Superconductivity
Pressure-induced reentrant superconductivity in a misfit layered compound $\mathrm{(SnS)_{1.15}(TaS_2)}$
Chutong Zhang, Jiajia Feng, Xiao Tang et al. (+10 more)
Misfit layered compounds are natural van der Waals
heterostructures in which electronically active transition-metal dichalcogenide layers are decoupled by incommensurate blocking layers, enabling bulk realization of quasi-two-dimensional
quantum states. Here we investigate the superconducting, transport,and structural properties of the misfit compound $\mathrm{(SnS)_{1.15}(TaS_2)}$ under pressures up to 150 GPa. The low-pressure superconducting phase is gradually suppressed and disappears near 14.7 GPa,accompanied by increasing residual resistance. Remarkably, a distinct superconducting phase reemerges above 80 GPa and persists to the highest pressures achieved. This reentrant superconductivity follows a pressure-induced sign reversal of the
Hall coefficient near 60 GPa and a nonmonotonic
evolution of the normal-state resistance, indicating an electronic reconstruction. No structural phase transition is detected over the entire pressure range. Our results demonstrate a pressure-driven electronic reconstruction leading to reentrant superconductivity in a misfit layered compound, establishing pressure as an effective route to engineer superconductivity and electronic states in natural van der Waals
heterostructures.
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All authors Chutong Zhang, Jiajia Feng, Xiao Tang, Xiangzhuo Xing, Na Zuo, Xiaolei Yi, Yan Meng, Xiaoran Zhang, Rajesh Kumar Ulaganathan, Raman Sankar, Xiaofeng Xu, Xin Chen, Xiaobing Liu
Materials Science
Influence of Hydrogen on Dislocation Relaxation in BCC Iron: Atomistic Mechanisms and Implications
Sanjay Manda, Madhur Gupta, Saurabh Kumar et al. (+4 more)
In this study, the influence of pure dislocation and hydrogen-dislocation interactions on anelastic response or internal friction relaxation peaks in bcc-iron was investigated. These relaxations are primarily governed by thermally activated kink nucleation and kink migration events. An atomistic multiscale framework, coupling molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations, was developed to investigate the underlying atomistic mechanisms behind dislocation-relaxation peaks. MD simulations revealed that the presence of hydrogen atoms near the dislocation core facilitates the kink nucleation process by reducing the nucleation barrier while enhancing the barrier for dislocation migration. The KMC model captured Snoek-Koster peaks arising from the Cottrell atmosphere formed by hydrogen atoms and clusters around the dislocation core, providing insights into the atomistic mechanisms controlling these relaxations. Furthermore, the proposed computational scheme elucidated a unique linear relationship between hydrogen content and the internal friction loss factor, offering a methodology for hydrogen detection and quantification.
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All authors Sanjay Manda, Madhur Gupta, Saurabh Kumar, Junaid Akhter, P. J. Guruprasad, Indradev Samajdar, Ajay S. Panwar
Materials Science
Mechanistic Insights into Li+ Transport Enabled by Isolated Sulfur Species in Li3PS4 Glasses
J. Pawelko, X. Rocquefelte, A. Tetenoire et al. (+3 more)
All-solid-state lithium-ion batteries have renewed interest in high-performance solid electrolytes. Li3PS4 (Li2S-P2S5) glasses are among the most studied due to their high ionic conductivity, traditionally ascribed to rotational motion of polyhedral units facilitating Li+ migration. Using ab initio molecular dynamics, we investigate Li-ion
diffusion in Li3PS4 glass, demonstrating that our structural model reproduces experimental
neutron and X-ray diffraction patterns and conductivity measurements. Importantly, we identify a previously unrecognized
diffusion mechanism: Li+ ions near isolated sulfur species (Sn with n = 1, 3) display significantly enhanced mobility, with atomic displacements up to 1.7 greater than those associated with bulkier polyhedral units. These results highlight the critical role of free sulfur species in promoting fast ionic transport, providing insights for the rational design of glass compositions with optimized conductivity for solid-state battery applications
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All authors J. Pawelko, X. Rocquefelte, A. Tetenoire, D. Le Coq, L. Calvez, E. Furet
Materials Science
Chalcogen Impurity Barriers in 2D Systems via Semi-Empirical/Machine Learning Modeling: A Survey over 4000 Materials
M. L. Pereira Junior, M. G. E. da Luz, P. Cesana et al. (+7 more)
Adequate characterization of two-dimensional materials with low energy barriers for
impurity adsorption is key for advancing applications based on catalysis, sensing, and surface functionalization. However, first-principles methods, such as DFT, are often computationally extremely expensive for feasible large-scale screenings. Given such a scenario, we address a data-driven approach which integrates the semi-empirical Extended Huckel Method with machine learning techniques to estimate adsorption energy barriers in the case of three relevant chalcogen
impurities, S, Se and Te. With this aim, we consider the 4036 2D materials found in the C2DB. The scheme employs the EHM to compute energy profiles along three in-plane migration paths, from which average barriers can be derived. The
equilibrium distance between the
impurity and the 2D surface is not calculated from a tie-consuming geometry optimization. Instead, it is estimated from a simple effective phenomenological expression. Physicochemical descriptors are then obtained from the Matminer library for curated features. Four different ML models are tested, with the XGBoost leading to the highest performance. We further use SHAP to verify the resulting predictions, focusing on the $\sim1,500$ materials displaying the lowest barrier values. As it could be anticipated, we establish that the average valence electron count, electronegativity, and atomic number are typically the most relevant attributes to validate the ML model. But we also are able to determine, for the different chalcogen atoms, which other few descriptors likewise considerably influence the adsorption properties. Our results show that when combined with interpretable ML protocols, EHM can produce a scalable framework for choosing 2D structures that exhibit the desired capture/release dynamics pertinent in a variety of utilization.
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All authors M. L. Pereira Junior, M. G. E. da Luz, P. Cesana, A. L. da Rosa, M. J. Piotrowski, D. Guedes-Sobrinho, T. A. S. Pereira, E. A. Moujaes, A. C. Dias, R. M. Tromer
Soft Condensed Matter
Coupling between Phase Separation and Geometry on a Closed Elastic Curve: Free Energy Minimization and Dynamics
Hanchun Wang, Ronojoy Adhikari and Michael E. Cates
We study the free energy and dynamics of a closed elastic filament (a one-dimensional curve in two dimensions) coupled to a scalar concentration field representing, for example, an absorbed species. The density variable has a tendency to phase-separate whereas the local spontaneous
curvature is concentration-dependent. We address analytically and by simulation both the free energy landscape and the dynamics (the latter comprising a coupled Willmore flow and Cahn–Hilliard gradient flow on the full differential geometry of a closed filament), addressing issues that previous work typically sidestepped by restricting to the Monge gauge. Specifically we find that the closure constraint for a deformable filament qualitatively changes the free energy landscape compared with either a rigid closed filament or an open elastic one, admitting metastable and stable states with more than one domain of each type. By numerical global free energy minimization we explore
equilibrium morphologies across a wide range of model parameters. For selected parameter values we present fully dynamical results, tracking the time
evolution of the various contributions to the free energy and confirming the emergence of both metastable and
equilibrium multi-domain morphologies.
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Superconductivity · Cross-listed from astro-ph.IM
Demonstrating Single Photon Counting with Kinetic Inductance Detectors from 3.8 to 25 $\mu$m
Wilbert G. Ras-Vinke, Kevin Kouwenhoven, Jochem J.A. Baselmans et al. (+4 more)
One of the primary objectives of modern astronomy is the atmospheric characterization of Earth-like
exoplanets at visible and infrared wavelengths. Achieving this goal requires extremely sensitive detectors capable of measuring faint signal of the
exoplanet at the single-
photon level while maintaining near-zero dark count rates. In the infrared, however, conventional semiconducting detector technologies struggle to meet these stringent requirements. In this work we demonstrate single-
photon counting with superconducting Microwave Kinetic Inductance Detectors at the wavelengths 3.8, 8.5, 18.5, and 25 $\mu$m and measure resolving powers ($E/\delta E$) of 9.9, 5.9, 3.2, and 3.3, respectively, with corresponding dark count rates of 4, 8, 34, and 48 mHz. Our membrane-based devices reach
phonon-loss limited performance at 3.8 $\mu$m, more than doubling the performance attainable with comparable solid-substrate devices. These results showcase the detector technology in the mid-infrared and the intricate measurement setup required for these sensitive detectors. We discuss how the detector design and measurement setup can be further optimized to increase the detector performance in the mid-infrared.
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All authors Wilbert G. Ras-Vinke, Kevin Kouwenhoven, Jochem J.A. Baselmans, Kenichi Karatsu, David J. Thoen, Vignesh Murugesan, Pieter J. de Visser
Materials Science
Growth-controlled photochromism in yttrium oxyhydride thin films deposited by HiPIMS and pulsed-DC magnetron sputtering
M. Zubkins, E. Letko, E. Strods et al. (+6 more)
The present study investigates photochromic oxygen-containing yttrium hydride (YHO) thin films deposited by reactive high power impulse magnetron sputtering (HiPIMS) and compares their photochromic, optical, and structural properties with those of films synthesized by reactive pulsed direct current magnetron sputtering (pulsed-DCMS). Optical emission spectroscopy reveals that, unlike pulsed-DCMS where Ar$^{+}$ ions dominate, HiPIMS discharges are characterised by strong Y$^{+}$ emission, evidencing high yttrium ionisation and substantial self-sputter recycling. The critical working pressure (P$_c$) required to obtain transparent and photochromic films is higher for HiPIMS (Pc $\approx$ 1.0 Pa) than for pulsed-DCMS (Pc $\approx$ 0.5 Pa). Although films deposited near Pc exhibit similar
solar transmittance (~72 %) and
lattice parameters (5.38–5.39 Å), the pulsed-DCMS film shows a substantially higher relative photochromic contrast (34 %) and a lower optical band gap (2.70 eV) compared with the HiPIMS film (9 % contrast and 2.94 eV). This difference is partly attributed to a lower oxygen-to-hydrogen atomic ratio in the pulsed-DCMS film. Structurally, HiPIMS films are largely polycrystalline with random out-of-plane crystallographic orientation, whereas pulsed-DCMS films exhibit a pronounced <100> out-of-plane preferred orientation. These results demonstrate that, beyond composition, thin-film growth conditions and microstructure play a crucial role in governing the photochromic performance of YHO.
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All authors M. Zubkins, E. Letko, E. Strods, V. Vibornijs, D. Moldarev, K. Sarakinos, K. Mizohata, K. Kundzins, J. Purans
Materials Science
A Comparative Study of Structural Representations for 2D Materials: Insights from Dynamic Collision Fingerprint and Matminer
Raphael M. Tromer, Isaac M. Felix, Rafael Besse et al. (+2 more)
In materials science, the selection of structural descriptors for machine learning protocols strongly influences predictive performance and the degree of physical interpretability that can be achieved from the derived models. Although more complex descriptors may improve numerical accuracy, they often represent extra computational load, also reducing transparency into the underlying structural information. A framework called the Dynamic Collision Fingerprint (DCF) was recently proposed with the goal of producing concise, physically significant representations, generating descriptors via dynamical probing of atomic structures. In this work, we
benchmark DCF using a
dataset composed of 120 two-dimensional carbon allotropes and compare its performance with the widely considered Matminer library. The analysis employs three regression models, linear regression, decision tree, and XGBoost, evaluated over train and test partitions ranging from 10% to 90% and repeated over multiple random seeds in order to characterize statistical variability. The obtained results demonstrate that DCF easily matches Matminer in terms of predicting accuracy across all learning
algorithms. However, it accomplishes this using descriptors that are significantly lower dimensional, pointing to manageable computing costs. Moreover, compared to the rather technical Matminer descriptions, the DCF exhibits considerably clearer physical interpretability. These findings suggest that DCF is a significant substitute for high-dimensional descriptor libraries as structural representation since it is both computationally flexible and physically grounded.
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All authors Raphael M. Tromer, Isaac M. Felix, Rafael Besse, Marcelo L. Pereira Junior, Marcos G. E. da Luz
Soft Condensed Matter
Exact Rheology of Uniform Shear Flow in a Gas of Inelastic and Rough Maxwell Particles
Andrés Santos and Gilberto M. Kremer
We investigate the steady uniform shear flow of a granular gas composed of inelastic and rough Maxwell particles. Exploiting the mean-field character of the model, we derive exact expressions for the collisional production rates of the second-degree moments and obtain a closed nonlinear solution for the stress and
spin-
spin tensors. The rotational-to-translational temperature ratio and the proportionality between the
spin-
spin and stress tensors are shown to be independent of the coefficient of normal restitution and determined solely by roughness and moment of inertia. The reduced normal stresses, shear stress, and shear rate are obtained explicitly in terms of two effective parameters generalizing the cooling and stress relaxation rates of the smooth model. From these results we derive exact expressions for the non-Newtonian shear viscosity, the first viscometric function, and the friction coefficient. The dependence of the rheological properties on the normal and tangential restitution coefficients is analyzed in detail, revealing strong non-Newtonian behavior and nonmonotonic effects of roughness. The results reduce, in the appropriate limits, to those of the inelastic Maxwell model for smooth particles and to the Pidduck gas in the elastic perfectly rough case.
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Quantum Gases
Metastable confinement in Rydberg lattice gauge theories
Yaohua Li, Devendra Singh Bhakuni, Yong-Chun Liu et al. (+1 more)
Confinement and string breaking are two fundamental phenomena in gauge theories. Signatures of both are currently pursued in
quantum-simulator experiments, opening a new angle on strongly interacting dynamics of gauge fields out of
equilibrium, complementary to traditional particle-physics settings. In this work, we report the emergence of metastable confinement dynamics in a U(1)
lattice gauge theory, originating from the competition between string tension and four-
Fermi coupling - a competition that naturally arises in Rydberg atom arrays. We show that the initial string state can be resonantly melted through controlled energy matching, a phenomenon we identify as resonant string breaking. We demonstrate this mechanism for both static and Floquet-driven systems, where periodic modulation generates a spectrum of tunable sideband resonances. Our work provides new insights into the mechanisms of confinement and string breaking driven by long-range interactions and time-dependent fields, which are available in current
quantum simulators on a variety of platforms.
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All authors Yaohua Li, Devendra Singh Bhakuni, Yong-Chun Liu, Marcello Dalmonte
Statistical Mechanics
Dephasing-induced relaxation in tight-binding chains with linear and nonlinear defects
Debraj Das, Andrea Gambassi, Stefano Iubini et al. (+1 more)
We investigate thermalization in a tight-binding chain with an on-site defect subject to local dephasing noise implemented as random phase kicks. For a single linear defect of strength $\epsilon$, we obtain an exact analytical description of the system spectrum and formulate the dephasing-induced dynamics in the eigenstate basis. We derive an approximate kinetic equation for mode populations that describes a continuous-time random walk in action space. The walk transition rates are defined by the overlap
matrix encoding the spatial structure of eigenstates that can be computed exactly. Analyzing the spectral properties of the equation, we show that defect-induced localized modes act as bottlenecks that strongly slow down relaxation, with rates scaling as $\epsilon^{-2}$ for strong defects. Using large-deviation theory, we characterize rare dynamical trajectories and identify distinct relaxation pathways associated with low- and high-activity regimes in action space. We provide numerical evidence that the large-deviation function exhibits a dynamical phase transition in the limit $\epsilon \to \infty$. We then extend our analysis to the nonlinear case, considering a single nonlinear defect embedded in either a linear or a fully nonlinear discrete Schrödinger equation. Numerical simulations reveal a qualitatively faster approach to
equilibrium than in the corresponding linear-defect model, driven by the amplitude-dependent weakening of the defect. Our results provide a unified framework for understanding thermalization, rare fluctuations, and relaxation pathways in
stochastic tight-binding systems.
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All authors Debraj Das, Andrea Gambassi, Stefano Iubini, Stefano Lepri
Materials Science
Substrate induced optimization of the Electrocatalytic Hydrogen Evolution Reaction (HER) performances of MoS2 thin film
Hafiz Sami-Ur-Rehman, Arpana Singh, Nunzia Coppola et al. (+11 more)
Molybdenum disulfide (MoS2) has emerged as a promising, cost-effective catalyst for hydrogen production via water splitting. We investigate the structural and electrocatalytic properties of MoS2 thin films deposited on different substrates (Al2O3, SiC, STO) to study their hydrogen
evolution reaction (HER) activity. In particular, in order to study the substrate influence on the stabilization of different polymorphic MoS2 phases, the films are synthesised using pulsed
laser deposition on substrates with different
crystal symmetries and
lattice parameters. All the deposited samples are characterized by X-Ray Diffraction, Raman Spectroscopy, Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy analyses. The films grown on Al2O3 substrates exhibit the best HER performance, likely due to the stabilization of the metastable 1T phase through the interfacial interactions between film and substrate. Presence of the 1T phase in the samples grown on Al2O3 improves the charge transfer efficiency and the electrochemically active surface with a better response to the applied potential, demonstrating their enhanced catalytic behaviour for hydrogen
evolution.
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All authors Hafiz Sami-Ur-Rehman, Arpana Singh, Nunzia Coppola, Pierpaolo Polverino, Sandeep Kumar Chaluvadi, Shyni Punathum-Chalil, Heinrich-Christoph Neitzert, Diana Sannino, Pasquale Orgiani, Alice Galdi, Cesare Pianese, Paolo Barone, Carmela Aruta, Luigi Maritato
Quantum Gases
Macroscopic quantum self-trapping in bosonic Josephson junctions: an exact quantum treatment
Andrea Bardin, Anna Minguzzi and Luca Salasnich
We investigate the fully
quantum evolution of the population imbalance in a perfectly symmetric Bose-Josephson junction modeled by a two-mode Bose-Hubbard
Hamiltonian, focusing on the validity of macroscopic
quantum self-trapping beyond the mean-field theory. We show that for any finite number of particles the exact
quantum dynamics leads to the breakdown of macroscopic
quantum self-trapping after a finite time, regardless of the initial state. Using the
symmetries of the Bose-Hubbard
Hamiltonian, we provide a mathematical demonstration of this result and analyze the spectral properties governing the dynamics. We identify a branching behavior in the
eigenvalues differences and a nontrivial structure of the population-imbalance amplitudes. These features allow us to distinguish two clearly different dynamical regimes and to elucidate the mechanism leading to the emergence of a quasi-MQST regime for large particle numbers. These findings bridge the gap between mean-field predictions and exact
quantum dynamics and provide insight into the emergence of classical nonlinear behavior from finite
quantum many-body systems.
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Soft Condensed Matter
Non-linear visco-elasto-plastic rheology of a viscous vertex model
Shalabh Kumar Anand and Matthias Merkel
Morphogenesis involves complex shape changes of biological tissues. Yet, tissue shape changes depend on tissue rheology, which in turn arises from the interplay of large numbers of
cells. Here, we link
cell- and tissue-scale mechanics by constructing mean-field rheological relations for the vertex model. In contrast to past work in the field, we study a vertex model with an explicit viscous friction. We also include two different cellular mechanisms creating active, anisotropic stresses. Our mean-field model accounts for
cell shape and the non-linear elastic and visco-plastic regimes. We validate our results by predicting the response to large-amplitude oscillatory shear. There are several vertex model variants, and comparing to results from the literature, we show that their rheology depends on a number of model details. Our approach should be sufficiently general to construct non-linear mean-field constitutive relations for any
cell-based tissue model.
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Superconductivity
Surface-localized topological superconductivity in nodal-loop materials: BdG analysis
Takeru Matsushima and Hiroki Tsuchiura
We theoretically study surface superconductivity in a nodal-line semimetal by combining a minimal tight-binding model with a layer-resolved Bogoliubov-de Gennes approach. In the normal state, the model realizes a bulk nodal loop and an associated drumhead surface band in a slab geometry with open boundaries in the $z$ direction: the central layers reproduce the bulk-like density of states, whereas the surface layer exhibits a sharp zero-energy peak originating from the drumhead states. On top of this band structure we introduce
chiral $p$-wave and $d_{x^2-y^2}$-wave superconducting channels and determine the layer-dependent gap amplitudes self-consistently. The
chiral $p$-wave order parameter is strongly enhanced at the outermost layers and decays within only a few layers towards the interior, while the $d$-wave order parameter is more than an order of magnitude smaller on all layers. The quasiparticle dispersion and surface local density of states in the
chiral $p$-wave state show that the drumhead band is efficiently gapped out and that the zero-energy peak in the normal surface spectrum is split into two coherence peaks, directly reflecting the induced superconducting gap. These results demonstrate that superconductivity driven by drumhead surface states is naturally biased toward a surface-localized
chiral $p$-wave pairing
symmetry and may offer qualitative guidance for interpreting surface-sensitive experiments on Pd-doped CaAgP.
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Materials Science
Self-foaming, Sintering-resistant Iron-Tungsten Powders Enable High-Cycle Thermochemical Hydrogen Storage
Jie Qi and David C. Dunand
H2-H2O redox cycling of iron powder beds at 650-800 {\deg}C offers a compact, safe, economical hydrogen storage method, but sintering-induced capacity loss has stalled its scalability for decades. Here, we show that adding redox-active tungsten to Fe powders solves this problem in static powder beds: Fe-25W (at%) alloyed powder self-foams during redox cycling via W gas-phase transport, increasing porosity and preserving capacity. In a custom automated reactor, a kilogram-scale powder bed reversibly stores 42g H2 and sustains 96+/-3% capacity utilization over 30 redox cycles. Temperature-resolved in-situ X-ray diffraction reveals a chemical-vapor-transport-mediated self-foaming mechanism that redistributes W to refine the microstructure, complemented by a contact-barrier stabilization mechanism during high-temperature holds. Partial-capacity cycling up to 90 cycles further confirms sintering resistance under incomplete redox conditions. These results establish Fe-W powder beds as a robust, scalable, and compact platform for safe, stationary hydrogen storage.
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Quantum Gases · Cross-listed from astro-ph.CO
(1+1)-Dimensional Schrödinger-Poisson equation with contact interaction
Óscar Rodríguez-Villalba, Ivan Saychenko, Massimo Pietroni et al. (+1 more)
We investigate the role of contact interactions in the dynamics of fuzzy dark matter (FDM) modeled through the Schrödinger-Poisson equation in one spatial dimension. While the $\Lambda$CDM paradigm successfully explains structure formation on large scales, its small-scale predictions remain in tension with observations. FDM offers an alternative framework, where local self-interactions can further influence the formation and
evolution of structures. We explore both attractive and repulsive contact interactions in static and expanding backgrounds. Using numerical simulations, we examine their impact on three key scenarios: the properties of the lowest-energy stationary solution, the relaxation of localized initial states, and the gravitational collapse of nonlocalized states. Our results show that contact interactions modify the density profile of the stationary solution and affect the onset of characteristic stages of gravitational collapse, particularly the shell-crossing event. In the (1+1) model, we confirm that relaxation does not converge to the lowest-energy stationary solution, even when local self-interactions are included. Taken together, local self-interactions play a relevant role in shaping the nonlinear dynamics of FDM and motivate further studies in higher-dimensional and cosmologically realistic settings.
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All authors Óscar Rodríguez-Villalba, Ivan Saychenko, Massimo Pietroni, Sandro Wimberger
Superconductivity
Hourglass Dirac chains enable intrinsic topological superconductivity in nonsymmorphic silicides
Shashank Srivastava, Dibyendu Samanta, Pavan Kumar Meena et al. (+8 more)
Nonsymmorphic crystalline
symmetries provide a robust route to
symmetry-protected electronic
topology, yet their role in stabilizing intrinsic topological superconductivity remains largely unexplored. Here, we report \ch{TaPtSi} as a new member of the superconducting nonsymmorphic silicide family, characterized via AC transport, magnetization, heat capacity, and
muon spin rotation/relaxation ($\mu$SR) measurements. Zero field $\mu$SR reveals spontaneous internal
magnetic fields below $T_{\rm c}$, establishing time reversal
symmetry breaking in \ch{TaPtSi}. First principles calculations on \ch{TaPtSi} and its isostructural nonsymmorphic superconducting analogues reveal the presence of
symmetry-protected hourglass dispersions. The "necks" of these dispersions form Dirac nodal rings and chains that reside near or intersect the
Fermi level. Guided by Ginzburg Landau
symmetry analysis, we identify an internally antisymmetric non
unitary triplet pairing state as the unique ground state consistent with the experimental phenomenology. Based on Bogoliubov de Gennes calculations, we further demonstrate that this state supports Majorana surface modes, establishing its intrinsically topological nature. These results reveal a systematic route by which nonsymmorphic
symmetry drives the interplay between hourglass Dirac chain
topology and unconventional triplet pairing, positioning equiatomic silicides as a unified materials platform for intrinsic topological superconductivity.
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All authors Shashank Srivastava, Dibyendu Samanta, Pavan Kumar Meena, Poulami Manna, Priya Mishra, Suhani Sharma, Prabin Kumar Naik, Rhea Stewart, Adrian D. Hillier, Sudeep Kumar Ghosh, Ravi Prakash Singh
Mesoscale and Nanoscale Physics
First-principles and tight-binding analysis of thermoelectricity in irradiated WSe$_2$
Cynthia Ihuoma Osuala, Tanu Choudhary, Raju K. Biswas et al. (+2 more)
Electronic and thermoelectric transport in zigzag monolayer WSe$_2$ nanoribbons are studied under monochromatic irradiation. The electronic structure is described within a six-orbital tight-binding framework constructed from the relevant tungsten and selenium orbitals, with atomic
spin-orbit coupling included explicitly. Periodic driving is incorporated via the Peierls substitution, and in the high-frequency limit the system is mapped onto an effective static Floquet
Hamiltonian with polarization-dependent renormalized hoppings. Coherent transport is evaluated using wave-function matching within the Landauer-Büttiker formalism. The
lattice thermal conductivity is obtained independently from density functional perturbation theory combined with an iterative solution of the
phonon Boltzmann transport equation. Light-induced hopping renormalization reshapes the band dispersion and transmission spectrum near the
Fermi level, modifying the Landauer transport integrals that determine electrical and thermal conductances and the Seebeck coefficient. Together with
spin-orbit-driven band splitting and reduced
lattice thermal conductivity from enhanced anharmonic scattering, this leads to a thermoelectric figure of merit $ZT$ exceeding unity over a broad temperature range.
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All authors Cynthia Ihuoma Osuala, Tanu Choudhary, Raju K. Biswas, Sudin Ganguly, Santanu K. Maiti
Superconductivity
Magnetoresistance Oscillations in Few-Layer NbSe2 in Superconducting Fluctuation Regime
Xiaolong Yin, Congzhe Cao, Yibin Feng et al. (+5 more)
Quantum interference phenomena in
superconductors, such as Josephson interference and Little-Parks oscillations, serve as powerful probes of phase coherence,
symmetry breaking and
vortex dynamics. However, they are typically observed in well-defined mesoscopic structures, and their behavior in the two-dimensional limit remains largely unexplored. Here, we report periodic magnetoresistance oscillations, superconducting interference patterns, and interfering diode effect in unpatterned few-layer NbSe2. These phenomena emerge exclusively within the superconducting fluctuation regime of thin samples, consistent with the enhanced anomalous metallic behavior of atomically thin NbSe2. The non-monotonic temperature dependence of both the oscillation amplitude and the diode efficiency can be captured by a model in which thermally activated
vortices traverse intrinsic supercurrent loops. Our results reveal that the observed interference phenomena originate from the lost of global phase coherence, providing a new route to accessing interference effects in unpatterned
superconductors.
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All authors Xiaolong Yin, Congzhe Cao, Yibin Feng, Kenji Watanabe, Takashi Taniguchi, Jiawei Mei, Qi-Kun Xue, Shuo-Ying Yang
Quantum Gases · Cross-listed from quant-ph
Generating entangled polaritonic condensates by pumping with entangled pairs of photons
N.A. Asriyan, A.A. Elistratov and A.V. Kavokin
We investigate the steady state of two single-mode uniform spatially separated polaritonic conden- sates exposed to resonant pumping with entangled pairs of
photons. We demonstrate the principal possibility of driving the system to an entangled state despite its exposure to noises arising from the excitonic reservoir and
photon leakage through the microcavity mirrors. Estimates are provided for the flux of entangled particles required to drive the system into a steady state that violates the partial-transpose criterion for
entanglement. Furthermore, we trace the
evolution of the system after a sudden disappearance of the entangled pumping. Our analysis provides estimates for the
entanglement lifetime in a system of two
exciton-polariton condensates
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Superconductivity
Interaction and disorder effects on Cooper instability in two-dimensional fractional Dirac semimetals
Hua Zang and Jing Wang
Employing a renormalization group analysis that allows for an unbiased treatment of competing physical ingredients, we systematically trace how the interplay between Cooper pairing and disorder scatterings governs the emergence or suppression of Cooper instability in the low-energy regime of fractional Dirac semimetals.In the clean limit, we find that the emergence of Cooper instability requires surpassing a finite interaction threshold $|\lambda_c|$, and depends sensitively on both the fractional exponent $\alpha$ and the transfer momentum $\mathbf{Q}=(Q,\phi)$. Specifically, bigger values of $\alpha$ enhance the tendency toward BCS instability. For $\alpha\in(0.001,0.61)$, the $(Q,\phi)$ parameter space separates into two distinct regions: Zone-\uppercase\expandafter{\romannumeral1}, where Cooper instability is suppressed, and Zone-\uppercase\expandafter{\romannumeral2}, where it is allowed. In the presence of disorders, we demonstrate that they can either promote or suppress Cooper instability. Disorder of type $\Delta_1$ or $\Delta_2$ enhances superconductivity by reducing the critical interaction threshold $|\lambda_c|$ and expanding the superconducting phase space (Zone-\uppercase\expandafter{\romannumeral2}). In sharp contrast, either $\Delta_0$ or $\Delta_3$ suppresses Cooper pairing by increasing $|\lambda_c|$ and shrinking the available phase space (Zone-\uppercase\expandafter{\romannumeral1}). Although Cooper instability can be enhanced when promotive disorders ($\Delta_1$, $\Delta_2$) coexist with a single suppressive disorder ($\Delta_0$ or $\Delta_3$), the suppressive influence of $\Delta_{0,3}$ generally dominates the promotive effects of $\Delta_{1,2}$ in the presence of all sorts of disorders. These results would be helpful for further studies of fractional Dirac semimetals and alike materials.
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Materials Science
Anti-Thermal Quenching Phosphors based on Metal Halides
Baowei Zhang and Liberato Manna
Thermal quenching (TQ) generally occurs in phosphors and is ascribed to the activation of non-radiative transitions at elevated temperatures. This effect limits the use of most phosphors in high-power/high-temperature applications, such as outdoor lighting and
laser systems. To achieve anti-TQ properties, structural design of phosphors is required. This usually follows two guidelines: (1) increasing
lattice rigidity to minimize thermal expansion; (2) converting thermal energy into radiative transitions to compensate for the non-radiative losses. While metal
oxides and metal nitrides dominate the field of commercial anti-TQ phosphors, metal halides - despite their inherently soft
lattices - have shown remarkable progress as anti-TQ phosphors in recent years. Here, we review the advances in anti-TQ metal halides (covering the time span from 2017, when first reports have appeared, till today) and discuss their mechanisms and applications. We argue that the low synthesis temperatures of metal halides and their high photoluminescence
quantum yields (PLQYs) make them promising candidates as anti-TQ phosphors. Furthermore, since the rich optical-physical processes underlying the anti-TQ effect in soft-
lattice in metal halides are only now beginning to be unraveled, this creates opportunities for many fundamental investigations.
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Superconductivity
Emergence of chiral $p$-wave and $d$-wave states in $g$-wave altermagnets
Tilen Cadez, Abraham Nathan Sunanta and Kyoung-Min Kim
Altermagnets emerge as a novel platform for realizing unconventional superconductivity through their exotic momentum-dependent
spin-splitting of electronic band structures. Recent experiments have uncovered a novel form of altermagnetism with distinctive $g$-wave
symmetry in CrSb. However, the potential for unconventional superconductivity arising from $g$-wave altermagnetism in such systems remains largely unexplored. In this study, we discover the emergence of
chiral superconducting states in three-dimensional $g$-wave altermagnetic metals. Through systematic self-consistent mean-field analysis on the extended attractive Hubbard model combined with $g$-wave altermagnetic exchange fields in a three-dimensional hexagonal
lattice, as observed in CrSb, we find that the altermagnetic
spin splitting of
Fermi surfaces favors
chiral $p$-wave states as the dominant pairing channel under strong altermagnetic fields and high electron densities, while
chiral $d$-wave states become predominant under weak altermagnetic fields and intermediate electron densities. Conversely, at weak altermagnetic fields and typical electron densities, non-
chiral $s$-, extended $s$-, or $f$-wave states become stabilized. We also showcase the possible experimental detection using the quasiparticle energy dispersions and the density of states to distinguish different pairing
symmetries. These findings underscore the potential of $g$-wave altermagnets to host sought-after
chiral and gapless superconductivity.
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Materials Science
Role of the Nephelauxetic Effect in Engineering Mn4+ Luminescence Kinetics for Lifetime-Based Thermometry
A. Basheer, M. Szymczak, M. Piasecki et al. (+3 more)
Although the considerable potential of luminescence thermometry based on emission kinetics has been widely demonstrated, reliable tools for the intentional prediction of thermometric performance remain limited. To address this challenge, the present work introduces an approach that enables a theoretical description of the 2E state lifetime of Mn4+ ions, as well as the absolute and relative sensitivities, in terms of the nephelauxetic effect within the group of double perovskites: Sr2InNbO6, Sr2InTaO6, Ba2InTaO6, and Ba2InNbO6. Our results clearly show that, contrary to common assumptions, the Dq/B ratio is not the primary factor governing either the spectroscopic behavior of Mn4+ ions or the thermometric performance of Mn4+-doped phosphors. Instead, the nephelauxetic beta1 parameter plays the dominant role. The empirical analysis carried out in this study led to the development of a predictive model that enables estimation of SAMAX and SRMAX values based exclusively on beta1. This methodology represents a significant step toward the rational design of lifetime-based luminescence thermometers with predefined thermometric characteristics tailored to the requirements of specific applications.
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All authors A. Basheer, M. Szymczak, M. Piasecki, A. M. Srivastava, M.G. Brik, L. Marciniak
Strongly Correlated Electrons
Phonons reflect dynamic spin-state order in LaCoO$_3$
Alsu Ivashko, Taishun Manjo, Maximilian Kauth et al. (+17 more)
We investigate
lattice dynamics in LaCoO$_3$ using inelastic
neutron and x-ray scattering over $T = 2\mbox{-}650\,\mathrm{K}$, spanning the
spin-state crossover at $T_{1} \approx 100\,\mathrm{K}$ and the
insulator–metal transition at $T_{2} \approx 550\,\mathrm{K}$. Comparison with quasi-harmonic $ab-initio$
lattice-dynamical calculations helps reveal anomalous softening of a $\approx 10\,\mathrm{meV}$ oxygen
phonon, confined to the temperature interval $T_{1} \leq T \leq T_{2}$ and localized in momentum space at $\boldsymbol{q}_{\mathrm{SSO}} = \left( \frac{1}{2},\frac{1}{2},\frac{1}{2} \right)_{c}$. This wave vector corresponds to the
spin-state ordering originally proposed by Goodenough [J. Phys. Chem. Solids 6, 287-297 (1958)]. Our results therefore provide momentum-resolved evidence for dynamic correlations of high-
spin and low-
spin Co$^{3+}$ states in LaCoO$_{3}$, linking
spin-state fluctuations to anomalous
phonon renormalization.
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All authors Alsu Ivashko, Taishun Manjo, Maximilian Kauth, Yuliia Tymoshenko, Adrian M. Merritt, Klaus-Peter Bohnen, Rolf Heid, Michael Merz, Andreas Eich, John-Paul Castellan, Alexandre Ivanov, Nathaniel Schreiber, Hong Zheng, J. F. Mitchell, Martin Meven, Jitae T. Park, Daisuke Ishikawa, Yuiga Nakamura, Alfred Q. Baron, Frank Weber
Materials Science
LLM-driven discovery for carbon allotropes with bond-network entropy
Yuzhou Hao, Yujie Liu, Xuejie Li et al. (+4 more)
The discovery of novel carbon allotropes with tailored thermal and mechanical properties is critical for advanced thermal management. However, exploring the vast configurational space of carbon using ab initio calculations remains computationally prohibitive. Driven by the rich topological landscape of carbon, where the competition between $sp, sp^2,$ and $sp^3$ hybridization states dictates material performance, we establish a closed-loop AI framework to explore this complex configurational space. We introduce a hybridization
entropy descriptor to guide the search beyond conventional forms. Here, we establish a closed-loop AI framework that synergizes a Large
Language Model (LLM) for structural generation with a Machine Learning Potential (MLP) for accelerated evaluation. Leveraging CrystaLLM to generate candidates and an iteratively refined MLP for high-fidelity validation, we screened thousands of structures to identify several stable allotropes with exotic properties. Specifically, we report “yne-diamond C$_{12}$” and “yne-hex-diamond C$_{8}$”, which exhibit extreme thermal anisotropy and ultralow in-plane shear stiffness arising from their mixed $sp$-$sp^3$ hybridization. Furthermore, we discovered a complex $sp$-$sp^2$-$sp^3$ hybridized C$_{12}$ phase that combines metallic conductivity with an anomalous negative Poisson's ratio. Notably, we identified a superhard phase (C16_3) possessing a calculated Vickers hardness (103.3 GPa) exceeding that of diamond 96 GPa). Microscopic analysis reveals that thermal transport in these materials is governed by the interplay between rigid frameworks and flexible linkers. This work expands the known carbon phase space and demonstrates the efficacy of coupling generative AI with machine learning potentials for the accelerated inverse design of functional materials.
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All authors Yuzhou Hao, Yujie Liu, Xuejie Li, Turab Lookman, Xiangdong Ding, Jun Sun, Zhibin Gao
Strongly Correlated Electrons
Quantum Monte Carlo study of the metal-insulator crossover in the square-lattice Hubbard model
Mingzhong Lu, Yu-Feng Song, Youjin Deng et al. (+1 more)
The interaction-driven
evolution from a
Fermi liquid to a Mott
insulator is a hallmark of strongly correlated
fermion systems. In this work, we present a numerically unbiased study of such metal-to-
insulator crossover in the half-filled square-
lattice Hubbard model at finite temperatures, employing auxiliary-field
quantum Monte Carlo method. By jointly analyzing thermodynamic and dynamical observables, we establish the crossover diagram of the model in the temperature-interaction ($T$-$U$) plane. With increasing $U$, our numerical results reveal an extended crossover regime, which we refer to as the Bad Metal, that separates the
Fermi liquid and Mott
insulator. During the crossover, we also examine the
antiferromagnetic spin correlations and observe pronounced nodal-antinodal dichotomy in the momentum-resolved single-particle spectral functions. Furthermore, we investigate the temperature dependence of several commonly used observables in the model. As representative results, we achieve an accurate map of the thermal
entropy across the crossover diagram, and identify the parameter regions in which the model exhibits the Pomeranchuk cooling, characterized by an adiabatic cooling with increasing $U$. Beyond offering a more refined understanding of the crossover phenomenon, our work also provides valuable
benchmark and guideline for future optical
lattice experiments on the square-
lattice Hubbard model.
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All authors Mingzhong Lu, Yu-Feng Song, Youjin Deng, Yuan-Yao He
Soft Condensed Matter
Praveen Kumar Singh, Salman Ahmad Khan and Soumik Das
Biological systems often operate at the boundary between order and chaos, transitioning from directed to irregular dynamics to achieve adaptability and robustness. Reproducing such transitions in artificial soft matter remains a central challenge. Here, we report a biomimetic regime of directron dynamics in achiral nematic
liquid crystals, in which coherent, directed motion collectively evolves into chaos. Driven by multi-directron interactions, the system develops coexisting directron families with competing trajectories, displaying randomized motion, dynamic assembly formation and spontaneous fission of high energy to low energy daughter directrons - all of which mimics the phenotypic diversity observed in biological groups. Above a critical electric field, these interactions drive the system into a chaotic state that is distinct from the directed behaviours reported previously. We further introduce a minimal dipole-based model that qualitatively captures the underlying physics of this transition. Together, our results establish an artificial active system in which chaos emerges intrinsically from interactions, offering a versatile platform to study biological dynamics and opening new avenues for
liquid-
crystal-based soft-matter applications involving adaptive transport, cargo delivery, and energy transduction
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Disordered Systems and Neural Networks
Exact mapping of a spin glass with correlated disorder to the pure Ising model
Hidetoshi Nishimori
We introduce an Ising
spin-glass model with correlated disorder which continuously interpolates between the pure
ferromagnetic Ising model and the Edwards-Anderson model with symmetric disorder. For this model, we prove that a Nishimori line (NL) can be defined, analogously to the Edwards-Anderson model, on which physical quantities can be expressed exactly in terms of those of the pure Ising model at a well-defined effective temperature on any
lattice in any dimension. For example, the energy on the NL is equal to the energy of the pure Ising model at the effective temperature up to a constant and a trivial factor. More remarkably, the specific heat on the NL equals the energy, not the specific heat, of the pure Ising model at the effective temperature, again up to a constant and a trivial factor. Gauge-noninvariant quantities such as the magnetization and correlation functions are exactly equal to the corresponding quantities of the pure Ising model at the effective temperature. These exact relations imply that the leading critical behavior at that multicritical point for the disorder-correlated model is pure-Ising-like, in contrast to the conventional multicritical universality class of the standard Edwards-Anderson model. Our results motivate further investigations of the relatively unexplored topic of correlations in disorder in
spin glasses and related problems.
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