed by Coulomb (dry) friction. For an initial high temperature, relaxation towards a cold state occurs much faster than that for an intermediate initial temperature, due to a large temperature overshooting in the latter case. This frictional Mpemba effect can be exploited to steer the motion of robots and granules.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
5 pages, 3 figures
Effect of RKKY and dipolar interaction on the nucleation of skyrmion in Pt/Co multilayer with Ir spacer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Shaktiranjan Mohanty, Brindaban Ojha, Bhuvneshwari Sharma, Ashutosh Rath, Chandrasekhar Murapaka, Subhankar Bedanta
Magnetic skyrmions, topologically protected spin textures, have emerged as promising candidates for next-generation spintronic applications. In this study, we investigate the stabilization of skyrmionic states in a uniquely engineered Pt/Co multilayer system with an Ir spacer, where both Ruderman Kittel Kasuya Yosida (RKKY) and dipolar interactions play a crucial role. The studied multilayer structure consists of a synthetic antiferromagnetic (SAF) configuration, where a single Ir layer facilitates strong antiferromagnetic coupling between two ferromagnetic regions: FM1 (top) and FM2 (bottom), each formed by repeated Co layers separated by Pt, enabling significant dipolar interactions. This FM1/Ir/FM2 configuration results in a distinctive skyrmionic hysteresis loop, driven by the interplay of dipolar and RKKY interactions. Magnetic force microscopy (MFM) imaging confirms the nucleation of isolated skyrmions, while magnetotransport measurements reveal a finite topological Hall effect (THE), indicating the chiral nature of these spin textures. Furthermore, we demonstrate that increasing the Co layer thickness leads to a reduction in magnetic anisotropy, which in turn results in the formation of relatively larger and denser skyrmions. Our findings establish a robust approach for stabilizing skyrmions through the combined effects of dipolar and RKKY interactions, offering new pathways for controlled skyrmion manipulation in spintronic devices.
Materials Science (cond-mat.mtrl-sci)
Extended Factorization Machine Annealing for Rapid Discovery of Transparent Conducting Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Daisuke Makino, Tatsuya Goto, Yoshinori Suga
The development of novel transparent conducting materials (TCMs) is essential for enhancing the performance and reducing the cost of next-generation devices such as solar cells and displays. In this research, we focus on the (Al$ _x$ Ga$ _y$ In$ _z$ )$ _2$ O$ _3$ system and extend the FMA framework, which combines a Factorization Machine (FM) and annealing, to search for optimal compositions and crystal structures with high accuracy and low cost. The proposed method introduces (i) the binarization of continuous variables, (ii) the utilization of good solutions using a Hopfield network, (iii) the activation of global search through adaptive random flips, and (iv) fine-tuning via a bit-string local search. Validation using the (Al$ _x$ Ga$ _y$ In$ _z$ )$ _2$ O$ _3$ data from the Kaggle “Nomad2018 Predicting Transparent Conductors” competition demonstrated that our method achieves faster and more accurate searches than Bayesian optimization and genetic algorithms. Furthermore, its application to multi-objective optimization showed its capability in designing materials by simultaneously considering both the band gap and formation energy. These results suggest that applying our method to larger, more complex search problems and diverse material designs that reflect realistic experimental conditions is expected to contribute to the further advancement of materials informatics.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
12pages, 6figures
Giant odd-parity magnetoresistance from proximity-induced topological states
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Tomoki Hotta, Le Duc Anh, Takahiro Chiba, Yohei Kota, Masaaki Tanaka
Magnetoresistance typically exhibits even symmetry with respect to the magnetic field, owing to time reversal symmetry (TRS) as dictated by Onsager reciprocity relations. However, in certain systems where TRS is broken, magnetoresistance may acquire an odd component with respect to the magnetic field, referred to as odd parity magnetoresistance (OMR). To date, reported OMR values have been modest, usually restricted to a few tens of percent even under high magnetic fields. Here, we report the discovery of a giant OMR reaching up to 1,150% under a relatively low field of 1 T in a heterostructure composed of 3 nm thick alpha Sn and a ferromagnetic semiconductor, (In,Fe)Sb. Although alpha Sn in this thickness range is a trivial narrow gap semiconductor, analysis of Shubnikov de Haas oscillations combined with ab initio calculations reveals the emergence of tilted topological surface states, induced via magnetic proximity from the (In,Fe)Sb layer. The observed OMR behavior is well explained by a Boltzmann transport model assuming the presence of oppositely tilted Weyl cones in the alpha Sn band structure. Our findings not only shed new light on the physics of OMR but also suggest promising avenues for its application in electronic and spintronic devices, such as ultrasensitive magnetic sensors.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Effect of quasiparticles on the parameters of a gap-engineered transmon
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
Daniil S. Antonenko, Pavel D. Kurilovich, Francisco J. Matute-Cañadas, Leonid I. Glazman
We evaluate the quasiparticle contribution to the frequency shift and relaxation rates of a transmon with the Josephson junctions connecting superconductors that have unequal energy gaps. The gap difference substantially affects the transmon characteristics. We investigate their dependence on the density and effective temperature of the quasiparticles, and on the nominal (unperturbed by the quasiparticles) transmon frequency. At temperatures low compared to the qubit frequency, the gap difference can induce an anomalous positive frequency shift, resulting in a non-monotonic temperature dependence of the transmon frequency. The qubit relaxation rate exhibits a resonance when the qubit frequency matches the gap difference; the shape of the resonance is strongly temperature-dependent. We propose to use these effects to access the details of the quasiparticle energy distribution.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 4 figures
Model Hamiltonian for Altermagnetic Topological Insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Rafael Gonzalez-Hernandez, Bernardo Uribe
We present models of topological insulating Hamiltonians exhibiting intrinsic altermagnetic features, protected by combined three-fold or four-fold rotational symmetries with time-reversal. We demonstrate that the spin Chern number serves as a robust topological invariant in two-dimensional systems, while for three-dimensional structures, the topological nature is characterized by the spin Chern numbers computed on the $ k_z$ =$ 0$ and $ k_z$ =$ \pi$ planes. The resulting phases support symmetry-protected boundary modes, including corner, hinges and surface states, whose structure is determined by the magnetic symmetry and the local magnetic moments. Our findings bridge the fields of altermagnetism and topological quantum matter, and establish a theoretical framework for engineering spintronic topological systems without net magnetization.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
11 pages, 6 figures
Tuning the Topological Properties of the Antiferromagnetic V(Bi${1-x}$Sb${x}$)${2}$Te${4}$ via Sb concentration
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
D. A-León, D.A. Landínez Téllez, J. Roa-Rojas, Rafael Gonzalez-Hernandez
The investigation of topological materials has uncovered groundbreaking phases of matter with significant implications for quantum technologies. Here, we explore the antiferromagnetic topological insulator family V(Bi$ _{1-x}$ Sb$ _{x}$ )$ _{2}$ Te$ _{4}$ ($ x$ =$ 0$ , $ 0.5$ , $ 1$ ), formed by introducing vanadium telluride (VTe) layers into the layered topological insulator (Bi$ _{1-x}$ Sb$ _{x}$ )$ _{2}$ Te$ _{3}$ . Our results reveal the tunability of the spin Hall conductivity (SHC) and its topological contribution, quantified by the recently introduced average Spin Chern Number (ASCN), via Sb concentration. The materials’ strong topological insulating behavior is established through spin-orbit coupling-induced band inversions, nontrivial $ \mathbb{Z}_2$ invariants, and the presence of topological surface states. These findings position V(Bi$ _{1-x}$ Sb$ _{x}$ )$ _{2}$ Te$ _{4}$ as promising candidates for next-generation spintronic devices and advanced quantum applications.
Materials Science (cond-mat.mtrl-sci)
10 pages, 6 figures
Phys. Rev. Materials 9, 054201 (2025)
Altermagnetism in 6H perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
The combination of a centrosymmetric crystallographic structure with local structural alternations and collinear antiferromagnetism can lead to broken PT (Parity $ \times$ Time-reversal) symmetry, resulting in altermagnets with non-relativistic spin-split bands. The 6H perovskites with composition A$ _3$ BB’$ _2$ O$ _9$ exhibit unique layered structural alternations and typically adopt an antiferromagnetic ground state. Here, we report the discovery that several 6H perovskites are indeed altermagnets exhibiting non-relativistic spin-split bands. We also explore the possible presence of net magnetization due to spin-orbit coupling in these materials, as well as the manifestation of giant piezomagnetism. Since the single crystals of 6H perovskites can be readily grown and cleavable, our findings provide a new avenue to study the cleaved atomically-flat surfaces of altermagnets with advanced experimental techniques such as spin-resolved scanning tunneling microscopy (STM) or spin-resolved angle-resolved photoemission spectroscopy (ARPES) to explore their spin splitting nature.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Altermagnetism and anomalous Hall effect in LaMn2Si2
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
By combining symmetry analysis and direct density functional calculations including the spin-orbit coupling, we demonstrate that LaMn2Si2 is an M-type altermagnet. Our results predict a large anomalous Hall effect, with a non-zero xy component of -360 S/cm, accompanied by a pronounced magneto-optical response. Remarkably, electron doping of LaMn2Si2 is predicted to substantially enhance the Hall conductivity, with values reaching up to -650 S/cm. These results suggest that silicates with general formula RM2Si2 can be an interesting platform for studying both altermagnetism and anomalous Hall effect.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Disorder driven crossover between anomalous Hall regimes in Fe$_3$GaTe$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Sang-Eon Lee, Minkyu Park, W. Kice Brown, Vadym Kulichenko, Yan Xin, S. H. Rhim, Chanyong Hwang, Jaeyong Kim, Gregory T. McCandless, Julia Y. Chan, Luis Balicas
The large anomalous Hall conductivity (AHC) of the Fe$ 3$ (Ge,Ga)Te$ 2$ compounds has attracted considerable attention. Here, we expose the intrinsic nature of AHC in Fe$ 3$ GaTe$ 2$ crystals characterized by high conductivities, which show disorder-independent AHC with a pronounced value $ \sigma{xy}^{\text{c}}\approx$ 420 $ \Omega^{-1}$ cm$ ^{-1}$ . In the low conductivity regime, we observe the scaling relation $ \sigma{xy}\propto\sigma{xx}^{1.6}$ , which crosses over to $ \sigma{xy} \simeq \sigma_{xy}^{\text{c}}$ as $ \sigma_{xx}$ increases. Disorder in low-conductivity crystals is confirmed by the broadening of a first-order transition between ferromagnetism and the ferrimagnetic ground state. Through density functional theory (DFT) calculations, we reveal that the dominant sources of Berry curvature are located a few hundred meV below the Fermi energy around the $ \Gamma$ -point. Therefore, Fe$ _3$ GaTe$ _2$ clearly exposes the disorder-induced crossover among distinct AHC regimes, previously inferred from measurements on different ferromagnets located in either side of the crossover region.
Materials Science (cond-mat.mtrl-sci)
9 pages, 6 figures
Physical Review B, 111, 184438 (2025)
Inhomogeneity identification by measuring magnetic quantum oscillations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
This study explores the identification of sample inhomogeneity via magnetic quantum oscillations analysis in semimetal NbSb$ _2$ . By doping Bi and Cr, we obtained a homogeneous Bi-doped sample and an inhomogeneous Cr-doped sample, whose homogeneity was confirmed by comparing the magnetic quantum oscillation before and after grinding the samples. The magnetic quantum oscillations in the inhomogeneous sample exhibited a distinct phase shift and unusual field-dependent amplitude, believed to result from a non-uniform Fermi energy. The analysis of the magnetic quantum oscillations demonstrated that the homogeneous Bi-doped sample can be interpreted by the symmetric and Lorentzian effective Fermi energy distribution, while the inhomogeneous Cr-doped sample exhibited an asymmetric distribution, illustrating an unconventional violation of the Lifshitz-Kosevich formula. This research provides a novel method for identifying material inhomogeneity and mitigating potential misinterpretations of magnetic quantum oscillations’ unusual phase, commonly seen as a nontrivial Berry phase indicator in topological materials studies.
Materials Science (cond-mat.mtrl-sci)
21 pages, 4 figures
Physica B: Condensed Matter, 670, 415321 (2023)
In-plane and interlayer magnetoresistance in FeSe
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
Taichi Terashima, Shinya Uji, Hiroaki Ikeda, Yuji Matsuda, Takasada Shibauchi, Shigeru Kasahara
We report measurements of the in-plane and interlayer magnetoresistance on FeSe. The in-plane magnetoresistance $ \Delta \rho_{ab}/\rho_{ab}(0)$ for $ B \parallel c$ is positive below $ T_s$ and grows with decreasing temperature, exceeding 2.5 at $ T$ = 10 K and $ B$ = 14 T. The field-direction dependence indicates that the in-plane magnetoresistance is basically determined by the $ c$ -axis component of the magnetic field. The interlayer magnetoresistance $ \Delta \rho_{c}/\rho_{c}(0)$ is negative below $ T_s$ but turns positive below $ \sim$ 18 K, which is probably due to the contamination of the large in-plane magnetoresistance. The field-direction dependence of the interlayer magnetoresistance can approximately be described by a standard formula for quasi-two-dimensional electron systems except near $ B \parallel ab$ . The experimental magnetoresistance near $ B \parallel ab$ is larger than the formula, which can be attributed to the so-called interlayer coherence peak. The large width of the peak indicates the correspondingly large interlayer transfer energy.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
7 pages, 7 figures
Superconducting coherence boosted by outer-layer metallic screening in multilayered cuprates
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
Junhyeok Jeong, Kifu Kurokawa, Shiro Sakai, Tomotaka Nakayama, Kotaro Ando, Naoshi Ogane, Soonsang Huh, Matthew D. Watson, Timur K. Kim, Cephise Cacho, Chun Lin, Makoto Hashimoto, Donghui Lu, Takami Tohyama, Kazuyasu Tokiwa, Takeshi Kondo
In multilayered high-Tc cuprates with three or more CuO2 layers per unit cell, the inner CuO2 planes (IPs) are spatially separated from the dopant layers and thus remain cleaner than the outer planes (OPs). While both interlayer coupling and the presence of clean IPs have been proposed as key factors enhancing superconductivity, their individual roles have been difficult to disentangle, as IPs and OPs typically become superconducting simultaneously. Here we investigate five-layer (Cu,C)Ba2Ca4Cu5Oy (Cu1245) with Tc = 78 K and three-layer Ba2Ca2Cu3O6(F,O)2 (F0223) with Tc = 100 K using ARPES, and uncover an unprecedented situation, in which only the IPs become superconducting while the OPs remain metallic at low temperatures. Model calculations indicate that more than 95% of the OP wavefunction remains confined to OP itself, with minimal hybridization from the superconducting IPs. In particular, we experimentally realize an ideal configuration: a single superconducting CuO2 layer sandwiched between heavily overdoped metallic outer layers, which screen disorder originating from the dopant layers. Strikingly, this clean CuO2 layer exhibits the largest superconducting gap among all known cuprates and coherent Bogoliubov peaks extending beyond the antiferromagnetic zone boundary – long regarded as the boundary beyond which coherence vanishes in heavily underdoped cuprates. Furthermore, a widely extended coherent flat band emerges at the Brillouin zone edge, overcoming the pseudogap damping effect. Our results introduce a new physical parameter, the degree of screening, to investigate the competition between superconductivity and the pseudogap, potentially shedding new light on its origin. The nearly disorder-free superconducting CuO2 layers offer a model platform for bridging the gap between disordered real materials and idealized theoretical models, which generally neglect disorder effects.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
AC/DC spin current in ferromagnet/superconductor/normal metal trilayer systems
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
Koki Mizuno, Hirone Ishida, Manato Teranishi
Spin pumping with superconductors has been extensively studied, particularly in double-layer systems. In this study, we investigate spin pumping in a trilayer system comprising a ferromagnetic insulator (FMI), a superconductor (SC), and a normal metal (NM). We derive the AC and DC spin currents in the NM layer induced by spin motion in the FMI under circularly polarized microwave irradiation. If we treat the spin motion as classical, the AC spin current is expressed. On the other hand, if we treat the spin motion as quantum quasiparticles, the DC spin current is derived. After these derivations, while the computational cost of evaluating the spin current is extremely high, we mitigate this using the Quantics Tensor Cross Interpolation (QTCI) method. We present numerical results showing the dependence of the spin current on temperature, microwave frequency, and superconductor layer thickness. Notably, the temperature dependence of AC and DC spin currents exhibits a coherence peak. Furthermore, we have discovered a transition structure in the dependence of the spin current on the thickness of the superconductor layer, where the dependence changes after a particular frequency.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Computational Physics (physics.comp-ph)
Spin-State Engineering of Single Titanium Adsorbates on Ultrathin Magnesium Oxide
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Soo-hyon Phark, Hong Thi Bui, We-hyo Seo, Yaowu Liu, Valeria Sheina, Curie Lee, Christoph Wolf, Andreas J. Heinrich, Roberto Robles, Nicolas Lorente
Single atomic adsorbates on ultrathin insulating films provide a promising route toward bottom-up quantum architectures based on atomically identical yet individually addressable spin qubits on solid surfaces. A key challenge in engineering quantum-coherent spin nanostructures lies in understanding and controlling the spin state of individual adsorbates. In this work, we investigate single titanium (Ti) atoms adsorbed on MgO/Ag(100) surfaces using a combined scanning tunneling microscopy and electron spin resonance. Our measurements reveal two distinct spin states, $ S = 1/2$ and $ S = 1$ , depending on the local adsorption site and the thickness of the MgO film. Density functional theory calculations suggest a Ti$ ^+$ configuration for the Ti adsorbates with approximately 3 electrons in the 4$ s$ and 3$ d$ valence shells. Using a multi-orbital atomic multiplet calculations the site dependence of the spin can be rationalized as a charge redistribution between spin-polarizing and depolarizing orbitals. These findings underscore the potential of surface-supported single atoms as spin qubits with tunable spin and charge states, enabling atom-by-atom control in the realization of a versatile quantum platform on surfaces.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Magnetic order dependent photoluminescence from high energy excitons in hBN protected few-layer CrSBr
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Xiaohua Wu, Junyang Chen, Mingqiang Gu, Yujun Zhang, Shanmin Wang, Yanan Dai, Qihang Liu, Yue Zhao, Mingyuan Huang
The detection and manipulation of the spin configurations in layered magnetic semiconductors hold significant interest for developing spintronic devices in two-dimensional limit. In this letter, we report a systematical study on the photoluminescence (PL) from the high energy excitons in few-layer CrSBr and its application on detecting the spin configurations. Besides the broad excitonic emission peak (Xl) at around 1.34 eV, we also observed another strong excitonic emission peak (Xh) at around 1.37 eV in hBN encapsulated 2L sample, which splits into two peaks in 3L and 4L samples. With help of the first principles calculations, we conclude that the Xh peak is associated with the transition between the top valence band and the second lowest conduction band, which is forbidden by the inversion symmetry in 1L CrSBr. Furthermore, the position and intensity of the Xh peak are strongly dependent on the interlayer magnetic order of the CrSBr samples, which provides an efficient way to probe their spin configurations. In addition, when the magnetic field is applied at the easy axis direction, we resolve an intermediate magnetic state besides the antiferromagnetic and ferromagnetic states in 3L and 4L samples. Our results reveal few-layer CrSBr as an ideal platform to study the interaction between the excitons and magnetism.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
First-principles study of Rh- and Pd-based kagome-layered shandites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Luca Buiarelli, Turan Birol, Brian M. Andersen, Morten H. Christensen
The shandite structure hosts transition metals arranged in kagome layers stacked rhombohedrally, and interspersed with post-transition metal ions and chalcogens. The electronic states near the Fermi level are dominated by the transition metal $ d$ -orbitals and feature saddle points near several of the high-symmetry positions of the Brillouin zone, most notably the F and L points. Combining symmetry considerations with ab initio methods, we study the electronic and structural properties of these materials with an emphasis on the connection between electronic saddle points at specific momenta and structural instabilities at these momenta. While the parent compounds studied are all found to be structurally stable in the $ R\bar{3}m$ space group under ambient conditions we show that, in specific compounds, moving the saddle point closer to the Fermi level using either hydrostatic pressure or doping, can induce a structural instability. The importance of the electronic degrees of freedom in driving this instability is supported by the dependence of the frequency of the soft phonon mode on the electronic smearing temperature, as is the case in charge density wave materials. Our first-principles calculations show that as the smearing temperature is increased, the compound becomes structurally stable again. Our findings survey the structural properties of a large family of shandite materials and shed light on the role played by saddle points in the electronic structure in driving structural instabilities in rhombohedrally stacked kagome-layered materials belonging to the $ R\bar{3}m$ space group.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
17 pages, 13 figures
Combinatorial Development of Amorphous/nanocrystalline Biphase Soft Magnetic Alloys with Silicon-steel like Saturated Magnetic Induction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Xuesong Li, Jing Zhou, Xiao Liu, Xibei Hou, Tengyu Guo, Bo Wu, Baoan Sun, Weihua Wang, Haiyang Bai
Maximization saturation magnetic induction (Bs) of soft magnetic alloys is essential for the high power-density electromagnetic devices. However, identifying the alloy compositions with high Bs often replies on the lab-intensive melt casting method and a high-throughput characterization on magnetic properties remains challenging. Here, we develop a new combinatorial method for fast screening alloys with optimal soft magnetic properties based on the high-throughput MOKE screening method. Based on the combinatorial method, we found that the alloys with a combination of high Bs and low coercivity (Hc) tend to have a feature of amorphous-nanocrystalline biphase microstructure. We also identified an amorphous/nanocrystalline alloy film with the composition the Fe68.09Co17.02B10.9Si4, exhibiting an ultra-high Bs up to 2.02 T that surpasses all amorphous/nanocrystalline alloys reported so far and is comparable to that of silicon steels, together with a high resistivity of 882 {\mu}{\Omega} {\dot} cm, about 17 times of silicon steels. Our high-throughput magnetic screening method provides a paradigm for understanding the relationship between microstructure and magnetic properties and the development of the next-generation soft magnetic materials.
Materials Science (cond-mat.mtrl-sci)
26 pages, 5 figures
Graphene-based quantum heterospin graphs
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Gabriel Martínez-Carracedo, Amador García-Fuente, László Oroszlány, László Szunyogh, Jaime Ferrer
We investigate from first principles a variety of low-dimensional open quantum spin systems based on magnetic nanographene structures that contain spin-1/2 and spin-1 triangulenes and/or olympicenes. These graphene nanostructures behave as localized spins and can be effectively described by a quantum bilinear-biquadratic Heisenberg Hamiltonian, for which we will compute the energy spectrum and the quantum numbers associated with the low-energy eigenstates. We propose the experimental realization of antiferromagnetic alternating spin chains using these graphene nanostructures, which result in ferrimagnetic systems whose ground state spin and degeneracy depend on the length of the chain. We also identify a double degeneracy in the total spin quantum number $ S$ in the first excited state for three-leg spin graphs (3-LSGs). This degeneracy depends on both the number of sites and the spin species that compose the 3-LSG. We identify the double degeneracy of the first excited state as a consequence of swapping transformation symmetry of the Hamiltonian.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages 7 figures
Terahertz spin-orbit torque as a drive of spin dynamics in insulating antiferromagnet Cr${2}$O${3}$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
R.M. Dubrovin, Z.V. Gareeva, A.V. Kimel, A.K. Zvezdin
Contrary to conventional wisdom that spin dynamics induced by current are exclusive to metallic magnets, we theoretically predict that such phenomena can also be realized in magnetic insulators, specifically in the magnetoelectric antiferromagnet $ \mathrm{Cr}{2}\mathrm{O}{3}$ . We reveal that the displacement current driven by the THz electric field is able to generate a N{é}el spin-orbit torque in this insulating system. By introducing an alternative electric dipole order parameter arising from the dipole moment at $ \mathrm{Cr}^{3+}$ sites, we combine symmetry analysis with a Lagrangian approach and uncover that the displacement current couples to the antiferromagnetic spins and enables ultrafast control of antiferromagnetic order. The derived equations of motion show that this effect competes with the linear magnetoelectric response, offering a novel pathway for manipulating antiferromagnetic order in insulators. Our findings establish insulator antiferromagnets as a viable platform for electric field driven antiferromagnetic spintronics and provide general design principles for non-metallic spin-orbit torque materials.
Materials Science (cond-mat.mtrl-sci)
9 pages, 3 figures
Machine learning Landau free energy potentials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Mauro Pulzone, Natalya S. Fedorova, Hugo Aramberri, Jorge Íñiguez-González
We show how to construct Landau-like free energy potentials using a machine-learning approach. For concreteness, we focus on perovskite oxide PbTiO$ _{3}$ . We work with a training set obtained from Monte Carlo simulations based on an atomistic ‘’second-principles’’ potential for PbTiO$ _{3}$ . We rely exclusively on data that would be experimentally accessible – i.e., temperature-dependent polarization and strain, both with and without external electric fields and stresses applied –, to explore scenarios where the training set could be obtained from laboratory measurements. We introduce a scheme that allows us to identify optimal polynomial models of the temperature-dependent free energy surface, mapped as a function of the homogeneous electric polarization and homogeneous strain. Our results for PbTiO$ _{3}$ show that a very simple polynomial – where only two parameters depend linearly on temperature – is sufficient to yield a correct description of the material’s behavior. Remarkably, the obtained models also capture the subtle couplings by which elastic strain controls key features of ferroelectricity in PbTiO$ _{3}$ – i.e., the symmetry of the polar phase and the discontinuous character of the transition –, despite the fact that no effort was made to include such information in the training set. We emphasize the distinctive aspects of our methodology (which relies on an original form of validation step) by comparing it with the usual machine-learning approach for model construction. Our results illustrate how physically motivated models can have remarkable predictive power, even if they are derived from a limited amount of data. We argue that such ‘’third-principles’’ models can be the basis for predictive macroscopic or mesoscopic simulations of ferroelectrics and other materials undergoing non-reconstructive structural transitions.
Materials Science (cond-mat.mtrl-sci)
Low energy excitations in A-site ordered SmBaMn2O6
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
Mirian Garcia Fernandez, Abhishek Nag, Stefano Agrestini, Sahil Tippireddy, Dirk Backes, Urs Staub, Taka-hisa Arima, Kejin Zhou
The electron in a solid can be considered a bound state of the three independent, fundamental degrees of freedom creating quasi-particles: spinons, carrying the electron spin; plasmons carrying the collective charge mode and orbitons carrying its orbital degree of freedom. These fundamental degrees of freedom could form ordering states in which dynamics or collective motions could occurr and manifest as low-energy excitations. The exotic properties that appear in the materials exhibiting these electronic orderings are associated with these low-energy excitations. Although the orbital order (OO) and its coupling to the spin system creates very interesting phenomena, the microscopic origin of OO has been much less explored than other electronic properties as it is very difficult to directly access experimental information from OO. Due to the recent improvement in energy resolution and flux, soft x-ray resonant inelastic scattering (RIXS) allows for a re-examination of orbital excitations in manganites. Here, we present a study of low energy excitations in half doped A-site ordered SmBaMn_{2}O_{6} through a combination of RIXS and soft x-ray resonant elastic scattering (REXS) measurements. The obtained experimental data confirm the OO at \mathbf{q} = (0.25, 0.25, 0) and find various low energy excitations below 200 meV. while several excitations can be assigned to be of magnetic and phononic origin, a group of excitations between 80 and 200 meV show a temperature dependence distinctively following that of the OO making them possible candidates for orbital excitations.
Strongly Correlated Electrons (cond-mat.str-el)
8 pages, 8 figures
Multilayer Cryogenic Powder Filters with Low Parasitic Capacitance
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Itishree Pradhan, Hao Li, Alina Rupp, Yosuke Sato, Henri Vo Van Qui, Miuko Tanaka, Toshiya Ideue, Erwann Bocquillon, Masayuki Hashisaka
We report the development of a cryogenic powder filter that simultaneously offers high attenuation of radio-frequency (RF) signals in the gigahertz (GHz) range and minimized parasitic capacitance to ground. Conventional powder filters, which consist of a signal line passing through a metal powder-filled housing, attenuate high-frequency signals via the skin effect. However, these designs often suffer from significant parasitic capacitance between the signal line and the grounded chassis, which can compromise the performance of sensitive measurement setups by limiting their frequency bandwidth. In this work, we demonstrate that a multilayer powder filter design effectively achieves both high RF attenuation and reduced parasitic capacitance. This solution suppresses sample heating due to the unintentional intrusion of RF signals through the wiring, without degrading the performance of the measurement setup.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Low Temperature Formation of Crystalline VO2 Domains in Porous 1 Nanocolumnar Thin Films for Thermochromic Applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
H. Acosta-Rivera, V. Rico, F.J. Ferrer, T.C. Rojas, R. Alvarez, N. Martin, A.R. Gonzalez-Elipe, A. Palmero
The formation of VO2 crystalline domains in amorphous substoichiometric nanocolumnar VOx thin films subjected to an oxidation process at temperatures below 300°C has been studied. It is obtained that values of [O]/[V] above 1.9 lead to the sole formation of V2O5 after oxidation, while values below 1.9 favor the formation of VO2, V3O7 and V2O5 crystalline domains for temperatures as low as 260°C. Moreover, it is found that the adsorption of oxygen and its incorporation into the film network produce a relevant volume expansion in a so-called swelling mechanism that makes pores shrink. Under some specific conditions, the low temperature oxidation does not only trigger the formation of VO2 domains but also a drastic reduction of oxygen-deficient amorphous VOx in the films, which clearly improves the overall transparency and thermochromic modulation capabilities. The changes in the optical and electrical properties of these films during the metal-insulator transition have been studied, finding the best performance when the stoichiometry of the film before oxidation is [O]/[V]=1.5 and the oxidation temperature 280°C. These conditions yield a relatively transparent coating that presents an optical modulation in the near-infrared range of nearly 50% and a drop of electrical resistivity of more than two orders of magnitude. A tentative model based on the volume increase experienced by film upon oxidation is proposed to link the structural/chemical features of the films and the formation of VO2 domains at such relatively low temperatures.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Nonlinear Magnetoelectric Edelstein Effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Jinxiong Jia, Longjun Xiang, Zhenhua Qiao, Jian Wang
The linear Edelstein effect is a cornerstone phenomenon in spintronics that describes the generation of spin magnetization in response to an applied electric field. Recent theoretical advances have reignited interest in its nonlinear counterpart, the nonlinear Edelstein effect, in which spin magnetization is induced by a second-order electric field. However, the intrinsic contribution to both effects is generally forbidden in systems preserving time-reversal symmetry ($ \mathcal{T}$ ) or composite symmetries such as $ \mathcal{T}\tau_{1/2}$ , where $ \tau_{1/2}$ denotes a half-lattice translation. In such systems, spin magnetization typically emerges either from extrinsic mechanisms but limited to metals due to their Fermi-surface property, or from dynamical electric fields with a terahertz driving frequency. Here, we propose a new mechanism for spin magnetization, arising from the interplay of magnetic and electric fields, termed the nonlinear magnetoelectric Edelstein effect. Remarkably, its intrinsic component, determined purely by the material’s band structure, can appear even in $ \mathcal{T}$ -invariant materials, but lacking inversion symmetry ($ \mathcal{P}$ ), including insulators. On the other hand, we illustrate that its extrinsic component can serve as a sensitive indicator of the Néel vector reversal in $ \mathcal{P}\mathcal{T}$ -symmetric antiferromagnetic materials, offering a novel route for antiferromagnetic order detection. To validate our theory, we perform explicit calculations using a two-band Dirac model and a tight-binding model on a honeycomb lattice, finding that both effects yield sizable spin magnetization. Our findings establish the nonlinear magnetoelectric Edelstein effect as a versatile platform for both exploring nonlinear spin physics and enabling symmetry-based detection of antiferromagnetic order.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
On the influence of powder particle size on single-track formation in laser powder bed fusion of AlSi10Mg alloy
New Submission | Other Condensed Matter (cond-mat.other) | 2025-08-01 20:00 EDT
Y. Solyaev, V. Dobryanskiy, Nguyen Long, Stanislav Chernyshikhin
In this paper, we present the results of single-track experiments conducted for different fractions of standard AlSi10Mg powder, which were sieved to achieve varying mean size of the particles. We observed strong differences in the melting behaviour of fractions at relatively low levels of input energy in laser powder bed fusion (LPBF) process. Namely, the remarkable particle size effect arises for the position of lack of fusion boundary, i.e. for the range of process parameters where the laser power becomes sufficient for complete through-thickness melting of the powder layer at given laser scanning speed. We established that this boundary corresponds to an approximately constant linear energy density at low levels of Peclet number (Pe < 2), while the constant enthalpy density defines this boundary at the higher levels (Pe > 2). Specifically, when the mean particle size ranges from 28 to 64 microns, the required linear energy density for stable track formation ranges from 50 to 167 J/m and the nominal enthalpy density ranges from 4.4 to 15 J/mm^3. Based on the scaling law analysis and numerical simulations, we show that observed phenomena can be attributed to the change of absorptivity of powder layer, which depends on particle size and packing density. Also, we show that the values of absorptivity identified based on the analysis of position of lack of fusion boundary (0.13-0.38 for powder size 64-28 microns) correlate well with those found from the analysis of melt pool width in the formed single-tracks.
Other Condensed Matter (cond-mat.other), Materials Science (cond-mat.mtrl-sci)
Spintronic temperature nanosensor based on the resonance response of a skyrmion-hosting magnetic tunnel junction
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Michail Lianeris, Davi Rodrigues, Andrea Meo, Dimitris Kechrakos, Anna Giordano, Mario Carpentieri, Giovanni Finocchio, Riccardo Tomasello
The increasing need for efficient thermal management in nanoelectronics requires innovative thermal sensing solutions, as conventional sensors often exhibit nonlinear responses, low sensitivity, and complex calibration. We predict a temperature dependence in the response of existing skyrmion based spintronic diodes and propose their use as nanoscale thermal sensors. These devices leverage magnetic skyrmions topologically protected spin textures known for their robustness, nanoscale dimensions, and low power dynamics. We demonstrate high thermal sensitivity with a linear temperature response over a wide range. This linearity, observed in both the amplitude and frequency of the skyrmion excitation, ensures redundancy that enables precise and reliable temperature measurement. In addition, the use of multilayer systems enhances the sensitivity and robustness of the device. These results provide a foundation for skyrmion-based caloritronic devices with promising applications in spintronic sensors, thermal management, nanoelectronics, and skyrmion-caloritronics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Quantum typicality approach to energy flow between two spin-chain domains at different temperatures
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-01 20:00 EDT
Laurenz Beckemeyer, Markus Kraft, Mariel Kempa, Dirk Schuricht, Robin Steinigeweg
We discuss a quantum typicality approach to examine systems composed of two subsystems at different temperatures. While dynamical quantum typicality is usually used to simulate high-temperature dynamics, we also investigate low-temperature dynamics using the method. To test our method, we investigate the energy current between subsystems at different temperatures in various paradigmatic spin-1/2 chains, specifically the XX chain, the critical transverse-field Ising chain, and the XXZ chain. We compare our numerics to existing analytical results and find a convincing agreement for the energy current in the steady state for all considered models and temperatures.
Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
9 pages, 7 figures
Enhanced negative capacitance in La-doped Pb(Zr${0.4}$Ti${0.6}$)O$_3$ ferroelectric capacitor by tuning bias voltage pulse to induce intrinsic domain switching kinetics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Ganga S. Kumar, Sudipta Goswami, Shubhasree Chatterjee, Dilruba Hasina, Miral Verma, Devajyoti Mukherjee, Chandan Kumar Ghosh, Dipten Bhattacharya
We report a remarkable enhancement of specific negative capacitance in multidomain La-doped Pb(Zr$ _{0.4}$ Ti$ _{0.6}$ )O$ _3$ (PLZT) ferroelectric capacitors when bias voltage pulse profile (amplitude and timescale) induces switching of the ferroelectric domains following intrinsic switching kinetics associated with minimum energy barrier. This is because of emergence of maximum domain wall density during switching" of the domains. Domain configuration changes from such an optimum” state if higher or lower bias voltage is applied at a much faster or slower rate. Phase-field simulation using time-dependent Ginzburg-Landau equation shows dependence of the domain wall density during switching on the bias voltage amplitude and its maximization at a specific bias voltage amplitude. The radius of curvature of the resulting polarization ($ P$ ) versus voltage ($ V$ ) hysteresis loop at the coercive voltage ($ V_C$ ) also turns out to be depending on whether or not intrinsic switching kinetics is followed. All these results indicate a close correlation among the bias voltage pulse profile (amplitude and time scale), domain wall density during switching, shape of the resulting ferroelectric hysteresis loop, and the transient negative capacitance. It may have important ramifications both in the context of physics behind negative capacitance in a multidomain ferroelectric capacitor and devices being developed by exploiting its advantages.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
14 pages, 13 figures; comments are welcome
Magnetically Programmable Surface Acoustic Wave Filters: Device Concept and Predictive Modeling
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Michael K. Steinbauer, Peter Flauger, Matthias Küß, Stephan Glamsch, Emeline D. S. Nysten, Matthias Weiß, Dieter Suess, Hubert J. Krenner, Manfred Albrecht, Claas Abert
Filtering surface acoustic wave (SAW) signals of specified frequencies depending on the strength of an external magnetic field in a magnetostrictive material has garnered significant interest due to its potential scientific and industrial applications. Here, we propose a device that achieves selective SAW attenuation by instead programming its internal magnetic state. To this end, we perform micromagnetic simulations for the magnetoelastic interaction of the Rayleigh SAW mode with spin waves (SWs) in exchange-decoupled Co/Ni islets on a piezoelectric LiTaO$ _3$ substrate. Due to the islets exhibiting perpendicular magnetic anisotropy, the stray-field interaction between them leads to a shift in the SW dispersion depending on the magnetic alignment of neighboring islets. This significantly changes the efficiency of the magnetoelastic interaction at specified frequencies. We predict changes in SAW transmission of 28.9 dB/mm at 3.8 GHz depending on the state of the device. For the efficient simulation of the device, we extend a prior energy conservation argument based on analytical solutions of the SW to finite-difference numerical calculations, enabling the modeling of arbitrary magnetization patterns like the proposed islet-based design.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Sextets in four-terminal Josephson junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
Miriam Rike Ebert, David Christian Ohnmacht, Wolfgang Belzig, Juan Carlos Cuevas
Multiterminal superconducting junctions have revitalized the investigation of the Josephson effect. One of the most interesting aspects of these hybrid systems is the occurrence of multi-Cooper pair tunneling processes that have no analog in two-terminal devices. Such correlated tunneling events are also intimately connected to the Andreev bound states (ABSs) supported by these structures. Josephson junctions with four superconducting terminals have attracted special attention because they are predicted to support ABSs with nontrivial topological properties. Here, we present a theoretical study of sextets, which are correlated tunneling processes involving three Cooper pairs and four different superconducting terminals. We investigate how sextets can be identified from the analysis of the current-phase relation, we show how sextets are connected to the hybridization of ABSs, and we discuss their existence in recent experiments on four-terminal devices realized in hybrid Al/InAs heterostructures.
Superconductivity (cond-mat.supr-con)
11 pages, 7 figures
Emergence of long-range non-equilibrium correlations in free liquid diffusion
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-01 20:00 EDT
Marco Bussoletti (1), Mirko Gallo (1), Amir Jafari (2), Gregory L. Eyink (2,3) ((1) Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, (2) Department of Applied Mathematics and Statistics, The Johns Hopkins University, (3) Department of Physics, The Johns Hopkins University)
It is experimentally well-established that non-equilibrium long-range correlations of concentration fluctuations appear in free diffusion of a solute in a solvent, but it remains unknown how such correlations are established dynamically. We address this problem in a model of Donev, Fai & Vanden-Eijnden (DFV), obtained from the high-Schmidt limit of the Landau-Lifschitz fluctuating hydrodynamic equations for a binary mixture. We consider an initial planar interface of the mean concentration field in an infinite space domain, idealizing prior experiments. Using methods borrowed from turbulence theory, we show both analytically and numerically that a quasi-steady regime with self-similar time decay of concentration correlations appears at long time. In addition to the expected ``giant concentration fluctuations’’ with correlations $ \propto r$ for $ r\lesssim L(t)=(Dt)^{1/2},$ with diffusivity $ D,$ a new regime with spatial decay $ \propto 1/r$ appears for $ r\gtrsim L(t).$ The quasi-steady regime arises from an initial stage of transient growth $ \propto t,$ confirming the prediction of DFV for $ r\gtrsim L(t)$ and discovering an analogous result for $ r\lesssim L(t).$ Our results give new insight into the emergence of non-equilibrium long-range correlations and provide novel predictions that may be investigated experimentally.
Statistical Mechanics (cond-mat.stat-mech)
12 pages, 8 figures
Run-and-Tumble Particles Learning Chemotaxis
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-01 20:00 EDT
Nicholas Tovazzi, Gorka Muñoz-Gil, Michele Caraglio
Through evolution, bacteria have developed the ability to perform chemotactic motion in order to find nourishment. By adopting a machine learning approach, we aim to understand how this behavior arises. We consider run-and-tumble agents able to tune the instantaneous probability of switching between the run and the tumble phase. When such agents are navigating in an environment characterized by a concentration field pointing towards a circular target, we investigate how a chemotactic strategy may be learned starting from unbiased run-and-tumble dynamics. We compare the learning performances of agents that sense only the instantaneous concentration with those of agents having a short-term memory that allows them to perform temporal comparisons. While both types of learning agents develop successful target-search policies, we demonstrate that those achieved by agents endowed with temporal comparison abilities are significantly more efficient, particularly when the initial distance from the target is large. Finally, we also show that when an additional length scale is imposed, for example by fixing the initial distance to the target, the learning agents can leverage this information to further improve their efficiency in locating the target.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
10 pages, 3 figures
Printable Nanocomposites with Superparamagnetic Maghemite ($γ$-Fe$_2$O$_3$) Particles for Microinductor-core Applications
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Mathias Zambach, Miriam Varón, Thomas Veile, Bima N. Sanusi, Matti Knaapila, Anders M. Jørgensen, László Almásy, Christer Johansson, Ziwei Ouyang, M. Beleggia, Cathrine Frandsen
We here present printable and castable magnetic nanocomposites containing superparamagnetic 11$ \pm$ 3 nm $ \gamma$ -Fe$ _2$ O$ _3$ particles in an insulating poly-vinyl alcohol polymer matrix. The nanocomposites feature well-dispersed particles with volume fractions between 10 and 45 %, as confirmed by small-angle neutron scattering. The magnetic volume susceptibility is as high as 17, together with negligible hysteresis at low frequency, and constant AC-response up to the high-kHz range. Measured hysteresis curves at 100-900 kHz with up to 110 mT induced $ B$ -fields in the nanocomposite show that power losses depend on $ B$ -field squared, and frequency to the power of 1-1.3. The only loss mechanism in the nanocomposite is hysteresis losses at $ >$ 100 kHz frequencies, where the largest particles in the 11$ \pm$ 3 nm distribution transition from the superparamagnetic to blocked regime. To mitigate the resulting hysteresis losses (up 10$ ^2$ -10$ ^5$ kW/m$ ^3$ ) a more narrow particle size distribution could be used for future materials. The presented material is eddy current-free and easily integrated into micro-fabrication protocols, as we demonstrate by fabrication of 3-turn print circuit board based inductors with cast/manual printed nanocomposite inductor cores, on which induction has been measured up to 100 MHz.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
12 (15) pages, 11 (12) Figures, 4 (5) tables in main document (including supplementary information)
Magnetic and magnetocaloric properties of the amorphous Tb${31}$Co${69}$ and Dy${31}$Co${69}$ thin films deposited on Si substrates
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
P. Skokowski (1), M. Matczak (1), Ł. Frąckowiak (1), T. Bednarchuk (2), M. Kowacz (1), B. Anastaziak (1 and 3), K. Synoradzki (1) ((1) Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland, (2) Institute of Low Temperatures and Structural Research, Polish Academy of Sciences, Wrocław, Poland, (3) NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland)
We present the structural, magnetic, and magnetocaloric properties of amorphous thin films Tb-Co and Dy-Co with stoichiometry Tb$ {31}$ Co$ {69}$ and Dy$ {31}$ Co$ {69}$ , deposited on naturally oxidized silicon Si (100) substrates. Samples with a thickness $ d=50$ nm covered with a protective Au overlayer with a thickness $ d{\rm Au} =5 $ nm were produced using the pulsed laser deposition technique. The X-ray diffraction analysis indicated the presence of a crystallized Laves phase in the prepared materials. Magnetization measurements as a function of temperature revealed ferrimagnetic behavior in both samples. We estimated the compensation temperature $ T{\rm comp}$ of the amorphous phase for Tb$ {31}$ Co$ {69}$ at 81.5 K and for Dy$ {31}$ Co$ {69}$ at 88.5 K, while we found the Curie temperature $ T{\rm C,\ Laves}$ of the crystallized Laves phases at 204.5 K and at 117 K, respectively. We investigated the magnetocaloric effect in a wide temperature range, covering $ T{\rm comp}$ of amorphous phases and $ T{\rm C,\ Laves}$ of crystallized Laves phases. The analysis for the magnetic field change of $ \Delta \mu_0H=5$ T showed values of the magnetic entropy change of $ -\Delta S{\rm M}=4.9$ mJ cm$ ^{-3}$ K$ ^{-1}$ at $ T{\rm comp}$ and $ -\Delta S{\rm M}=6.6$ mJ cm$ ^{-3}$ K$ ^{-1}$ at $ T_{\rm C,\ Laves}$ for Tb$ {31}$ Co$ {69}$ , while for Dy$ {31}$ Co$ {69}$ , we determined the values of $ -\Delta S{\rm M}=35$ mJ cm$ ^{-3}$ K$ ^{-1}$ at $ T{\rm comp}$ and $ -\Delta S{\rm M}=28$ mJ cm$ ^{-3}$ K$ ^{-1}$ at $ T{\rm C,\ Laves}$ .
Materials Science (cond-mat.mtrl-sci)
Cohesion mediated layering in sheared grains
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-01 20:00 EDT
We consider pattern formation in a sheared dense mixture of cohesive and non-cohesive grains. Our findings show that cohesive grains, which would typically form distributed agglomerates, instead segregate into percolating stripes or layers when the cohesive grain concentration ($ c_o$ ) and cohesion strength ($ C$ ) increase – in a way that the average agglomerate size and the average normal stress collapse onto a single curve when plotted against $ c_oC$ . Our central proposal is that the development of interfaces between cohesive and non-cohesive grains is akin to phase separation in binary molecular mixtures driven by an effective free energy, although we are dealing with a non-equilibrium system; we setup the segregation flux such that the effect of this free energy is activated only upon application of the external driving. By constructing the segregation flux proportional to the gradient of the variational derivative of the free energy, we closely reproduce the layering in the steady-state limit. We find a robust correspondence between the parameter $ c_o C$ in the discrete simulations and the parameters in the free energy.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Chemical Physics (physics.chem-ph)
Theory of ultrafast conductance modulation in electrochemical protonic synapses by multiphase polarization
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Michael L. Li, Dingyu Shen, Jesus A. del Alamo, Martin Z. Bazant
Three-terminal electrochemical ionic synapses (EIoS) have recently attracted interest for in-memory computing applications. These devices utilize electrochemical ion intercalation to modulate the ion concentration in the channel material. The electrical conductance, which is concentration dependent, can be read separately and mapped to a non-volatile memory state. To compete with other random access memory technologies, linear and symmetric conductance modulation is often sought after, properties typically thought to be limited by the slow ion diffusion timescale. A recent study by Onen et al.[1] examining protonic EIoS with a tungsten oxide (WO3) channel revealed that this limiting timescale seemed irrelevant, and linear conductance modulation was achieved over nanosecond timescales, much faster than the bulk ion diffusion. This contrasts with previous studies that have shown similar conductance modulation with pulse timescales of milliseconds to seconds. Understanding the phenomena behind these conductance modulation properties in EIoS systems remains a crucial question gating technological improvements to these devices. Here, we provide a theoretical explanation that demonstrates how linearity and symmetry arise from consistent control over the electrolyte-WO3 interface. Comparing these past works, changes in the WO3 channel crystallinity were identified, affecting material thermodynamics and revealing that the device achieving nanosecond pulse timescales underwent phase separation. Coupling of electric field polarizatino and increased electron conductivity in high-concentration filaments, the reaction environment at the gate electrode can be controlled, resulting in ideal conductance modulation within the diffusion-limited regime. This work highlights the potential for phase-separating systems to overcome the traditional diffusion barriers that limit EIoS performance.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 5 figures
Active Filaments on Curved Surfaces: From Single Filaments to Dilute Suspensions
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-01 20:00 EDT
Giulia Janzen, Euan D. Mackay, Rastko Sknepnek, D. A. Matoz-Fernandez
Curvature plays a central organizational role in active polymer dynamics. Using large-scale Langevin-dynamics simulations, we study active semiflexible filaments confined to smooth curved surfaces and map how curvature, bending rigidity, and activity interact. We find geodesic alignment, curvature lensing, and curvature-induced trapping. In particular, regions of negative Gaussian curvature localize filaments and hinder global surface exploration. These results show how surface geometry can be used to control the organization and transport of active matter on curved substrates
Soft Condensed Matter (cond-mat.soft)
How to Incorporate Higher-order Interactions in Analog Ising Machines
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-01 20:00 EDT
Robbe De Prins, Guy Van der Sande, Peter Bienstman, Thomas Van Vaerenbergh
Ising machines (IMs) are specialized devices designed to efficiently solve combinatorial optimization problems. Among such problems, Boolean Satisfiability (SAT) is particularly relevant in industrial applications. To solve SAT problems using IMs, it is crucial to incorporate higher-order interactions. However, in analog IMs, interactions of different orders scale unevenly with the continuous spin amplitudes, introducing imbalances that can significantly degrade performance. We present a numerical comparison of methods to mitigate these imbalances, evaluating time-to-solution and success rate on Uniform Random 3-SAT instances from the SATLIB benchmark set. Our results show that the most effective approach employs spin interactions that are proportional to the signs of spins, rather than their continuous amplitudes. This generalizes our previous work, which showed that such interactions best mitigate imbalances induced by external fields in quadratic analog IMs. In this work, its advantage becomes substantially more pronounced, as it naturally mitigates imbalances across all interaction orders. We further demonstrate that smooth approximations of this method make it compatible with analog hardware. Our findings underscore the central role of spin-sign-based interactions in enabling robust and scalable analog IM dynamics.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Adaptation and Self-Organizing Systems (nlin.AO), Cellular Automata and Lattice Gases (nlin.CG), Applied Physics (physics.app-ph)
16 pages, 7 figures, including Supplementary Material
Implementing Pseudofractal Designs in Graphene-Based Quantum Hall Arrays using Minkowski-Bouligand Algorithms
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Dominick S. Scaletta, Ngoc Thanh Mai Tran, Marta Musso, Dean G. Jarrett, Heather M. Hill, Massimo Ortolano, David B. Newell, Albert F. Rigosi
This work introduces a pseudofractal analysis for optimizing high-resistance graphene-based quantized Hall array resistance standards (QHARS). The development of resistance standard device designs through star-mesh transformations is detailed, aimed at minimizing element count. Building on a recent mathematical framework, the approach presented herein refines QHARS device concepts by considering designs incorporating pseudofractals (which may be expressed as star-mesh transformations). To understand how future QHARS pseudofractal designs enable varying sizes of neighborhoods of available quantized resistance, Minkowski-Bouligand algorithms are used to analyze fractal dimensions of the device design topologies. Three distinct partial recursion cases are explored in addition to the original full recursion design, and expressions for their total element counts are derived. These partial recursions, assessed through their fractal dimensions, offer enhanced flexibility in achieving specific resistance values within a desired neighborhood compared to full recursion methods, albeit with an increased number of required elements. The formalisms presented are material-independent, making them broadly applicable to other quantum Hall systems and artifact standards.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Milli-Tesla Quantization enabled by Tuneable Coulomb Screening in Large-Angle Twisted Graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
I. Babich, I. Reznikov, I. Begichev, A. E. Kazantsev, S. Slizovskiy, D. Baranov, M. Siskins, Z. Zhan, P. A. Pantaleon, M. Trushin, J. Zhao, S. Grebenchuk, K. S. Novoselov, K. Watanabe, T. Taniguchi, V. I. Falko, A. Principi, A. I. Berdyugin
The electronic quality of graphene has improved significantly over the past two decades, revealing novel phenomena. However, even state-of-the-art devices exhibit substantial spatial charge fluctuations originating from charged defects inside the encapsulating crystals, limiting their performance. Here, we overcome this issue by assembling devices in which graphene is encapsulated by other graphene layers while remaining electronically decoupled from them via a large twist angle (~10-30°). Doping of the encapsulating graphene layer introduces strong Coulomb screening, maximized by the sub-nanometer distance between the layers, and reduces the inhomogeneity in the adjacent layer to just a few carriers per square micrometre. The enhanced quality manifests in Landau quantization emerging at magnetic fields as low as ~5 milli-Tesla and enables resolution of a small energy gap at the Dirac point. Our encapsulation approach can be extended to other two-dimensional systems, enabling further exploration of the electronic properties of ultrapure devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Influences of the Minkowski-Bouligand Dimension on Graphene-Based Quantum Hall Array Designs
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Dominick S. Scaletta, Ngoc Thanh Mai Tran, Marta Musso, Valery Ortiz Jimenez, Heather M. Hill, Dean G. Jarrett, Massimo Ortolano, Curt A. Richter, David B. Newell, Albert F. Rigosi
This work elaborates on how one may develop high-resistance quantized Hall array resistance standards (QHARS) by using star-mesh transformations for element count minimization. Refinements are made on a recently developed mathematical framework optimizing QHARS device designs based on full, symmetric recursion by reconciling approximate device values with exact effective quantized resistances found by simulation and measurement. Furthermore, this work explores the concept of fractal dimension, clarifying the benefits of both full and partial recursions in QHARS devices. Three distinct partial recursion cases are visited for a near-1 Gigaohm QHARS device. These partial recursions, analyzed in the context of their fractal dimensions, offer increased flexibility in accessing desired resistance values within a specific neighborhood compared to full recursion methods, though at the cost of the number of required devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Temperature-dependent Photoluminescence and Raman Spectroscopy of Selenium Thin Film Solar Cells
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Rasmus S. Nielsen, Axel G. Medaille, Arnau Torrens, Oriol Segura-Blanch, Seán R. Kavanagh, David O. Scanlon, Aron Walsh, Edgardo Saucedo, Marcel Placidi, Mirjana Dimitrievska
Selenium is experiencing renewed interest as a elemental semiconductor for a range of optoelectronic and energy applications due to its irresistibly simple composition and favorable wide bandgap. However, its high volatility and low radiative efficiency make it challenging to assess structural and optoelectronic quality, calling for advanced, non-destructive characterization methods. In this work, we employ a closed-space encapsulation strategy to prevent degradation during measurement and enable sensitive probing of vibrational and optoelectronic properties. Using temperature-dependent Raman and photoluminescence spectroscopy, we investigate grown-in stress, vibrational dynamics, and electron-phonon interactions in selenium thin films synthesized under nominally identical conditions across different laboratories. Our results reveal that short-range structural disorder is not intrinsic to the material, but highly sensitive to subtle processing variations, which strongly influence electron-phonon coupling and non-radiative recombination. We find that such structural disorder and grown-in stress likely promote the formation of extended defects, which act as dominant non-radiative recombination centers limiting carrier lifetime and open-circuit voltage in photovoltaic devices. These findings demonstrate that the optoelectronic quality of selenium thin films can be significantly improved through precise control of synthesis and post-deposition treatments, outlining a clear pathway toward optimizing selenium-based thin film technologies through targeted control of crystallization dynamics and microstructural disorder.
Materials Science (cond-mat.mtrl-sci)
Electron Doping Stabilization of Highly-Polar Supertetragonal BaSnO3
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Qing Zhang, Karin M. Rabe, Xiaohui Liu
Could electrons stabilize ferroelectric polarization in unpolarized system? Basically, electron doping was thought to be contrary to polarization due to the well-known picture that the screening effect on Coulomb interaction diminishes ferroelectric polarization. However, in this paper, we propose a novel mechanism of stabilizing highly-polar supertetragonal BaSnO3 by electron doping. With moderate compressive strain applied, less than -5.5%, BaSnO3 exhibits stable nonpolarized normal tetragonal structure and an unstable supertetragonal state which is characterized with extremely large c/a ratio and giant polarization. We found that the band gap of the supertetragonal state is much smaller than the normal tetragonal state, with a difference around 1.2eV. Therefore, the energy of the doped electrons selectively favors the smaller gap supertetragonal state than the larger band gap normal tetragonal state, and the critical strain to stabilize the supertetragonal phase could be reduced by electron doping. This mechanism guarantees the controllable supertetragonal structures by electron doping and ensures the coexistence of giant polarization and conducting in high-mobility BaSnO3, and is promising to design high-mobility ferroelectrics conductor.
Materials Science (cond-mat.mtrl-sci)
Current-induced spin-orbit torque on the surface of a transition metal dichalcogenide connected to a two-dimensional ferromagnet CrI$_3$: Effects of twisting and gating
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Leyla Majidi, Azadeh Faridi, Reza Asgari
Motivated by recent progress in employing two key classes of two-dimensional materials-topological insulators and transition-metal dichalcogenides (TMDCs)-as spin sources for generating spin-orbit torque (SOT), we investigate current-induced spin polarization and the resulting SOT in bilayers composed of a TMDC (WSe$ _2$ or MoSe$ _2$ ) and ferromagnetic chromium iodide (CrI$ _3$ ), beyond the linear response regime. Using the steady-state Boltzmann equation, we find that intra-band transitions yield a strong field-like torque on the CrI$ _3$ layer, while inter-band transitions give rise to a comparatively weaker damping-like torque in the WSe$ _2$ /CrI$ _3$ system. Remarkably, the damping-like component is enhanced by up to three orders of magnitude in n-doped MoSe$ _2$ , reaching a strength comparable to the field-like torque, which itself is an order of magnitude larger than that in the WSe$ _2$ -based bilayer. Both torque components exhibit strong asymmetry between n-type and p-type doping in WSe$ _2$ and MoSe$ _2$ systems. Furthermore, we demonstrate that the twist angle plays a crucial role: depending on the TMDC and chemical potential, twisting can reverse the sign of the SOT and significantly modulate its magnitude. Finally, we show that a transverse gate electric field enables substantial tunability of the SOT, by nearly one order of magnitude, and induces a sign reversal at a twist angle of $ 10.16^{\circ}$ .
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
11 pages, 10 figures
Interface crossing behavior of prolate microswimmers: thermo and hydrodynamics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-01 20:00 EDT
Rishish Mishra, Harish Pothukuchi, Harinadha Gidituri, Juho Lintuvuori
Motivated by recent experiments of motile bacteria crossing liquid-liquid interfaces of isotropic- nematic coexistence (Cheon et al., Soft Matter 20: 7313-7320, 2024), we study the dynamics of prolate microswimmers traversing clean liquid-liquid interfaces. Using large-scale lattice Boltzmann simulations, we observe that neutrally wetting swimmers can be either trapped or cross the in- terface, depending on their initial angle, swimming speed and the interfacial tension between the two fluids. The simulation results are rationalized by considering a competition between interfacial (thermodynamic) and active (hydrodynamic) forces. The swimmers get trapped at the interface due to a thermodynamic trapping force, akin to Pickering effect, when the forces from interfacial tension dominate over the swimming forces. The trapping behavior can be captured by calculating a critical capillary number by balancing the interfacial and active energies. This prediction agrees remarkably well with the numerical simulations as well as the bacterial experiments of Cheon et al., (Soft Matter 20: 7313-7320, 2024). Finally, our results demonstrate that the torque resulting in a reorientation of the swimmers parallel to the interface have both hydro and thermodynamic components.
Soft Condensed Matter (cond-mat.soft)
Structural Distortions Control Scaling of Exciton Binding Energies in Two-Dimensional Ag/Bi Double Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Pierre Lechifflart, Raisa-Ioana Biega, Linn Leppert
Three-dimensional metal halide double perovskites such as Cs$ _2$ AgBiBr$ _6$ exhibit pronounced excitonic effects due to their anisotropic electronic structure and chemical localization effects. Their two-dimensional derivatives, formed by inserting organic spacer molecules between perovskite layers, were expected to follow well-established trends seen in Pb-based 2D perovskites, namely, increasing exciton binding energies with decreasing layer thickness due to enhanced quantum and dielectric confinement. However, recent experimental and computational studies have revealed anomalous behavior in Ag/Bi-based 2D perovskites, where this trend is reversed. Using ab initio many-body perturbation theory within the $ GW$ and Bethe-Salpeter Equation frameworks, we resolve this puzzle by systematically comparing experimental structures with idealized models designed to isolate the effects of octahedral distortions, interlayer separation, and stacking. We find that structural distortions, driven by directional Ag d orbital bonding, govern the momentum-space origin and character of the exciton, and are the primary cause of the observed non-monotonic trends. Furthermore, we explore how interlayer distance and stacking influence band gaps and exciton binding energies, showing that, despite different chemistry, the underlying confinement physics mirrors that of Pb-based 2D perovskites. Our results establish design principles for tuning excitonic properties in this broader class of layered, lead-free materials.
Materials Science (cond-mat.mtrl-sci)
Boosting Photodetection via Plasmonic Coupling in Quasi-2D Mixed-n Ruddlesden-Popper Perovskite Nanostripes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Brindhu Malani S, Eugen Klein, Ronja Maria Piehler, Rostyslav Lesyuk, Christian Klinke
Quasi-2D metal halide perovskites have emerged as a promising material for photodetection due to excellent optoelectronic properties, simple synthesis, and robust stability. Albeit, developing high-performance photodetectors based on low-dimensional quasi-2D metal halide perovskite nanoparticles remains challenging due to quantum and dielectric confinement effects. Several approaches have been employed to improve efficiency, with plasmonic nanostructures being among the most effective ones. The resonant energy transfer and coupling between plasmons and excitons play a vital role in enhancing device performance. Here, we demonstrate enhanced photodetection of quasi-2D perovskite nanostripes resulting from the incorporation of octadecanethiol (ODT) functionalized Ag nanostructure arrays (ANA). Using colloidal lithography, ANA were fabricated. Reflectance spectroscopy and finite element method (FEM) simulations show that ANA supports localised surface plasmon resonance (LSPR) modes that spectrally coincide with the absorption and emission band of the perovskite. This spectral overlap enables interesting coupling interactions between the excitons and plasmons. The ODT-functionalized ANA photodetectors exhibit weak to intermediate coupling, resulting in a photocurrent enhancement factor of 838 %. They achieve photoresponsivities of up to 70.41 mA W^-1, detectivities of 1.48\ast10^11 Jones and external quantum efficiencies of 21.55 %, which are approximately 10 times higher than those of the reference photodetector. We present an approach to optimize the plasmon-exciton coupling and non-radiative energy transfer for developing high-performance plasmonic-perovskite hybrid photodetectors.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
27 pages, 6 figures
Structural and thermodynamic stability of hexagonal-diamond $\text{Si}{1 - x - y},\text{Ge}{x},\text{B}_{y}$ alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-01 20:00 EDT
Marc Túnica, Francesca Chiodi, Michele Amato
Pushing dopant concentrations beyond the solubility limit in semiconductors – a process known as hyperdoping – has been demonstrated as an effective strategy for inducing superconductivity in cubic-diamond Si and SiGe materials. Additionally, previous studies have reported that several polytypes of Si may exhibit a type-I superconducting state under high pressure. In this work, we employ ground-state Density Functional Theory simulations to investigate the effects of both low and high B doping concentrations on the structural and thermodynamic properties of hexagonal-diamond SiGe alloys, with a systematic comparison to their cubic-diamond counterparts. Our results highlight three key findings: (i) structural analysis confirms that the lattice parameters of SiGeB alloys adhere to a ternary Vegard’s law, consistent with observations in cubic-diamond SiGe alloys. However, at high doping concentrations, B incorporation can locally disrupt the hexagonal symmetry, particularly in the presence of B clustering; (ii) dopant formation energy calculations reveal that B is thermodynamically more stable in the hexagonal phase than in the cubic phase across all Ge concentrations, regardless of the doping level; (iii) mixing enthalpy calculations demonstrate that hyperdoped hexagonal-diamond SiGe alloys are thermodynamically stable across the full range of Ge compositions and that their tendency for hyperdoping is more favorable than that of cubic-diamond SiGe alloys. Taken together, these findings indicate that hyperdoping is experimentally viable in hexagonal-diamond SiGe alloys and, in light of previous evidence, position these materials as a promising platform for the exploration of superconductivity in group IV semiconductors.
Materials Science (cond-mat.mtrl-sci)
21 pages, 7 figures
Floquet Non-Bloch Formalism for a Non-Hermitian Ladder: From Theoretical Framework to Topolectrical Circuits
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Koustav Roy, Dipendu Halder, Koustabh Gogoi, B. Tanatar, Saurabh Basu
Periodically driven systems intertwined with non-Hermiticity opens a rich arena for topological phases that transcend conventional Hermitian limits. The physical significance of these phases hinges on obtaining the topological invariants that restore the bulk-boundary correspondence, a task well explored for static non-Hermitian (NH) systems, while it remains elusive for the driven scenario. Here, we address this problem by constructing a generalized Floquet non-Bloch framework that analytically captures the spectral and topological properties of time-periodic NH systems. Em- ploying a high-frequency Magnus expansion, we analytically derive an effective Floquet Hamiltonian and formulate the generalized Brillouin zone for a periodically driven quasi-one-dimensional system, namely, the Creutz ladder with a staggered complex potential. Our study demonstrates that the skin effect remains robust (despite the absence of non-reciprocal hopping) across a broad range of driving parameters, and is notably amplified in the low-frequency regime due to emergent longer- range couplings. We further employ a symmetric time frame approach that generates chiral-partner Hamiltonians, whose invariants, when appropriately combined, account for the full edge-state struc- ture. To substantiate the theoretical framework, we propose a topolectrical circuit (TEC) that serves as a viable experimental setting. Apart from capturing the skin modes, the proposed TEC design faithfully reproduces the presence of distinct Floquet edge states, as revealed through the voltage and impedance profiles, respectively. Thus, our work not only offers a theoretical framework for exploring NH-driven systems, but also provides an experimentally feasible TEC architecture for realizing these phenomena stated above in a laboratory.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Applied Physics (physics.app-ph), Quantum Physics (quant-ph)
Comments are welcome
Particle localization on helical nanoribbons: Quantum analog of the Coriolis effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Radha Balakrishnan, Rossen Dandoloff, Victor Atanasov, Avadh Saxena
We derive the Schrödinger equation for a particle confined to the surface of a normal and a binormal helical nanoribbon, obtain the quantum potentials induced by their respective curved surface geometries, and study the localized states of the particle for each ribbon. When the particle momentum satisfies a certain geometric condition, the particle localizes near the inner edge for a normal ribbon, and on the central helix for a binormal ribbon. This result suggests the presence of a pseudo-force that pushes the particle transversely along the width of the ribbon. We show that this phenomenon can be interpreted as a quantum analog of the Coriolis effect, which causes a transverse deflection of a classical particle moving in a rotating frame. We invoke Ehrenfest’s theorem applicable to localized states and identify the quantized angular velocities of the rotating frames for the two ribbons. If the particle is an electron, its localization at a specific width gives rise to a Hall-like voltage difference across the ribbon’s width. However, unlike in the Hall effect, its origin is not an applied magnetic field, but the ribbon’s curved surface geometry. When a normal helical ribbon is mechanically flipped to a binormal configuration in a periodic fashion, it results in a periodic electron transport from the inner edge to the center, giving rise to a quantum AC voltage. This can be used for designing nanoscale electromechanical devices. Quantum transport on a helical nanoribbon can be controlled by tuning the bends and twists of its surface, suggesting diverse applications in biopolymers and nanotechnology.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
26 pages, 4 figures
Applying the Worldvolume Hybrid Monte Carlo method to the Hubbard model away from half filling
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
Masafumi Fukuma, Yusuke Namekawa
The Worldvolume Hybrid Monte Carlo (WV-HMC) method [arXiv:2012.08468] is an efficient and low-cost algorithm for addressing the sign problem. It mitigates the sign problem while avoiding the ergodicity issues that are intrinsic to algorithms based on Lefschetz thimbles. In this study, we apply the WV-HMC method to the Hubbard model away from half filling, which is known to suffer from a severe sign problem. We compute the number density on lattices of spatial size $ 6 \times 6$ and $ 8 \times 8$ at inverse temperature $ \beta = 6.4$ using $ N_t = 20$ Trotter steps. Our results show that the WV-HMC method remains effective even in parameter regions where non-thimble Monte Carlo methods fail due to severe sign problems. In this work, we employ direct solvers for fermion matrix inversion, with a computational cost of $ O(N^3)$ , where $ N$ is the number of degrees of freedom and proportional to the spacetime lattice volume. An alternative algorithm employing pseudofermions and iterative solvers, which reduces the cost to $ O(N^2)$ at the expense of careful parameter tuning, will be discussed in a separate publication.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Lattice (hep-lat), High Energy Physics - Theory (hep-th)
33 pages, 19 figures
Discovery of spontaneous mesoscopic strain waves in nematic domains using dark-field X-ray microscopy
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
Kaan Alp Yay, W. Joe Meese, Elliot Kisiel, Matthew J. Krogstad, Anisha G. Singh, Rafael M. Fernandes, Zahir Islam, Ian R. Fisher
Electronic nematic order is a correlated phase of matter in which low-energy electronic states spontaneously break a discrete rotational symmetry of a crystal lattice. Bilinear coupling between the electronic nematic and strains of the same symmetry yields a single pseudoproper ferroelastic phase transition at which both the nematic and lattice strain onset concurrently. To minimize elastic energy, the crystal forms structural twin domains, each with a distinct orientation of the nematic director (i.e. each with a specific sign of the induced shear strain). While the effects of externally induced strains on these domains are well established, the intrinsic behavior of spontaneous strain fields within individual domains has been hitherto unexplored, largely due to the lack of appropriate experimental tools. Here, we report the discovery of spontaneous mesoscopic strain waves within individual nematic domains of an underdoped iron-based superconductor, observed using dark-field X-ray microscopy (DFXM). This technique combines high spatial and reciprocal-space resolution with full-field, bulk-sensitive imaging, enabling direct visualization of subdomain strain modulations emerging concurrently with the onset of nematic order. The elastic compatibility relations that govern inhomogeneous strains in continuous solids provide a natural mechanism for the emergent strain waves that we observe. Our findings reveal a broadly relevant form of strain self-organization and position DFXM as a powerful tool for probing the local interplay between lattice strain and electronic order.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
53 pages, 13 figures
Compatible Instability: Gauge Constraints of Elasticity Inherited by Electronic Nematic Criticality
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
W. Joe Meese, Rafael M. Fernandes
Electronic nematicity is widely observed in quantum materials with varying degrees of electronic correlation, manifesting through charge, spin, orbital, or superconducting degrees of freedom. A phenomenological model capable of describing this broad set of systems must also account for nemato-elasticity, by which nematic and elastic degrees of freedom become intertwined. However, being a tensor gauge field theory, elasticity must satisfy the compatibility relations which guarantee the integrability of lattice deformations. Here, we develop a formalism for nemato-elasticity that manifestly respects the elastic compatibility relations. We show that these constraints bifurcate the phase space of nematic fluctuations into two orthogonal sectors: one compatible and thus critical, the other incompatible and therefore gapped. The suppression of the latter leads to universal direction-selective nematic criticality in any crystal lattice. Moreover, the critical nematic modes are protected from pinning effects induced by microscopic defect strains, which necessarily induce both longitudinal and transverse correlated random fields. Finally, our results also reconcile seemingly contradictory nematic phenomena, such as the mean-field character of the nematic transition and the widespread presence of domain formation.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
7 pages, 3 figures
Theory of Electronic Nematic Criticality Constrained by Elastic Compatibility
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-01 20:00 EDT
W. Joe Meese, Rafael M. Fernandes
The defining property of electronic nematicity – the spontaneous breaking of rotational symmetry – implies an unavoidable coupling between the nematic order parameter and elastic strain fields, known as nemato-elasticity. While both quantities are rank-2 tensors, the strain tensor is constrained through the Saint Venant compatibility relations. These three coupled second-order partial differential equations arise from the lattice displacement vector’s role as a potential field, and they reflect the underlying gauge invariance of geometric deformations which are violated only in the presence of crystalline defects. In this work, we develop a theory of nemato-elasticity that incorporates elastic compatibility explicitly through a co-rotating helical basis. With our formalism, we show elasticity bestows tensor compatibility upon the nematic order parameter by suppressing incompatible nematic fluctuations. As a result, nemato-elasticity is markedly different from bare nematicity. In ideal media devoid of defects, we show the suppression of incompatible nematicity underlies direction-selective criticality, even in the absence of crystalline anisotropy. In systems with defects, meanwhile, we show that elastic pinning fields emanate from quenched defects, generating random longitudinal and transverse conjugate fields for the local nematic order parameter. The coexistence of direction-selective nematic criticality with pinning effects from random fields is explained within our theory from the transformation to the helical basis, implying that local experimental probes of nematicity will be influenced by a linear – but nonlocal – combination of long-ranged and short-ranged helical nematic modes. Because the compatibility relations are gauge constraints endowed in the isotropic medium, our results constitute universal features of nemato-elastic criticality present in all crystalline systems.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
37 pages, 9 figures
Unveiling In-Gap States and Majorana Zero Modes in Superconductor-Topological Insulator Bilayer model
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-01 20:00 EDT
Umesh Kumar, Rafal Rechcinski, Tatiana de Picoli, Jukka Vayrynen, Satoshi Okamoto
Interfaces between topological insulators and superconductors are promising platforms for realizing Majorana zero modes (MZMs) via the superconducting proximity effect. We introduce a bilayer model consisting of the surface states of a three-dimensional topological insulator (3DTI) coupled to an $ s$ -wave superconductor and systematically study the role of interlayer tunneling strength ($ t_\perp$ ). We find that increasing $ t_\perp$ shifts the proximity-induced (PrI) gap minima away from the $ \Gamma$ -point, giving rise to momentum-selective interference patterns that manifest as spatial oscillations in the in-gap states. By introducing an antidot with a magnetic vortex in the SC layer, we investigate the nature of in-gap states including MZMs and Caroli-de Gennes-Matricon (CdGM) modes. With increasing hybridization strength, the energy separation between MZMs and CdGM states increases, enhancing the isolation of MZMs. Importantly, in the strong hybridization limit, the leading CdGM separation remains large inspite of the decrease in the PrI gap. Spin- and spatial-resolved wavefunction analysis reveals angular momentum asymmetries absent in conventional $ s$ -wave systems. A direct comparison with a standalone $ s$ -wave superconductor confirms the emergence of distinct $ p$ -wave-like features in the bilayer geometry. Our results provide experimentally relevant predictions for tuning the stability of MZMs and their differentiation from the CdGM modes in SC-3DTI heterostructures and offer a theoretical framework for probing unconventional superconductivity in engineered topological systems.
Superconductivity (cond-mat.supr-con)
18 pages, 8 figures
Two-dimensional Disordered Projected Branes: Stability and Quantum Criticality via Dimensional Reduction
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-08-01 20:00 EDT
Alexander C. Tyner, Vladimir Juricic, Bitan Roy
The interplay of disorder and dimensionality governs the emergence and stability of electronic phases in quantum materials and quantum phase transitions among them. While three-dimensional (3D) dirty Fermi liquids and Weyl semimetals support robust metallic states, undergoing disorder-driven Anderson localization transitions at strong disorder and the later ones exhibiting additional semimetal-to-metal transition at moderate disorder, conventional two-dimensional (2D) non-interacting systems localize for arbitrarily weak disorder. Here, we show that 2D disordered projected branes, constructed by systematically integrating out degrees of freedom from a 3D cubic lattice via the Schur decomposition, faithfully reproduce the full quantum phase diagram of their 3D parent systems. Using large-scale exact diagonalization and kernel polynomial method, we numerically demonstrate that 2D projected branes host stable metallic and semimetallic phases. Remarkably, the critical exponents governing the semimetal-to-metal and metal-insulator transitions on such 2D projected branes are sufficiently close to those of their 3D counterparts. Our findings thus establish 2D projected branes as genuine quantum holographic images of their higher-dimensional disordered parent crystals, supporting stable semimetallic and metallic phases that are otherwise inaccessible in conventional 2D lattices. Finally, we point to experimentally accessible metamaterial platforms, most notably the photonic lattices with tunable refractive-index disorder, as promising systems to realize and probe these phenomena.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech)
19 Pages, 11 Figures, and 2 Tables
Projected branes as platforms for crystalline, superconducting, and higher-order topological phases
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-01 20:00 EDT
Archisman Panigrahi, Bitan Roy
Projected branes are constituted by only a small subset of sites of a higher-dimensional crystal, otherwise placed on a hyperplane oriented at an irrational or a rational slope therein, for which the effective Hamiltonian is constructed by systematically integrating out the sites of the parent lattice that fall outside such branes [Commun. Phys. 5, 230 (2022)]. Specifically, when such a brane is constructed from a square lattice, it gives rise to an aperiodic Fibonacci quasi-crystal or its rational approximant in one dimension. In this work, starting from square lattice-based models for topological crystalline insulators, protected by the discrete four-fold rotational ($ C_4$ ) symmetry, we show that the resulting one-dimensional projected topological branes encode all the salient signatures of such phases in terms of robust endpoint zero-energy modes, quantized local topological markers, and mid-gap modes bound to dislocation lattice defects, despite such linear branes being devoid of the $ C_4$ symmetry of the original lattice. Furthermore, we show that such branes can also feature all the hallmarks of two-dimensional strong and weak topological superconductors through Majorana zero-energy bound states residing near their endpoints and at the core of dislocation lattice defects, besides possessing suitable quantized local topological markers. Finally, we showcase a successful incarnation of a square lattice-based second-order topological insulator with the characteristic corner-localized zero modes in its geometric descendant one-dimensional quasi-crystalline or crystalline branes that feature a quantized localizer index and endpoint zero-energy modes only when one of its end points passes through a corner of the parent crystal. Possible designer quantum and meta material-based platforms to experimentally harness our theoretically proposed topological branes are discussed.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn), Superconductivity (cond-mat.supr-con)
21 Pages and 14 Figures (For full Abstract, see manuscript)