CMP Journal 2026-02-23
Statistics
Nature: 1
Nature Materials: 2
Nature Physics: 1
Nature Reviews Materials: 1
Nature Reviews Physics: 1
arXiv: 51
Nature
Markovnikov hydroamination of terminal alkenes via phosphine redox catalysis
Original Paper | Photocatalysis | 2026-02-22 19:00 EST
Flora Fan, Kassandra F. Sedillo, Alexander J. Maertens, Abigail G. Doyle
Main-group catalysts that mimic transition metal reactivity can expand substrate tolerance and enable transformations not currently possible with metal catalysis1. The discovery that PIII and PV phosphorus intermediates can undergo transition metal-like two-electron chemistry raises the question whether radical PIV intermediates can mimic other elementary steps in organometallic chemistry2,3. Here we describe a phosphine-photoredox catalyst system that promotes intermolecular Markovnikov hydroamination of unactivated terminal alkenes with numerous classes of N-H azoles, a reaction that is not possible with late transition metal catalysis. Experimental and computational mechanistic studies support a new elementary step for main group catalysis wherein a phosphine radical cation activates the alkene to nucleophilic amination by the azole, a step otherwise associated with transition metals. Given the broad value of nucleophilic alkene functionalization in transition metal catalysis, this PIV mechanism could offer new opportunities for main group element catalysis and chemical synthesis.
Photocatalysis, Reaction mechanisms
Nature Materials
Six-state clock physics in an atomically thin antiferromagnet
Original Paper | Magnetic properties and materials | 2026-02-22 19:00 EST
Frank Y. Gao, Dong Seob Kim, Chao Lei, Ajesh Kumar, Xinyue Peng, Xiaohui Liu, Francesco Barantani, Shangjie Zhang, Kyoung Pyo Lee, Kalaivanan Raju, David Lujan, Saba Arash, Sankar Raman, Shang-Fan Lee, Mengxing Ye, Xiaoqin Li, Allan H. MacDonald, Edoardo Baldini
The study of collective behaviour driven by spontaneous symmetry breaking and topology is crucial for understanding phase transitions in quantum matter. The two-dimensional (2D) XY model, describing spins with continuous in-plane rotational symmetry, hosts the topological Berezinskii-Kosterlitz-Thouless (BKT) transition, where vortex-antivortex binding induces quasi-long-range order. This model was later extended to include anisotropy fields, leading to the six-state clock model, which predicts the instability of the BKT phase toward true long-range order at low temperatures. Here we investigate this physics in the van der Waals antiferromagnet NiPS3 using nonlinear optical micropolarimetry. As the material is thinned to a monolayer, its magnetic response switches abruptly from the 3D XXZ behaviour of multilayers to a distinct 2D regime consistent with a BKT state. Upon further cooling, the monolayer BKT phase becomes unstable and transforms into a pinned state with long-range order. These results, corroborated by Monte Carlo simulations, open pathways to explore spin vortices and topological dynamics in 2D antiferromagnets.
Magnetic properties and materials, Nonlinear optics, Phase transitions and critical phenomena, Surfaces, interfaces and thin films, Topological defects
Crystal-facet-directed all-vacuum-deposited perovskite solar cells
Original Paper | Condensed-matter physics | 2026-02-22 19:00 EST
Xinyi Shen, Wing Tung Hui, Shuaifeng Hu, Fengning Yang, Junke Wang, Jin Yao, Atse Louwen, Bryan Siu Ting Tam, Lirong Rong, David P. McMeekin, Kilian Lohmann, Qimu Yuan, Matthew C. Naylor, Manuel Kober-Czerny, Seongrok Seo, Philippe Holzhey, Karl-Augustin Zaininger, M. Greyson Christoforo, Perrine Carroy, Vincent Barth, Fion Sze Yan Yeung, Nakita K. Noel, Michael Johnston, Yen-Hung Lin, Henry J. Snaith
Vacuum-based deposition is a scalable, solvent-free industrial method ideal for uniform coatings on complex substrates. However, all-vacuum-deposited perovskite solar cells fabricated by thermal evaporation trail solution-processed counterparts in efficiency and stability due to film quality challenges, necessitating advancement and improved understanding. Here, we report a co-evaporation route for 1.67-eV wide-bandgap perovskites by introducing a PbCl2 co-source to optimize film quality. We promote perovskite formation with pronounced (100) ‘face-up’ orientation and deliver a certified all-vacuum-deposited solar cell with 18.35% efficiency (19.3% in the laboratory) for 0.25-cm2 devices (18.5% for 1-cm2 cells). These cells retain 80% of peak efficiency after 1,080 h under the ISOS-L-2 protocol. Leveraging operando hyperspectral imaging, we provide spatiotemporal spectral insight into halide segregation and trap-mediated recombination, correlating microscopic luminescence features with macroscopic device performance while distinguishing radiative from non-ideal recombination channels. We further demonstrate 27.2%-efficient 1-cm2 evaporated perovskite-on-silicon tandem cells and outdoor stability of all-vacuum-deposited tandems in Italy, retaining ~80% initial performance after eight months.
Condensed-matter physics, Solar cells
Nature Physics
Sensing with discrete time crystals
Original Paper | Condensed-matter physics | 2026-02-22 19:00 EST
Leo Joon Il Moon, Paul M. Schindler, Ryan J. Smith, Emanuel Druga, Zhuo-Rui Zhang, Marin Bukov, Ashok Ajoy
Prethermal discrete time crystals are non-equilibrium states of matter with long-range spatiotemporal order and a subharmonic response stabilized by many-body interactions under periodic driving. The robustness of time-crystalline order to perturbations in the drive protocol makes these systems attractive for quantum sensing. Here we exploit the sensitivity of prethermal discrete time crystal order to deviations in its order parameter to implement the frequency-selective detection of time-varying magnetic fields in a system of strongly driven, dipolar-coupled 13C nuclear spins in a diamond. Incorporating an oscillating field into the time crystal dynamics extends its lifetime exponentially, producing a sharp resonant response in the order parameter. The sensor linewidth is set by the time crystal lifetime alone, as strong interspin interactions help stabilize the time-crystalline order. The device operates in the 0.5-50-kHz range–a challenging frequency regime for sensors based on atomic vapour or electronic spins–and achieves competitive sensitivity. The sensing principle we demonstrate is robust to drive errors and sample inhomogeneities, and is applicable across a range of physical platforms including superconducting circuits, neutral atoms and trapped ions.
Condensed-matter physics, Quantum metrology, Statistical physics, thermodynamics and nonlinear dynamics
Nature Reviews Materials
Photonic exceptional points in engineered materials and their emerging applications
Review Paper | Metamaterials | 2026-02-22 19:00 EST
Haoye Qin, Wenjing Lv, Zhe Zhang, Zijin Yang, Jue Li, Mengyao Li, Bo Li, Ji Zhou, Romain Fleury, Patrice Genevet, Qinghua Song, Cheng-Wei Qiu
Enabled by the coalescence of eigenvalues and eigenstates, exceptional points (EPs) in non-Hermitian photonic systems have revolutionized the control of light-matter interactions and sparked growing interest across diverse material and structural platforms. This Review synthesizes advances in engineered materials that harness EPs across three key domains: band EPs in dielectric photonic crystals, wherein radiation-induced loss transforms Hermitian degeneracies into exceptional rings and bulk Fermi arcs; scattering EPs in hybrid dielectric or lossy metasurfaces, enabling unidirectional reflectionless propagation; and Jones EPs in plasmonic and anisotropic materials, which exploit chiral degeneracies for asymmetric scattering and holographic multiplexing. We highlight emerging phenomena in dynamic EP control using tunable materials such as graphene, phase-change media and micro-electromechanical systems, which enable real-time modulation, topological phase transitions and the direct observation of non-Hermitian braiding. The topological properties of EPs, manifested in phase accumulation and half-integer polarization charges, support key applications in wavefront shaping and singular optics. New frontiers involve the integration of EPs with other concepts, including bound states in the continuum, Dirac points, nonreciprocity and magnetic tunability. Bridging non-Hermitian physics with material-engineered platforms paves the way for adaptive photonic devices, topological meta-architectures and machine learning-driven designs, charting a path towards next-generation nanophotonics.
Metamaterials, Optics and photonics
Nature Reviews Physics
Simulating fermions with a digital quantum computer
Review Paper | Computational science | 2026-02-22 19:00 EST
Riley W. Chien, Mitchell Chiew, Brent Harrison, Jason Necaise, Weishi Wang, Maryam Mudassar, Campbell McLauchlan, Thomas M. Henderson, Gustavo E. Scuseria, Sergii Strelchuk, James D. Whitfield
Quantum computers are expected to become a powerful tool for studying physical quantum systems. Consequently, a number of quantum algorithms to determine the physical properties of such systems have been developed. Although qubit-based quantum computers are naturally suited to the study of spin-1/2 systems, systems containing other degrees of freedom must first be encoded into qubits. Transformations to and from fermionic degrees of freedom have long been an important tool in physics and chemistry, which is now finding another application in the simulation of fermionic systems on quantum computers based on qubits. In this Review, we discuss methods for encoding fermionic degrees of freedom into qubits.
Computational science, Information theory and computation, Quantum chemistry, Quantum simulation
arXiv
Fracture Properties of Green Nano Fibrous Network with Random and Aligned Fibre Distribution: A Hierarchical Molecular Dynamics and Peridynamics Approach
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Razie Izadi, Raj Das, Nicholas Fantuzzi, Patrizia Trovalusci
Polylactic acid (PLA) nanofibrous networks have gained substantial interest across various engineering and scientific disciplines, such as tissue engineering, drug delivery, and filtration, due to their unique and multifunctional attributes, including biodegradability, tunable mechanical properties, and surface functionality. However, predicting their mechanical behaviour remains challenging due to their structural complexity, multiscale features, and variability in material properties. This study presents a hierarchical approach to investigate fracture phenomena in both aligned and randomly oriented nanofibrous networks by integrating atomistic modelling and nonlocal continuum mechanics, namely peridynamics. At the nanoscale, all-atom molecular dynamics simulations are employed to apply tensile loads to freestanding pristine and silver-doped PLA nanofibres, where key mechanical properties such as Young’s modulus, Poisson’s ratio, and critical energy release rate are determined. A new method is introduced to transfer data from molecular dynamics to peridynamics by ensuring convergence of the tensile response of a single fiber in both frameworks. This nano-to-micro coupling technique is then used to examine the Young’s modulus, fracture toughness in modes I and II, and crack propagation in PLA nanofibrous networks. The proposed framework can also incorporate the effects of surface coating and fiber arrangements on the measured properties. This research paves the way for the development of stronger and more durable eco-friendly nanofibrous networks with optimised performance.
Materials Science (cond-mat.mtrl-sci)
International Journal of Engineering Science, Volume 204, 2024, 104136, ISSN 0020-7225
Inelastic Constitutive Kolmogorov-Arnold Networks: A generalized framework for automated discovery of interpretable inelastic material models
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Chenyi Ji, Kian P. Abdolazizi, Hagen Holthusen, Christian J. Cyron, Kevin Linka
A key problem of solid mechanics is the identification of the constitutive law of a material, that is, the relation between strain and stress. Machine learning has lead to considerable advances in this field lately. Here we introduce inelastic Constitutive Kolmogorov-Arnold Networks (iCKANs). This novel artificial neural network architecture can discover in an automated manner symbolic constitutive laws describing both the elastic and inelastic behavior of materials. That is, it can translate data from material testing into corresponding elastic and inelastic potential functions in closed mathematical form. We demonstrate the advantages of iCKANs using both synthetic data and experimental data of the viscoelastic polymer materials VHB 4910 and VHB 4905. The results demonstrate that iCKANs accurately capture complex viscoelastic behavior while preserving physical interpretability. It is a particular strength of iCKANs that they can process not only mechanical data but also arbitrary additional information available about a material (e.g., about temperature-dependent behavior). This makes iCKANs a powerful tool to discover in the future also how specific processing or service conditions affect the properties of materials.
Materials Science (cond-mat.mtrl-sci), Artificial Intelligence (cs.AI), Computational Physics (physics.comp-ph)
Families of localized modes of Bose-Einstein condensates enabled by incommensurate optical lattice and photon-atom interactions
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-02-23 20:00 EST
Pedro S. Gil, Vladimir V. Konotop
We consider a Bose-Einstein condensate (BEC) loaded into a one-dimensional optical cavity under the combined action of an external potential and atom-cavity coupling with mutually incommensurate periods. Such configuration enables the localization of matter waves even in the absence of two-body interactions. We study families of localized modes within the mean-field approximation for red and blue detunings from atomic and cavity resonances in relatively shallow quasiperiodic lattices, beyond the validity of the tight-binding approximation. The parameter regimes supporting localization of atomic wave packets are identified. The system exhibits two types of bistability manifested as distinct photon numbers under otherwise identical conditions. One type arises from the coexistence of multiple families of localized modes, typical of conservative nonlinear systems, while the other stems from the multivalued dependence of the families on system parameters, characteristic of systems exhibiting hysteresis. BEC in a cavity may also display pseudodegeneracy, understood as the existence of two distinct atomic-density distributions corresponding to the same atomic and photon numbers (although different chemical potentials). The stability of the localized modes is analyzed. It is shown that, owing to the strong impact of long-range interactions on stability, a two-localized-mode configuration can operate as an XOR logic gate.
Quantum Gases (cond-mat.quant-gas), Pattern Formation and Solitons (nlin.PS)
9 pages, 5 figures
Phys. Rev. Research 8, 013194 (2026)
Scaling invariance: a bridge between geometry, dynamics and criticality
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-02-23 20:00 EST
Edson D. Leonel, Diego F. M. Oliveira
Scale invariance is a central organizing principle in physics, underlying phenomena that range from critical behaviour in statistical mechanics to transport and chaos in nonlinear dynamical systems. Here we present a unified and physically motivated exploration of scaling concepts, emphasizing how invariance under rescaling transformations emerges across systems of increasing dynamical complexity. Rather than adopting a purely abstract approach, we combine simple geometrical constructions, analytical arguments, and prototypical dynamical models to build physical intuition. We begin with elementary, easily reproducible examples governed by a single control parameter, showing how power-law behaviour naturally arises when characteristic scales are absent. We then extend the discussion to nonlinear dynamical systems exhibiting local bifurcations, where two scaling variables control the relaxation toward stationary states. In this context, scaling invariance manifests through critical exponents, crossover phenomena, and critical slowing down, allowing systems of different dimensionality to be grouped into universality classes. Finally, we address continuous phase transitions in chaotic dynamical systems, including transitions from integrability to non-integrability and from bounded to unbounded diffusion. By drawing on concepts traditionally associated with statistical mechanics, such as order parameters, susceptibilities, symmetry breaking, elementary excitations, and topological defects, we show how these transitions can be interpreted within a coherent scaling framework. Taken together, the examples discussed here demonstrate that scaling invariance provides a unifying language for understanding structure, transport, and criticality in nonlinear systems, bridging deterministic dynamics and nonequilibrium statistical physics in a transparent and physically intuitive manner.
Statistical Mechanics (cond-mat.stat-mech), Chaotic Dynamics (nlin.CD)
Direct imaging of a topological nematic phase in a spin-compensated magnet
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-02-23 20:00 EST
Weihang Lu, Camron Farhang, Yuchuan Yao, Pratap Pal, Hao Zhang, Shaofeng Han, Shi-Zeng Lin, Chang-Beom Eom, Jing Xia
Density waves conventionally describe the periodic modulation of charge or spin, yet the spatial modulation of electronic topology has remained elusive. Here, we report the discovery of a Berry-curvature density wave in the noncollinear antiferromagnet Mn3NiN with compensated spins. Using high-precision Sagnac Kerr microscopy, we directly image micrometer-scale modulations of the Berry curvature. These topological ripples exhibit orientations unpinned to the crystal lattice, forming a nematic phase that spontaneously breaks rotational symmetry. We attribute this instability to field-induced spatial variations of the spin texture driven by competing magnetic interactions. This discovery unveils a new class of collective order in spin-compensated magnets arising from the geometric phase of the wavefunction itself and offering a tunable degree of freedom for topological spintronics based on antiferromagnets and altermagnets.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
Precise Determination of the Long-Time Asymptotics of the Diffusion Spreadability of Two-Phase Media
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Shaobing Yuan, Salvatore Torquato
The time-dependent diffusion spreadability $ \mathcal{S}(t)$ is a powerful dynamical probe of the microstructure of two-phase heterogeneous media across length scales [Torquato, S., \emph{Phys. Rev. E.}, 104 054102 (2021)]. It has been shown that when the spectral density takes the power-law form $ \tilde{\chi}_{V}(\mathbf{k})\sim |\mathbf{k}|^\alpha$ as the wavenumber $ |\mathbf{k}|$ tends to zero, the normalized excess spreadability $ \mathscr{s}^{ex}(t)$ [proportional to $ \mathcal{S}(\infty)-\mathcal{S}(t)$ ] scales as $ \mathscr{s}^{ex}(t)\sim t^{-\frac{d+\alpha}{2}}$ in the long-time limit $ t\to\infty$ , enabling one to determine the infinite-wavelength scaling exponent $ \alpha$ . An algorithm that allows one to reliably extract the exponent $ \alpha$ from long-time spreadability data was previously devised [Wang, H., Torquato, S., \emph{Phys. Rev. Appl.}, 17 034022 (2022)]. In this paper, we further improve this procedure to obtain $ \alpha$ even more accurately by incorporating higher-order correction terms to the long-time asymptotics and by utilizing analyticity properties of $ \tilde{\chi}{_V}(k)$ at the origin. We illustrate our procedure by analyzing hyperuniform ($ \alpha> 0$ ), typical nonhyperuniform ($ \alpha=0$ ), and antihyperuniform ($ -d < \alpha <0$ ) models of two-phase media. In addition, by combining the large-$ t$ asymptotic expansion of $ \mathscr{s}^{ex}(t)$ with the small-$ t$ expansion, we have devised a two-point Padé approximant to approximate $ \mathscr{s}^{ex}(t)$ for all $ t$ with just a few parameters. Our findings facilitate the characterization of the microstructure of two-phase media across length scales as obtained from numerical spreadability data or experimental data obtained from NMR relaxation measurements. Our work can also be applied in the inverse design of two-phase microstructures with targeted spreadability behaviors.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn), Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
17 pages, 9 figures
Leveraging mechanical resonances for the selection of promising materials in complex phase spaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Christopher A. Mizzi, Osman El-Atwani, Tannor T.J. Munroe, Saryu Fensin, Boris Maiorov
The “high-entropy” paradigm has been applied to a central challenge in materials science, the design of new functional materials with enhanced performance for targeted applications, with some notable successes over the last twenty years. However, the immensity of the high-entropy design space remains a major impediment to discovering optimal compositions with tailored microstructures. Suites of high-throughput computational tools have been developed to address this problem, but there is a compelling need to inform these models with fast, economical, non-destructive, and versatile experimental guidance. In this work, we demonstrate mechanical resonance measurements can address this need. Mechanical resonance measurements enable the rapid, non-destructive assessment of materials created by novel syntheses and/or processes and provide high-accuracy determinations of elastic constants to directly benchmark models. We exemplify these capabilities on W-Ta-Cr-V-Hf and Mo-Nb-Ti-V-Zr refractory high-entropy alloys and suggest methodologies for the wider adoption and application of mechanical resonance measurements.
Materials Science (cond-mat.mtrl-sci)
El Agente Sólido: A New Age(nt) for Solid State Simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Sai Govind Hari Kumar, Yunheng Zou, Andrew Wang, Jesús Valdés-Hernández, Tsz Wai Ko, Nathan Yue, Olivia Leng, Hanyong Xu, Chris Crebolder, Alán Aspuru-Guzik, Varinia Bernales
Quantum chemistry calculations are a key component of the materials discovery process. The results from first-principles explorations enable the prediction of material properties prior to experimental validation. Despite their impact, the practical use of first-principles methods remains limited by the expertise required to design, execute, and troubleshoot complex computational workflows. Even when workflows are successfully built, they are sometimes rigid and not adaptable to different use cases. Recent advances in large language models (LLMs) and agentic systems offer a pathway to flexibly automate these processes and lower barriers to entry. Here, we introduce El Agente Sólido, a hierarchical multi-agent framework for automating solid-state quantum chemistry workflows using the open-source Quantum ESPRESSO simulation package. The framework translates high-level scientific objectives expressed in natural language into end-to-end computational pipelines that include structure generation, input file construction, workflow execution, and post-processing analysis. El Agente Sólido integrates density functional theory with phonon calculations and machine-learning interatomic potentials to enable efficient and physically consistent simulations. Extensive benchmarking and case studies demonstrate that El Agente Sólido reliably executes a wide range of solid-state calculations, highlighting its potential to improve reproducibility and accelerate computational materials discovery
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
42 pages, 31 figures, 18 tables
Ab initio Monte Carlo prediction of order-to-disorder transitions in multicomponent MXenes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
This letter predicts unprecedented order-to-disorder transition behaviors in multicomponent MXenes using an integrated and improved first-principles Monte Carlo (MC) framework. The improvements include (i) structural relaxation and (ii) selective atom swapping during MC iterations for more accurate and efficient predictions. Using (TiMo)-based double transition metal (DTM) carbide MXenes as a model system, ab initio MC simulations reveal that surface termination and coordination environments play critical roles in governing chemical ordering in MXenes. Specifically, the formation of out-of-plane MXene (o-MXenes) with Mo segregation to outermost metallic layers (M’) is only driven by the oxygen (O) termination at prismatic sites. In contrast, O termination at octahedral sites and fluorine (F) termination at both prismatic and octahedral sites always promote the formation of o-MXenes with Ti-segregated to M’ layers. Furthermore, changing the F/O ratio at prismatic termination sites or alternating the atomic coordination within the MXene lattices can induce an order-to-disorder transition in DTM MXenes.
Materials Science (cond-mat.mtrl-sci)
7 pages, four figures
Microwave Imaging of Edge Conductivity in Graphene at Charge Neutrality and Quantum Hall States
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-02-23 20:00 EST
Hongtao Yan, Chun-Chih Tseng, Anzhuoer Li, Manish Kumar, Kaile Wang, Shizai Chu, Kenji Watanabe, Takashi Taniguchi, Allan H. MacDonald, Matthew Yankowitz, Keji Lai
We report local conductivity imaging of edge states in monolayer graphene by millikelvin microwave impedance microscopy (MIM). At the charge-neutrality point, as the magnetic field increases, the local conductivity at the edge drops to zero more slowly than in the bulk. This behavior is consistent with the calculated spatial profile of the charge gap in the canted antiferromagnetic phase. For comparison, we also perform microwave imaging of integer quantum Hall states away from neutrality, which host dissipationless chiral edge channels. The evolution of the edge signal as a function of the bulk gap is fundamentally different between the Landau level filling factor $ \nu = 0$ and $ |\nu| \ge 1$ integer quantum Hall states, which can be qualitatively explained by numerical simulations and theoretical analysis. Our results provide a comprehensive microscopic picture of the edge and bulk states as the Fermi level moves across the unique Landau-level spectrum of graphene.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Observation of Room-temperature Charge Density Wave Correlations via Coherent Phonon Spectroscopy in Sn-doped Kagome Superconductor CsV$_3$Sb$_5$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-02-23 20:00 EST
Qinwen Deng, Andrea Capa Salinas, Suchismita Sarker, Leon Balents, Stephen D. Wilson, Liang Wu
In this work, we perform ultrafast time-resolved reflectivity measurements to track the evolution of charge density wave (CDW) correlations in Sn-doped Kagome superconductor CsV$ _3$ Sb$ _{5-x}$ Sn$ _x$ . By extracting the coherent phonon spectrum, we evidence robust signatures of CDW correlations at temperature and doping ranges far beyond the phase boundary of long-range CDW order. Remarkably, we unveil short-range CDW correlations survive up to room temperature in $ x = 0.32$ Sn-doped CsV$ _3$ Sb$ _5$ , supported by synchrotron X-ray diffraction measurements. We point out the introduction of quenched disorder by Sn doping can pin the CDW and form static short-range CDW, which can explain the observed persistent CDW signatures. Our results thus corroborate the ubiquity and robustness of CDW correlations in Sn-doped CsV$ _3$ Sb$ _5$ and provide new insights on the role of disorders on the CDW correlations in AV$ _3$ Sb$ _5$ family.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Accepted to Physical Review B
Efficient photocatalytic CO2 Reduction to C2+ Products with Pt1-xPdxSn4 Dirac Nodal Arc Semimetal
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Kangwang Wang, Jie Zhan, Jun Liu, Zaichen Xiang, Wanyi Zhang, Lingyong Zeng, Kai Yan, Yan Sun, Huixia Luo
The photochemical CO2 reduction reaction represents a zero-carbon pathway for converting CO2 into value-added chemicals, yet its industrial implementation has been constrained by low selectivity and product diversity. Dirac nodal arc semimetals characterized by ultrahigh carrier mobility with over 25000 cm2 V-1 s-1 offer a promising platform to search for efficient catalysts for CO2 conversion. Herein, we demonstrate that strategic Pt incorporation into PdSn4 optimizes the electronic structure and carrier dynamics of this Dirac semimetal. Experimental and theoretical analyses reveal that the resulting Pd-Sn-Pt local electronic structure redistributes charge density around Pd and Pt atoms, which facilitates C-C coupling via \astOC-COH and \astOC-CHOH intermediates and enhances carrier mobility by 40% versus the pristine PdSn4 single crystal. The optimized Pd0.4Pt0.6Sn4 single crystal achieves C2H4 with formation rate of 0.000328 mol g-1 h-1, product selectivity of 73.1% and electron-based selectivity of 89%. This work establishes electronic-structure-tunable Dirac semimetals as a new paradigm for multi-carbon photochemical CO2 reduction, providing a design strategy for next-generation photocatalysts.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
26 pages, 6 figures
Advanced Material, 2026, e18317
Optical and Hall conductivity of the two dimensional Hubbard model: effective theory description, sign-problem-free Monte Carlo simulation and applications to the cuprate superconductors
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-02-23 20:00 EST
Exact formulas for the optical conductivity and the Hall conductivity of the two dimensional Hubbard model are derived in terms of an effective theory description of the local moment fluctuation in the system. In this framework, the quantum Monte Carlo simulation of the electromagnetic response of such a strongly correlated electron system becomes sign-problem-free in many physically relevant cases. In particular, it is sign-problem-free when we assume the widely used Millis-Monien-Pines form for the phenomenological susceptibility in the effective action of the fluctuating local moment, even though these local moments are now subjected to Landau damping as a result of their coupling to the itinerant quasiparticle on the fermi surface. This is true more generally when a $ \varphi^{4}$ term is included in the effective action and is thus not restricted to the Gaussian limit. Here we demonstrate the power of this framework by studying the effect of thermal fluctuation of the local moment on the optical conductivity $ \sigma^{xx}(\omega)$ and the Hall conductivity $ \sigma^{xy}(\omega)$ of the cuprate superconductors. Both $ \sigma^{xx}(\omega)$ and $ \sigma^{xy}(\omega)$ calculated are found to exhibit a two-component structure, with a Drude component at low energy and a mid-infrared component at higher energy. Depending on the relative importance of the hole pocket and the electron pocket on the reconstructed fermi surface and the coupling strength to the local moment, the Drude component in $ \mathrm{Im}\sigma^{xy}(\omega)$ can be either positive or negative.(full-length abstract can be found in the main text.)
Strongly Correlated Electrons (cond-mat.str-el)
19 pages, 7 figures. Some results of arXiv:2404.11224 are included here, but rewritten in a much broader perspective
Method for real-time monitoring of paramagnetic reactions using spin relaxometry with fluorescent nanodiamonds
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
Trent Ralph, Erin S. Grant, Lianne Lay, Sepehr Ahmadi, David A. Simpson
Spin relaxometry using fluorescent nanodiamonds (FNDs) has been applied successfully to sense numerous paramagnetic target molecules such as free radicals and metalloproteins. However, despite their high sensitivity, T1 spin relaxation measurements are often hampered by their slow acquisition speed. Here, we demonstrate a method that allows for real-time monitoring of paramagnetic chemical reactions. We demonstrate T1 spin relaxometry from thousands of FNDs using an optimised cuvette-based system integrating an avalanche photodiode operated in linear mode, and a fast, fieldprogrammable gate array (FPGA) for data collation. We demonstrate chemical monitoring of the reduction of Cu(II) to Cu(I) ions in-solution with a 15 second integration using an optimised T1 sensing protocol. Our method achieves more than two orders of magnitude speed up with an order of magnitude reduction in cost when compared with traditional techniques. With further technical improvements, we believe this in-solution method could be extended to sense the sub-second chemical kinetics of paramagnetic molecules in solution.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 3 figures
Irradiation-Driven Recrystallization in Fusion-Grade Tungsten: A Mesoscale, Microstructure-Aware Model
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Jinxin Yu, Sicong He, Giacomo Po, Jason R. Trelewicz, Timothy J. Rupert, Jaime Marian
Tungsten (W) is the leading candidate material for plasma-facing components in fusion reactors, yet its upper operational temperature is limited by premature grain growth and recrystallization processes. Irradiation adds further complications by generating defect clusters and transmutation products that alter both the driving forces and kinetics of grain boundary motion. In this work, we develop a physics-based, multiscale framework that couples crystal plasticity, stochastic cluster dynamics, and discrete grain boundary dynamics to model the co-evolution of plastic deformation, irradiation damage, and grain growth in fusion-grade tungsten polycrystals. The approach enables simulations on realistic microstructures with arbitrary grain size and misorientation distributions, without recourse to mean-field simplifications. The model captures (i) the spatial heterogeneity of dislocation density distribution during hot working; (ii) irradiation-induced defect accumulation under fusion conditions, and (iii) the buildup of chemical and elastic driving forces for grain boundary migration and microstructural evolution. Parametric studies demonstrate the dominant influence that temperature has on thermally activated grain-boundary mobility, a weaker dependence on prior strain, and a pronounced retardation of recrystallization by rhenium segregation arising from neutron transmutation. Under fusion energy irradiation conditions, our framework predicts a substantial reduction of the effective recrystallization temperature relative to unirradiated microstructures, while Re production restores and even elevates this limit. By providing quantitative projections of recrystallization kinetics and in-service recrystallization temperatures, this work establishes a predictive tool for assessing the lifetime and operational envelope of W-based plasma-facing materials under fusion conditions.
Materials Science (cond-mat.mtrl-sci)
37 Pages, 14 figures
Extended Mean-Field Theory for the 2D Hubbard Model in Degenerate Dilute Electron Gases: Fluctuations, Superconducting Dome, and Interaction Mechanisms in Strontium Titanate
New Submission | Superconductivity (cond-mat.supr-con) | 2026-02-23 20:00 EST
Xing Yang, Xinyu Zhang, Xuchang Zhang
Strontium titanate ($ \mathrm{SrTiO_3, STO}$ ) dome-shaped superconducting transition temperature as a function of chemical potential, consistent with STO experiments, and shows that tunable s-wave and d-wave symmetries are modulated by doping. Superconducting fluctuations validate the mean-field approximation at low temperatures but destroy pairing at higher temperatures. The charge-density-wave order competes with superconductivity, enhances the effective electron mass inversely with the chemical potential, and increases with the interaction strength $ U$ and the temperature $ T$ . SDW order is rare and fragile, while an additional magnetic term induces subtle band splitting. These findings suggest e-e contributions to STO’s transport anomalies and provide criteria to distinguish e-e from e-ph origins, offering insights for engineering higher $ T_c$ in dilute systems.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Lattice and Orbital-Resolved Fermiology of Metallenes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Kameyab Raza Abidi, Mohammad Bagheri, Pekka Koskinen
Atomically thin metallenes have emerged as a new member of the two-dimensional (2D) materials family. Recent experimental realization of metallenes in the Ångström limit has further intensified interest in this class of 2D materials. However, achieving sub-atomic insight into them demands the most detailed and systematic characterization of their electronic structure. Such understanding is essential for the rational design and exploitation of their properties in plasmonics, catalysis, and quantum optics. Existing electronic-structure studies are either scattered or focus on a few selected systems, and a comprehensive view of their band structures and Fermi surfaces remains missing. Here, we address this gap by studying 45 elemental metallenes in six monolayer lattices (honeycomb, square, hexagonal, and their buckled forms) using density-functional theory. We found that lattice type primarily fixes the shape and radial placement of the Fermi-lines, while out-of-plane buckling introduces controlled modifications: it shortens long straight Fermi-line segments, and occasionally creates, removes, or merges small Fermi-line pockets. The electronic configuration determines which orbital type dominates the Fermi level. We summarized Fermiology using a single score for each element, termed pocketness, derived from four descriptors that combine element properties (symmetry, coordination) with electronic characteristics (dispersion, Fermi-surface topology). This score enables targeted angle-resolved photoemission spectroscopy (ARPES) tests, controlled Lifshitz transitions, and provides a predictive basis for transport and device applications.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Computational Physics (physics.comp-ph)
Achieving Robust Extrapolation in Materials Property Prediction via Decoupled Transfer Learning
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Tasuku Sugiura, Teruyasu Mizoguchi
Machine learning has revolutionized materials property prediction, yet fails catastrophically when extrapolating beyond training distributions-precisely the capability required for discovering unprecedented materials. Graph neural networks (GNNs) exhibit this collapse because end-to-end training fundamentally couples learned representations to target property distributions, preventing genuine extrapolation. We demonstrate that decoupled transfer learning-separating pretrained GNN feature extractors from simple regressors-overcomes this barrier. Pretrained features provide transferable structural knowledge, while simple regressors enable smooth extrapolation by maintaining learned trends beyond training boundaries. Benchmarked on layered intercalation compounds through four rigorous extrapolation scenarios and a temporal Materials Project split, our framework achieves 68% error reduction (RMSE: 0.881 vs. 2.778 eV/atom) versus end-to-end GNNs for extrapolation. Failure analysis reveals extrapolation succeeds for continuous chemical space but fails for discontinuous space, establishing clear design principles. Validated on Fermi energy prediction, this framework is immediately deployable using existing pretrained models, requiring no architectural innovations-transforming ML-driven materials discovery.
Materials Science (cond-mat.mtrl-sci)
15 pages, 2 tables, 4 figures, 10 supplementary figures, 1 supplementary table
Ultrafast Band-Gap Renormalization in Bilayer Graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
Eduard Moos, Zhi-Yuan Deng, Hauke Beyer, Arpit Jain, Chengye Dong, Li-Syuan Lu, Joshua A. Robinson, Kai Rossnagel, Michael Bauer
We demonstrate, by femtosecond time- and angle-resolved photoemission spectroscopy, that photoinduced interlayer charge transfer in a heterostructure consisting of Bernal-stacked bilayer graphene and a single atomic layer of silver on 6H-SiC(0001) transiently modulates the intrinsic potential landscape across the silver-graphene interface. This acts as an ultrafast optoelectronic gate that drives momentum-dependent band renormalizations, resulting in a transient band-gap opening on femtosecond timescales. Simultaneously, the photogenerated hot-carrier population enhances electronic screening, leading to subsequent closing of the band-gap beyond the thermal equilibrium value. These findings reveal two different mechanisms for photoinduced, reversible control of the electronic band structure in bilayer graphene – interlayer charge transfer and hot-carrier-enhanced screening – providing a general framework for the ultrafast control of electronic properties in graphene-based heterostructures. This opens up novel pathways for the realization of ultrafast optoelectronic devices and the exploration of correlated quantum phases in bilayer graphene under non-equilibrium conditions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other)
A mobility based approach to transport in chiral fluids
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-02-23 20:00 EST
Filippo Faedi, Erik Kalz, Ralf Metzler, Abhinav Sharma
Chiral fluids, for which the mobility tensor has antisymmetric, off-diagonal components, exhibit transport phenomena absent in conventional systems, including interaction-enhanced diffusion and negative mobility. While these effects have been predicted theoretically and observed in simulations, their microscopic origin has remained unclear. Here, we address this question using a mobility-based nonequilibrium approach, analysing the steady-state drift of a tracer driven through an interacting chiral fluid. We show that, under strong chirality, the tracer generates a reversed density wake, in which regions of particle accumulation and depletion are inverted compared to the achiral case. This structural inversion of the wake provides a unified physical mechanism underlying both enhanced diffusion and negative mobility. Furthermore, we demonstrate that these phenomena are robust to changes in the interaction potential, highlighting their generality as a consequence of odd mobility.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
A contour for the entanglement negativity of bosonic Gaussian states
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-02-23 20:00 EST
We construct a contour function for the logarithmic negativity and the logarithm of the moments of the partial transpose of the reduced density matrix for multimode bosonic Gaussian states of a free lattice model. In one spatial dimension, numerical results are obtained for harmonic chains either in the ground state or at finite temperature, by considering, respectively, either a subsystem made by two adjacent or disjoint blocks on the line or a bipartition of the circle. The contour function of the logarithmic negativity diverges only at the entangling points, while the contour function for the logarithm of the moments of the partial transpose is divergent also at the boundary of the bipartite subsystem, as functions of the position. In a two-dimensional conformal field theory, analytic expressions that describe these divergencies are discussed. In one spatial dimension, we explore the partial derivative of the logarithmic negativity of two adjacent intervals with respect to the logarithm of the harmonic ratio of their lengths while their ratio and the other parameters are kept fixed. Considering the ground state of the harmonic chain on the line and in the massive regime, we report numerical results showing that this quantity displays a monotonically decreasing behaviour.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th), Quantum Physics (quant-ph)
62 pages, 14 figures
Electron-phonon coupling revealed by charge density fluctuations in cuprate superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2026-02-23 20:00 EST
Martina Fedele, Giacomo Merzoni, Marco Moretti Sala, Francesco Rosa, Nicholas B. Brookes, Floriana Lombardi, Sergio Caprara, Giacomo Ghiringhelli, Riccardo Arpaia
Electron-phonon coupling (EPC) governs lattice dynamics, charge transport, and collective electronic phases in quantum materials. In several families of unconventional superconductors, including transition-metal dichalcogenides and kagome metals, growing evidence points to a cooperative role of EPC and dynamic charge-density fluctuations (CDF) in stabilizing superconductivity. However, how the EPC strength evolves across phase diagrams and relates to superconducting properties in strongly correlated systems remains an open question. Here we investigate the interplay between phonons and the CDF recently identified in cuprate superconductors. Using resonant inelastic x-ray scattering, we track the dispersion and intensity of bond-stretching phonons in YBa$ _2$ Cu$ _3$ O$ _{7-\delta}$ over wide ranges of doping, temperature, and momentum. We find that both the phonon softening at the CDF wave vector and the EPC strength, extracted from a pronounced phonon intensity anomaly, are maximized near $ p = 0.19$ , where superconducting properties are optimal and CDF intensity is strongest. These results identify dynamic charge-density fluctuations, rather than quasi-static charge density waves, as the dominant source of phonon renormalization in cuprates, and establish a direct correlation between EPC strength and the superconducting dome. More broadly, our measurements highlight EPC as a doping-dependent property of correlated materials, shaped by the electronic environment in which lattice vibrations are embedded.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
34 pages, 11 figures
Physical Pictures for Quasisymmetry in Crystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Bryan D. Assunção, Emmanuel V. C. Lopes, Tome M. Schmidt, Gerson J. Ferreira
Quasisymmetry (QS) provides a novel route to understand and control near-degeneracies, Berry curvature, optical selection rules, and symmetry-protected phenomena in quantum materials. Here we give physical interpretations of the emergence of QS operators across multiple material families. Using density functional theory and the $ \mathbf{k}\cdot\mathbf{p}$ formalism, we identify QS subspaces and calculate their representation matrices, quantifying the quasisymmetry via a metric $ \epsilon$ that measures subspace invariance. For Sn/SiC and transition-metal dichalcogenide monolayers, QS corresponds to an emergent mirror symmetry, whereas in wurtzite crystals it manifests as an emergent spatial inversion. By contrast, for AgLa the QS appearing in avoided crossings is inherited from a nearby high-symmetry point rather than being an emergent lattice symmetry. Combining group-theoretical analysis and $ \mathbf{k}\cdot\mathbf{p}$ modeling, our results establish concrete physical pictures for QS and provide practical criteria to diagnose it in first-principles calculations.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages, 7 figures
Exact response functions for a compressible thin fluid layer with odd viscosity
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-02-23 20:00 EST
Abdallah Daddi-Moussa-Ider, Yuto Hosaka, Shigeyuki Komura
Fluids composed of chiral active components can exhibit odd viscosity, a property that breaks time-reversal and parity symmetries. We investigate the hydrodynamic response to monopole and dipole singularities in a compressible thin fluid layer with odd viscosity, supported by a conventional lubrication layer. Using the two-dimensional Green’s function in Fourier space, we derive exact analytical solutions for the flow and pressure fields. These solutions provide a detailed description of the hydrodynamic interactions governing the motion of colloidal particles and microswimmers in confined chiral fluids, offering insight into the role of odd viscosity in modifying particle dynamics and collective behavior. The derived results are directly applicable to modeling transport, control, and self-organization phenomena in active and chiral microfluidic systems.
Soft Condensed Matter (cond-mat.soft), Fluid Dynamics (physics.flu-dyn)
11 pages, 6 figures
Second-Coordination-Sphere Cation Substitution as a Tool for Controlling Phase Transitions and Performance of the Luminescence Thermometry
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Muhammad T. Abbas, M. Szymczak, M. Fandzloch, D. Szymanski, A. Sieradzki, L. Marciniak
Despite the exceptionally high relative sensitivities achieved by luminescent thermometers based on first-order structural phase transitions, their principal limitation lies in the inherently narrow thermal operating range associated with the transition temperature. In this work, we demonstrate that partial substitution of Li+ by Na+ ions in the second coordination sphere of Eu3+ ions in LiYO2 enables a substantial shift of the phase transition temperature, thereby allowing controlled optimization of the thermometric performance. This approach represents a significantly more cost-effective and efficient strategy for tuning the phase transition temperature compared with the previously proposed substitution of Y3+ by other lanthanide ions. Importantly, we show that lowering the transition temperature through Na+ incorporation simultaneously introduces static compositional disorder and local lattice strain. As a consequence, the enthalpy difference between the competing structural phases decreases, and the cooperativity of the lattice distortion is reduced, indicating a gradual weakening of the first-order character of the phase transition. Our results demonstrate that such structural modifications, while effective in shifting the transition temperature, inevitably lead to a reduction in the relative sensitivity of phase-transition-based luminescent thermometers.
Materials Science (cond-mat.mtrl-sci)
Correlated phases of moat-band excitons in two-dimensional systems
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-02-23 20:00 EST
L. Maisel Licerán, S. H. Boeve, H. T. C. Stoof
We study two-dimensional systems of interacting excitons with a moat dispersion, for which the ground-state energy manifold presents a ring of discrete or continuously degenerate minima around a single point in momentum space. At low densities and for an idealized, perfectly degenerate moat, we show that the excitons undergo statistical transmutation and stabilize a chiral spin liquid. At higher densities, the moat dispersion favors Bose-Einstein condensation into states occupying multiple momenta, leading to inhomogeneous condensate phases and potentially supersolidity. We discuss the impact of band-structure warping present in realistic systems and argue that it generically stabilizes Bose-condensed phases over the chiral spin liquid, and analyze the superfluid response of the former which is unconventional due to the moat band. We also demonstrate that a proper renormalization of the exciton-exciton interaction is essential for describing these phases, and show that even purely repulsive interactions can favor inhomogeneous condensates. To further explore inhomogeneous condensate phases, we employ a Gross-Pitaevskii framework with a pseudopotential approximation and map out the resulting phase diagram. We show that the presence of degenerate dispersion minima can drive supersolidity already at weak coupling, in contrast to systems with a standard parabolic dispersion. Finally, we discuss our results in the context of real excitonic systems and argue that moat-band-induced supersolidity can be within experimental reach for realistic values of the model parameters.
Quantum Gases (cond-mat.quant-gas), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
A Computational Study of Organic Molecular Crystals for Photocatalytic Water Splitting
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
James D. Green, Daniel G. Medranda, Hong Wang, Andrew I. Cooper, Jenny Nelson, Kim E. Jelfs
Organic crystalline materials are potential candidates for photocatalytic overall water splitting (OWS). Although organic crystals have been heavily investigated for application in organic electronics, such as organic light-emitting diodes (OLEDs) and solar cells, there have been comparatively fewer studies into OWS in these materials. A major challenge is the large number of electronic and structural criteria that must be met for a material to make a viable OWS photocatalyst. Optical absorption, reduction and oxidation potentials and charge-transport properties are among the key considerations, and these are influenced both by molecular properties and the solid-state packing arrangement, making computational modelling challenging. Here, we investigate a series of known organic electronic materials that have published crystal structures using periodic density functional theory (DFT) and compare their calculated electronic properties of optical absorption and reduction and oxidation potentials with literature experimental data. Furthermore we perform a series of gas-phase molecular calculations which show a good agreement with literature data and periodic DFT for the optoelectronic properties of the organic molecular crystals studied, showing that gas-phase molecular calculations could be used to screen organic crystals for OWS at a reduced computational cost.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Bright-dark exciton splitting in lead halide perovskite crystals accessed via quantum beats in photon echoes
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
M. Alex Hollberg, O. Nestoklon, Artur V. Trifonov, Stefan Grisard, Oleh Hordiichuk, Dmitry N. Dirin, Maksym V. Kovalenko, Dimitri R. Yakovlev, Manfred Bayer, Ilya A. Akimov
Understanding the fine structure of excitons is crucial for optoelectronic and quantum photonic applications of lead halide perovskites. It is demonstrated that polarization-sensitive photon echo spectroscopy in magnetic field provides a powerful method to access coherent exciton dynamics and reveal their energy level structure, which is hidden by inhomogeneous broadening. Exciton quantum beats observed in both Faraday and Voigt geometries offer a precise probe of the energy splittings among the four 1$ s$ exciton states, enabling determination of the fine structure and bright-dark splittings. Application of this technique to bulk mixed halide perovskite crystals FA$ _{0.9}$ Cs$ {0.1}$ PbI$ {2.8}$ Br$ {0.2}$ reveals a bright-dark exciton splitting of $ \Delta\mathrm{X}=0.46~$ meV, along with electron and hole Landé $ g$ factors $ g\mathrm{e}=3.38$ and $ g\mathrm{h}=-1.14$ , respectively. The quantum beats persist on timescales of 20–50$ $ ps, demonstrating remarkably robust spin and optical coherences at cryogenic temperature of 2$ ~$ K. The decay of the quantum beats of the outer doublet is governed by dephasing due to dispersion of the bright-dark splitting of $ \sim0.06$ meV caused by localization potential fluctuations, while dephasing in the bright exciton inner doublet originates from a small zero field splitting of $ \sim0.035~$ meV due to anisotropic potentials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
9+10 pages, 4+7 figures, 1+2 tables
Machine-learning force-field models for dynamical simulations of metallic magnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-02-23 20:00 EST
Gia-Wei Chern, Yunhao Fan, Sheng Zhang, Puhan Zhang
We review recent advances in machine learning (ML) force-field methods for Landau-Lifshitz-Gilbert (LLG) simulations of itinerant electron magnets, focusing on scalability and transferability. Built on the principle of locality, a deep neural network model is developed to efficiently and accurately predict the electron-mediated forces governing spin dynamics. Symmetry-aware descriptors constructed through a group-theoretical approach ensure rigorous incorporation of both lattice and spin-rotation symmetries. The framework is demonstrated using the prototypical s-d exchange model widely employed in spintronics. ML-enabled large-scale simulations reveal novel nonequilibrium phenomena, including anomalous coarsening of tetrahedral spin order on the triangular lattice and the freezing of phase separation dynamics in lightly hole-doped, strong-coupling square-lattice systems. These results establish ML force-field frameworks as scalable, accurate, and versatile tools for modeling nonequilibrium spin dynamics in itinerant magnets.
Strongly Correlated Electrons (cond-mat.str-el), Machine Learning (cs.LG), Computational Physics (physics.comp-ph)
9 pages, 5 figures
AIP Advances 16, 025031 (2026)
Electrodynamics of swift-electron momentum transfer to a large spherical nanoparticle
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
Jesús Castrejón-Figueroa, Jorge Luis Briseño-Gómez, Eduardo Enrique Viveros-Armas, José Ángel Castellanos-Reyes, Alejandro Reyes-Coronado
Swift electrons from highly focused beams produced in aberration-corrected scanning transmission electron microscopes offer a powerful route for probing and manipulating matter at the nanoscale. Although linear momentum transfer from swift electrons to nanoparticles has been investigated theoretically and experimentally, subsequent analyzes revealed that several earlier predictions relied on non-causal dielectric functions or insufficient numerical convergence, leading to spurious sign reversals in the transferred momentum. Here, we derive analytical expressions and develop a numerically efficient electrodynamic framework to compute the linear momentum transferred from a swift electron to an isolated spherical nanoparticle described by a fully causal, local dielectric response. We apply our framework to large nanoparticles with 50 nm radius and explicitly resolve the spectral density of linear momentum transfer across the full frequency domain. Using causal dielectric functions for aluminum and bismuth, we analyze the role of electron velocity, impact parameter, and material-specific resonances. We find that, when causality and full multipolar convergence are enforced, the net transverse linear momentum transferred to spherical nanoparticles remains attractive toward the electron trajectory for all nanoparticles considered, despite the presence of material-dependent sign changes in individual electric and magnetic contributions. These results contrast with earlier theoretical predictions of net repulsive behavior and indicate that additional physical mechanisms beyond the present isolated, local description are required to account for experimentally observed repulsion. Our work establishes a robust reference framework for momentum transfer calculations and provides quantitative benchmarks relevant for electron-beam-based nanoscale manipulation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph), Optics (physics.optics)
14 pages, 9 figures, 7 appendices
Properties of Liquid Crystalline Elastomer Foams
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-02-23 20:00 EST
Oliver Dai, Andrew Terentjev, Eugene M. Terentjev
We investigate how controlled foaming alters the mechanical dissipation of liquid crystalline elastomers (LCEs). Using thermal expandable microspheres, we generate homogeneous foams with precisely tuned bubble volume fractions up to 13% and compare their behaviour with non-mesogenic silicon analogues. We show that microsphere expansion induces a particle-centred mesogenic interphase arising from local elastic distortion and preferential alignment of mesogenic units at the inclusion surface. At low bubble volume fraction (0.5 to 5%), these interfaces remain spatially isolated and produce a pronounced no-monotonic enhancement of damping, with the loss factor reaching tan-delta=0.2 even in the isotropic regime. At higher loading, interphase overlaps and mechanical constraints suppress this effect, and the dissipation returns towards baseline elastomeric values. Large-strain tensile tests and impact experiments exhibit the same non-monotonic trend, demonstrating that low density LCE forms achieve the highest mechanical energy absorption per unit mass. Compared with conventional high porosity polymer foams used for acoustic damping, these materials retain sufficient mechanical integrity to sustain impact loads, establishing a microstructural route to engineer high-performance damping in soft solids.
Soft Condensed Matter (cond-mat.soft)
T-linear specific heat in pressurized and magnetized Shastry-Sutherland Mott insulator SrCu2(BO3)2
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-02-23 20:00 EST
Jing Guo, Pengyu Wang, Cheng Huang, Chengkang Zhou, Menghan Song, Xintian Chen, Ting-Tung Wang, Wenshan Hong, Shu Cai, Jinyu Zhao, Jinyu Han, Yazhou Zhou, Qi Wu, Shiliang Li, Zi Yang Meng, Liling Sun
The pressurized Shastry-Sutherland Mott insulator SrCu2(BO3)2 has been found to host a plaquette-singlet phase and an antiferromagnetic phase that break different symmetries this http URL recent experiment showed that their transition is of a first order nature, which seems against the pursuit of exotic and deconfined degrees of freedom in this famous frustrated quantum magnet. We found a new direction in this study. By applying a magnetic field to the material, we discover that SrCu2(BO3)2 exhibits a universal and metallic T-linear specific heat behavior in a large magnetitic field range close to the pressure of zero-field first order transition between plaquette-singlet and antiferromagnetic phases. Such an unexpected gapless response from an electronically gapped Mott insulator could be attributed to magnetized Dirac spinons liberated by the combined effect of magnetic field and pressure, consistently seen from our quantum many-body thermal tensor network computation of the Shastry-Sutherland model under magnetic field. Such a robust and universal T-linear specific heat phase points out the richness of the phase diagram of the material expanded by the axes of pressure and magnetic field and is calling for new theoretical frameworks to its full explanation.
Strongly Correlated Electrons (cond-mat.str-el)
20 pages, 4 figures
RHEED pattern classification by a convolutional neural network for the growth of chalcogenide thin films and nanostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Nathan Muetzel, Viet Luu, Sara Bey, Muhsin Abdul Karim, Kota Yoshimura, Xinyu Liu, Marwan Gebran, Badih A. Assaf
The use of reflection high energy electron diffraction (RHEED) plays a critical role for in-situ characterization in molecular beam epitaxy, pulsed laser deposition and sputtering. While sensitive to crystal symmetries and morphology, it is used ubiquitously to determine the growth modes of thin films. However, analysis of RHEED patterns depends on skilled experts and is therefore difficult to incorporate into the growth strategy in real-time. The development of machine learning (ML) processes, specifically convolutional neural networks (CNNs), presents a unique opportunity towards real-time RHEED pattern recognition. In this study, we develop a CNN model that can accurately classify four common and distinct RHEED patterns present in chalcogenide thin film growth. Its reached accuracy reached 94.9% for single run and 91.2% when averaged over 20 seeds. Our network is able to distinguish the nucleation of three common growth modes encountered in epitaxy, namely Volmer Weber, Stransky-Krastanov and Frank-van der Merwe, potentially enabling future automation of substrate temperature and shutter control informed by RHEED data. The network is material-agnostic and distinguishes the VW process with greater than 98% accuracy but is somewhat more limited in its ability to properly classify roughening and the initiation of Stransky-Krastanov growth. Our findings show that ML techniques can be successfully implemented even in cases where there is no detailed knowledge of growth chemistry providing an avenue towards real-time incorporation of ML to control nanostructure nucleation and thin film morphology.
Materials Science (cond-mat.mtrl-sci)
accepted
Quadrupole formation and coupling to magnetic and structural degrees of freedom in the $5d^1$ double perovskites Ba$_2$MgReO$_6$ and Ba$_2$NaOsO$_6$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Francesco Martinelli, Claude Ederer
We investigate the interplay between charge, magnetic, and structural degrees of freedom in the isostructural and isoelectronic $ 5d^1$ double-perovskites Ba$ _2$ MgReO$ _6$ and Ba$ _2$ NaOsO$ _6$ . Using first-principles-based electronic structure calculations, we show that both materials exhibit a tendency toward spontaneous quadrupolar order in the cubic paramagnetic phase, which is slightly weaker in Ba$ _2$ NaOsO$ _6$ than in Ba$ _2$ MgReO$ _6$ . Our analysis further reveals an intimate coupling between the local magnetic moments and charge quadrupoles, mediated by the strong spin-orbit interaction, that leads to the unusual canted configuration of magnetic moments observed in these systems. When structural degrees of freedom are included, the two materials exhibit pronounced differences. In Ba$ _2$ MgReO$ 6$ the strong coupling to Jahn-Teller distortions stabilizes the antiferroic $ \mathcal{Q}{x^2-y^2}$ order, yielding excellent agreement with available experimental data. In contrast, the Jahn-Teller coupling is significantly weaker in Ba$ _2$ NaOsO$ _6$ and appears insufficient to stabilize the antiferroic quadrupolar order. While this is consistent with the absence of any measurable long-range structural distortion above the magnetic transition temperature, it contrasts with experimental results indicating a strong canting of the magnetic moments. Our analysis thus successfully describes the mechanisms shaping the properties of the Re-compound while a full quantitative description of the magnetic ground state of Ba$ _2$ NaOsO$ _6$ is still elusive.
Materials Science (cond-mat.mtrl-sci)
12 pages, 5 figures, 1 table
Phonon assisted light absorption and emission in cubic-Boron Nitride
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Ashwin Pillai, Elena Cannuccia, Aurelien Manchon, Fulvio Paleari, Claudio Attaccalite
Cubic boron nitride (cBN) is a wide-bandgap polymorph of boron nitride whose optical response remains only partially understood due to the coexistence of indirect electronic transitions and strong exciton-phonon coupling. Using first-principles many-body perturbation theory, we investigate the optical properties of cBN by combining GW quasiparticle corrections with Bethe-Salpeter equation calculations of excitonic effects. Phonon-assisted absorption and emission processes are explicitly included through the exciton-phonon coupling formalism. We find that phonon-mediated optical transitions provide a dominant contribution to both absorption and luminescence spectra, partially reconciling the discrepancy between the theoretical optical gap ($ \simeq$ 11 eV) and experimental emission around 6-7 eV. Our results demonstrate the importance of including exciton-phonon interactions for the correct interpretation of experimental spectra, offering new insights into light emission in wide-bandgap materials.
Materials Science (cond-mat.mtrl-sci)
Emergence of generic first-passage time distributions for large Markovian networks
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-02-23 20:00 EST
Julian B. Voits, Ulrich S. Schwarz (Heidelberg University)
First-passage times are often the most relevant aspect of a complex Markovian network, because they signify when information processing has resulted in a definite decision. Previous studies have shown that for kinetic proofreading networks in the limit of large network size the first-passage time distribution converges either to a delta or to an exponential distribution. Remarkably, these two forms correspond to the two extreme distributions of minimal and maximal entropy for a fixed mean, respectively. Here we build on the connection between first-passage times and graph theory to show that these two limits are not model-specific, but arise generically in Markovian networks from the distribution of the eigenvalues of the generator matrix. A deterministic peak emerges when infinitely many eigenvalues contribute, while the exponential limit arises from a single dominant eigenvalue. We also show that the exponential limit emerges robustly for reversible networks when a backward bias exists. In contrast, the deterministic limit is not obtained from a simple reversal of this condition, but under structurally tighter conditions, revealing a fundamental asymmetry between both regimes. Our theoretical analysis is illustrated and validated by computer simulations of one-step master equations and random networks.
Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph), Molecular Networks (q-bio.MN)
15 pages, 7 figures, mathematical supplement with one additional figure
Large Pyroelectric Enhancement in Freestanding Epitaxial BaTiO3 Membranes on Si
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Ajay Kumar, Asraful Haque, Shubham Kumar Parate, Harshal DSouza, Jishnu NK, Binoy Krishna De, Srinivasan Raghavan, Pavan Nukala
Ferroelectric membranes transferred onto arbitrary substrates provide reduced mechanical clamping at the interfaces that can diminish the effective polarization-rotation barrier offering a pathway to engineer larger electromechanical and thermally driven responses in oxide electronics. Here, we report integration of single crystalline thin film BaTiO3 (BTO) ferroelectric membrane on Si and demonstrate a 4x at 30C and 34x at 60C enhancement of pyroelectric coefficient compared to clamped films. The BTO membrane is grown epitaxially on a water-soluble Sr3Al2O6 sacrificial layer, released by selective dissolution, and transferred onto Si, yielding a strain-relaxed membrane with robust intrinsic polarization. Temperature dependent piezoresponse force microscopy (PFM) reveals pronounced thermally driven evolution of domain orientation, consistent with reduced barriers for dipolar modulation in the freestanding state. Variable-temperature Kelvin probe force microscopy (KPFM) quantifies an effective pyroelectric coefficient of ~75 uC/m^2K at 30C and 450 uC/m^2K at 60C with a detectivity of 40 m^2K^-1at room temperature. These results establish lead-free freestanding BTO membranes as a promising silicon-integrable platform for cryogen-free infrared detection and waste-heat energy management.
Materials Science (cond-mat.mtrl-sci)
18 pages, 11 Figures
Martensitic laminate geometry controls electronic phase transitions in a Mott insulator
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Ziming Shao, Benjamin Gregory, Suchismita Sarker, Jacob Ruff, Ivan K. Schuller, Yoav Kalcheim, Andrej Singer
Symmetry-lowering structural phase transitions result in multiple degenerate structures whose coexistence is determined by macroscopic strain compatibility. In quantum materials, these structural transformations often couple to electronic degrees of freedom, yet how the structural arrangements influence electronic phase transitions remains poorly understood. By analyzing hundreds of diffraction peaks from X-ray reciprocal space mapping, we determine the lattice basis vectors and mutual orientations of all coexisting phases in epitaxial V2O3 thin films after a symmetry-lowering transformation coincident with a metal-insulator transition. We identify the orientations of interfaces between all coexisting structures using the theory of martensitic phase transformations and find that the low temperature structure comprises finely tuned layered mixtures of alternating twin variants, akin to metal alloys. By comparing films grown on various substrate orientations, we show that the metal-insulator transition temperature increases monotonically with the degree to which these layered mixtures satisfy macroscopic strain compatibility imposed by the substrate.
Materials Science (cond-mat.mtrl-sci)
Analytical solutions for a charged particle with white, thermal, and active noises in the presence of a uniform magnetic field
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-02-23 20:00 EST
Y. J. Kang, S. K. So, Kyungsik Kim
We study the two-dimensional equations of motion for a charged particle subjected to white, thermal, and active noises in uniform a magnetic field. By deriving the corresponding Fokker Planck equation, analytical solutions for the joint probability density are obtained in different time domains.
Statistical Mechanics (cond-mat.stat-mech)
21 pages
Magnetic Force Imaging of 2D Topological Insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
Timothy W. Carlson, Swathi Kadaba, Motahhare Mirhosseini, Maria Kolesnik-Gray, Gabriel Marcus, Lindsey J. Gray, Anthony Walsh, Vojislav Krstic, D. L. Carroll
Two-dimensional topological insulators are central to our understanding of the connection between topological symmetries in a material and its band electronics. Within this class of materials, a breadth of complex quantum behaviors, such as persistent spin-polarized current states in the presence of a broken time reversal symmetry, and temperature-independent topological protection of quantum states, are thought to exist. However, current studies using photoemission and spectroscopic analyses or transport experiments fail to provide insight into the interplay between the physical 2D manifold and the band topology itself, since they do not provide spatial resolution of the phenomena to be understood. In this work, we develop a methodology for applying magnetic force microscopy to such systems to address this issue. Using well-characterized 2D crystallites of bismuth telluride ($ Bi_2$ Te_3$ ), we image the magnetic signal directly associated with topological edge states. The observed phase contrast is remarkably robust at a temperature of 25°C and occurs across crystallite sizes and shapes. A detailed analysis of the magnetic imaging suggests that the current observed is composed of two parts: the first is a persistent current ($ I_{Persistent}$ ) as predicted by theory, and the second is due to Faraday induction, $ I_{Faraday}$ . Damping dynamics of the cantilever during imaging further suggest that this Faraday EMF is established by spin accumulation along the 1D edge channel of the crystal, which then converts to a charge current in the presence of time reversal symmetry breaking, creating a novel form of rectification in the channel. This unexpected result can prompt new ideas for topology-based circuit elements with extremely low losses and power consumption.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Toroidal Fermi-surface geometry and phonon-limited transport in nodal-line semimetals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
Aman Anand, Alessandro De Martino
Nodal-line semimetals (NLSs) can display unconventional quasiparticle dynamics and charge transport properties due to their extended band degeneracy and the peculiar geometry of their Fermi surface. We consider electron-acoustic phonon scattering as the dominant relaxation mechanism and compute the quasiparticle decay rate and dc conductivity by solving the linearized semiclassical Boltzmann equation in a minimal model of a doped circular NLS. We find that the toroidal geometry of the Fermi surface gives rise to two parametrically distinct Bloch-Grüneisen temperatures, associated with momentum transfers along the poloidal and toroidal directions, respectively. As a result, an intermediate temperature window opens between these two scales, in which the decay rate follows $ \Gamma\propto T^2$ , while the conductivity follows $ \sigma\propto T^{-2}$ . We also obtain the low- and high-temperature asymptotic behaviors, and discuss implications for ARPES and transport measurements in candidate NLS materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages, 3 figures
Finely Tunable Thermal Expansion of NiTi by Stress-Induced Martensitic Transformation and Thermomechanical Training
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Won Seok Choi, Won-Seok Ko, Yejun Park, Edward L. Pang, Jong-Hoon Park, Hye-Hyun Ahn, Yuji Ikeda, Pyuck-Pa Choi, Blazej Grabowski
Tailoring the thermal expansion of martensitic materials by crystallographic texture and anisotropic variation of lattice parameters is a promising route to a flexible design of thermally stable systems. NiTi alloys are prototype materials in this respect, with shape-memory and superelastic properties owing to their thermoelastic martensitic transformations. Here, we propose a method to realize finely tunable coefficients of thermal expansion (CTE) for the NiTi alloy based upon a special combination of mechanical and thermal training. We achieve a near-zero in-plane CTE that is smaller in value than that of the FeNi-based Invar alloy. Atomistic simulations and theoretical calculations guide the method design and clarify the underlying mechanisms of the relationship between the processing conditions, the microstructural evolution, and the thermal expansion behavior. The directions for further, finer adjustments of the CTE without constraints on the shape of the materials are indicated.
Materials Science (cond-mat.mtrl-sci)
47 pages, 20 figures, 2 tables
Acta Materialia 302 (2026) 121623
Near-optimality of conservative driving in discrete systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-02-23 20:00 EST
Jann van der Meer, Andreas Dechant
Transferring a physical system from an initial to a final state while minimizing energetic losses is an interdisciplinary control problem that bridges stochastic thermodynamics and optimal transport theory. Recent research typically considers problems in which the optimal solution is realized via conservative forces, but whether this situation applies depends on the problem’s constraints. In systems with complex topologies like discrete networks, the optimal, dissipation-minimizing protocol involves applying nonconservative forces along cycles if the timescales of the transitions in the network are fixed. We show that although nonconservative driving is optimal in this setting, a conservative protocol exists whose dissipation is at most twice the optimal one. This finding is complemented with an example modeling transport across an energy barrier, which illustrates such improvements of order 1 explicitly. Qualitatively, conservative driving falls short of achieving optimality because direct transport across the barrier is avoided. We conclude with a discussion that the optimality of nonconservative driving might be a generic phenomenon: As fewer degrees of freedom can be optimized, additional degrees of freedom due to adding nonconservative forces become more significant.
Statistical Mechanics (cond-mat.stat-mech)
Responsive Disorder in a Metal-Organic Framework Enables Solid-State Reservoir Computing
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-02-23 20:00 EST
Guy Greenbaum, Will R. Branford, Andrew L. Goodwin
Complex systems with nonlinear response mechanisms can be applied as reservoir computers for energy-efficient machine learning tasks. Historically explored at the macro- and meso-scale, physical reservoir computing has recently been extended to the atomic scale via chemical mixtures with strong and dynamic heterogeneity. Here we explore the possibility that configurational degeneracy within disordered materials might form the basis for solid-state atomic-scale reservoirs. Our proof-of-concept uses the disordered metal-organic framework DUT-8, which undergoes a series of disorder-disorder transitions on exposure to different guest species. We show that variations in X-ray diffuse scattering associated with these transitions function as suitable readouts for machine learning applications. A combination of nonlinearity and memory effects in the DUT-8 response allows the system to carry out both classification and time-series machine learning tasks with accuracies comparable to those of mesoscale physical reservoir computers. Our results suggest a new avenue for exploiting correlated disorder in solid phases whenever the nature of that disorder can be modulated through external perturbations-a phenomenon we term `responsive disorder’.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci)
A stochastic simulation of the dislocation-mediated etching of porous GaN distributed Bragg reflectors
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Piotr Sokolinski, Ben Thornley, Zetai Xu, Thom R. Harris-Lee, Menno J. Kappers, Rachel A. Oliver
Distributed Bragg reflectors (DBRs) can be fabricated by electrochemically etching nitride epitaxial structures consisting of alternating layers of highly n-type doped and non-intentionally doped (NID) GaN. Threading dislocations (TDs) can be electrochemically etched into transport pipelines that can carry the etchant through the NID layers to access the doped material. Experimentally this has been shown to involve a mechanism where the etching pathway may follow one TD into a doped layer and then propagate sideways through the doped layer to continue via a different TD. Across multiple layers this process creates complex pore structures that have been described as ‘cascades’. Here, we build a stochastic simulation for the DBR etching process that can reproduce some key features of the observed microstructures including the cascade morphology. By comparing the simulation output to samples etched at a range of voltages, we show that we can reproduce variations in experimental chronoamperometry data with applied bias by varying the probability of etching the doped layers within the simulation. The outputs of the resulting simulations replicate the experimentally observed cascade morphology. At higher voltages, experimental data reveal a lower proportion of cascade features, a trend that is also replicated by the simulations for relevant probability values. Outputs of the simulations also correlate well with experimental chronoamperometry data for samples where - unlike in a DBR - the thicknesses of the doped layers vary through the epitaxial multilayer, suggesting that the probabilistic simulation can be applied to a range of structures to help understand the dislocation-mediated electrochemical etching process.
Materials Science (cond-mat.mtrl-sci)
19 pages, 10 figures
Modeling of a magnetic field sensor based on spin Hall magnetoresistance
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-02-23 20:00 EST
Syeda Farwa Bukhari, Alessandro Magni, Witold Skowroński, Elena Losero, Vittorio Basso, Carlo Appino, Piotr Wiśniowski, Juergen Langer, Berthold Ocker, Dario Daghero, Michaela Kuepferling
Next-generation spintronic sensors aim to overcome the limitations of traditional tunneling-magnetoresistance (TMR) devices, such as complex manufacturing, high $ 1/f$ noise, and significant offsets. This work presents a comprehensive modeling and experimental validation of a magnetic field sensor based on Spin Hall Magnetoresistance (SMR) in a Wheatstone bridge configuration. Utilizing a multiphysics approach, we simulate the interplay between SMR, Anisotropic Magnetoresistance (AMR), and Spin-Orbit Torque (SOT) using a Stoner-Wohlfarth model complemented by a Fuchs-Sondheimer analysis of current distribution. To account for the presence of magnetic domains, we incorporate a modified Stoner-Wohlfarth framework that considers non-uniform magnetization and domain wall motion through a “truncated astroid” approach, allowing for a statistical distribution of single-domain particles. The model is validated against experimental measurements of Pt/$ \text{Fe}{60}\text{Co}{20}\text{B}{20}$ and Ta/$ \text{Fe}{60}\text{Co}{20}\text{B}{20}$ bilayers patterned into Hall bars and Wheatstone bridges. The model provides critical design guidelines for optimizing material properties, layer thickness, and device layout to minimize power consumption and maximize sensitivity in SMR-based sensing applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
34 pages, 10 figures
Disentangling Entropic, Active, and Frictional Forces in Cytoskeletal Crosslinking
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-02-23 20:00 EST
Cedrik Barutel, Sebastian Fürthauer
The forces that mixtures of motorized and passive crosslinking proteins collectively generate between cytoskeletal filaments within our cells are the key drivers of active cellular mechanics. Despite their importance, a unified theory to describe such crosslinking forces has so far been missing. In this paper, we derive a theory that predicts the forces generated collectively by crosslinking proteins linking two biopolymer filaments from measurable filament and crosslinker properties, using out-of-equilibrium thermodynamics. Our framework allows us to decompose the forces generated by crosslinkers into three separate components: entropic, active, and frictional. In doing so, it offers a clear physical interpretation of the fundamental mechanisms by which crosslinking proteins self-organize and collectively generate forces. We demonstrate the robustness and utility of this framework by applying it to four different experiments that probe the combined roles of passive and motorized crosslinkers. For each experiment, our theoretical approach allows us to disentangle the relative contributions of entropic, active, and frictional forces, clarifying how different physical processes underpin collective force production. In turn, this makes it possible to quantitatively compare and predict how various crosslinker combinations influence force generation between filaments, pattern formation along filaments, and the dynamics of filament pairs.
Soft Condensed Matter (cond-mat.soft)
12 pages, 5 figures
Mitigation of Magnetic Flux Trapping in Superconducting Electronics Using Moats
New Submission | Superconductivity (cond-mat.supr-con) | 2026-02-23 20:00 EST
Rohan T. Kapur, Sergey K. Tolpygo, Alex Wynn, Pauli Kehayias, Adam A. Libson, Collin N. Muniz, Michael J. Gold, Justin L. Mallek, Danielle A. Braje, Jennifer M. Schloss (MIT Lincoln Laboratory, Lexington, MA, USA)
Magnetic flux (vortex) trapping remains a major obstacle to very large scale integration in superconducting electronics. Moats – etched regions in circuit layers placed in ground planes and around critical circuitry – offer a simple passive approach to sequester flux. Here, we systematically examine the effectiveness of moat arrays in superconducting niobium films as a function of geometry (size, shape, and density) and background magnetic field. By measuring the vortex expulsion field, we estimate the flux saturation number and flux trapping temperature for a range of geometries. We find that many moat designs effectively sequester flux in magnetically shielded environments (< 1 $ \mu$ T), with high-aspect-ratio rectangular “slit” moats providing the strongest mitigation at minimal area cost. However, our measurements show that moats alone do not eliminate flux trapping in non-ideal films, as vortices can preferentially pin at material defects. These results provide design guidance for flux mitigation in superconducting integrated circuits and highlight the need for combined optimization of circuit geometries and materials.
Superconductivity (cond-mat.supr-con), Applied Physics (physics.app-ph)
11 pages, 8 figures, 2 tables, 59 references
Overlap locking and non-perturbative effects in spin glasses
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-02-23 20:00 EST
Silvio Franz, Giorgio Parisi, Federico Ricci-Tersenghi
We study the phenomenon of the locking of the order parameter (or synchronization) in spin glasses at low temperatures. When two systems with independent disorders are coupled, their overlaps become similar. A crucial question is how this effect depends on the strength of the coupling between the two systems. Non-perturbative phenomena are present when $ 1 \ll \Delta H \ll N$ , being $ \Delta H$ the coupling Hamiltonian and $ N$ the size of the system. In this intermediate-coupling region, the effect is related to finite-size free-energy corrections and to the correlations in the Dyson hierarchical spin glass, a model that mimics the physics of finite-dimensional systems. We study this phenomenon in the mean-field approach, both analytically and numerically, and we finally compute the critical exponents for finite-volume corrections in mean-field theory and for the decay of correlations in the Dyson hierarchical model.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
15 pages, 9 figures, submitted to PNAS
Benchmarking Graph Neural Networks in Solving Hard Constraint Satisfaction Problems
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-02-23 20:00 EST
Geri Skenderi, Lorenzo Buffoni, Francesco D’Amico, David Machado, Raffaele Marino, Matteo Negri, Federico Ricci-Tersenghi, Carlo Lucibello, Maria Chiara Angelini
Graph neural networks (GNNs) are increasingly applied to hard optimization problems, often claiming superiority over classical heuristics. However, such claims risk being unsolid due to a lack of standard benchmarks on truly hard instances. From a statistical physics perspective, we propose new hard benchmarks based on random problems. We provide these benchmarks, along with performance results from both classical heuristics and GNNs. Our fair comparison shows that classical algorithms still outperform GNNs. We discuss the challenges for neural networks in this domain. Future claims of superiority can be made more robust using our benchmarks, available at this https URL.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG)
Phase-field simulations of nucleation, growth, and coarsening of $β_1$ precipitates in Mg-Nd alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-02-23 20:00 EST
Lingxia Shi (1), Stephen DeWitt (1), David Montiel (1), Qianying Shi (1), John Allison (1), Katsuyo Thornton (1 and 2) ((1) Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, United States, (2) Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, United States)
The spatial distribution and morphology of precipitates formed during aging are key factors that determine the precipitation hardening response of various magnesium-rare earth alloys. In recent years, the use of high-performance computing clusters and massively parallel frameworks has enabled quantitative simulations of the evolution of individual and multiple precipitates at relevant length and time scales. However, predictive modeling of precipitate evolution remains challenging, in part because many key thermodynamic and kinetic parameters governing the underlying physics are either unknown or have a high degree of uncertainty. In this work, we developed a workflow in which experimental data were used to parameterize a phase-field model to perform two-dimensional (2D) simulations of concurrent nucleation and evolution of $ \beta_1$ precipitates in magnesium-neodymium alloy during aging. Matrix composition and precipitate number density at different aging times were obtained from atom probe tomography and transmission electron microscopy measurements, respectively. We applied a stereological method to estimate the three-dimensional (3D) number densities from experimental cross-sectional transmission electron micrographs. The estimated 3D number density data were then converted to effective 2D number densities. The effective 2D number density and composition data were used to determine the required model parameters by minimizing the discrepancy between simulation and experimental results. The parameterized model allows for quantitative phase-field simulations of nucleation and growth of $ \beta_1$ precipitates, which can be employed to optimize aging time to achieve a target number density of precipitates. This work highlights an approach to overcome the challenges associated with parameterizing a coupled phase-field and nucleation model.
Materials Science (cond-mat.mtrl-sci)
43 pages, 9 figures, including Supplementary Information