Statistical Mechanics
Exact and variational identities for free energy differences in strongly coupled open systems
Mohammad Rahbar and Christopher J. Stein
We derive exact identities for open systems connecting two
equilibrium endpoints without imposing microscopic reversibility, detailed balance (DB), fluctuation-dissipation structure, or local detailed balance (LDB) on the driven dynamics. The identities express the
Hamiltonian of mean force (HMF) free energy differences through exponential moments and an explicit chi-squared overlap between the endpoint marginals. In the frozen-coupling regime, the HMF shift reduces to a bare-system increment and admits a trajectory-level heat-work-reference decomposition. The exact relations then reduce the problem to a scalar-action law. A maximum-
entropy construction gives a Bessel-form scalar-action law, independent of the microscopic system, environment, and number of degrees of freedom at the level of the variational reconstruction. This law provides three outputs from the same sampled configurations: the HMF free energy difference, the endpoint-overlap burden, and a Hessian uncertainty estimate. Since many systems in biology, chemistry, physics and engineering violate the underlying assumptions of the standard Jarzynski identity, we validate the framework on a reduced-dimensional model with a non-Liouvillian, phase-space-compressing ramp followed by underdamped Langevin relaxation. The standard Jarzynski work
estimator fails for this ramp because phase-space preservation is broken and no compensating Jacobian correction is included, whereas the present endpoint identities recover the exact HMF free energy difference, and the variational construction reproduces it within its local uncertainty.
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Strongly Correlated Electrons · Cross-listed from hep-th
Continuum limit of gauged tensor network states
Gertian Roose and Erez Zohar
It is well known that all physically relevant states of gauge theories lie in the sectors of the
Hilbert space which satisfy the Gauss law. On the
lattice, the manifeslty gauge invariant subspace is known to be exactly spanned by gauged tensor networks. In this work, we demonstrate that the continuum limit of certain types of gauged tensor networks is well defined and leads to a new class of states that may be helpful for the non-perturbative study of gauge theories directly in the continuum.
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Materials Science
Dual-Mode Luminescent Thermometry in LiYO2:Nd3+,Yb3+ Enabled by Structural Phase Transition and Phonon-Assisted Energy Transfer
M. Tahir Abbas, M. Szymczak, D. Szymanski et al. (+3 more)
In this work, a dual-mode luminescent thermometer operating via both ratiometric and lifetime-based readout strategies was developed, enabled by the coexistence of two thermally driven effects: a structural phase transition in LiYO2 and a
phonon-assisted energy transfer from Yb3+ to Nd3+. As demonstrated, changes in the shape of the emission band of Yb3+ ions corresponding to the 2F5/2 -> 2F7/2 electronic transition, induced by the phase transition, enabled the design of a ratiometric thermometer with a maximum relative sensitivity (SR) of 3.1% K^-1 for LiYO2 doped with 10% Yb3+ and 1% Nd3+ at 290 K. In contrast, the temperature-dependent Yb3+ -> Nd3+ energy transfer facilitated the development of a lifetime-based thermometer with a maximum SR of 1.5% K^-1 for 20% Nd3+ at 378 K. In both approaches, tuning the Nd3+ concentration allowed modulation of both the sensitivity and the temperature at which the maximum SR occurred. This was achieved by shifting the phase transition temperature and increasing the probability of interionic energy transfer, respectively. Notably, the temperature ranges corresponding to the maximum SR for the ratiometric and lifetime modes were distinct, effectively broadening the thermal operating window of the sensor. Additionally, it was shown that LiYO2 doped with Nd3+ and Yb3+ can also be used as a temperature sensor through the ratio of luminescence intensities recorded at two different time gates. Furthermore, the results confirmed that the
phonon-assisted energy transfer process plays the dominant role in shaping the luminescence kinetics, surpassing the influence of the structural phase transition. Overall, this study identifies LiYO2:Nd3+,Yb3+ as a promising candidate for
multimodal luminescent temperature sensing applications.
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All authors M. Tahir Abbas, M. Szymczak, D. Szymanski, M. Drozd, G. Chen, L. Marciniak
Mesoscale and Nanoscale Physics
Magnetotransport properties of an unconventional Rashba spin-orbit coupled two-dimensional electronic system
Aryan Pandita and SK Firoz Islam
We study the magnetotransport properties of a two-dimensional electronic system with unconventional Rashba
spin-orbit coupling in which the system is described by a pair of
chiral spin texture in each
spin branch, and the chirality is opposite in two
spin branches. We obtain the Landau levels analytically and find that intra-
spin and/or inter-
spin Landau level crossing occurs. We compute the longitudinal conductivity and
quantum Hall conductivity using the Kubo formalism based on linear response theory. We find that the usual Shubnikov-de Haas oscillation in longitudinal conductivity appears that can be made purely
spin polarized by adjusting the
Fermi level suitably. We observe a beating pattern in the Shubnikov-de Hass oscillation in the intra-
spin branches, which arises due to the superposition of Shubnikov-de Hass oscillations corresponding to two bands in each
spin branch. This is contrary to the conventional Rashba system, where such beating is due to the superposition of Shubnikov-de Hass oscillations corresponding to the two
spin-branches. On the other hand, we note that
quantum-
Hall conductivity exhibits usual quantization in units of $e^2/h$ corresponding to each
spin dependent Landau level. However, the Landau level crossing gives rise to the double jump in the
Hall conductivity if the
Fermi level is placed precisely at the crossing point.
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Soft Condensed Matter · Cross-listed from physics.optics
M3Scope a 3D multimode multiplane microscope for imaging nanoscale dynamics in soft matter
Steven Huysecom, Francisco Bevilacqua, Roger Bresoli Obach et al. (+6 more)
Fast, volumetric imaging that integrates multiple imaging modalities is essential for probing dynamic, heterogeneous soft and biological matter. Here, we present the M3Scope, a simple yet versatile multiplane microscope that extends widefield detection with a modular multimode cube to enable dual color fluorescence, polarization-resolved, and correlative brightfield fluorescence imaging while (i) preserving simultaneous 3D acquisition at high frame rates (100 fps) and (ii) requiring minimal realignment. We demonstrate its potential by investigating
polymer dynamics across multiple spatial and temporal scales. In an acrylamide type polymerizing network, dual color tracking of 100 nm and 300 nm fluorescent probes revealed size dependent viscosities diverging from 15 mPa.s to 40 mPa.s after gelation. Polarization resolved rotational tracking of gold bipyramids yielded viscosities within 10 percent of theoretical values in 80 to 95 percent glycerol and remained accurate in the high-viscosity regime (bigger than 400 mPa.s) where translational motion is undetectable. Fluorescence brightfield imaging correlated structural changes during poly(isopropyl acrylamide) (pNIPAM) phase separation as well as variations in tracer diffusivity, linking morphology and dynamics in 3D. Taken together, these results show that the M3Scope delivers high speed volumetric imaging with flexible modality switching, providing a powerful platform for studying dynamic, heterogeneous systems across disciplines, from
polymer physics to
cell mechanobiology.
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All authors Steven Huysecom, Francisco Bevilacqua, Roger Bresoli Obach, Sudipta Seth, Luis M. Liz-Marzan, Dagmar R. D hooge, Johan Hofkens, Susana Rocha, Boris Louis
Materials Science
Scalable data-driven modeling of microstructure evolution by learning local dependency and spatiotemporal translation invariance rules in phase field simulation
Zishuo Lan, Qionghuan Zeng, Weilong Ma et al. (+10 more)
Phase-field (PF) simulation provides a powerful framework for predicting microstructural
evolution but suffers from prohibitive computational costs that severely limit accessible spatiotemporal scales in practical applications. While data-driven methods have emerged as promising approaches for accelerating PF simulations, existing methods require extensive training data from numerous
evolution trajectories, and their inherent black-box nature raises concerns about long-term prediction reliability. This work demonstrates, through examples of grain growth and spinodal decomposition, that a minimalist Convolutional Neural Network (CNN) trained with a remarkably small
dataset even from a single small-scale simulation can achieve seamless scalability to larger systems and reliable long-term predictions far beyond the temporal range of the training data. The key insight of this work lies in revealing that the success of CNN-based models stems from the
alignment between their inductive biases and the physical priors of phase-field simulations specifically, locality and spatiotemporal translation invariance. Through effective receptive field analysis, we verify that the model captures these essential properties during training. Therefore, from a reductionist perspective, the surrogate model essentially establishes a spatiotemporally invariant regression mapping between a grid point's local environment and its subsequent state. Further analysis of the model's feature space demonstrates that microstructural
evolution effectively represents a continuous redistribution of a finite set of local environments. When the model has already encountered nearly all possible local environments in the early-stage training data, it can reliably generalize to much longer
evolution timescales, regardless of the dramatic changes in global microstructural morphology.
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All authors Zishuo Lan, Qionghuan Zeng, Weilong Ma, Xiangju Liang, Yue Li, Yu Chen, Yiming Chen, Xiaobing Hu, Junjie Li, Lei Wang, Jing Zhang, Zhijun Wang, Jincheng Wang
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Rotational Jamming of Plasmonic Optical Matter Driven by Chiral Light
Ashutosh Shukla, Sneha Boby, Rahul Chand et al. (+1 more)
Plasmonic Optical matter (OM), composed of optically bound metallic particles, can be rotated by transferring the
spin angular momentum (SAM) of
chiral light to the assembly. Rotating OM is a promising platform for optical micromachines, with potential applications in plasmofluidics and soft robotics. Understanding the dynamic states of such Brownian, micro-mechanical systems is a relevant issue. One key problem is understanding kinetic jamming and clogging. Studies of driven multiparticle systems have revealed that under suboptimal driving, the systems can stop moving, showing jamming transitions. It is important to identify dynamic regimes where crowding competes with driving and is susceptible to jamming in the context of optical micromachines. Through experiments supported by numerical simulations, we reveal assemblies with well-defined hexagonal or triangular
symmetry that efficiently harness the SAM of incident
chiral light, resulting in stable rotation. However, as the plasmonic-particle assembly grows and its dimensions approach the beam waist, new particles can disrupt this order. This causes a transition to a fluid-like state with less-defined
symmetry, correlated with a significant reduction in transferred torque, causing rotation to stagnate or cease. We suggest this behaviour is analogous to a rotational jamming transition, where the rotational motion is arrested. Our findings establish a clear relationship between the structural
symmetry of the OM assembly and its ability to harness SAM, providing new insights into controlling
chiral light-matter interactions and offering a novel platform for studying jamming transitions.
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All authors Ashutosh Shukla, Sneha Boby, Rahul Chand, G. V. Pavan Kumar
Materials Science
Wavelength-commensurate anatase TiO\_2 particles for ro-bust and functional Mie resonances across the visible and near infrared
Pedro Tartaj, Yurena Luengo, Pedro Moronta et al. (+3 more)
Earth-abundant materials exhibiting Mie resonances across the visible and near-infrared offer opportunities for efficient and sustainable sensing, thermal regulation, and sunlight harvesting. For anatase TiO$_2$, a broadband optical and abundant material, Mie calculations indicate that robust resonances require size tunability and monodispersity (standard deviation, $\lesssim$ 5%) over an extended range (0.5-2 $\mu$m) not yet experimentally covered, while maintaining a refractive index above 2 to ensure optical contrast, for example with biomolecules. Here, we demonstrate that a simple UV-assisted thermal hydrolysis route yields anatase particles that meet all these criteria and remain aqueous-processable. Consequently, the materials display intense and modulable Mie resonances across the visible/near-infrared regions (including biological windows), outperforming previous results that were limited by size. Strong optical resonances combined with ambient-temperature processability enable robust, broadband, label-free detection of transparent biomolecules. Our insights advance precise synthesis and Mie-based photonics of an earth-abundant material, and indicate the potential for cost-effective and rapid-on-demand integration via printing technologies, further enhanced by anatase's biocompatibility and photochemical properties.
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All authors Pedro Tartaj, Yurena Luengo, Pedro Moronta, Luisina Forzani, Alvaro Blanco, Cefe López
Strongly Correlated Electrons
Measurement protocol for detecting correlated topological insulators in synthetic quantum systems
Yixin Ma, Chao Xu and Shenghan Jiang
Two-dimensional topological
insulators, characterized by
symmetry-protected anomalous boundary modes, have been generalized to the strongly correlated regime for both bosonic and fermionic systems. As correlated topological
insulators (TI) approach experimental realization in
quantum simulators, conventional probes, such as transport measurements, are not easily applicable to these synthetic platforms. In this study, we focus on two examples of correlated TI: a bosonic TI protected by $\mathbb{Z}_2\times U(1)$
symmetry and the fermionic
quantum spin Hall insulator protected by time-reversal
symmetry. We propose a unified, readily implementable protocol based on measuring the disorder parameter $\langle\exp(\mathrm{i}\theta \hat{Q}_A)\rangle$ for a large subregion $A$, with $\hat{Q}_A$ the total charge operator within $A$. Our key finding is that this quantity exhibits non-analytical dependence on $\theta$ for correlated TI, a signature robust against decoherence. We establish this diagnostic through both numerical simulations and analytical derivations. This protocol is well-suited for implementation on near-term
quantum simulation platforms, providing a direct route to experimentally confirm correlated TI.
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Materials Science
Magnetic Frustration Enforced Electronic Reconstruction in Ni intercalated NbSe$_{2}$: Suppression of Electronic Orders
Ashutosh S. Wadge, Alexander Kazakov, Xujia Gong et al. (+14 more)
We investigate the single
crystals of Ni$_{0.19}$NbSe$_2$, revealing that Ni intercalation profoundly alters the physical properties of NbSe$_2$.
Magnetic measurements clearly show that the system is magnetically frustrated with
antiferromagnetic ordering below 23.5\,K, with an irreversibility temperature near 10\,K, and a
magnetic hysteresis with a small net
magnetic moment. Overall, the system can be described as an inhomogeneous
antiferromagnetic phase with
magnetic disorder and
magnetic frustration. We found two Curie-Weiss temperatures of -80\,K for the field in the ab-plane and -137\,K for the field out of plane, which are a consequence of anisotropic interactions in
spin space and favor an orientation of the
spin along the c-axis. Temperature-dependent resistivity shows a complete suppression of both charge density waves and superconducting order down to 300\,mK. Angle-resolved photoemission spectroscopy at 84\,K reveals a $\overline{\Gamma}$-centered electron pocket in Ni$_{0.19}$NbSe$_2$, which is absent in pristine NbSe$_2$. The electronic structure results show a shift of the van Hove singularity (VHS), which is the main cause of the suppression of the electronic orders. These results align with recent theoretical predictions that Ni intercalation with cationic disorder favors frustrated
antiferromagnetic stripe states, shifts the VHS and reconstructs the
Fermi surface in NbSe$_2$. Our findings position Ni$_{0.19}$NbSe$_2$ within a magnetically frustrated, non-superconducting regime, highlighting how partial intercalation and disorder drive complex
magnetic order and the
Fermi surface reconstruction in low-dimensional
quantum materials.
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All authors Ashutosh S. Wadge, Alexander Kazakov, Xujia Gong, Daniel Jastrzebski, Bogdan J. Kowalski, Artem Lynnyk, Lukasz Plucinski, Amar Fakhredine, Ryszard Diduszko, Marta Aleszkiewicz, Jedrzej Korczak, Dawid Wutke, Marcin Rosmus, Rafal Kurleto, Natalia Olszowska, Carmine Autieri, Andrzej Wisniewski
Disordered Systems and Neural Networks
Competing Localizations on Disordered Non-Hermitian Random Graph Lattice
S Rahul and A Harshitha
Phase transitions in one-dimensional
lattice systems are well established and have been extensively studied within both Hermitian and non-Hermitian frameworks. In this work, we extend this understanding to a more general setting by investigating localization and delocalization transitions and the behavior of the non-Hermitian skin effect (NHSE) using a tight-binding model on a generalized random graph
lattice. Our model incorporates three key parameters, asymmetric hopping $\Delta$, on-site disorder $W$, and a random long-range coupling $p$ that together define the underlying random graph structure. By varying $p$, $\Delta$, and the disorder strength, we explore the interplay between
topology, randomness, and non-Hermiticity in determining localization properties. Our results show a strong competition between skin effect driven and Anderson driven localizations across parameter regimes. Notably, even in the presence of strong disorder, skin effect driven localization coexists with Anderson-driven localization. We further discuss the relevance of these results to machine-learning architectures and information propagation in complex networks and other real-world problems.
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Mesoscale and Nanoscale Physics
Emergent electronic insulating states in a one-dimensional moiré superlattice
Jianfeng Bi, Masaki Minamikawa, Ruige Dong et al. (+11 more)
Two-dimensional (2D) van der Waals (vdW) moiré superlattices have provided a powerful knob to engineer a plethora of new
quantum states. However, extending such moiré engineering to one-dimensional (1D) vdW systems has remained challenging. Here we report the moiré-engineered electronic insulating states in a new 1D moiré superlattice, by crystallographically aligning an armchair single-walled carbon nanotube (SWNT) to 2D hexagonal boron nitride (hBN) substrate. Remarkably, we observe the emergence of pronounced insulating states at charge neutrality point (CNP), full and half moiré fillings in
lattice-aligned armchair SWNT/hBN
heterostructures by low-temperature electrical transport measurements. In strong contrast, armchair SWNT devices without hBN
alignment do not show any of these insulating behaviors, providing compelling evidence for the significant 1D moiré effect. Our density functional theory (DFT) and tight-binding calculations reveal that synergetic nanotube partial flattening and in-plane
lattice reconstruction at 1D moiré interface expand the most stable AB' stacking regions (carbon on top of boron) and open sizable band gaps at both CNP and full moiré fillings at the single-particle level. Our one-body theory predicts no band gaps at half moiré fillings, suggesting that electron correlation and/or electron-
phonon interaction may give rise to these emergent insulating behaviors in our 1D moiré systems. Our work establishes a new and definite moiré engineering route for 1D vdW materials and opens an exciting avenue for exploring interaction-induced
quantum phases in 1D.
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All authors Jianfeng Bi, Masaki Minamikawa, Ruige Dong, DongJun Kang, Zihan Weng, Shaoqi Sun, Kenji Watanabe, Takashi Taniguchi, Ryosuke Okumura, Huizhen Wu, Naoto Nakatsuji, SeokJae Yoo, Mikito Koshino, Sihan Zhao
Materials Science · Cross-listed from physics.med-ph
Lanthanides-Based Nanoparticles Conjugated with Rose Bengal for FRET-Mediated X-Ray-Induced PDT
Batoul Dhaini, Joël Daouk, Hervé Schohn et al. (+8 more)
In order to find a good candidate for Förster Resonance Energy Transfer (FRET)-mediated X-ray-induced photodynamic therapy (X-PDT) for the treatment of cancer, lanthanide (Ln)-based AGuIX nanoparticles (NPs) conjugated with Rose Bengal (RB) as a photosensitizer (PS) were synthesized. X-PDT overcomes the problem of the poor penetration of visible light into tissues, which limits the efficacy of PDT in the treatment of deep-seated tumors. It is essential to optimize FRET efficiency by maximizing the overlap integral between donor emission and acceptor absorption and lengthening the duration of the donor emission. In this study, we optimized energy transfer between a scintillator (Sc) as a donor and a PS as an acceptor. Terbium (Tb) and Gadolinium (Gd) as Scs and Rose RB as a PS were chosen. The study of energy transfer between Tb, Gd and RB in solution and chelated on AGuIX NPs proved to be FRET-like. RB was conjugated directly onto AGuIX NPs (i.e., AGuIX Ln@RB), and the use of a spacer arm (i.e., AGuIX Ln@spacer arm-RB) increased FRET efficiency. Singlet oxygen production by these NPs was observed under UV–visible illumination and X-ray irradiation. The in vitro bioassay demonstrated 52%
cell death of U-251MG derived from human malignant glioblastoma multiforme at a concentration of 1 $\mu$M RB after illumination and irradiation (2 Gy, 320 kV, 10 mA, 3 Gy/min at 47 cm). In addition, the RB-coupled NRP-1-targeting peptide (i.e., K(RB)DKPPR) was conjugated onto AGuIX NPs by a thiol-maleimide click chemistry reaction, and an affinity in the nM range was observed.
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All authors Batoul Dhaini, Joël Daouk, Hervé Schohn, Philippe Arnoux, Valérie Jouan-Hureaux, Albert Moussaron, Agnès Hagege, Mathilde Achard, Samir Acherar, Tayssir Hamieh, Céline Frochot
Quantum Gases
Generalized Gross-Pitaevskii Equation for 2D Bosons with Attractive Interactions
Michał Suchorowski, Fabian Brauneis, Hans-Werner Hammer et al. (+2 more)
We introduce a generalized Gross-Pitaevskii equation that provides a nonlinear framework for studying two-dimensional (2D) attractive Bose systems. Its defining feature is the logarithmic density dependence of the coupling constant, which breaks the scale invariance inherent in the standard mean-field equations. This framework allows straightforward calculations of the system properties arising from the
quantum anomaly. As a first illustration, we study universal bound states in free space, commonly referred to as
quantum droplets. Then, we analyze breathing modes and quench dynamics in trapped systems, paving the way for a systematic exploration of non-
equilibrium phenomena in 2D attractive Bose systems. Finally, we predict the existence of universal excited states, including
vortex configurations, which may be more accessible to experimental investigation than the ground state. Our results provide a robust theoretical foundation for studying both static and dynamical properties of finite systems, and offer guidance for the design of future experiments.
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All authors Michał Suchorowski, Fabian Brauneis, Hans-Werner Hammer, Michał Tomza, Artem G. Volosniev
Materials Science
MATAI: A Generalist Machine Learning Framework for Property Prediction and Inverse Design of Advanced Alloys
Yanchen Deng, Chendong Zhao, Yixuan Li et al. (+10 more)
The discovery of advanced metallic
alloys is hindered by vast composition spaces, competing property objectives, and real-world constraints on manufacturability. Here we introduce MATAI, a generalist machine learning framework for property prediction and inverse design of as-cast
alloys. MATAI integrates a curated
alloy database, deep neural network-based property predictors, a constraint-aware optimization engine, and an iterative AI-experiment feedback loop. The framework estimates key mechanical propertie, sincluding density, yield strength, ultimate tensile strength, and elongation, directly from composition, using multi-task learning and physics-informed inductive biases.
Alloy design is framed as a constrained optimization problem and solved using a bi-level approach that combines local search with symbolic constraint programming. We demonstrate MATAI's capabilities on the Ti-based
alloy system, a canonical class of lightweight structural materials, where it rapidly identifies candidates that simultaneously achieve lower density (<4.45 g/cm3), higher strength (>1000 MPa) and appreciable ductility (>5%) through only seven iterations. Experimental validation confirms that MATAI-designed
alloys outperform commercial references such as TC4, highlighting the framework's potential to accelerate the discovery of lightweight, high-performance materials under real-world design constraints.
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All authors Yanchen Deng, Chendong Zhao, Yixuan Li, Bijun Tang, Xinrun Wang, Zhonghan Zhang, Yuhao Lu, Penghui Yang, Jianguo Huang, Yushan Xiao, Cuntai Guan, Zheng Liu, Bo An
Materials Science
pynxtools: A Python framework for generating and validating NeXus files in experimental data workflows
Sherjeel Shabih, Lukas Pielsticker, Florian Dobener et al. (+19 more)
Scientific data across physics, materials science, and materials engineering often lacks adherence to FAIR principles (Barker et al., 2022; Jacobsen et al., 2020; M. D. Wilkinson et al., 2016; S. R. Wilkinson et al., 2025) due to incompatible instrument-specific formats and diverse standardization practices. pynxtools is a Python software development framework with a command line interface (CLI) that standardizes data conversion for scientific experiments in materials science to the NeXus format (Klosowski et al., 1997; Könnecke, 2006; Könnecke et al., 2015) across diverse scientific domains. NeXus defines data storage specifications for different experimental techniques through application definitions. pynxtools provides a fixed, versioned set of NeXus application definitions that ensures convergence and
alignment in data specifications across, among others, atom probe
tomography, electron microscopy, optical spectroscopy, photoemission spectroscopy, scanning probe microscopy, and X-ray diffraction. Through its modular plugin architecture pynxtools provides conversion of data and metadata from instruments and electronic lab notebooks to these unified definitions, while performing validation to ensure data correctness and NeXus compliance. pynxtools can be integrated directly into Research Data Management Systems (RDMS) to facilitate parsing and normalization. We detail one example for the RDM system NOMAD. By simplifying the adoption of NeXus, the framework enables true data interoperability and FAIR data management across multiple experimental techniques.
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All authors Sherjeel Shabih, Lukas Pielsticker, Florian Dobener, Andrea Albino, Theodore Chang, Carola Emminger, Lev Ginzburg, Ron Hildebrandt, Markus Kühbach, Rubel Mozumder, Tommaso Pincelli, Martin Aeschlimann, Marius Grundman, Walid Hetaba, Carlos-Andres Palma, Laurenz Rettig, Markus Scheidgen, José Antonio Márquez Prieto, Claudia Draxl, Sandor Brockhauser, Christoph Koch, Heiko B. Weber
Materials Science
Graphene assisted III-V epitaxy towards substrate recycling
Naomie Messudom, Antonella Cavanna, Ali Madouri et al. (+6 more)
Re-using the substrate is identified as a method for reducing the cost of high efficiency III-V
solar cells. The approach investigated here consists in inserting a
graphene layer onto a (001)GaAs substrate prior to the epitaxial growth of GaAs. To obtain a monocrystalline GaAs grown layer, the
graphene layer is patterned, followed by a two-step epitaxial growth, here performed by molecular beam epitaxy (MBE). The first step is a selective area growth of GaAs in
graphene openings, followed by a lateral overgrowth, under a modulated Ga flux. The second step, after reaching coalescence, consists in a regular growth under continuous Ga supply. It is observed that the pattern orientations relative to the crystallographic direction of the GaAs substrate below the
graphene have an influence on GaAs morphology and quality. The best result was obtained for patterns oriented along [1__10]+22.5{\textdegree} with a
graphene coverage of 50%, with a significantly reduced roughness down to 3.3 nm.
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All authors Naomie Messudom, Antonella Cavanna, Ali Madouri, Carlos Macias, Nathalie Bardou, Laurent Travers, Stéphane Collin, Jean-Christophe Harmand, Amaury Delamarre
Materials Science
Giant tunneling magnetoresistance based on spin-valley-mismatched ferromagnetic metals
Kan Yan, Li Cheng, Yizhi Hu et al. (+3 more)
Half metals, which are amenable to perfect
spin filtering, can be utilized for high-magnetoresistive devices. However, available half metals are very limited. Here, we demonstrate that materials with intrinsic
spin-valley-mismatched (SVM) states can be used to block charge transport, resembling half metals and leading to
giant tunneling magnetoresistance. As an example, by using first-principles transport calculations, we show that
ferromagnetic 1T-VSe$_2$, 1T-VS$_2$, and 2H-VS$_2$ are such
spin-valley-mismatched metals, and
giant magnetoresistance of more than 99% can be realized in
spin-valve van der Waals (vdW) junctions using these metals as electrodes. Owing to the intrinsic mismatch of
spin states, the central-layer materials for the vdW junctions can be arbitrary nonmagnetic materials, in principle. Our research provides clear physical insights into the mechanism for high magnetoresistance and opens new avenues for the search and design of high-magnetoresistance devices.
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All authors Kan Yan, Li Cheng, Yizhi Hu, Junjie Gao, Xiaolong Zou, Xiaobin Chen
Strongly Correlated Electrons · Cross-listed from math-ph
The zipper condition for $4$-tensors in two-dimensional topological order and the higher relative commutants of a subfactor arising from a commuting square
Yasuyuki Kawahigashi
Researchers in condensed matter physics recently study two-dimensional topological order in terms of tensor networks involving certain 3- and 4-tensors. Their 3-tensors satisfying the "zipper condition" play an important role there and such 3-tensors can be made into certain 2-tensors by combining two wires into one. We identify their 4-tensors with bi-
unitary connections in Jones' subfactor theory in operator
algebras with precise normalization constants. Then we prove that their 2-tensors satisfying the zipper condition are the same as flat fields of strings in subfactor theory which correspond to elements in the higher relative commutants of the subfactor arising from the bi-
unitary connection. This is what we expect, since the zipper condition is a kind of pentagon relations, but we clarify what conditions are exactly needed for this – we do not need the flatness or the finite depth condition for the bi-
unitary connection. We actually generalize their 4-tensors so that the four index sets of the 4-tensors can be all different and work on a "half-version" of the zipper condition.
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Materials Science
Numerical Modeling of Cu2MnSnS4/FeSi2 Dual-Absorber Solar Cell Achieving High Efficiency
Hasib Md Abid Bin Farid and Md Tashfiq Bin Kashem
Dual-absorber
solar cells represent a promising approach to surpass the efficiency limit of single-junction devices by extending spectral absorption and minimizing thermalization losses. Among earth-abundant thin-film materials, kesterites have attracted considerable interest, however, the well-studied Cu2ZnSnS4 (CZTS) continues to face challenges related to antisite disorder and secondary phase formation. Replacing Zn with Mn in Cu2MnSnS4 (CMTS) mitigates these limitations, improving cation ordering and electronic quality while maintaining favorable optical properties. Yet, despite its potential, CMTS remains largely unexplored in multi-absorber configurations-only one prior study has reported a CMTS-based dual-absorber device. In this work, we present a comprehensive numerical investigation of a CMTS-FeSi2 dual-absorber thin-film
solar cell using the one-dimensional
solar cell capacitance simulator (SCAPS-1D). FeSi2, with its narrow band gap (0.87 eV) and strong near-infrared absorption, serves as an ideal bottom absorber to complement CMTS, enabling broader spectral utilization. The study systematically examines the effects of geometrical, electronic, and interfacial parameters on carrier transport, and overall device performance. The optimized device delivers an impressive power conversion efficiency of 34.9%, with VOC = 0.79 V, JSC = 51.07 mA/cm2, and a fill factor of 85.91%. These findings demonstrate that integrating FeSi2 with CMTS not only enhances carrier collection and spectral harvesting but also establishes a new pathway toward high-efficiency, sustainable, and environmentally benign thin-film photovoltaics.
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Strongly Correlated Electrons
Competition between Weak Localization and Antilocalization of Dirac-like Fermions in a Spin-Polarized Two-Dimensional Electron Gas at KTaO3 (111) Interface
Hui Zhang, Daming Tian, Xiaobing Chen et al. (+7 more)
Quantum transport phenomena in two-dimensional electron gases (2DEGs) at
oxide interfaces have garnered significant interest owing to their potential in spintronic and
quantum information technologies. Here, we systematically investigate the
quantum conductance corrections of
spin-polarized 2DEGs formed at the interfaces between two insulating
oxides,
ferromagnetic EuTiO3 (ETO) films and (111)-oriented KTaO3 (KTO) substrates. The anomalous
Hall effect and hysteretic magnetoresistance provide clear evidence for long-range
ferromagnetic order in the 2DEGs, which could be attributed to interfacial Eu doping in combination with the
magnetic proximity effect of the ETO layer. The breaking of time-reversal
symmetry by ferromagnetism in the 2DEGs, and with the assistance of
spin-orbit coupling effect, gives rise to a nontrivial Berry phase. This results in a competition between weak localization (WL) and weak antilocalization (WAL) in the
quantum transport of Dirac-like
fermions at the KTO (111) interfaces. Notably, this competitive behavior can be effectively tuned by optical gating via a photoexcitation-induced shift of the
Fermi level. Our findings demonstrate a controllable platform based on
spin-polarized
oxide 2DEGs for
quantum transport, opening new avenues for
spin-orbitronic and topological electronic applications.
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All authors Hui Zhang, Daming Tian, Xiaobing Chen, Lu Chen, Min Li, Yetong Bai, Fengxia Hu, Baogen Shen, Jirong Sun, Weisheng Zhao
Materials Science
Electric Field-Induced Phase Transitions and Hysteresis in Ferroelectric HfO2 Captured with Machine Learning Potential
Po-Yen Chen and Teruyasu Mizoguchi
Electric field-induced studies, including phase transition and polarization hysteresis, for ferroelectric HfO2 at the atomic scale are critical since they can largely affect its application in ferroelectric and dielectric devices. However, conventional first-principles approaches are computationally limited in capturing large-scale atomic dynamics under realistic field conditions. Here, to enable electric-field-driven molecular dynamics simulations, we develop a machine learning potential (MLP) tailored for HfO2, coupled with an in-situ Born effective charge (BEC) model. This framework enables us to capture key phenomena, including field-induced phase transitions, polarization switching, and strain-dependent dielectric responses, with high fidelity and computational efficiency. Notably, we reproduce hysteresis loops and phase transition barriers consistent with AIMD results and reveal possible electric-field-induced polarization activation in the monoclinic phase. Our approach offers a scalable and transferable tool for atomistic exploration of functional
oxides and paves the way for data-driven design of ferroelectric devices.
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Other Condensed Matter
Chiral orbital/spin textures and Edelstein effects in monolayer Janus TMDs
Pratik Sahu, Sashi Satpathy and Birabar Ranjit Kumar Nanda
We investigate the orbital and
spin Edelstein effect(OEE and SEE) in two-dimensional Janus transition metal dichalcogenides (TMDs) of the form MXX$^\prime$ $(M = Mo,\ W,\ Nb;\ X/X^\prime = S,\ Se,\ Te)$ with the aid of density functional theory calculations and tight-binding model
Hamiltonian studies. The chalcogen layers $X$ and $X^\prime$, break the mirror
symmetry to introduce an internal electric field $E_{int}$ normal to the plane, which is responsible for OEE and SEE. Our results show that in a non-Janus framework, the wavefunctions at the valence and conduction bands are dominated with the $|x^2-y^2>$, $|xy>$, and $|z^2>$ orbitals. Due to the $E_{int}$ of the Janus system, these orbitals are now intermixed with the $|xz>$ and $|yz>$ orbitals to produce a robust orbital texture around the valleys $\Gamma,K$ and $K^\prime$. The
spin orbit coupling, in addition to the formation of a
spin texture, introduces a chirality reversal to the orbital texture. An applied in plane electric field creates both OEE and SEE with the former being one order higher in magnitude. This makes the Janus materials promising for
spin-orbitronics. Our work paves the way for further experimental exploration for orbital and
spin orbital torque in Janus TMDs.
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Materials Science · Cross-listed from physics.optics
Broadband Solar Selective Absorber with Dallenbach-type Bilayer Structure Achieved Using Carbon Nanotube Membranes with Tailored Optical Spectra
Hengkai Wu, Taishi Nishihara, Mioko Hizukuri et al. (+3 more)
Spectrally selective absorbers that maximize
solar absorption and minimize thermal radiation loss are crucial for efficient
solar thermal energy harvesting. However, limitations imposed by the intrinsic properties of conventional materials hinder the fabrication of interference-based absorbers with desired optical properties. Herein, a high-performance
solar absorber with a Dallenbach-type dielectric-metal tandem structure was fabricated using an ultrathin, subquarter-wavelength thickness single-walled carbon nanotube (SWCNT) membrane with tailored optical spectra as the absorbing layer. By mixing multiple SWCNT
chiral structures, the optical response of the absorbing layer was tailored to approximate a theoretical complex refractive index spectrum of dielectrics; therefore enabling high
solar absorptance, low infrared emittance, and a low angular dependence with a simple
bilayer structure. The fabricated proof-of-concept 1 cm$^2$ absorber exhibited excellent spectral selectivity (
solar absorptance/infrared emittance of 0.84/0.03), and an
equilibrium temperature of $\approx 190^\circ$C ($270^\circ$C) under nonconcentrated ($2\times$ concentrated) sunlight, considerably outperformed a blackbody-like absorber. This study presents a high-performance
solar absorber with a simple planar structure and proposes a concept of designing dielectric with the desired optical properties by mixing various types of structure-sorted SWCNTs.
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All authors Hengkai Wu, Taishi Nishihara, Mioko Hizukuri, Takeshi Tanaka, Hiromichi Kataura, Yuhei Miyauchi
Materials Science
Re-refinement of the structure of the planar hexagonal phase of ZnO nanocrystals
Musen Li, Lingyao Zhang, Wei Ren et al. (+1 more)
The planar hexagonal phase of ZnO, known as h-ZnO, g-ZnO, {\alpha}-ZnO, the Bk structure, the 5-5 phase, the {\alpha}-BN phase, etc., has P63/mmc
symmetry and is implicated in ferroelectric switching mechanisms for wurtzite-ZnO. It is well-known in thin films on substrates and to be stabilized by external pressure, but critical is its possible existence in high-purity nanocrystals under ambient conditions. Indeed, a
crystal structure has been reported, but this work remains controversial as first-principles calculations predict very different structural properties. Herein, the original experimental data is re-refined, through phase-shift determination and Morlet wavelet transformation, that molecular dynamics simulations associate with a P63/mmc structure with
lattice parameters at room temperature of a = 3.45{\pm}0.02 Å and c = 4.46{\pm}0.02 Å. These values are 0.35 Å and 0.80 Å, respectively, larger than those previously reported and in good agreement with computational predictions. This confirms that ZnO nanocrystals can form a metastable planar hexagonal phase. It provides key information pertaining to polarization switching in ZnO, its derivatives, and general wurtzite-structured materials.
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All authors Musen Li, Lingyao Zhang, Wei Ren, Jeffrey R. Reimers
Materials Science
Beyond empirical models: Discovering new constitutive laws in solids with graph-based equation discovery
Hao Xu, Yuntian Chen and Dongxiao Zhang
Constitutive models are fundamental to solid mechanics and materials science, underpinning the quantitative description and prediction of material responses under diverse loading conditions. Traditional phenomenological models, which are derived through empirical fitting, often lack generalizability and rely heavily on expert intuition and predefined functional forms. In this work, we propose a graph-based equation discovery framework for the automated discovery of constitutive laws directly from multisource experimental data. This framework expresses equations as directed graphs, where nodes represent operators and variables, edges denote computational relations, and edge features encode parametric dependencies. This enables the generation and optimization of free-form symbolic expressions with undetermined material-specific parameters. Through the proposed framework, we have discovered new constitutive models for strain-rate effects in
alloy steel materials and the deformation behavior of lithium metal. Compared with conventional empirical models, these new models exhibit compact analytical structures and achieve higher accuracy. The proposed graph-based equation discovery framework provides a generalizable and interpretable approach for data-driven scientific modelling, particularly in contexts where traditional empirical formulations are inadequate for representing complex physical phenomena.
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Mesoscale and Nanoscale Physics
Enhanced Thermoelectricity in Nanowires with inhomogeneous Helical states
Zahra Aslani, Fabio Taddei, Fabrizio Dolcini et al. (+1 more)
Semiconductor nanowires (NWs) with strong Rashba
spin-orbit coupling (RSOC), when exposed to a suitably applied Zeeman field, exhibit one-dimensional helical channels with a
spin orientation locked to the propagation direction within the
magnetic energy gap. Here, by adopting a scattering-
matrix approach applied to a tight-binding model of the NW, we demonstrate that the thermoelectric (TE) properties can be widely controlled by tuning the misalignment angle $\phi$ between the
spin-orbit directions of two NW segments. In particular, when the RSOC vectors are antiparallel (Dirac paradox configuration) we predict a significant violation of the Wiedemann-Franz law, and a strong enhancement of the Seebeck coefficient and the $ZT$ figure of merit. We also show that the Zeeman gap determines the optimal energy window for doping and temperatures. These results suggest that controlling the
spin-orbit field direction, which can be achieved with suitably applied wrap gates, is a promising alternative for tuning and optimizing the TE response in
quantum-coherent semiconducting NW devices.
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All authors Zahra Aslani, Fabio Taddei, Fabrizio Dolcini, Alessandro Braggio
Mesoscale and Nanoscale Physics
Observation of Shapiro Steps in the Charge Density Wave State Induced by Strain on a Piezoelectric Substrate
Koji Fujiwara, Takuya Kawada, Natsumi Nikaido et al. (+4 more)
Recent development in nanotechnology has enabled us to investigate the dynamic properties of van der Waals materials on a piezoelectric substrate. Here we report on the dynamics of charge density wave (CDW) in NbSe$_{3}$ nanowires induced by surface acoustic waves (SAWs). Clear peaks in the differential resistance were observed at the resonant frequency of the SAW device. These peaks known as Shapiro steps are typically observed by applying an rf current to NbSe$_{3}$ nanowires. We found that the Shapiro steps induced by SAWs show several distinct features from the ones induced by an rf current. Our detailed study revealed that a strain induced by SAWs plays a significant role in the Shapiro steps. The result clearly demonstrates the importance of the strain in CDW materials and paves the way for strain-induced device applications.
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All authors Koji Fujiwara, Takuya Kawada, Natsumi Nikaido, Jihoon Park, Nan Jiang, Shintaro Takada, Yasuhiro Niimi
Materials Science
Potential-Programmed Operando Ensembles Govern Nitrate Electroreduction
Xue-Chun Jiang, Jia-Lan Chen, Wei-Xue Li et al. (+1 more)
Electrocatalyst surfaces continuously reorganize on the timescale of catalytic turnover, obscuring the identification of active sites under operando conditions and hindering rational catalyst design. Here, we resolve the operando Cu(111) electrolyte interface for nitrate-to-ammonia electroreduction (NO3RR) via a multiscale modeling framework accelerated by a coverage-aware machine-learning potential. Rather than a single "average coverage" site, the working interface is a potential-gated statistical ensemble of 34 interconverting adsorbate motifs between -0.10 and -1.00 V (vs. SHE). Potential-driven shifts in motif populations produce a volcano-shaped activity trend peaking at -0.70 V, where the site-normalized turnover frequency reaches 0.015 s-1 with nearly 100% Faradaic efficiency to ammonia. The activation barriers across >150 transition states collapse into a single linear relationship with the excess charge on the reacting Cu atoms ({\Delta}qCu), identifying interfacial charge redistribution as a unifying kinetic descriptor. The maximum activity arises not from uniform moderate coverage but from a 2NO/2NH2 quadrilateral microensemble that tunes {\Delta}qCu to an intermediate value, simultaneously lowering the N-O cleavage and N-H formation barriers. Reconceptualizing "coverage" as an ensemble of local microenvironments decouples thermodynamic stability from catalytic productivity. This perspective furnishes a parameter-free strategy by controlling motif populations and interfacial charge via the potential to program high-coverage electrocatalysis beyond the NO3RR.
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All authors Xue-Chun Jiang, Jia-Lan Chen, Wei-Xue Li, Jin-Xun Liu
Strongly Correlated Electrons
Quantum fluctuations associated with first-order magnetic transition in a frustrated kagome lattice antiferromagnet
Zhongchen Xu, Xinyang Liu, Cuiwei Zhang et al. (+7 more)
Intense
quantum fluctuations arising from geometrical frustrations in kagome-
lattice magnets provide a feasible approach to exotic
quantum states. Here, we document an unexpected isosymmetric first-order
magnetic transition in the recently synthesized frustrated kagome-
lattice antiferromagnet Nd3ScBi5, which is characterized by significant latent heat and a pronounced magnetocaloric effect, as well as discontinuous Raman shifts and negligible hysteresis. Employing the magnetocaloric effect as a detection method, in conjunction with systematical field-dependent physical properties, we uncover a distinctive 1/2 magnetization plateau phase with significant
quantum fluctuations. Our study unveils Nd3ScBi5 as a prototypical model with an emerging phase of enhanced
quantum fluctuations triggered by first-order
magnetic transitions.
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All authors Zhongchen Xu, Xinyang Liu, Cuiwei Zhang, Shuai Zhang, Feng Jin, Junsen Xiang, Quansheng Wu, Xianmin Zhang, Peijie Sun, Youguo Shi