CMP Journal 2026-07-20
Statistics
Nature Physics: 1
Nature Reviews Materials: 1
Nature Reviews Physics: 1
arXiv: 63
Nature Physics
Attosecond response of molecules to impulsive ionization
Original Paper | Chemical physics | 2026-07-19 20:00 EDT
Taran Driver, Zhaoheng Guo, Erik Isele, Gilbert Grell, Marco Ruberti, Jordan T. O’Neal, Oliver Alexander, Sandra Beauvarlet, David Cesar, Joseph Duris, Douglas Garratt, Kirk A. Larsen, Siqi Li, Přemysl Kolorenč, Gregory A. McCracken, Daniel Tuthill, Zifan Wang, Nora Berrah, Christoph Bostedt, Kurtis Borne, Xinxin Cheng, Louis F. DiMauro, Gilles Doumy, Paris L. Franz, Andrei Kamalov, Xiang Li, Ming-Fu Lin, Razib Obaid, Antonio Pícon, River R. Robles, Daniel Rolles, Artem Rudenko, Moniruzzaman Shaikh, Daniel S. Slaughter, Nicholas S. Sudar, Emily Thierstein, Kiyoshi Ueda, Enliang Wang, Anna L. Wang, Thorsten Weber, Thomas J. A. Wolf, Linda Young, Zhen Zhang, Vitali Averbukh, Oliver Gessner, Philip H. Bucksbaum, Matthias F. Kling, Alicia Palacios, Fernando Martín, Jon P. Marangos, Peter Walter, Agostino Marinelli, James P. Cryan
When matter interacts with energetic radiation it can undergo sudden, or impulsive, ionization. This process can drive chemical change and occurs widely in space and planetary atmospheres, yet its comprehensive description challenges our current theoretical and computational capabilities as it requires advanced treatment of electron correlation and nonadiabatic dynamics beyond the Born-Oppenheimer approximation. Here we measure the response of the para-aminophenol molecule to sudden ionization. Using attosecond X-ray absorption spectroscopy, we resolve the ultrafast dynamics of the ionized molecule with atomic precision. A subfemtosecond decay corresponds to states undergoing non-radiative decay, whereas few-femtosecond oscillatory signatures are associated with electronic wavepacket motion in stable cation states that later couple to nuclear motion. We compare our measurement with state-of-the-art computational modelling, qualitatively reproducing the observed response across multiple timescales. These results provide a benchmark for computational models of sudden ionization and ultrafast charge motion in matter.
Chemical physics, Optics and photonics
Nature Reviews Materials
Engineering bamboo as a multiscale platform for carbon-negative materials
Review Paper | Biomaterials | 2026-07-19 20:00 EDT
Tian Bai, Mahyar Panahi-Sarmad, Jie Yan, Ran Bi, Ming He, Chunping Dai, Guangping Han, Chaoji Chen, Orlando J. Rojas
Carbon-negative materials are increasingly central to credible net-zero strategies; however, their climate benefits depend on transparent life-cycle boundaries, realistic end-of-life scenarios and carbon storage. Bamboo is a fast-growing lignocellulosic resource that combines high biomass productivity with the ability to sequester atmospheric carbon in long-lived materials. Beyond its rapid growth, bamboo exhibits a hierarchical structure extending from molecular composition to cell-wall ultrastructure and tissue organization that influences transport, reactivity, mechanical performance and carbon retention. In this Review, we position bamboo as a multiscale materials platform in which chemical functionality, structural organization and processing pathways can be deliberately engineered to tailor performance and service lifetime. We examine how bond-selective chemistry, controlled hydration and structural modification strategies enable the conversion of bamboo into materials across multiple dimensional scales, including structural composites, functional laminates, fibre-based systems and nanoscale building blocks. We further discuss how process intensity, product durability and cascade utilization influence the extent to which these materials provide net climate benefits. By linking molecular design, hierarchical structure and life-cycle carbon accounting, we establish a framework connecting accessibility, reactivity and carbon permanence in bamboo-derived materials. Finally, we highlight the remaining challenges in structural control, durability and end-of-life design that will need to be overcome for bamboo materials to deliver meaningful climate benefits.
Biomaterials, Composites, Sustainability
Nature Reviews Physics
Universal bounds on entropy production from fluctuating coarse-grained trajectories
Review Paper | Chemical physics | 2026-07-19 20:00 EDT
Udo Seifert
Entropy production is arguably the most universally applicable measure of non-equilibrium behaviour, particularly for systems coupled to a heat bath. This setting encompasses driven soft matter as well as biomolecular, biochemical and biophysical systems. Despite the central role of entropy production, direct measurements of it remain challenging, especially in small systems dominated by fluctuations. The main difficulty arises because not all degrees of freedom that contribute to entropy production are experimentally accessible. A key question, therefore, is how to infer entropy production from coarse-grained observations, such as time series of experimentally measurable variables. Over the past decade, stochastic thermodynamics has provided several inequalities that yield model-free lower bounds on entropy production from such coarse-grained data. The major approaches rely on observations of coarse-grained states, fluctuating currents or ticks, correlation functions of coarse-grained observables, and waiting-time distributions between ‘Markovian’ events, which correspond to transitions between mesoscopic states. Here, I systematically review these techniques valid under the sole assumption of a Markovian (that is, memoryless) dynamics on an underlying, not necessarily observable, network of states or following a possibly high-dimensional Langevin equation. I discuss in detail the large class of non-equilibrium steady states and highlight extensions of these methods to time-dependent and relaxing systems. Although our focus is on mean entropy production, I also summarize recent progress in quantifying entropy production along individual coarse-grained trajectories.
Chemical physics, Statistical physics
arXiv
Thermo-elastic properties of hydrated epoxy-graphene nanocomposites from ensemble-based molecular dynamics simulations
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Maxime Vassaux, Werner A. Müller, James L. Suter, Alexandros Anastasiou, Martin Simmons, David Tilbrook, Peter V. Coveney
Epoxy-based materials are inherently hygroscopic, absorbing moisture from the environment, which can significantly alter their short and long-term performance. The presence of graphene is often considered as a potential candidate to act as a microscopic barrier, mitigating the adverse effects of hydration on the matrix. This study investigates the impact of hydration on the glass transition and elastic mechanical properties of epoxy resins and their graphene nanocomposites, focusing on water content up to 5 %wt. Using large-ensemble molecular dynamics simulations, we analyze the temperature-driven glass transition and mechanical response of both neat epoxy and epoxy-graphene systems under varying hydration levels. Our results reveal a distinct threshold at 3 %wt water content: below this, hydration primarily reduces the glass transition temperature, while mechanical properties remain unaffected. Beyond 3 %wt, however, the mechanical properties deteriorate, highlighting a non-linear sensitivity to water uptake. Furthermore, we emphasize the critical role of ensemble size in ensuring the reliability of molecular dynamics predictions for such heterogeneous systems. Our simulations demonstrate that ensembles substantially larger than current state-of-the-art standards are necessary to achieve converged distributions of the predicted mechanical properties, particularly in highly heterogeneous hydrated epoxy-graphene nanocomposites. These findings provide novel insights into the hydration behavior of epoxy-based materials and underscore the potential of graphene to enhance their environmental resistance. This work also advances the understanding of structure-property relationships in polymer nanocomposites, offering guidance for the design of more robust materials in humid environments.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Spontaneous Nanopatterning and Strain Relaxation in SiGe Layers Grown by Oxidative Solid Phase Epitaxy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Sophie E. Bierer, Trevor R. Smith, Arezoo Mafi, Sunzhuoran Wang, Chengqian Liao, Vatsalkumar Patel, Andrew P. Knights, Ryan B. Lewis
The wafer-scale monolithic integration of III-V materials on Si would lead to revolutionary optoelectronic hardware for data, computing and other applications. However, heteroepitaxy of III-Vs on Si requires overcoming the large lattice and thermal mismatches between the materials and reducing threading dislocations densities. In this work, we explore the oxidative solid phase epitaxy (SPE) of Ge+ implanted Si(111) to form ultra-thin strain-relieving SiGe metamorphic buffer layers for heteroepitaxy on Si. The SPE process is shown to result in a nanopatterning of the Ge concentration variation across the sample surface, visible by scanning and transmission electron microscopy (SEM and TEM). The concentration patterning is the result of a hexagonal network of Shockley partial dislocations at the SiGe/Si interface. Analyzing the pattern spacing observed by SEM is demonstrated as an easy, non-destructive method for obtaining the local strain state of SiGe layers. This work is important for engineering ultra-thin SiGe metamorphic buffer layers for III-V optoelectronics heteroepitaxy on the silicon platform.
Materials Science (cond-mat.mtrl-sci)
Main text: 17 pages, 5 figures. Supporting information: 11 pages, 6 figures
Nanoscale stray fields from micromagnets for optimal spin qubit architecture
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Sandrine Lopes, Quentin Schaeverbeke, Matthieu M. Desjardins, Daniel Lacour, Michel Hehn, François Montaigne
On-chip micromagnets generate local magnetic-field asymmetries, enabling electrical control of spin qubits via electric dipole spin resonance and their integration into circuit quantum electrodynamics (QED) architectures. Accurate prediction of spin-qubit performance requires modeling micromagnet stray fields beyond the saturated-magnet approximation, accounting for nonuniform magnetization. Here, we combine thin-film characterization of Co, Co/Ta multilayers, and CoFe films with nanoscale stray-field measurements using NV-center magnetometry in the unsaturated regime to establish a reliable micromagnetic simulation framework. We show that CoFe micromagnets generate antisymmetric fields in double quantum-dot geometries exceeding +/- 100mT, owing to their high saturation magnetization and favorable magnetocrystalline anisotropy. For spin qubits coupled to microwave resonators, the predicted spin-photon coupling reaches $ \left| g_s/g_c \right| \approx 0.5$ , where $ g_c$ denotes the charge-photon coupling strength of the underlying charge qubit, highlighting the potential for high-fidelity operations in circuit QED architectures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
16 pages, 5 figures
Field-induced first order transitions and phase coexistence in the Kitaev quantum spin liquid candidate BaCo2(AsO4)2
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Tanner J. Legvold, Bin Gao, Rong-Zhu Lin, Violet Williams, Tong Chen, Dehong Yu, Chien-Lung Huang, Gage Eichman, Renjie Lui, Benedetta Flebus, Pengcheng Dai, Douglas Natelson
BaCo2(AsO4)2 (BCAO) is an insulating Kitaev quantum spin liquid candidate with a rich low-temperature phase diagram. Below 5 K, it exhibits double-zigzag magnetic order. Upon application of an in-plane magnetic field, the magnetic structure first transforms into an up-up-down (UUD) state near 0.12 T and then enters a fully spin-polarized ferromagnetic (FM) state near 0.5 T. In the narrow field regime close to the polarized phase, a finite residual thermal conductivity has been reported, suggesting a possible field-induced quantum spin liquid phase. Using neutron scattering, we show that the field-induced double-zigzag-to-UUD transition near 0.15 T is accompanied by the emergence of a cluster of localized UUD spin excitations that coexist with conventional spin waves. Upon further increasing field, BCAO undergoes a first-order UUD-to-FM transition with coexistence of UUD and FM phases, accompanied by a sharp response in the spin Seebeck coefficient. These results do not support a quantum spin liquid scenario near the UUD-to-FM critical field. Instead, modeling indicates that the broad excitations arise from bound spin-flip pairs, while a low-lying dispersive branch near the FM phase boundary carries the same sign of magnetization as the FM order. These excitations naturally account for the observed sign of the spin Seebeck response and are likely relevant to the thermal conductivity near the critical field.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
19 pages, 5 figures + supporting info, 20 pages and 5 figures
Fragmented ETH: Prethermalization, Timescales, and Ensemble Inequivalence
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-07-20 20:00 EDT
C. L. Sriram, Soumya Kanti Pal, Lea F. Santos
We investigate how finite quantum systems with strong long-range interactions approach thermal equilibrium. Nearly conserved quantities inherited from the fully connected limit fragment the Hilbert space and give rise to a many-body spectrum split into energy bands. As a result, equilibration becomes anomalously slow and proceeds through long-lived prethermal plateaus. This two-stage equilibration process is, however, not universal. We uncover the mechanism that determines which observables and initial states exhibit, or evade, prethermal plateaus. We also develop a perturbative theory that provides analytical expressions for both the height of the prethermal plateau and its timescale. Despite the lack of global ergodicity, quantum chaos develops within individual energy bands, enabling the definition of microcanonical ensembles within the bands. This supports a band-resolved formulation of thermalization, which we term fragmented eigenstate thermalization hypothesis (fETH). Unlike conventional ETH, finite-size scaling in fETH obeys a symmetry-imposed selection rule that restricts which system sizes can be compared. This band-resolved description has direct consequences for equilibrium statistical mechanics. While microcanonical ensembles remain confined to a single band, canonical ensembles mix different bands. This mismatch explains ensemble inequivalence without invoking equilibrium phase transitions. Our results apply to a broad class of Hamiltonians exhibiting Hilbert-space fragmentation.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
25 pages, 11 figures; comments are welcome
Dynamical Polarization from Hidden Spin and Orbital Textures in p-Wave Magnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Yantao Li, Jacob Linder, Pavlo Sukhachov
Period-averaged descriptions often miss essential features of driven quantum matter. We show that the micromotion of an optically driven $ p$ -wave magnet unveils a hidden net spin polarization, absent from both the equilibrium and period-averaged spin textures, which remain odd in momentum. This spin polarization oscillates at the drive frequency and is resonantly enhanced at the interband gap set by nonrelativistic exchange splitting. The drive further activates an orbital angular momentum governed by interband quantum geometry. While its linear response remains momentum-odd, nonlinear rectification yields a static, momentum-even orbital polarization for suitably oriented driving fields. These results establish $ p$ -wave magnets as a source of resonant ac spin and rectified dc orbital polarization: effects invisible to any period-averaged treatment.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
9 pages, 3 figures
Phase-Field Simulation of Dendrite Evolution in All-Solid-State Sodium Batteries during Cycling
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Chengyin Wu, Wolfgang Windl, Jung-Hyun Kim, Yanzhou Ji
Dendrite growth during cycling remains a critical challenge for all-solid-state batteries (SSBs), limiting the full realization of their inherent safety and high energy density. In particular, the mechanisms of continuous dendrite penetration during charge-discharge cycling remain poorly understood and are difficult to characterize experimentally. This study applies a phase-field model, informed by density functional theory calculations, to rationalize and visualize the dendrite penetration behaviors during cycling in sodium (Na) SSBs with pure Na or Na-Sb alloy anodes and polycrystalline Na$ _3$ SbS$ _4$ electrolyte. We show that dendrite stripping is intrinsically asymmetric with respect to plating due to grain boundary geometry, leading to the formation of isolated Na metal that persists between cycles. This residual Na metal becomes kinetically stabilized at grain-boundary junctions and is readily reactivated during subsequent plating, thereby accelerating and amplifying dendrite penetration. We further investigate the effects of applied voltage, solid-electrolyte microstructure, and anode chemistry on this phenomenon. These findings establish isolated Na metal as a key contributor for continued dendrite propagation in Na SSBs and provide design principles for stabilizing anode/electrolyte interfaces in Na SSBs.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Ab initio time-dependent GW approach for nonequilibrium exciton-phonon coupled dynamics across momentum space
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Zhenfa Zheng, Benran Zhang, Jiawei Ruan, Chih-En Hsu, Zien Zhu, Supavit Pokawanvit, Felipe H. da Jornada, Hung-Chung Hsueh, Ting Cao, Mauro Del Ben, Yang-Hao Chan, Steven G. Louie, Zhenglu Li
The dynamics of optical excitations in materials generally involves intertwined electron-hole (e-h) and electron-phonon (e-ph) interactions out of equilibrium. However, a full theoretical description of such nonequilibrium dynamics requires a systematic treatment of the coherent excitonic excitations and exciton-phonon interactions across the entire crystal momentum space in real time, which remains a major challenge and out of reach for first-principles approaches. Here, we present a new ab initio time-dependent adiabatic GW methodology that incorporates full finite-momentum e-h and e-ph couplings, enabling real-time simulations of the coherently coupled exciton-phonon dynamics. The excitonic excitations are naturally described by the equation of motion of the interacting single-particle density matrix, whereas their couplings to phonons are formulated within a linear-response framework, hence the simulations can be efficiently carried out within a primitive unit cell. We demonstrate the capabilities of this new approach by investigating the direct-to-indirect exciton transitions in monolayer WSe2 in a pump-probe setup of time-resolved and angle-resolved photoemission spectroscopy. Our results reveal that the phonon-mediated ultrafast intervalley dynamics of excitons of this system is within ~0.5 ps, manifested as in-gap photoemission intensity transfer from the K-valley to the Q-valley. This work establishes a comprehensive and practical nonequilibrium Green’s function framework for accurately simulating nonequilibrium and coherent excitations involving coupled excitons and phonons from first principles.
Materials Science (cond-mat.mtrl-sci)
Data-efficient reconstruction of critical quantum dynamics via blind fractional-envelope extrapolation
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Hyunju Kim, Hyun-Yong Lee, Heung-Sik Kim
Simulating real-time dynamics of quantum systems is often limited to short times by entanglement growth. Finite-pole reconstructions such as linear prediction and related machineries extrapolate such data reliably when the spectrum is a finite set of excitations, but at criticality the low-energy spectrum is a power-law continuum $ A(\omega)\sim|\omega|^{\alpha-1}$ – a branch cut whose real-time tail $ G(t)\sim t^{-\alpha}$ finitely many poles cannot represent. Here we develop a fractional-calculus-motivated envelope extrapolation for such data. Its structure is motivated by a fractional form of Schwinger–Dyson (fSD) equation, in which the Laplace symbol $ s^{\alpha}$ carries the branch cut analytically while the residual self-energy remains meromorphic. On real data we employ the corresponding operational alternative – the exponent $ \alpha$ is selected blindly inside the fit window, the signal is detrended by $ t^{\alpha}$ , the residual is fitted by a stabilized finite-pole model, and the algebraic envelope is restored. On the critical XXZ chain this blind fractional-envelope method (fSD for short) extrapolates short-time data typically several-fold more accurately than finite-pole methods, with the exponent $ \alpha$ identified blindly from the fit window alone and bracketing the closed-form Luttinger value at weak coupling. The same blind search finds the $ z=2$ dilute-magnon exponent $ \alpha=1/2$ at the $ \Delta=1$ saturation transition, and the advantage persists in the gapped free-magnon phase with its sharp band edges. On noncritical dynamical mean-field spectra, whose low-frequency response is regular, fSD by contrast fails to select any stable fractional envelope and reduces to the standard pole result rather than manufacturing a spurious power law, making it an efficient and accurate route to quantum critical dynamics when only short simulation times are accessible.
Strongly Correlated Electrons (cond-mat.str-el)
14 pages, 9 figures
exa-PD: A scalable high-performance workflow for multi-element phase diagram construction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Zhuo Ye, Feng Zhang, Maxim Moraru, Weiyi Xia, Ying Wai Li, Yongxin Yao, Cai-Zhuang Wang
Exa-PD is a highly parallelizable workflow designed for the construction of multi-element phase diagrams (PDs). It uses standard sampling techniques, molecular dynamics (MD) and Monte Carlo (MC) as implemented in the LAMMPS package, to simultaneously sample multiple phases over a fine temperature-composition mesh for free-energy calculations. Parsl serves as the global workflow engine, coordinating large ensembles of MD and MC tasks to achieve massive parallelization with strong scalability. The resulting free energies of liquid and solid phases are then fed to CALPHAD modeling via the PyCalphad package to construct multi-element PDs.
Materials Science (cond-mat.mtrl-sci), Distributed, Parallel, and Cluster Computing (cs.DC), Computational Physics (physics.comp-ph)
5 pages, 3 figures. The source code associated with this work is available at this https URL
Exploring the Potential of BY3 (Y = P, As) Monolayers as High-Capacity and Rapid-Diffusion Anodes for Sodium-Ion Batteries
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Jakkapat Seeyangnok, Joongjai Panpranot, Udomsilp Pinsook
The rapid advancement of sodium-ion batteries (SIBs) demands robust anode materials capable of delivering high specific capacities while maintaining rapid ion transport kinetics. In this work, we employ first-principles density functional theory (DFT) to systematically evaluate the two-dimensional BX3 (X = As, P) monolayers as high-performance anode candidates for SIBs. Our calculations reveal that both the BAs3 and BP3 frameworks exhibit excellent mechanical and dynamical stability alongside an intrinsic metallic character. These materials demonstrate a strong thermodynamic affinity for Na adsorption, driven by a synergistic ionic and covalent bonding mechanism that highly favors the H3 hollow site. Furthermore, they facilitate exceptionally fast charge and discharge kinetics, characterized by ultralow optimal Na-ion migration barriers of 0.19 eV and 0.26 eV for BAs3 and BP3, respectively. Crucially, projected density of states (PDOS) analyses confirm that both systems preserve their robust metallic conductivity even at their maximum theoretical sodiation limits (Na120B8X24), ensuring continuous and efficient electron transport throughout the electrochemical cycle. We predict low, stable average open-circuit voltages of 0.15 V for BAs3 and 0.18 V for BP3, alongside ultrahigh theoretical specific capacities of 1365 mAh g-1 and 3875 mAh g-1, respectively, which significantly outperform contemporary 2D SIB anodes. These compelling theoretical findings establish the BX3 monolayers as outstanding, structurally resilient candidates for next-generation, high-energy-density energy storage systems.
Materials Science (cond-mat.mtrl-sci)
10 pages, 6 Figures
Symbolic Predicate-Guided Language Agents for Inverse Design of Perovskite Oxides
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Dong Hyeon Mok, Seoin Back, Victor Fung, Guoxiang Hu
Efficient discovery of high-performance materials has been pursued through a variety of data- and AI-driven strategies, among which inverse design, generating materials from desired target properties, has emerged as an important paradigm. Large language models (LLMs) offer a complementary route for inverse materials design because their reasoning and in-context learning capability can be used not only to propose candidates but also to demonstrate interpretable design principles. In this work, we introduce a domain specific language (DSL)-guided strategy to improve the reasoning and design capability of LLM agents by translating natural language design rules into symbolic predicates encoded in a predefined chemistry DSL. These predicates allow the LLM agent to obtain statistical evidence from the accumulated materials data, enabling the agent to evaluate and refine its own reasoning during the design loop. Based on this strategy, we developed a multi-agent materials design framework, called Operational Rule-grounded CHEmical Search Through Reasoning Agents (ORCHESTRA), and applied it to the inverse design of double perovskite oxides under multiple target-property objectives. The results show that symbolic predicates help the LLM identify unsupported rules, validate newly proposed rules and improve the rule store over iterative design cycles. Compared with a strategy relying only on natural language rules, the DSL-guided framework showed the potential to improve materials design performance, particularly for challenging target properties. These findings suggest that mathematical and statistical grounding can enhance the reasoning capability of LLM agents in materials science and that LLM-based inverse design can be performed effectively without large task-specific datasets or additional model training.
Materials Science (cond-mat.mtrl-sci)
Terahertz Time-Domain Spectroscopy as a Universal Defect Fingerprinting Tool for Organic Halide Perovskite Solar Cells
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Inhee Maeng, Young Mi Lee, Jinwoo Park, Seung Jae Oh, Min-Cherl Jung
Organic-inorganic hybrid perovskites (OHPs) deliver certified single-junction power conversion efficiencies (PCEs) exceeding 26% and perovskite-silicon tandem values surpassing 34%, yet a substantial gap with the Shockley-Queisser (S-Q) limit persists-primarily due to grain-boundary (GB) defects that drive non-radiative recombination, ion migration, and degradation. Rational passivation demands a non-contact tool capable of identifying and quantifying specific defect species in device-relevant thin films, a capability absent from conventional probes. This short review demonstrates that terahertz time-domain spectroscopy (THz-TDS, 0.3-3.0 THz) fulfills this role. Across four OHP compositions fabricated by sequential vacuum evaporation (SVE)-MAPbI3, MAPbBr3, FAPbI3, and CsPbI3-the THz spectral window captures both intrinsic phonon modes and GB-localized molecular defect vibrations, enabling species-specific, quantitative characterization at room temperature. Notably, the oscillator strength of the SVE-specific 1.58 THz absorption in MAPbI3 scales linearly with XPS-quantified CH3NH2 defect concentration, establishing THz-TDS as a direct, non-destructive defect meter. Building on these findings, we propose a three-pillar framework for THz-guided defect engineering: (I) quantitative defect measurement via oscillator-strength analysis, (II) material-specific fingerprint identification from a systematically constructed THz library, and (III) fingerprint-guided defect elimination with real-time feedback-together defining a closed-loop quality-control cycle that connects spectroscopic diagnosis to passivation strategy and, ultimately, to enhanced solar-cell efficiency.
Materials Science (cond-mat.mtrl-sci)
New viewpoint for the defect detection using THz-wave absorption property in halide perovksite materials
Hot-Carrier Distribution Spectroscopy by Transconductance in Two-Dimensional Field-Effect Transistors
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
The transconductance $ g_m = dI_D/dV_G$ of a field-effect transistor (FET) is conventionally read as a proxy for carrier density. We show that it is instead a spectroscopic probe of the carrier distribution: because $ g_m$ weights the spectral current $ j(E)$ by the gate-voltage derivative $ \partial f(E)/\partial V_G$ and integrates over energy, it is sensitive to the \emph{shape} of $ f(E)$ , not merely its integrated weight $ n$ . We develop an energy-resolved transport framework for two-dimensional (2D) FETs and, within a gate-independent spectral-kernel approximation, derive the decomposition $ g_m = g_m^{(n)} + g_m^{(\alpha)}$ into the conventional density-modulation term $ g_m^{(n)}$ and a distribution-shape-driven term $ g_m^{(\alpha)}$ . The latter, obtained as the residual after subtracting the smooth density-modulation background from the measured $ g_m$ , exhibits a characteristic anomalous peak at a gate voltage $ V_G^{\rm pk}$ . This peak has no counterpart in equilibrium transport and \emph{cannot be explained by carrier density modulation alone}. With the spectral kernel calibrated, the peak position and height – extracted from standard DC/lock-in $ g_m$ sweeps – constrain the hot-carrier energy $ E_0$ , spectral width $ \sigma$ , and generation threshold $ n_c$ , realizing a steady-state, all-electrical spectroscopy of the carrier distribution. An optional time-resolved extension further recovers the carrier relaxation time $ \tau$ from the transient response following a pump excitation, establishing the 2D FET as a distribution-function spectrometer that requires no optical readout.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
16 pages, 8 figures
Symmetry-Enforced Dirac Fermions and Structural Metastability in Pentagonal Monolayers of Transition-Metal Ditellurides
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Manoj Gadtoula, Clayton Conner, Avinash Sah, Ronghao Luo, Guang Bian
The recent synthesis of pentagonal PdTe$ _2$ monolayer motivates broader research interests in transition-metal ditellurides whose electronic phases are governed by symmetry and structural reconstruction. The pentagonal phase of transition-metal ditellurides exhibits electronic properties that are dramatically different from those of its hexagonal counterpart due to its lower crystalline symmetry. Using first-principles calculations, we study monolayer $ X$ Te$ _2$ ($ X=\mathrm{Pd},\mathrm{Pt},\mathrm{Ni}$ ) in both hexagonal and pentagonal polymorphs. By constructing a continuous structural interpolation between the hexagonal and pentagonal phases, we show that the semimetal (hex)-to-semiconductor (penta) transition occurs only after an intermediate structural threshold rather than at the onset of symmetry reduction. The gap opening coincides with the formation of Te–Te dimers, which drive the bonding–antibonding splitting of the Te $ p$ states and reorganize the band edges. In addition, the nonsymmorphic symmetry of the pentagonal phase enforces band degeneracies at the Brillouin-zone boundary, leading to symmetry-protected two-dimensional (2D) Dirac states. These results establish pentagonal $ X$ Te$ _2$ monolayers as a new class of 2D semiconductors in which symmetry constraints and local bonding collectively shape the unconventional semiconducting electronic structure.
Materials Science (cond-mat.mtrl-sci)
28 pages, 5 figures, 2 tables
General and scalable vapor etching and transformation platform for two-dimensional materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Zhiguo Du, Jikai Zhang, Jonas Björk, Zongju Cheng, Ningjun Chen, Qi Zhao, Hao Chen, Yuxuan Ye, Guang Yang, Haiyang Wang, Bin Li, Johanna Rosen, Shubin Yang
Two-dimensional (2D) nanomaterials derived from non-van der Waals (non-vdW) solids offer exceptional physicochemical properties, yet their synthesis is impeded by intrinsic covalent/metallic bonding and high surface reactivity of the precursors. Here, we report a general vapor-phase etching and transformation platform for producing a library of 36 2D carbides, nitrides, and carbonitrides, exhibiting electrical conductivities spanning six orders of magnitude. Using reactive vapors like hydrogen chloride, we selectively remove A-layers from MAX phases to yield well-defined layers (MXenes), including previously inaccessible semiconducting Hf2CTx. By varying the reactive vapor environment, MXenes can be engineered at X-site and surface-termination site and even be transformed into non-vdW layers such as 2D MAX phases. This general and scalable vapor-phase platform reframes 2D material synthesis, opening new avenues for various applications.
Materials Science (cond-mat.mtrl-sci)
Topology and compact molecular orbitals in twisted bilayer WSe$_2$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Chenyuan Li, Rwik Dutta, Fang Xie, James R. Chelikowsky, Jennifer Cano, Mit H. Naik, Qimiao Si
Recent observations of superconductivity in twisted bilayer WSe$ _2$ (tWSe$ _2$ ) have motivated theoretical proposals for unconventional pairing mechanisms. A central question is whether band topology plays an essential role in the system’s correlation physics. In this letter, we develop a first-principles-based description of the top moiré valence bands in tWSe$ 2$ . Using density functional theory (DFT) calculations, we identify the bands in the relevant range of twist angles to be topologically non-trivial, with the top valence bands carrying Chern numbers $ C=(+1,+1)$ for the $ K$ valley. In order to treat the strong correlation physics, we construct compact molecular orbitals directly from the DFT wave functions through a partial Wannierization procedure and with the guidance of spinful $ C{3z}$ symmetry representations. This yields a localized $ f$ orbital together with a complementary topological $ c$ orbital, allowing us to extract hopping and hybridization amplitudes from first principles. The resulting parameters provide an ab initio benchmark for the effective Hamiltonian. Our work establishes a foundation for understanding superconductivity in moiré TMDs and highlights tWSe$ _2$ as a promising platform for exploring topological superconductivity.
Strongly Correlated Electrons (cond-mat.str-el)
6 + 5 pages; 4 + 5 figures
Isothermal compression of a Fermi gas to deep quantum degeneracy
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-07-20 20:00 EDT
Kirill Karpov, Jonas Auch, Eduard Heidt, Florian Kiesel, Alexandre De Martino, Christian Groß
The standard approach for generating deeply degenerate quantum gases is evaporative or sympathetic cooling in a harmonic trap, after which the gas has reached its minimum entropy. All subsequent state transformations rely on adiabatic changes of a closed system, and coupling to the environment or non-adiabatic processes monotonically increase the entropy. Here, we demonstrate that this experimental paradigm can be bypassed by utilizing species-selective trapping with a low-dissipation optical tune-out trap in a dual-species mixture. We successfully reduce the entropy of a two-component fermionic quantum gas via isothermal compression within a bosonic bath, reaching deep quantum degeneracy of $ T/T_F = 0.024^{+0.007}$ , with $ T_F$ the Fermi temperature. By characterizing the cross-dimensional relaxation and thermalization, we demonstrate that cooling light fermions with heavy bosons remains efficient and fast, even deep in the degenerate regime, where the thermalization time is found to be independent of $ T/T_F$ . Our results pave the way for direct cooling within optical lattices, box traps, or other complex potentials, thereby eliminating the reliance on adiabatic state transformations to reach strongly interacting many-body regimes.
Quantum Gases (cond-mat.quant-gas)
Long range spatial correlations in the periodically driven transverse field Ising model
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
We consider a periodically driven transverse field Ising model and study the long-time behavior of the correlations between the excitations in the spin chain. We show that the longest correlation length is defined by the interference between the topological defects induced by the analog of the Kibble-Zurek mechanism and those induced by the Floquet resonance. We show that although the correlations always have a finite correlation length since the system is integrable, the correlation length can be made arbitrarily large by tuning the drive period.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Strong intervalley mixing between copropagating quantum Hall edge channels in a silicon MOSFET
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Gento Yamahata, Takase Shimizu
Copropagating quantum Hall edge channels provide a promising platform for compact electron interferometry and flying quantum states. In silicon, the valley degree of freedom offers a natural alternative to spin-resolved edge channels because spin-flip scattering is strongly suppressed by the weak spin-orbit interaction. Here, we investigate interchannel transitions between copropagating valley edge channels in a double-layer-gated silicon metal-oxide-semiconductor field-effect transistor. With the bulk filling factor set to $ \nu=2$ , two spin-polarized valley edge channels are brought into close proximity near a depleted side gate. We observe strong intervalley mixing, with a transition probability close to 1/2, indicating nearly complete equilibration between the two valley edge channels. In contrast, interchannel transport between edge channels with different spin orientations shows negligible transition probability, consistent with suppressed spin-flip scattering in silicon. These results demonstrate that intervalley coupling at a Si/SiO$ _2$ interface can provide a beam-splitter-like operation for copropagating valley edge channels, establishing a key building block toward compact silicon quantum Hall interferometers.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Absence of Spin-Glass Order on Migdal–Kadanoff Hierarchical Lattices near Three Dimensions
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-07-20 20:00 EDT
Manaka Okuyama, Masayuki Ohzeki
We derive a rigorous sufficient condition for the absence of spin-glass order in the Ising spin glass with symmetric binary couplings on Migdal–Kadanoff (MK) hierarchical lattices with even branching number. The key observation is that a single exact renormalization-group step creates zero effective bonds with positive probability, thereby reducing the problem to bond percolation on the corresponding hierarchical lattice. When the induced dilution exceeds the percolation threshold, both spin-glass order and stiffness are absent at all temperatures, including zero temperature. As a consequence, our criterion gives a rigorous proof that the Ising spin glass on the square lattice does not exhibit a spin-glass phase within the MK approximation. More unexpectedly, by choosing sufficiently large scale factors and branching numbers, we construct MK hierarchical lattices whose fractal dimensions are arbitrarily close to three from below but still exhibit no spin-glass order. This sharply contrasts with numerical estimates obtained for MK hierarchical lattices with relatively small scale factors and branching numbers, which placed the lower critical dimension near (2.52).
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mathematical Physics (math-ph)
7 pages, 1 figure
Kinetic Theory for the Shear Viscosity of Dense Binary Dipolar Fluid Mixtures
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Christopher Devik Fjeldstad, Roberto Troncoso, Astrid S. de Wijn
We construct a kinetic theory for the shear viscosity of dense binary fluid mixtures of strongly-interacting dipolar hard spheres. We derive an expression for the pairwise correlations in the binary mixtures that is accurate up to packing fractions around 0.35. The approach is based on Enskog-Thorne theory, and inspired by the theory for dense pure fluids developed by Pousaneh and de Wijn. It relies on effective coupling parameters obtained from the pure fluids combined with mixing rules and a heuristic expression for the collision integral. We compare our results to viscosities obtained numerically from molecular-dynamics simulations of dipolar hard-sphere fluids. Our expression for the shear viscosity of the binary mixtures captures the density and composition dependent behavior of the binary dipolar fluids up to packing fraction of $ \xi \lesssim 0.3$ without any mixture-derived fit parameters.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
15 pages, 7 figures
How Topology Shapes the Phase Behavior of Polyelectrolytes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
David Beyer, Pierre J. Walker, Lena Tarrach, Zhen-Gang Wang, Christian Holm
We develop a topology-specific theory of polyelectrolyte coacervation using the random phase approximation and apply it to both simple and complex coacervation. Our results for stars and dendrimers show that more compact chain topologies display a greater propensity for liquid-liquid phase separation, as a function of both Bjerrum length and salt concentration. For mixtures of different topologies, we demonstrate that differences in polymer topology alone are sufficient to drive multiphase coacervation of polyelectrolytes, which we rationalize in terms of an effective $ \chi$ parameter. Analysis of a simplified global phase diagram reveals that the propensity for such topology-driven phase separation is largest at a finite molecular weight. Overall, our results establish polymer topology as a powerful design lever for tuning the phase diagram of charged macromolecules independently of molecular weight, net charge, and monomer chemistry, since changes in topology enable fine-tuning of the effective charge density without altering these molecular characteristics.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
Bifurcation reordering programs snap-through symmetry in folded elastic ribbons
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Weicheng Huang, Qun Zhang, Bohan Zhang, Mingchao Liu
Snap-through in slender elastic structures is often viewed as a sudden transition between stable configurations, yet the pathway taken during this transition can differ fundamentally. A structure may snap while preserving symmetry, or first lose symmetry and pass through an asymmetric state before reaching its final configuration. What selects between these pathways remains less well understood, especially when the geometry and loading are themselves symmetric. Here, we show that snap-through symmetry can be programmed by reordering competing bifurcations in folded elastic ribbons. We study an elastic ribbon with two localized folds placed symmetrically about the midpoint and show that varying the fold position changes the relative order of two instabilities: a symmetry-breaking pitchfork bifurcation and a saddle-node bifurcation on the symmetry-preserving branch. When the pitchfork bifurcation occurs first, the ribbon loses symmetry before snapping and follows an asymmetric pathway. Conversely, when the saddle-node bifurcation occurs first, the ribbon loses stability while remaining on the symmetric branch, resulting in a symmetry-preserving transition. Combining experiments, discrete differential geometry simulations and numerical continuation, we map this exchange in bifurcation ordering and construct a phase diagram that predicts the switch between asymmetric and symmetric snap-through regimes. A reduced-order double-mass von Mises truss model captures the same mechanism as a generic competition between symmetry-breaking and symmetry-preserving instabilities. These results establish bifurcation reordering as a geometric mechanism for programming snap-through pathways in slender elastic structures, offering a design principle for multistable systems, morphing structures and instability-based mechanical devices.
Soft Condensed Matter (cond-mat.soft)
19 pages, 7 figures
Statistical equivalence of reduced gravity and enhanced friction in granular packings
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Haiyang Lu, Zhikun Zeng, Houfei Yuan, Chengjie Xia, Hanyu Li, Chijin Zhou, Zihang Xu, Yujie Wang
Using X-ray tomography, we compare granular packings prepared under buoyancy-reduced effective gravity with normal gravity packings of particles with systematically varied friction. We show that reducing gravity lowers the random loose packing limit in a manner analogous to increasing friction. Granular packings under reduced gravity and with enhanced friction exhibit identical volume distributions, compactivity, and entropy, indicating that both routes sample statistically equivalent Edwards volume ensembles of mechanically stable states. This equivalence originates from a common relaxation of the mechanical stability constraint: under both conditions, fewer particles are required to participate in the underlying load-bearing bridge structures, leading to a lower contact-number requirement and a higher density of mechanically stable states. Nevertheless, reduced gravity retains a distinct contact-scale signature through more isotropic contact orientations. These findings identify gravity as a physical control governing the statistical accessibility of mechanically stable states within the Edwards framework and provide a unified statistical description of granular packings formed through different physical routes.
Soft Condensed Matter (cond-mat.soft)
20 pages, 6 figures
First-Order Topological FFLO Transition and Superconducting Diode Sign Reversal in Altermagnetic Nanowires
New Submission | Superconductivity (cond-mat.supr-con) | 2026-07-20 20:00 EDT
Bo Fu, Kaizhi Bai, Chang-An Li, Shun-Qing Shen
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state conventionally emerges via a second-order phase transition driven by finite magnetization. Here we show that a spin-orbit-coupled nanowire proximitized to $ d$ -wave altermagnets – with zero net magnetization – can realize topological FFLO states through a first-order transition, marked by a sharp sign-reversing superconducting diode effect. The altermagnetic field generates band-resolved competing pairing channels, giving rise to a double-valley free energy landscape whose global minimum switches discontinuously. It consequently leads to a first-order topological FFLO transition with simultaneous jumps in the Cooper pairing amplitude and finite center-of-mass momentum. Remarkably, this discontinuous topological reconfiguration substantially enhances the diode efficiency and drives a characteristic sharp sign reversal across the transition. The mechanism of such exotic phenomena is captured by Ginzburg–Landau theory. Our results provide a field-free altermagnetic route to topological FFLO states and identify their direct transport fingerprint.
Superconductivity (cond-mat.supr-con)
13 pages, 8 figures
Drift-Induced Nonreciprocal Hyperbolic Polaritons in Graphene/$α$-MoO$_3$ Heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Achieving optical isolation requires breaking symmetry between forward- and backward-propagating light, a long-standing challenge at the nanoscale in the absence of magnetic fields. Here we theoretically demonstrate electrically tunable nonreciprocal phonon-plasmon polaritons in a graphene/$ \alpha$ -MoO$ _3$ /SiC heterostructure operating in the mid-infrared. A dc current in graphene induces a wavevector-dependent Doppler shift that breaks reciprocity and generates strong directional asymmetry in hybrid plasmon-phonon propagation. In the reciprocal regime, hybridization between graphene plasmons and hyperbolic phonon polaritons in $ \alpha$ -MoO$ _3$ , further shaped by the SiC substrate, enables gate-controlled transitions of isofrequency contours, including canalization along orthogonal crystal axes. At drift velocities of 5% of the Fermi velocity, the system exhibits pronounced momentum-dependent nonreciprocity with contrast reaching $ \sim$ 0.3, while directions orthogonal to the drift remain unaffected due to symmetry imposed constraints. Real-space calculations confirm that this momentum-space asymmetry translates into directional near-field intensity modulation. These results establish current-biased van der Waals heterostructures as a platform for electrically tunable, magnet-free nonreciprocal nanophotonics in the mid-infrared.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 4 figures
Interface-Engineered Giant Multistate Resistance Switching in Altermagnetic CrSb Multiferroic Tunnel Junctions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Zhi Yan, Yuwen Hua, Yueting Li, Xujin Zhang, Jianhua Xiao, Xiaohong Xu
Altermagnets enable spin-split transport without stray magnetic fields, yet converting their momentum-dependent spin splitting into a strong tunnel-junction response requires interface-selected tunneling channels. Here, using density functional theory combined with nonequilibrium Green’s function calculations, we demonstrate giant multistate resistance switching in CrSb/$ \alpha$ -In$ _2$ Se$ _3$ altermagnetic multiferroic tunnel junctions. The response is governed not by the bulk spin splitting of CrSb alone, but by a symmetry-selected interfacial mechanism in which Cr/Sb terminations and \textit{h}-BN or graphene insertion layers determine spin-channel matching, while ferroelectric polarization reshapes the electrostatic barrier. Symmetric and asymmetric terminations reverse the correspondence between parallel/antiparallel Néel-vector configurations and high-/low-resistance states, showing that the actual alignment of interfacial Cr moments selects the dominant tunneling channels. Monolayer-In$ _2$ Se$ _3$ junctions exhibit four nonvolatile resistance states, with tunneling magnetoresistance (TMR) and tunneling electroresistance (TER) reaching 1626% and 2206%, respectively, and increasing to 9576% and 4144% upon Fermi-level shifting. Finite-bias calculations further reveal robust spin filtering and tunable spin-polarized currents. Extending the barrier to bilayer In$ _2$ Se$ _3$ introduces interlayer polarization coupling, enabling eight resistance states with maximum TMR and TER values of $ 3.77\times10^{4}%$ and $ 4.18\times10^{5}%$ , respectively. These results establish interface symmetry, spin-channel matching, and ferroelectric barrier reconstruction as design principles for stray-field-free multistate spintronic tunnel devices.
Materials Science (cond-mat.mtrl-sci)
21 pages, 9 figures
Two-step growth of (In,Ga)N pseudo-substrates on GaN templates by plasma-assisted molecular beam epitaxy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Huaide Zhang, Jingxuan Kang, Aidan F. Campbell, Jonas Lähnemann, Oliver Brandt, Lutz Geelhaar
(In,Ga)N layers are grown by plasma-assisted molecular beam epitaxy on GaN templates. We introduce a two-step protocol that involves switching the growth conditions from initially N-stable to metal-stable. Reflection high-energy electron diffraction as well as scanning electron and atomic force microscopy reveal that the first step results in a rough intermediate surface with open pits, whereas the final surface is smooth. The narrow linewidth of the photoluminescence band indicates an excellent compositional homogeneity of the upper layer. Its in-plane lattice constant is determined to be $ \approx$ 3.26 Åfrom X-ray diffraction measurements. This combination of favorable properties makes these layers attractive as pseudo-substrates for the growth of red-emitting (In,Ga)N light-emitting diodes. In particular, the approach presented here does not require any complex external processing and is, thus, scalable and economical.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Contactless terahertz mapping of wafer-scale superconducting NbTiN thin films
New Submission | Superconductivity (cond-mat.supr-con) | 2026-07-20 20:00 EDT
Yayi Lin, Marc Neis, Marcello Pio Guardascione, Janine Lorenz, Thomas J. Smart, F. Stefan Tautz, Felix Lüpke, Frederik Bolle, Martin Dressel, Rami Barends, Pavel A. Bushev, Marc Scheffler
For large-scale superconducting quantum technology, e.g. quantum computing, the homogeneity of wafer-scale superconducting thin films is vital for consistent performance of the fabricated devices. Terahertz (THz) spectroscopy as a contactless and non-destructive measurement technique is a powerful tool to characterize the superconducting films. In this work, a set of niobium titanium nitride (NbTiN) thin films on 4-inch and 6-inch silicon wafers, grown via plasma-enhanced magnetron sputtering, are investigated via THz spectroscopy: full wafers are mapped at room temperatures and exemplary segments are characterized at cryogenic temperatures. The deviations in observed sheet resistance depend on the used deposition device and the film thickness. While the deviations in superconducting sheet kinetic inductance match those of the normal-state sheet resistance, the critical temperature and energy gap exhibit little variation. This THz mapping technique demonstrates the feasibility of evaluating wafer-scale superconducting thin films before lithography, facilitating preparation of the thin films for reproducible device fabrication.
Superconductivity (cond-mat.supr-con)
7 pages, 5 figures
Machine-learning test of the single-ion model for $dd$ excitations in cuprates
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Maryia Zinouyeva, Leonardo Martinelli, Riccardo Arpaia, Nicholas B. Brookes, Daniele Di Castro, Kurt Kummer, Floriana Lombardi, Giacomo Merzoni, Francesco Rosa, Alessandro Tarasio, Enrico Tassi, Flora Yakhou-Harris, Ezio Puppin, Marco Moretti Sala, Giacomo Ghiringhelli
We investigate $ dd$ excitations in Resonant Inelastic X-ray Scattering spectra of YBa$ _2$ Cu$ _3$ O$ _6$ and La$ _2$ CuO$ _4$ using the local single-ion model. The data are analyzed by conventional global fitting and by a convolutional neural network trained within the same theoretical framework. For YBa$ _2$ Cu$ _3$ O$ _6$ , the excited state energies obtained with the two methods coincide, leading to the $ xy$ , $ 3z^2-r^2$ , $ xz/yz$ sequence for increasing energy. This result validates the use of machine learning tools for the analysis of RIXS spectra dominated by $ dd$ excitations. By contrast, for La$ _2$ CuO$ _4$ , the two methods do not converge to a single solution, revealing the limitations of the single-ion model in describing $ dd$ excitations in cuprates and pointing to the role of additional contributions beyond a purely local picture in shaping high-energy excitations.
Strongly Correlated Electrons (cond-mat.str-el)
Controlling charge and spin currents through nonreciprocal dissipative processes
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-07-20 20:00 EDT
Catalin-Mihai Halati, Jean-Sébastien Bernier
We investigate the generation and control of both charge and spin currents via nonreciprocal dissipative mechanisms in a two-dimensional spinful fermionic atom quantum system with broken inversion and time-reversal symmetries. Within the Gorini-Kossakowski-Sudarshan-Lindblad master equation formalism and using an approach based on the time-dependent generalized Gibbs ensemble, we identify in the weak dissipative coupling regime the minimal set of nonreciprocal jump operators required to induce charge and spin currents and to control both their direction and magnitude. We find that in the presence of finite tunneling, Rashba coupling and magnetic field, the combine application of two jump operators nonreciprocally coupling each spin species to a different spatial direction of motion is sufficient to generate both types of current. Furthermore, by tuning the degree of nonreciprocity of the jump operators we modify the dominant transport mechanism from spin to charge. Finally, we checked that this nonreciprocal current generation mechanism is robust to the application of dephasing noise as even in the presence of this additional dissipative process the steady-state occupation distributions for the quasiparticle modes of the Hamiltonian remains non-trivial, an essential requirement to obtain non-zero currents.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Reversible and irreversible dynamical topological transitions of magnetic Hopfions
New Submission | Other Condensed Matter (cond-mat.other) | 2026-07-20 20:00 EDT
S. Y. Lu, H. M. Dong, D. X. Yu, K. Chang
Magnetic Hopfions are three-dimensional (3D) topological solitons characterized by a nonzero Hopf invariant and offer a promising platform for 3D spintronics. While their static stabilization has been widely studied, their nonlinear dynamics under alternating magnetic (AM) fields remain largely unexplored. We show, using 3D micromagnetic simulations and analytical mode analysis, that an AM field drives two qualitatively distinct dynamical regimes of a confined magnetic Hopfion. In the weak-field regime, resonant excitation of intrinsic Hopfion modes induces a nonlinear instability and an irreversible topological reconfiguration from a Hopfion to a toron. In contrast, in the strong-field regime, the system undergoes reversible field-locked topological switching at GHz frequencies, with the magnetization periodically alternating between a topologically trivial ferromagnetic configuration and a Hopfion state. The switching pathway is selected by the driving frequency: a 2 GHz field drives a breathing pathway associated with the low-frequency collective response, whereas a 40 GHz field produces a nonresonant rotational pathway governed by strong Zeeman-torque-driven precession and field locking. These results identify field amplitude and frequency as independent control knobs and reveal that reversible Hopfion switching can arise either from nonlinear continuation of low-frequency collective motion or from nonresonant high-frequency field locking.
Other Condensed Matter (cond-mat.other)
Scaling regimes of the Kuramoto-Sivashinsky equation from the functional renormalization group
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-07-20 20:00 EDT
Liubov Gosteva, Nicolás Wschebor, Léonie Canet
We revisit the renormalization group (RG) approach to the one-dimensional stochastic Kuramoto-Sivashinsky (KS) equation and show that previous approaches based on perturbative Wilsonian RG with a sharp cutoff are not valid, even though they yield a qualitatively correct picture. The reason is that taking momentum derivatives while using the sharp cutoff is not well-defined in some cases and leads to intrinsic divergencies. This is a well-known problem of Wilsonian RG, which can be simply cured by using a smooth cutoff, and employing the functional renormalization group (FRG) framework. We establish the flow equations for the KS model within the FRG, and demonstrate that it flows to the Kardar-Parisi-Zhang (KPZ) fixed point at large scales. We then calculate the full two-point correlation function over a wide range of momenta and frequencies. We show that it exhibits three universal scaling regimes that we characterize: the KPZ regime (with dynamical exponent $ z=3/2$ ), the Edwards-Wilkinson regime (with $ z=2$ ) and the recently discovered inviscid regime (with $ z=1$ ). The latter develops over an extended range of large wavenumbers and originates from the vanishing of the effective viscosity. Lastly, we investigate the large-scale behavior of the deterministic KS equation by studying the limit of vanishing noise and we determine the scales where the KPZ regime can emerge in the deterministic case.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th), Chaotic Dynamics (nlin.CD)
18 pages, 6 figures
A Flickering Resonance Degeneracy on Entropy-Ruled Charge Transport in the Extended Hopping Sites for Biological Systems: Role of Static-to-Dynamic Disorder Transition
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-07-20 20:00 EDT
Charge transport (CT) in biological systems is of great interest due to its role in various functional activities like photobiology, bioenergetics, redox catalytic and other metabolic activities, etc. It has been observed by various studies that the presence of a dynamic disorder in biomolecules facilitates charge dynamics in the intermediate transport regime, i.e., far from hopping and towards a bank-like mechanism. Hitherto, the dynamic disorder (in a time scale, coupling between electronic and nuclear dynamics) weightage on CT in molecules is not well-established for the measurement of molecular conductivity from small to long-range ordering. With this motivation, we propose the flickering resonance-coupled entropy-ruled charge transport theory for transfer-rate and diffusion-based mobility (D/{\mu}) calculations. The proposed analytical formalism incorporates the impact of dynamic disorder-correlated degeneracy (in a flickering-resonance manner) on the entropy-ruled electron transfer rate and diffusion-mobility, which are valid for localized hopping, delocalized band transport, and regimes in between. By this approach, it has been observed that the dynamics-driven electronic site matching probability enhances the degeneracy, which is quantified by the differential entropy. The analysis clearly shows that for ultra-fast dynamical and degenerate cases, the entropy-ruled mobility is transformed as band mobility, rather than the thermally activated hopping or diffusion process.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
18 pages, 5 Figures
Fermion parity of an Andreev molecule probed by nonlocal Josephson effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
S. Annabi, H. Riechert, K. Watanabe, T. Taniguchi, J. Griesmar, E. Arrighi, L. Bretheau, J.-D. Pillet
Fermion parity is a fundamental property of superconducting many-body states. Here, we show that the global fermion parity of a delocalized superconducting state can be detected locally by exploiting the nonlocal Josephson effect. Using a carbon nanotube-based Andreev molecule formed by two coupled quantum-dot Josephson junctions, we observe a pronounced nonlocal Josephson response and demonstrate the formation of delocalized Andreev molecular states extending across both junctions. We further show that changes in the molecular ground-state parity manifest as characteristic $ \pi$ -phase shifts in the nonlocal response. Supported by a minimal theoretical model, these results identify global fermion parity as an experimentally accessible degree of freedom in hybrid superconducting circuits that can be readily revealed through the nonlocal Josephson effect.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con), Quantum Physics (quant-ph)
17 pages, 10 figures
Quantum and classical entropic complexity of the thermal state: coherence, decoherence, and the ergodic-to-localized crossover in random-matrix and many-body models
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-07-20 20:00 EDT
Does thermal averaging preserve signatures of eigenstate complexity? We study the entropic complexity C = S_1 - S_2 (Shannon minus second-order Renyi entropy) across the ergodic-to-localized crossover of three disordered models: the Rosenzweig-Porter (RP) ensemble, the power-law banded random matrix (PLBRM) ensemble, and the random-field Heisenberg chain. We compare a wavefunction-level quantity C_eig to the complexity of the thermal (Gibbs) state before and after pointer-basis dephasing, via the trace (C_tr) and diagonal (C_diag) complexities. The answer is mostly no: thermal averaging strongly suppresses, but does not eliminate, eigenstate-complexity signatures. C_eig develops a pronounced mid-phase maximum in RP and, at matching fractal dimension, in the structurally independent PLBRM model; a high-statistics scan resolves a weak (about 10%) but reproducible thermal shadow of this peak in the thermal diagonal complexity. This feature is confined to the two random-matrix models; in the Heisenberg chain the eigenstate complexity instead peaks at the many-body localization transition. A second, genuinely thermal feature, an edge just inside the ergodic phase, has no eigenstate counterpart and, in PLBRM, recedes with system size. Both features are tracked by scale-invariant crossover indicators: the log-ratio of the trace and diagonal crossover temperatures, which vanishes upon localization, and the relative entropy of coherence. Entropic complexity thus cleanly separates thermal-state and eigenstate physics: a sharp wavefunction-level feature, reproducible across unrelated random-matrix constructions, leaves only a faint, structurally distinct imprint on thermal observables.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
14 pages, 8 figures
Thermal Order by Disorder in Resonating-Valence Bond States on the Checkerboard Lattice
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Giorgi Gogaberishvili, Nika Kurdadze, Kirill Shtengel
We derive a local spin-1/2 Hamiltonian with a resonating valence bond ground state on the checkerboard lattice. The state is characterized by the exponential decay of singlet-singlet correlations, whereas dimer-dimer correlations decay with a power law in the corresponding Quantum Dimer model. This observation leads to a novel mechanism for thermal Order by Disorder whereby thermal decoherence suppresses destructive quantum interference between different contributions to the correlations in the ground state and results in a qualitatively different, quasi-long-range ordered mixed state.
Strongly Correlated Electrons (cond-mat.str-el)
10 pages, including 6 pages of Supplementary Materials
Electrothermal control of spin-reorientation transition in Co/Fe_3GaTe_2 heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Po-Wei Chen (1,2,3), Ming-Hsien Hsu (1), Cheng-Ying Hsiao (1), Ming-Yang Ho (1), Masahiro Haze (4), Yan-Ru Chu (1), Yu-Cheng Shao (5), Po-Chun Chang (6), Chen-Yu Ou (1), Ruei Chen (1), Ko-Fan Chen (1), Chung-Ting Ke (3), Chao-Hung Du (6), Yukio Hasegawa (4), Wen-Chin Lin (1). ((1) Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan. (2) Department of Physics, The University of Osaka, Toyonaka, Osaka, Japan. (3) Institute of Physics, Academia Sinica, Taipei, Taiwan. (4) Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan. (5) National Synchrotron Radiation Research Center, Hsinchu, Taiwan. (6) Department of Physics, Tamkang University, New Taipei City, Taiwan.)
Electrical control of magnetic anisotropy in van der Waals (vdWs) magnets is a key step toward reconfigurable two-dimensional spintronics, yet how a conventional metallic ferromagnet competes with a van der Waals magnet across a direct interface has remained largely unexplored. Here we demonstrate reversible thermal and electrothermal control of a spin-reorientation transition in Co/Fe_3GaTe_2 (FGaT) heterostructures. As Joule heating weakens the FGaT anisotropy, the heterostructure switches from an out-of-plane- to an in-plane-dominated state at a reorientation temperature of approximately 311 K, well below the Curie temperature, consistent with an exchange-mediated anisotropy competition between the Co overlayer and FGaT. An electrically driven device shows a closely matching loop evolution within an 80-100 mW power window, reversibly over five measurement cycles, consistent with an electrothermal origin. In a Co-free FGaT device, Kerr microscopy traces the switching to a power-tunable domain nucleation barrier and demonstrates power-thresholded, field-assisted magnetization reversal at a threshold near 15 mW. These results demonstrate electrothermal anisotropy competition as a route to heat-assisted and device-level control of vdWs magnetism.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Photoelectrical readout and Ramsey interferometry of single shallowly implanted NV centers in diamond
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Ilia Chuprina, Christoph Findler, Johannes Lang, Petr Siyushev, Fedor Jelezko
Photoelectrical readout of the electronic spin state of the nitrogen-vacancy (NV) center in diamond is attracting significant interest due to the numerous advantages it possesses compared with conventional fluorescence readout. The higher charge carrier rate compared to the photon rate and the integration of the detection scheme on a chip can significantly advance quantum sensing and computing with color centers in diamond. Until now, photoelectric readout has been performed on ensembles of NV centers or single NV centers deep in ultrapure diamond substrates. However, many applications require the artificial creation and precise placement of shallow NV centers, and photoelectric detection of such centers has been challenging. Here we demonstrate photoelectrical readout and coherent control of the electronic spin of implanted shallow ($ \sim$ 10 nm) NV centers buried by diamond overgrowth. The photoelectrically measured Ramsey $ T_2^\ast$ agrees with conventional fluorescence readout and shows no measurable dependence on the readout photocurrent, for both shallow implanted and deep ingrown NV centers. We further find that overgrowth improves photoelectric readout by suppressing the background photocurrent. These results establish photoelectric readout as a viable route to chip-integrated, electrically detected nanoscale sensing and to spin registers based on engineered shallow NV centers.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
7 pages, 3 figures, Supplemental Material
Ultrametric organization of energy landscapes on random Erdős–Rényi graphs: topological origin of barrier hierarchy
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-07-20 20:00 EDT
We investigate the ultrametric organization of energy landscapes defined on sparse random Erdős–Rényi graphs. Each graph vertex is assigned a random free energy from a uniform distribution over an interval of width $ \Delta F$ , and the kinetics are modeled by a Markov process with Kramers transition rates. Using spectral decomposition of the rate matrix, we construct a kinetic Mahalanobis metric between basins of attraction. Computational experiments for graphs with $ V=5000$ vertices and $ E=5000$ edges show that the degree of nontrivial ultrametricity increases monotonically from $ \approx42%$ for $ \Delta F=10$ kJ/mol to $ \approx96%$ for $ \Delta F=1000$ kJ/mol. We prove a limit theorem: as $ \Delta F\to\infty$ , the logarithmic asymptotics of this metric converge pointwise to the classical single-linkage ultrametric. For finite $ \Delta F$ , corrections from suboptimal paths are exponentially suppressed with increasing $ \Delta F$ , so that the metric becomes asymptotically ultrametric. Our results suggest that ultrametricity is a universal property of sparse, locally tree-like networks with rugged energy landscapes in the limit of large energy spreads.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn), Numerical Analysis (math.NA)
26 pages, 2 tables
Zigzag ordering, defects, and anomalous relaxation in antiferromagnetic Kuramoto lattices
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-07-20 20:00 EDT
Priyanka D. Bhoyar, Prashant M. Gade
We investigate the nonequilibrium ordering dynamics of coupled Kuramoto oscillators with negative nearest-neighbor coupling, which induces a zigzag antiferromagnetic ordering. In one dimension, the defect density exhibits anomalously slow coarsening, decaying as $ (D(t)\sim t^{-1/4})$ before saturating at a system-size-dependent time $ (t_c(N)\sim N^z)$ with (z=2). The local persistence probability follows a stretched-exponential form, $ (P(t)\sim \exp(-c t^\alpha))$ , with $ (\alpha=1/4)$ . These exponents are observed are independent of the magnitude of the coupling, which merely rescales the characteristic time scale. The equality $ (\alpha=\delta=1/4)$ together with (z=2) is consistent with a distinct universality class. These results demonstrate that deterministic nonlinear dynamics and geometric frustration alone are sufficient to generate slow relaxation and anomalous scaling, without quenched disorder or stochastic noise. A continuum approximation and the corresponding coarse-grained partial differential equation provide a theoretical explanation for the observed anomalous exponents, while linear stability analysis accounts for the emergence of the zigzag ordered state. In two dimensions, geometric frustration inhibits complete ordering and gives rise to long-lived metastable domain-wall structures. An initial transient defect decay is observed before crossover and saturation. These results demonstrate how frustration and continuous phase variables can fundamentally modify coarsening dynamics and generate anomalously slow relaxation in deterministic many-body systems.
Statistical Mechanics (cond-mat.stat-mech)
Property-dependent material times
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Aude Y. Amari, Lorenzo Costigliola, Jeppe C. Dyre
We analyze simulations of physical aging following large temperature up-jumps from equilibrated, slowly relaxing states. Specifically, we consider up-jumps from temperatures T=0.43 and T=0.37 to T=0.48 in a binary Lennard-Jones mixture. The Tool-Narayanaswamy (TN) concept of a universal material time was recently shown to become less effective in rationalizing the aging response for such large jumps [Amari et al., Phys. Rev. E 113, 045411 (2026)]. Here, we investigate whether the performance of the TN formalism can be improved by assigning a separate material time to each observable. We examine the potential-energy time-autocorrelation function, the self-intermediate scattering function, and the time-dependent mean-square displacement. As part of this study, we perform a detailed analysis of the extent to which the triangular relation, a necessary condition for the existence of a material time, is satisfied. We find that, for all three properties, the best data collapse is obtained when each property is parameterized by its own material time. The degree of improvement varies considerably among the observables, however; it is most pronounced for the mean-square displacement.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
13 figure, 18 pages
Disentangling topological and anomalous Hall contributions of skyrmions using Kerr microscopy and thermal transport measurements
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
H.Heyen, M. Vogel, F. Gossing, J. Walowski, K. Dahmen, J. McCord, M. Münzenberg
The topological Hall effect is a valuable tool to indicate the presence of topologically protected magnetic structures. In this work, we present topological Hall effect measurements originating from topologically protected skyrmions in Ta/CoFeB/MgO single-layer thick films with a one nanometer thick magnetic layer. The simultaneous occurrence of the small topological Hall effect and the dominating anomalous Hall effect in this material system makes direct detection challenging as compared to bulk or multilayer systems. In electronic transport measurements, both effects’ contributions impact electron trajectories in the same way, overlapping in the measurement signal, and require disentanglement. Magneto-optical Kerr microscopy was used to image the surface magnetization, enabling the separation of the topological Hall effect from other Hall effect contributions. These measurements reveal a topological Hall resistivity of $ 249(18),$ \si{\pico\ohm\meter} for Ta/CoFeB/MgO layer stacks at room temperature. Magneto-optical Kerr effect (MOKE) measurements also allow tracking skyrmion formation during external magnetic field sweeps to confirm their occurrence when measuring the topological Hall effect. We verify this outcome by comparing the results with thermal and electrical transport measurements from which we calculate the overall topological quantity that gives rise to the topological Nernst and Hall effect, respectively.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other)
26 pages, 8 figures
Altermagnetism without a long-range order
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
V. E. Valiulin, A. V. Mikheyenkov, K. I. Kugel
The Kugel-Khomskii spin-pseudospin model, originally developed for transition-metal compounds with orbital degrees of freedom, has recently been reinterpreted in the context of altermagnetism. In this work, we theoretically investigate the emergence of altermagnetic behavior in the absence of long-range magnetic or orbital order. Using the rotation-invariant Green’s function method for the SU(2) x SU(2) symmetric model on a square lattice and on a linear chain, we analyze spin-spin and spin-pseudospin correlation functions, excitation spectra, heat capacity, and susceptibilities. We show that beyond a critical intersubsystem exchange Kc(T), a composite state arises with nonzero spin-pseudospin correlations, even though the average spin and pseudospin at each site are zero. The excitation spectrum splits into acoustic and optical branches, with nodal lines along qx = qy - a direct signature of altermagnetic symmetry. A peak in heat capacity and a jump in susceptibility are observed at the phase boundary. In 1D, the phase boundary is nonmonotonic and demonstrates reentrant transition. These results establish the concept of an “altermagnetic paramagnet” or “altermagnetic liquid” without long-range order, relevant for low-dimensional and strongly fluctuating systems.
Strongly Correlated Electrons (cond-mat.str-el)
Nonuniform pressure helps structural superlubricity
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Melisa M. Gianetti, Viet Hung Ho, Bjørn Haugen, Graham Cross, Astrid S. de Wijn
Structural superlubricity, nearly vanishing friction between two structurally incommensurate crystalline surfaces, is a promising avenue for reducing friction in applications, but requires very specific and well-controlled conditions. One of those conditions is perfectly uniform atomically flat surfaces. Real-world surfaces are generally rough, leading to nonuniform pressure distributions. We investigate the effects of nonuniform pressure distributions on structural superlubricity, using analytical calculations for rigid contacts as a basis, and molecular-dynamics simulations for a simple model to include the crucial effects of elasticity. We show that a key ingredient is the vanishing pressure at the edge of the contact, and that this leads to improved scaling depinning and scaling behaviour, leading to lower friction. We thus show that nonuniform pressure distributions actually help structural superlubricity, rather than hinder it.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
11 pages, 5 figures
Fast temperature up steps as a test of the Tool-Narayanaswamy formalism
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Armand Rykner, Marceau Hénot, François Ladieu
We investigated the aging dynamics of a glass-forming liquid triethyl-2-acetylcitrate (TEAC), following fast temperature up steps with amplitudes ranging from 0.3 to 13.6 K. The initial states were either at equilibrium or prepared at increasing levels of out-of-equilibrium through a prior down step experiment. Our goal was to test the predictive power of the Tool-Narayanaswamy (TN) formalism which assumes that the non-linear re-equilibration of a liquid can be linked to its linear response to a small perturbation. We determined the TN parameters for steps with small to moderate amplitude ($ \leq$ 3.3 K) and crucially took advantage of down step aging experiments below the glass transition temperature to constrain the determination of the equilibrium relaxation time. We tested the TN predictions and found very good agreement for differences in fictive temperature characterizing the distance from equilibrium as high as 10 K. For larger steps, however, the prediction progressively fails to capture the aging dynamics. This likely indicates that the re-equilibration mechanism is no longer related to the equilibrium dynamics. Finally, we discuss the possibility of obtaining a general criterion for the limit of validity of the TN formalism, which we compare to other systems from the literature.
Soft Condensed Matter (cond-mat.soft)
10 pages, 9 figures
Phase-controlled quasi-bound states in the continuum and thermoelectric enhancement in Majorana-quantum-dot nanostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Alejandro Garrido, David Zambrano, Hishan Farfán-Bachiloglu, Juan Pablo Ramos-Andrade, Vladimir Juričić, Pedro Orellana
We investigate how the interplay between Majorana zero modes (MZMs) and bound states in the continuum (BICs) governs the electronic thermoelectric response of a crossbar-shaped quantum dot (QD) coupled to two topological-superconductor nanowires. Using the Green-function formalism, exact linear-response energy integrals, and their low-temperature Sommerfeld expansion, we analyze the spectral and thermoelectric properties of the system. We show that symmetry breaking converts BICs into quasi-BICs, allowing them to contribute to electrical and thermal transport and thereby generate a finite thermoelectric response. While unequal nanowire lengths, reflected in different intra-Majorana coupling strengths, produce only a modest enhancement of $ ZT_{el}$ , detuning the QD level increases $ ZT_{el}$ by approximately one order of magnitude. Superconducting-phase control produces a much stronger enhancement, reaching $ ZT_{el} \simeq 0.75$ through a quadratic transmission zero and a pronounced violation of the Wiedemann-Franz law. The low-temperature values $ ZT^{max}{el} \simeq 0.755$ and $ \mathscr{L} /\mathscr{L}{0} = 21/5$ are universal consequences of this quadratic antiresonance. Our results establish phase-tunable thermoelectric signatures of the Majorana-coupled interference structure and identify superconducting-phase control as an efficient means of engineering the electronic response of topological hybrid nanostructures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 7 figures
Qubit encodings in the p-orbital-valley spectrum for enhanced coherence and tunable two-qubit interaction
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
John H. Caporaletti, J. P. Kestner
We propose encoding a qubit in a two-level subspace spanned by the lowest $ p$ -orbital state in the excited valley of an anisotropic quantum dot and the excited $ p$ -orbital in the ground valley, which we dub the $ pOv$ qubit. There is an avoided crossing between these states due to valley-orbit coupling (VOC) induced by alloy disorder, enabling complete single-qubit control using baseband electrical control of the dot anisotropy. We find that `sweet spots’ exist at specific dot orientations where the instantaneous eigenstates are first-order insensitive to charge noise. Using a phenomenological two-level fluctuator (TLF) dipole noise model, we estimate an average dephasing time of $ T_2^\ast\approx 10,\mu\text{s}$ and a quality factor of $ Q\sim 10^4$ . Alternatively, encoding in the $ p$ -orbital states in the ground valley near the isotropic dot point, we show that one can induce a similar sweet spot via an out-of-plane magnetic field. Finally, we find that two-qubit gates for the $ pOv$ qubit are mediated by the quadrupole-quadrupole Coulomb interaction and can be electrically tuned from zero to $ \sim 1~\text{GHz}$ by adjusting the relative orientation of the anisotropic dots, providing a novel pathway towards scalable quantum computation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
16 pages, 8 figures
Drosophila of phonon-mediated superconductivity: Full Eliashberg theory of the jellium model
New Submission | Superconductivity (cond-mat.supr-con) | 2026-07-20 20:00 EDT
Christophe Berthod, Louk Rademaker, Dirk van der Marel
We present a full numerical solution of the Migdal–Eliashberg equations for the jellium model of phonon-mediated superconductivity. We find very low critical temperatures below 1~K, in contrast to earlier claims that the jellium model for hydrogen solids might reach room-temperature superconductivity. Our results suggest that full momentum and frequency dependence of the gap function and normal self-energy should be taken into account for accurate $ T_c$ estimates.
Superconductivity (cond-mat.supr-con)
Negative quantum friction in nanoscale water flows: the Wigner picture
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Adriano Tiribocchi, Marco Lauricella, Efthimios Kaxiras, Sauro Succi
We explore the phenomenon of “quantum” friction based on a single-particle model patterned after the Wigner equation describing electrons flow in a solid wall confining nanoscale water flows. The numerical simulations show a clear signature of negative quantum friction, namely a net momentum transfer from the electrons in the solid wall to the flowing water molecules. Such net momentum transfer results into a sizeable reduction of the water friction, up to forty percent, depending on the strength of the coupling between classical and quantum fluctuations. Our results offer the prospect of a theoretical framework bridging classical and quantum description by using continuum kinetic theories and particle-based simulations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Fluid Dynamics (physics.flu-dyn)
8 pages, 7 figures
Magnons reveal topology and dynamics of a skyrmion crystal
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Raphael Ayache, Nilotpal Chakraborty, Manabendra Kuiri, Quentin Benichou, Antonio Lacerda-Santos, Lilian Seyve, Himadri Chakraborti, Leo Pugliese, Kenji Watanabe, Takashi Taniguchi, Cosimo Gorini, Roderich Moessner, Benoit Doucot, Preden Roulleau
Although individual skyrmions are topologically protected objects, their cooperative crystalline order is fragile, easily disrupted by thermal fluctuations or other external perturbations. Probing the internal dynamics of such a crystal is both compelling and challenging, as its intricate and delicate spin texture must remain stable during measurement. Here, we engineer a nanoscale graphene junction hosting a skyrmion Wigner crystal, embedded between magnon emitters and detectors. The skyrmion crystal geometry leaves a striking imprint on magnon transport: as the gate voltage is varied, near-periodic windows of sharp fluctuations in magnon count are detected across the entire sample. We develop an interpretation that this results from skyrmions being added one by one to a quasi-one-dimensional array. Each burst of the fluctuations thus corresponds to the entry of an additional skyrmion, during which the lattice stiffness reduces. The impinging magnons induce and act as a probe of non-equilibrium collective dynamics of the crystal. These results establish a real-space probe of topological spin textures in quantum Hall-type insulating ground states via magnon transport and open opportunities to explore correlated, topologically ordered phases in moire and multilayer graphene systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Deconfined quantum critical point in a dissipative spin-1/2 chain
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Longye Lu, Shifeng Cui, Wenan Guo
Open quantum spin systems offer a previously unexplored route to realizing deconfined quantum criticality. We consider a spin-1/2 $ J$ -$ Q_3$ chain, consisting of an antiferromagnetic (AFM) Heisenberg exchange and a competing multi-spin interaction favoring a valence-bond solid (VBS) state, with each spin component coupled to a bosonic bath. Using non-Abelian bosonization and renormalization-group (RG) analysis, combined with large-scale quantum Monte Carlo (QMC) simulations, we determine the phase diagram and the associated phase transitions of the model. We show that strong dissipation stabilizes an AFM phase for sub-Ohmic, Ohmic, and super-Ohmic baths. Continuous AFM-VBS transitions at finite dissipation are found upon increasing the multi-spin interaction in both the sub-Ohmic and Ohmic regimes. Critical properties are obtained through perturbative RG analysis and QMC simulations. In the Ohmic case, the critical point features spinon deconfinement and emergent O(4) symmetry. In the sub-Ohmic regime, the transition may also involve spinon deconfinement, provided that spinons remain deconfined in the dissipative VBS phase. In addition, in the super-Ohmic regime, we propose a transition from AFM phase to a quasi-long-range ordered phase.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 4 figures. Supplemental materials: 15 pages, 11 figures
Structural Relaxation Enables Millisecond Infrared Photodetection in Selenium Iodine Semiconductors
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
The optoelectronic performance of amorphous and partially crystalline semiconductors is strongly governed by structural disorder, yet establishing direct correlations between structural evolution and carrier transport remains challenging. Here, we show that the solid state optoelectronic response of selenium iodine (SeI2) is dictated by its transformation from a metastable glassy phase into an ordered lamellar structure. Vertically resolved transport measurements reveal pronounced depth-dependent electrical conductivity within thick SeI2 films, arising from compositional and structural inhomogeneity developed during solidification. Immediately after solidification, the glassy SeI2 network exhibits sluggish carrier transport and persistent photoconductivity. Upon prolonged structural relaxation, however, the material undergoes significant transport enhancement, enabling millisecond-scale infrared photodetection with a response time of 4.3 ms, stable operation up to 8 kHz modulation frequency, and shot-noise-limited detectivities of 108 Jones at 1550 nm and 1011 Jones in the visible. Spatial photocurrent mapping demonstrates highly uniform carrier collection despite the self-assembled lamellar morphology, while infrared thermal imaging confirms practical imaging capability over a broad temperature range. These results establish structural relaxation as a powerful strategy for engineering carrier transport in selenium-based semiconductors and position SeI2 as a promising solution-processable platform for infrared photodetection and thermal imaging.
Materials Science (cond-mat.mtrl-sci)
The main manuscript and the Supplementary Information have been merged into a single PDF file and uploaded
Coherent driving of displacive Higgs fluctuations in superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2026-07-20 20:00 EDT
Jacopo Fiore, Irene Zanotti, Kota Katsumi, N. P. Armitage, Claudio Castellani, Goetz Seibold, Lara Benfatto
Intense phase-stable terahertz (THz) laser pulses can drive collective modes coherently via multi-photon excitation pathways in a manner different than the standard resonant mechanism operative in linear response. Here we show that in superconductors the nonlinear optical response can be enhanced when excited quasiparticles activate a (non-resonant) static displacement of the superconducting order parameter, in full analogy with the displacive excitation of coherent phonons in opaque materials. By combining numerical simulations with analytical results we demonstrate that the displacive mechanism to excite the Higgs mode is operative in both $ s$ -wave and $ d$ -wave superconductors. We validate this prediction experimentally by the temperature dependence of the phase of the nonlinear first harmonic in superconducting $ s$ -wave NbN. We also discuss how the order-parameter relaxation at large times, which can be experimentally accessed via pump-probe protocols is connected to energy-dissipative processes. Our results offer a novel perspective on the ability of intense THz fields to measure, and eventually control, the parametric dependence of the optical response on collective degrees of freedom.
Superconductivity (cond-mat.supr-con)
Programmable transport of rotating particles in obstacle arrays
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-07-20 20:00 EDT
Marcos Puerto, Alfredo Alexander-Katz, Juan L. Aragones, J.V. Alvarez
Rotating colloids, or spinners, in obstacle arrays exhibit frequency-set stationary orbits and currents set by the competition between an inertial, Magnus-like lift and short-range attraction. Fully resolved lattice-Boltzmann simulations reveal the hydrodynamic coupling and identify the lift mechanism, while a symmetry-based Langevin model captures the resulting balance. In periodic lattices, the superposition of scalar and vector potentials produces two robust orbital regimes: corner states, in which spinners orbit individual posts, and inner states, in which orbits couple across four neighboring obstacles. Slow frequency modulation toggles these states and produces directed, stepwise transport across the grid. This establishes a minimal hydrodynamic mechanism, controlled by a single driving parameter, for programmable guidance of active rotors in structured environments.
Soft Condensed Matter (cond-mat.soft)
9 pages, 7 figures
Phys. Rev. Research 8, 033071 (2026)
Emergent Interfacial Magnetism in Epitaxial RuO$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Yudi Yang, Zhuang Qian, Shi Liu, Congjun Wu
The magnetic ground state of the altermagnet candidate RuO$ _2$ remains controversial, with magnetic signatures observed mainly in epitaxial films. Here we show, using first-principles calculations, that magnetism in epitaxial RuO$ _2$ can emerge as an interfacial boundary phase at TiO$ _2$ /RuO$ _2$ interfaces. While TiO$ _2$ -induced epitaxial strain alone does not make (001)-oriented RuO$ _2$ magnetic, explicit TiO$ _2$ /RuO$ _2$ interfaces stabilize sizable Ru moments confined to the first few Ru layers. Charge-density and orbital-resolved analyses reveal interfacial electronic reconstruction, and substrate doping provides a route to tune the induced moments. In symmetric TiO$ _2$ /RuO$ _2$ /TiO$ _2$ heterostructures, the two magnetic interfaces couple through the metallic RuO$ _2$ spacer, producing a thickness-dependent alternation between weak-ferromagnetic and compensated altermagnetic states. Our results identify interface engineering as a practical route to stabilize and control fragile magnetism in RuO$ _2$ .
Materials Science (cond-mat.mtrl-sci)
Subgrain-resolved Analysis of Degradation in Cu Metallization via Scanning 3DXRD and Thermomechanical Modeling
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Nikhil Prabhu, Laura Neumann, Michael Reisinger, James A. D. Ball, Cedric Corley-Wiciak, Manuel Petersmann, Agnieszka Corley-Wiciak, Jonathan Wright, Carsten Detlefs, Martin Diehl
Metallization layers play a key role in the performance and reliability of modern power semiconductor devices. During short-circuit events, rapid heating of power metallization layers induces thermomechanical incompatibility stresses, which may contribute to material degradation and impact device performance. In this work, potential degradation hotspots associated with thermomechanical loading in Cu power metallization are investigated using a combined experimental–computational approach. Scanning three-dimensional X-ray diffraction measurements are coupled with thermomechanical crystal plasticity simulations to probe the evolution of grain-resolved plastic deformation during rapid cyclic loading. This integrated approach provides insight into the microstructural processes governing degradation hotspot formation, laying the groundwork for future microstructure-informed, physics-based reliability assessment of Cu metallization.
Materials Science (cond-mat.mtrl-sci)
7 pages, 4 figures, submitted to Microelectronic Engineering (ESREF 2026 Special Issue)
Excitonic structure in CsPbBr$_3$ nanocubes, nanorods and nanoplatelets: the effect of dimensionality
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-07-20 20:00 EDT
Jose L. Movilla, Josep Planelles, Juan I. Climente
We present a theoretical study comparing the excitonic ground state properties of CsPbBr$ _3$ nanocrystals with different dimensionality: nanorods (1D), nanoplatelets (2D) and nanocubes (3D). All three systems are described on equal footing, by means of a general variational effective mass model, which captures the influence of quantum confinement, dielectric confinement, electron-hole correlations and polaronic effects (within a Haken model). The strongly confined directions squeeze the exciton (X) wavefunction and enhance Coulomb attractions along the weakly confined directions. This stimulates superradiance, thus making radiative recombination rates speed up from cubes to platelets and to rods, in line with recent experiments. The anisotropic local field factor is a secondary, yet non-negligible, mechanism further enhancing radiative rates. X binding energies are also determined primarily by the directions of strong confinenement, which is also consistent with experiments. Weakly confined directions become however influential for small aspect ratios. Dielectric confinement plays a major role in determining the binding energies, and less so in the interparticle-distances. For all dimensionalities, the biexciton (XX) geometry is that of a distorted tetrahedron, rather than squared or linear distributions that would result in Coulomb-governed 2D and 1D structures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 figures
Quantum Fisher information of magnetic quantum phase transition on Kondo lattice
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-07-20 20:00 EDT
Yuan Fang, Lei Chen, Mounica Mahankali, Fang Xie, Yiming Wang, Shouvik Sur, Qimiao Si
Strange metals exemplify highly collective quantum many-body systems that call for new means of characterization, and there is considerable potential for quantum information approaches contributing to the cause. We investigate multipartite entanglement across the quantum phase transition of a Kondo lattice model using the quantum Fisher information (QFI). We show that the QFI associated with the spin components transverse to the order parameter characterizes the destruction of heavy quasiparticles in the Kondo-destroyed magnetic-ordered phase. The physical origin of this observation is elucidated through an analysis of the antiferromagnetic Heisenberg model. We propose to test the results in terms of both unpolarized and polarized inelastic neutron scattering measurements in the ordered part of the heavy fermion phase diagram. Our findings illustrate how different operators of a many-body system can be employed to not only witness multipartite entanglement in different sectors and but also elucidate the overall physics across different parts of the phase diagram.
Strongly Correlated Electrons (cond-mat.str-el)
7+8 pages, 3+5 figures
Atomistic mechanism of corrosion-induced grain boundary migration in NiCr alloys in molten FLiNaK
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Sadia Khan, Hamdy Arkoub, Miaomiao Jin
Corrosion of Ni-Cr structural alloys in molten fluoride salts is a persistent material degradation problem, yet the atomistic role of grain boundaries in this process remains poorly understood. Here we use reactive molecular dynamics to investigate corrosion of NiCr alloys in molten FLiNaK across four representative grain boundaries ($ \Sigma3(111)$ , $ \Sigma11(113)$ , $ \Sigma5(012)$ , and $ \Sigma5(013)$ ) and corresponding bulk surfaces. Surface crystallography controls the initial dissolution stage, while grain boundary character governs the spatial localization and longer-time evolution of corrosion. We further identify a corrosion-driven grain boundary migration mechanism in which fluorine localization, preferential chromium dissolution, and vacancy-mediated mobility together drive interfacial motion away from the dealloyed region. The coherent $ \Sigma3(111)$ boundary suppresses these processes, indicating low-energy special boundaries as targets for grain boundary engineering of corrosion-resistant Ni-Cr alloys.
Materials Science (cond-mat.mtrl-sci)
22 pages, 6 figures
A Dynamical Phase-Field Model for the Optical Properties of Ferroelectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-07-20 20:00 EDT
Aiden Ross, Anya Frazer, Venkatraman Gopalan, Long-Qing Chen
Ferroelectric materials are promising platforms for controllable photonic devices because of the strong coupling between their spontaneous polarization and optical properties. Yet, these materials remain challenging to design because of the close connection between the ferroelectric domain structure and optical response, which no existing theoretical approach can capture. Here, we develop a dynamical phase-field model that directly couples the ferroelectric order to the local optical response by introducing an electronic polarization field. This approach enables the prediction of the spatially resolved temperature- and wavelength-dependent optical properties in complex ferroelectric microstructures. Applying this method to BaTiO3 thin films, we investigate the evolution of the local refractive index and electro-optic response under varying electric fields and temperatures. We show that the ferroelectric domain structure strongly modifies the local electro-optic response, exceeding 4000 pm/V near domain walls, several times larger than the bulk single crystal value (r_51=1300 pm/V). Our simulations quantitatively reproduce the electro-optic coefficient measured in BaTiO3 on silicon films and capture the temperature-dependent behavior across multiple ferroelectric phase transitions, revealing the role of phase competition and coexistence in determining the electro-optic response. More broadly, this work establishes a general approach for predicting light-matter interactions in complex ferroelectric microstructures, enabling the computational design of ferroelectric materials for photonics.
Materials Science (cond-mat.mtrl-sci)
Nonequilibrium thermodynamics of feedback-control: a phase-space perspective
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-07-20 20:00 EDT
Maxwell demons can convert knowledge into thermodynamic advantage by using measurement-acquired information. However, standard formulations of this problem assume that the demon has access to the system’s entire phase space, an assumption that fails in many practical applications. Here, I address this problem by deriving fluctuation relations for general feedback-controlled systems, including such singular cases. The central quantity is a generalized notion of unavailable information: a portion of the acquired information that cannot be used to extract useful work. Finally, a Szilard engine with finite resolution illustrates these results. In the high-resolution limit, the information acquired by the demon may diverge, yet the extractable work remains finite. This work shows that this occurs because an equally divergent amount of information becomes unavailable.
Statistical Mechanics (cond-mat.stat-mech)
4+5 pages, 3 figures