Strongly Correlated Electrons
Gossamer Superconductivity in Moiré WSe$_2$ Bilayer
Hui-Ke Jin, Guangyue Ji, Zhan Wang et al. (+2 more)
Moiré transition metal dichalcogenides have served as a versatile platform for simulating Hubbard physics. Recent experiments have identified robust superconductivity in moiré
bilayer WSe$_2$ for certain twist angles. Here, we propose the gossamer nature of the superconductivity recently discovered at half-filling and zero displacement field in twisted WSe$_2$. By mapping the moiré continuum system to an effective extended single-orbital Hubbard model on the triangular
lattice, we employ renormalized mean-field theory to investigate the strong-coupling phase diagram. We find that a moderate Coulomb repulsion partially suppresses charge fluctuations while preserving a finite density of mobile doublons and holes. In this regime, the interplay between extended kinetic hoppings and
antiferromagnetic superexchange stabilizes a
chiral $d+id$ superconducting phase. Our results naturally account for the twist-angle-dependent
evolution from a Mott
insulator to a
superconductor and eventually to a correlated metal. Furthermore, the model demonstrates that this half-filled pairing state vanishes rapidly upon density doping, consistent with experimental observations.
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All authors Hui-Ke Jin, Guangyue Ji, Zhan Wang, Jie Wang, Fu-Chun Zhang
Materials Science
The high K anomaly in ScAlN explained
Ilan Shalish
The integration of scandium aluminum nitride (ScAlN) into functional
heterostructures has pushed
semiconductor device physics into an extreme piezoelectric regime. Accurately determining the fundamental clamped dielectric permittivity (\epsilon_33^S) of these
alloys remains a major challenge, as standard density functional theory systematically overestimates this specific parameter due to well-known bandgap-underestimation limits. Furthermore, electrical capacitance-voltage (C-V) measurements of real-world devices do not yield this clamped baseline; instead, they capture an effective permittivity inflated by linear electromechanical coupling. Because epitaxial thin films are unconstrained in the out-of-plane direction, small-signal electrical measurements dynamically induce macroscopic
lattice strain via the inverse piezoelectric effect. By applying these specific mechanical boundary conditions to the coupled equations of state, we utilize the analytical relation for operational permittivity: \epsilon_eff=\epsilon_33^S+e_33^2/C_33. Leveraging highly accurate first-principles predictions for the structural and piezoelectric tensors, we invert this model to extract the true, uninflated clamped dielectric baseline directly from experimental thin-film data. This approach circumvents the conventional limitations of pure first-principles dielectric calculations, flawlessly resolving the theoretical-experimental discrepancy and providing a critical framework for accurate device simulation in highly polar nitrides.
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Statistical Mechanics
Information-Geometric Signatures of Nonconservative Driving
Andrea Auconi and Sosuke Ito
We propose an information-
geometric signature of nonconservative driving that detects violations of detailed balance using the Kullback–Leibler divergence and the Fisher information. For Markov jump processes satisfying detailed balance, we show that, near
equilibrium, the acceleration of the Kullback–Leibler divergence relative to the
equilibrium state is given by twice the Fisher information with respect to time. In contrast, for relaxation toward a nonequilibrium steady state, this relation is generally violated even near the steady state. We refer to the resulting discrepancy as the relaxation gap and derive a lower bound on the steady-state
entropy production rate in terms of this gap. We demonstrate that this bound is particularly tight for networks with simple cyclic
topologies. Finally, we show that analogous relations and bounds hold for Fokker–Planck dynamics.
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Materials Science
Spontaneous Topological Locking and Symmetry Restoration of Meron Lattices in Synthetic Antiferromagnets
Gülşen Doğan and Ümit Ak{\i}nc{\i}
Synthetic antiferromagnets offer a robust platform for stabilizing fractional topological textures, effectively circumventing the limitations of
ferromagnetic systems. In this study, we utilize large-scale Monte Carlo simulations to investigate the spontaneous topological locking and structural
symmetry restoration of meron-antimeron
crystals within SAF
bilayers subjected to easy-plane
magnetic anisotropy. In the uncoupled monolayer limit, increasing anisotropy induces an extreme core-shrinking effect that physically expands the inter-core distance and triggers a $C_4 \rightarrow C_2$
symmetry breaking. However, the introduction of an ultra-weak interlayer
antiferromagnetic exchange acts as an active structural scaffold. For rigid
crystals, this coupling strictly enforces vertical synchronization, forming robust
antiferromagnetic bimeron dipoles and fully restoring the macroscopic $C_4$ rotational
symmetry. Furthermore, in highly expanded, pre-collapse
crystals, we observe an anomalous interlayer-induced
lattice compression that actively maximizes the exchange energy. At extreme anisotropy limits where macroscopic crystalline order irrecoverably collapses, the
bilayer coupling continues to enforce a strict local topological locking of surviving isolated defects. These findings reveal a fundamental decoupling between local vertical synchronization and global structural order, providing a comprehensive theoretical roadmap for stabilizing and manipulating fractional topological textures in beyond-skyrmion spintronic architectures.
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Materials Science
Defect-Engineered Beryllium Dinitride (BeN2) Monolayer with Light-Metal Decoration for Reversible High-Capacity Hydrogen Storage
Wael Othman, Ibrahim Alghoul, K-F. Aguey-Zinsou et al. (+2 more)
Hydrogen (H2) possesses the highest gravimetric energy density of any chemical fuel and is the most abundant element in the universe. However, its extremely low volumetric energy density at standard conditions imposes a fundamental materials challenge for safe, efficient, and reversible storage. Here, we report a defect-engineered 2D beryllium dinitride (BeN2) monolayer that enables stable light-metal functionalization for high-capacity H2 storage. A 2 x 2 supercell containing two intrinsic beryllium vacancies accommodates four Li, Na, and K atoms without clustering, exhibiting strong average metal-vacancy binding energies of -3.80, -2.94, and -3.18 eV, respectively. Ab initio molecular dynamics simulations at 400 K confirm the thermal stability of the metal-decorated frameworks and the suppression of metal aggregation. The vacancy-stabilized alkali-metal centers generate localized charge polarization that facilitates the adsorption of up to 20 H2 molecules per supercell, with average adsorption energies of -0.182 eV (Li), -0.191 eV (Na), and -0.171 eV (K), making the adsorption reversible under near-ambient conditions. The corresponding gravimetric H2 storage capacities reach 11.64, 9.82, and 8.49 wt percent, respectively, significantly exceeding the US Department of Energy (DOE) ultimate target of 6.50 wt percent. Moreover, thermodynamic analysis further confirms favorable adsorption-desorption behavior within practical operating windows. These results establish vacancy-defected light-metal decorated BeN2 as a viable design strategy for high-density, reversible H2 storage, providing a scalable framework for engineering polar lightweight materials for energy storage applications.
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All authors Wael Othman, Ibrahim Alghoul, K-F. Aguey-Zinsou, Nacir Tit, Tanveer Hussain
Materials Science
A Correction Method for Crack Area Overestimation in Phase-Field Fracture
M. Castillón, J. Segurado and I. Romero
Phase-field fracture models are known to overestimate the crack area, a discrepancy that compromises the accuracy of fracture predictions. This issue stems from the diffuse crack representation and numerical artifacts, such as strain localization, where the phase-field variable artificially saturates across finite elements. Existing correction strategies, including mesh-dependent factors and skeletonization
algorithms, have significant limitations. Mesh-based corrections are often unreliable for unstructured meshes, while skeletonization can be complex and inaccurate for intricate crack
topologies, especially in three dimensions. This paper introduces a novel and robust framework to correct this overestimation. Our approach is founded on the principle of energy equipartition, where the energy contributions from the phase-field and its gradient are equal as the length-scale parameter approaches zero. Since numerical artifacts primarily affect the phase-field term while leaving the gradient term largely unperturbed, we propose that the crack area can be accurately approximated as twice the gradient-dependent energy. This method is inherently mesh-independent and readily applicable to the entire domain, including 3D simulations. The proposed methodology is validated against
benchmarks with analytical solutions and compared with established methods like skeletonization to demonstrate its accuracy. It is then applied to complex geometries with curvilinear crack paths and evaluated in a three-dimensional simulation.
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Soft Condensed Matter
Linear and Non-Linear Rheology of Single and Double Cross-Linked Biopolymer Networks under Viscous Shear Flow
Nasrollah Hajaliakbari, David Head and Oliver Harlen
In this research study, a numerical tool, which is based on a version of Slender Body theory, has been used and also modified to simulate the mechanical behaviour of single- and double-cross-linked biopolymer networks (hydrogel) under oscillatory shear flow. The hydrodynamic interactions among fibres of intertwined networks were considered. Then, the stress and
Fourier coefficients (i.e. shear
moduli) were evaluated for both linear and nonlinear regimes. It was found that the double peaks (two-step yielding) of two double network at 100% maximum strain amplitude (nonlinear regime) cannot happen due to changes in fibre
alignments and seed numbers, although the crosslinkers between two subnetworks present, which was previously reported in the literature. In fact, we also observed two peaks for single network in nonlinear regime. Furthermore, it was shown that the stress-strain curve of double network is not predicted by just superimposing the results from the corresponding single networks at 5% maximum strain amplitude (linear regime), but this prediction can be provided at 100% maximum strain amplitude (nonlinear regime). The
Fourier coefficients and corresponding amplitude (an indication of nonlinearity effects) for double network were quite considerable from zero to fifth modes in nonlinear regime, despite enough zero and first modes in linear regime. It was also shown that the nonlinearity effects can be related to the morphology of the initial structure, i.e. the seed number rather than the flow condition for the single network. These results can help scientists to better design enhance fibrous materials used in wound healing or tissue engineering.
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Strongly Correlated Electrons
Numerical evidence of a critical point in the (2+1)D SO(5) nonlinear sigma model with Wess-Zumino-Witten term
Yuan Da Liao, Bin-Bin Chen, Junchen Rong et al. (+3 more)
We develop an optimized continuous-field
quantum Monte Carlo (QMC)
algorithm to investigate the projected SO(5) nonlinear sigma model with a Wess-Zumino-Witten term, which describes half-filled Dirac
fermions in 2+1 space-time dimensions akin to
graphene and Yukawa coupled to a quintuplet of compatible mass terms. Our
algorithm reduces the computational complexity to $O(\beta N_{\mathbf{q}} N_\phi^2)$, yielding a speedup of a factor of $N_\phi$ (the number of
magnetic fluxes, i.e., system size) relative to prior works [1-4]. This advance enables us to simulate system sizes up to $N_\phi=140$ on the
torus and $N_\phi=59$ on the sphere, far exceeding the maximum sizes previously accessed, and to map out the universal phase diagram of the model on both geometries. Most notably, we identify and characterize a critical point that separates an SO(5)-broken ordered phase at small coupling from an SO(5)-symmetric disordered phase at large coupling. The critical point becomes multicritical upon the inclusion of terms that break the SO(5)
symmetry down to $\mathrm{U}(1) \times \mathrm{SU}(2)$, relevant for the deconfined phase transition between Néel
antiferromagnetic and valence-bond-solid orders in
quantum magnets. Our finding of a multicritical point in the phase diagram of the SO(5) nonlinear sigma model with Wess-Zumino-Witten term resolves the long-standing open question of its global structure, and our QMC
algorithm opens a new avenue for systematic studies of projected
Hamiltonians, ranging from correlated flat bands to fractional
quantum (anomalous)
Hall systems.
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All authors Yuan Da Liao, Bin-Bin Chen, Junchen Rong, Fakher F. Assaad, Lukas Janssen, Zi Yang Meng
Materials Science
Beyond lead halide perovskites: visible light photovoltaics with phase engineered bismuth-based oxide double-perovskites, Bi2MCrO6 (M = Fe, Mn)
N P Vikas, Ranjit K Pradhan, Somdutta Mukherjee et al. (+4 more)
Lead poisoning and notorious ambient instability in lead-based halide perovskites pave the way for the exploration of alternative materials for affordable and efficient
solar cell fabrication. An important prerequisite to this end is the optoelectronic evaluation of the proposed material. Here we report, optoelectronic characterization of Bi2FeCrO6 (BFCO) and Bi2MnCrO6 (BMCO) thin films vis-à-vis performance of photovoltaic
cells. Solution-deposited thin films (350-450 nm) of the above compositions demonstrate a double-perovskite structure with monoclinic P21/c
symmetry, albeit with mixed cation valences and deep-level defects. A thorough optoelectronic evaluation exhibits large optical absorption in the visible range ({\alpha} ~ 104 -105 cm-1), and high carrier density, ~1017-20 cm-3. Ultraviolet photoelectron spectroscopy measurement allowed determination of the positions of the band-edges (valence band maximum and conduction band minimum), required for the selection of carrier transport layers. In its first, BMCO-based FTO/SnO2/BMCO/Spiro-OMeTAD/Ag
solar cell produced a maximum 3.56% conversion efficiency. Using numerical simulation, we predict that with suitable defect control, the above conversion efficiency can increase significantly.
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All authors N P Vikas, Ranjit K Pradhan, Somdutta Mukherjee, Udai P Singh, Biplab K Patra, Ravi P Srivastava, Amritendu Roy
Materials Science
Deterministic positioning of circular Bragg gratings using atomic force lithography for high-performance quantum dot light sources
Sai Abhishikth Dhurjati, Moritz Langer, Yared G. Zena et al. (+6 more)
Semiconductor quantum dots (QDs) grown by molecular beam epitaxy are excellent
quantum emitters, but their random spatial distribution hinders deterministic coupling to optical microcavities. We demonstrate a room-temperature atomic force microscopy (AFM)-assisted nano-oxidation lithography technique enabling QD positioning with a radial displacement of $51(28)$ nm. Free-standing asymmetric circular Bragg gratings incorporating AFM-positioned GaAs QDs exhibit a $245$-fold photoluminescence enhancement and fine-structure splitting (FSS) comparable to bulk QDs. Polarization-resolved spectroscopy and finite-difference time-domain simulations show robust emission for displacements up to $50$ nm (Stokes parameter $\lvert S \rvert < 0.05$ ). The devices display stable FSS and polarization imbalance below $5 \, \%$ , confirming precise, reproducible
alignment and potential for high fidelity devices. This scalable approach enables deterministic integration of high-performance QDs with photonic cavities, advancing practical
quantum light sources for
quantum information technologies.
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All authors Sai Abhishikth Dhurjati, Moritz Langer, Yared G. Zena, Ahmad Rahimi, Liesa Raith, Martin Bauer, Frank H. P. Fitzek, Riccardo Bassoli, Caspar Hopfmann
Materials Science
Enhanced Valley Polarization via Nonlinear Cascaded Quantum-Geometric Selection Rules
Quentin Courtade, Sotirios Fragkos, Dominique Descamps et al. (+4 more)
The
quantum geometric properties of Bloch electrons fundamentally govern light-matter interactions and optical selection rules in solids. In semiconducting transition-metal dichalcogenides, circularly polarized excitation near the band edge enables valley-selective interband transitions, providing the basis for valleytronics. While nonlinear optical protocols are being developed to manipulate and probe valley selection rules, they largely rely on band-edge transitions that proceed via virtual intermediate states. Here, we demonstrate a doubly resonant cascaded nonlinear pathway from the valence band to high-lying states, mediated by a real intermediate state whose participation substantially reshapes the valley optical selection rules. Using time- and angle-resolved extreme-ultraviolet photoemission spectroscopy in combination with a time-dependent Lindblad master-equation formalism, we show that this cascaded nonlinear photoexcitation produces a substantially enhanced high-lying valley polarization compared to the conventional linear optical response near the band edge. The extension of the
quantum-geometry-based selection rules to the nonlinear regime and high-lying bands offers new perspectives for ultrafast valleytronics and should play a determinant role in strong-field-driven phenomena in
quantum materials.
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All authors Quentin Courtade, Sotirios Fragkos, Dominique Descamps, Stéphane Petit, Yann Mairesse, Michael Schüler, Samuel Beaulieu
Soft Condensed Matter
Adhesion-controlled sliding and the Stribeck curve in hydrophobic soft contacts
Ruibin Xu, Charlotte Spies, Michele Scaraggi et al. (+1 more)
We present an experimental and theoretical study of dry and glycerol-lubricated sliding for polymethyl methacrylate (PMMA) cylinders with different surface roughness sliding on polydimethylsiloxane (PDMS) rubber. This system represents a hydrophobic soft contact, where adhesion may persist even in the presence of the lubricant and thereby modify both the real contact area and the sliding response. Dry-friction measurements, combined with contact-area calculations that include adhesion, provide a baseline for the lubricated study. For the two sandblasted surfaces, the measured Stribeck curves are described reasonably well by a mean-field mixed-lubrication theory with a fitted velocity-independent effective interfacial shear stress. In contrast, the smooth surface exhibits qualitatively different behavior. We attribute this to an adhesion-controlled sliding mode involving macroscopic Schallamach-wave-like instabilities at low sliding speeds, which are progressively suppressed as the sliding speed increases and forced wetting reduces direct solid-solid contact. The results show that, for soft hydrophobic contacts, the Stribeck curve cannot always be understood from classical fluid flow and load sharing alone. For sufficiently smooth and adhesive surfaces, adhesion changes not only the real contact area but also the sliding mode itself.
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All authors Ruibin Xu, Charlotte Spies, Michele Scaraggi, B.N.J. Persson
Strongly Correlated Electrons · Cross-listed from quant-ph
Interplay of Nonstabilizerness and Ergotropy in Quantum Batteries
Tanoy Kanti Konar and Jakub Zakrzewski
Nonstabilizerness plays an essential role in the efficient simulation of
quantum systems on
quantum computers. In this work, we investigate its role in the context of
quantum batteries (QBs). To this end, we consider a system of N
spin-1/2 particles, with the left half serving as the charger and the right half as the battery. By studying different classes of interactions between the charger and the battery, we quantify the amount of nonstabilizerness required to store work in the QB. Our results reveal a strong correlation between the ergotropy stored in the battery and the total nonstabilizerness of the composite system whenever the
Hamiltonian preserves a U(1)
symmetry. In contrast, this correspondence is generally lost for more generic interactions. A similar behavior is observed for
unitary circuit dynamics. Finally, we examine the complementary scenario in which the battery is initialized in a nonstabilizer state and subsequently charged through Clifford
evolution. In this case, we find that the maximum average charging power is nonmonotonic in the initial nonstabilizerness. Remarkably, the highest average power can be achieved even when the initial state carries no magic (nonstabilizerness), demonstrating that initial magic is not a necessary ingredient for generating optimal charging power.
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Materials Science
Pressure induced Electronic and Structural Transition in Ba$_2$NiTeO$_6$
Bidisha Mukherjee, Supratik Mukherjee, Mrinmay Sahu et al. (+5 more)
This study explores the pressure
evolution of the double perovskite Ba$_2$NiTeO$_6$ by employing experimental and computational techniques. For the study of structural and vibrational properties, synchrotron X-ray diffraction (XRD) and micro-Raman spectroscopic experiments at high-pressures were carried out. As a complementary study, DFT simulations of the structural properties as a function of pressure were performed to support and explain the experimental findings. Furthermore, the electronic and
magnetic properties as a function of pressure were investigated using DFT. Our study reveals a structural phase transition from a rhombohedral $R\bar{3}m$ to a monoclinic $C2/m$ phase at high pressure, accompanied by a significant increase in bulk modulus. Certain anomalies were observed in Raman mode frequencies at lower pressures of about 1 GPa, indicating changes in the electronic structure with a modification from direct to indirect bandgap in the sample. A minimum in the Raman mode full-width-half-maximum (FWHM) at about 11 GPa, coincides with an increase in ordering in the sample, indicated by a drop in the distortion index of Ni-O$_6$ octahedra as well as a discontinuity in the $c/a$ ratio.
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All authors Bidisha Mukherjee, Supratik Mukherjee, Mrinmay Sahu, Bhagyashri Giri, A C Gracia Castro, G Vaitheeswaran, Konstantin Glazyrin, Goutam Dev Mukherjee
Strongly Correlated Electrons
Renormalization group analysis for bosonization coefficients in half-odd-integer Kitaev spin chains
Jianxun Li, Chao Xu and Wang Yang
Based on a renormalization-group (RG) analysis, we study the bosonization formulas for
spin-$S$ Kitaev-Gamma and Kitaev-Heisenberg-Gamma chains in the parameter regime $K<0$, $\Gamma>0$, and $J>0$, with $S$ being a half-odd integer. We find that the effects associated with the breaking of emergent continuous
symmetries in the bosonization formulas scale as $1/S$ in the large-$S$ limit, in qualitative agreement with density-
matrix renormalization-group (DMRG) results for Kitaev-Gamma chains. For Kitaev-Heisenberg-Gamma chains, the low-energy excitations are characterized by incommensurate gapless wave vectors, and
symmetry analysis yields ten independent bosonization coefficients, five of which are predicted by the RG analysis to be independent of the Heisenberg coupling up to linear order. Our results provide useful input for determining
magnetic ordering tendencies in two-dimensional Kitaev
spin models within a quasi-one-dimensional approach.
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Statistical Mechanics · Cross-listed from q-bio.QM
Expanding functional protein sequence space using high entropy generative models
Roberto Netti, Emily Hinds, Francesco Calvanese et al. (+3 more)
Boltzmann Machines trained on evolutionary sequence data have emerged as a powerful paradigm for the data-driven design of artificial
proteins. However, the relationship between model architecture, specifically parameter density, and experimental performance remains poorly understood. Here, we investigate this relationship using the Chorismate Mutase enzyme family as a model system. We compare standard fully connected Boltzmann Machines for Direct Coupling Analysis (bmDCA) with sparse models generated via progressive edge activation (eaDCA) and edge decimation (edDCA). We identify a maximum-
entropy model (meDCA) along the decimation trajectory that represents an optimal balance between constraint satisfaction and the flexibility of the probability distribution. We synthesized and tested artificial sequences from all models using an in vivo complementation assay, finding that all architectures, regardless of sparsity, generate functional enzymes with high success rates, even at significant divergence from natural sequences. Despite this functional equivalence, we demonstrate that the meDCA model samples a viable sequence space that is more than fifteen orders of magnitude larger than its low-
entropy counterparts. Furthermore, comparative analyses reveal that high-
entropy models systematically minimize overfitting and better capture the local neutral spaces surrounding natural
proteins. These findings suggest that while various models satisfying coevolutionary statistics can generate functional sequences, high-
entropy Boltzmann Machines provide a superior representation of the underlying evolutionary fitness landscape.
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All authors Roberto Netti, Emily Hinds, Francesco Calvanese, Rama Ranganathan, Martin Weigt, Francesco Zamponi
Statistical Mechanics
Kévin Bilaï Biloa and Olivier Pierre-Louis
Navigation in complex and noisy environments is a key issue in diverse fields from biology to engineering. Despite extensive progress in numerical optimization methods for computing
navigation policies, insights into how disorder reshapes optimal
navigation remain elusive. To address this question, we investigate the
navigation of a Brownian particle in a disordered energy landscape, modeled as a
lattice with randomly distributed traps. Using dynamic programming, we compute the optimal
navigation policies that minimize the mean first-passage time to a target site. To quantify the impact of disorder, we introduce a density of change from a Kullback-Leibler divergence, which captures how the optimal policy is reshaped by either the presence of disorder or the knowledge of its configuration. Our results reveal a non-monotonic dependence of the change of the policy on trap concentration, with a pronounced maximum. In the fluctuation-dominated regime where the
navigation bias is weak, we derive an analytical expression for the density of change, and demonstrate that the maximum occurs unexpectedly at low trap concentrations.
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Materials Science
Gauge-Field-Mediated Symmetry Breaking of Matters Under Electromagnetic Fields and Its Impact on Spin Dynamics
Uiseok Jeong, Esmaeil Taghizadeh Sisakht, Angel Rubio et al. (+3 more)
When a condensed-matter system is subjected to external electromagnetic fields, the gauge-invariant formulation of physical operators must explicitly incorporate the gauge-field contribution. However, in the context of
spin-orbit coupling (SOC), this gauge-field term is often regarded as negligible or merely additive compared to the canonical SOC, which is typically localized near atomic cores. Here, we demonstrate that the
symmetry breaking and consequent
spin dynamics are governed by the gauge-field term, without which the
spins remain
symmetry-constrained. We perform real-time time-dependent density functional theory calculations to investigate
spin-orbit dynamics, focusing on representative cases with mirror, glide, and screw-rotational
symmetry. We demonstrate that when the gauge-field term in the time-dependent
Hamiltonian perturbs the
symmetry of the canonical term, a dynamical
spin state gradually develops during the time
evolution, beyond the
symmetry-frozen states. We suggest that, for nonequilibrium
spin-orbit dynamics, the gauge-invariant formulation of SOC is not only formally required but also quantitatively essential, even for a weak external field.
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All authors Uiseok Jeong, Esmaeil Taghizadeh Sisakht, Angel Rubio, Carsten A. Ullrich, Kyoung-Whan Kim, Noejung Park
Mesoscale and Nanoscale Physics
Theory of transmittance of narrow quantum wires intersection in 2D systems
L. S. Braginsky and M. V. Entin
Two-dimensional nanosystems the characteristic sizes of which are less than the quasiparticle wavelength have been studied. This parameter allows replacement of the Shrödinger equation by the Laplace one. The latter permits us exact solution using the conformal mapping technique. Bulged 1D
quantum wires based on 2D system are considered. The electron states in these systems have been studied. The transmittance of the intersection between the narrow
quantum strips has been studied. It is assumed that strip widths are less than the electron wavelength, so that they are the tunnel conductors. The transmittances of T-like and X-like wire crossings have been found.
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Materials Science
Adjacent Sink Strengths Used in Multiscale Kinetic Rate Equation Simulations of Defects and Impurities in Solids
Tommy Ahlgren
Kinetic Rate Equation (kRE) modeling is widely used to simulate defect and
impurity evolution in solids over experimentally relevant time and length scales. However, conventional kRE formulations include only random-position sink strengths, which adequately describe trapping of defects created at random
lattice sites but fail to capture the enhanced retrapping of defects released directly adjacent to traps during detrapping or dissociation events. This omission leads to systematic errors, including underestimated thermal desorption (TDS) peak temperatures and incorrect kinetic parameters when fitting to experimental data. In this work, we derive for the first time analytical expressions for the adjacent sink strength, including correction for finite
impurity diffusion jump length. We provide a practical implementation strategy for integrating these expressions into kRE simulations. Comparisons with kinetic Monte Carlo (kMC)
benchmarks demonstrate that adjacent sink strengths dominate the retrapping probability and are essential for reproducing the correct temperature dependence of TDS release peaks. Simulations that employ only random sink strengths can still be tuned to match TDS spectra; however, the resulting fitted trapping energies, detrapping frequencies, and
diffusion parameters are often physically inconsistent. The adjacent sink strength formulation introduced here significantly improves the predictive capability of kRE modeling, enabling accurate multiscale simulations of defect and
impurity behavior in materials. This framework also establishes a foundation for future extensions, including adjacent sink strengths associated with extended defects such as dislocations and grain boundaries, offering new opportunities to resolve persistent discrepancies between experimental and simulated trapping energetics.
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Strongly Correlated Electrons
Influence of ligand field and correlation on the electronic structure of NiO and CoO from DFT+DMFT calculations
Daniel Mutter, Frank Lechermann, Daniel F. Urban et al. (+1 more)
The intriguing physics and rich application potential of strongly correlated first-row transition metal
oxide compounds result from the complex interplay of several factors that influence the electronic structure. To shed light on the effect of composition, structure, and correlation strength, we apply a well-established charge self-consistent combination of density functional theory and dynamical mean field theory, which has proven to give electron binding energies in good agreement to experimentally derived excitation spectra. For paramagnetic NiO and CoO, we analyze the effect of rock-salt and zincblende structures and their different ligand fields on the spectral functions. By varying the value of the interaction parameter U, different correlation strengths among the transition-metal 3d electrons are considered, as well as the effect of additionally accounting for correlations in the oxygen 2p orbitals by a self-interaction-correction pseudopotential scheme. It is shown that this combined DFT+sicDMFT approach leads to spectral functions and band gaps close to experimental data, thereby offering a time-efficient alternative to using a fully correlated model which would treat both, metal and oxygen ligand electrons within DFT+DMFT.
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All authors Daniel Mutter, Frank Lechermann, Daniel F. Urban, Christian Elsässer
Materials Science
Scale-Dependent Input Representation and Confidence Estimation for LLMs in Materials Property Prediction
Shuichiro Ozawa, Izumi Takahara and Teruyasu Mizoguchi
Large
language models (LLMs) are increasingly applied to materials science. However, the relationship between prediction accuracy, input representation, and model scale remains unclear, and reliable methods for assessing prediction confidence have not yet been established. In this study, we fine-tune two Llama models of different scales (1B and 8B) using low-rank adaptation (LoRA) on an inorganic
crystal structure
dataset. We systematically evaluate five input representations, namely chemical composition,
crystal summary, local environment description, full text description, and crystallographic information files (CIF), for formation energy and bandgap prediction. Our results show that the optimal input representation depends on model scale. The 1B model performs better with compact representations, whereas the 8B model maintains high accuracy even with longer natural-
language descriptions and CIF inputs. Across both model scales,
crystal summaries that include space-group information consistently outperform composition-only inputs, indicating that
symmetry information serves as a robust and informative feature. We further analyze the relationship between prediction error and the mean negative log-likelihood (mean NLL) of
tokens corresponding to predicted numerical values. While no clear correlation is observed in base models, fine-tuned models exhibit a consistent trend in which lower mean NLL corresponds to smaller prediction errors. This result suggests that mean NLL can serve as a practical confidence indicator without requiring additional training. These findings demonstrate that both input representation and model scale play critical roles in LLM-based materials property prediction, and that mean NLL provides an effective and computationally efficient measure of prediction confidence.
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Mesoscale and Nanoscale Physics
First-principles prediction of chiral-phonon-induced orbital accumulation
A. Pezo, A. Manchon, Y. Nii et al. (+2 more)
Chiral phonons offer a route to transfer angular momentum without relying on
magnetic order, but their electronic response in metals remains poorly understood from perspectives beyond
spin-based scenarios. Using first-principles calculations, we show that coherent
chiral lattice motion generates orbital accumulation and, through
spin-orbit coupling, a smaller accompanying
spin accumulation. Our approach evaluates orbital and
spin expectation values directly from strain perturbed ab initio
Hamiltonians in the long-wavelength limit, where the
phonon perturbation is represented by
symmetry adapted circular
lattice distortions. We show that the response is controlled mainly by orbital character, near-degeneracies, and electron-
phonon coupling, rather than by
spin-orbit coupling alone. These results identify light transition metals as promising platforms for
chiral-
phonon-driven orbitronics.
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All authors A. Pezo, A. Manchon, Y. Nii, K. Ando, T. Kato
Materials Science
Influence of twist angle on ultrafast charge separation in WS2-graphene heterostructures
Niklas Hofmann, Leonard Weigl, Johannes Gradl et al. (+4 more)
Van der Waals (vdW)
heterostructures, formed by stacking two-dimensional materials, offer highly tunable electronic and optical properties, with the twist angle between layers acting as a critical tuning parameter. While its impact on moiré patterns, band structure, and correlated states is well-established, the influence of twist angle on ultrafast charge transfer remains controversial. Here, we employ time- and angle-resolved photoemission spectroscopy (trARPES) to directly probe ultrafast charge transfer in epitaxially grown WS\textsubscript{2}-
graphene heterostructures with twist angles of 0$^{\circ}$ and 30$^{\circ}$. Upon photoexcitation at $\hbar\omega = 3.1\,\mathrm{eV}$, we observe efficient charge separation at 0$^{\circ}$, while at 30$^{\circ}$, electron and hole transfer occur at similar rates. Our results highlight the crucial role of the twist angle in controlling charge separation efficiency, offering valuable insights for designing vdW
heterostructures for applications in photovoltaics and optoelectronics.
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All authors Niklas Hofmann, Leonard Weigl, Johannes Gradl, Stiven Forti, Domenica Convertino, Camilla Coletti, Isabella Gierz
Mesoscale and Nanoscale Physics
Cubic edge dispersion in a semi-Dirac Chern insulator
Marta García Olmos, David Martín Tejedor, Mario Amado et al. (+2 more)
Topological edge states in Chern
insulators are typically characterized by a linear dispersion relation inherited from the Dirac structure of the bulk
Hamiltonian. Here we show that this paradigm can be fundamentally altered in systems with anisotropic semi-Dirac band structures. We introduce a minimal two-band
lattice model realizing a semi-Dirac Chern
insulator and determine its topological phase diagram analytically. Using a mass-domain-wall approach in a semi-infinite geometry, we derive an explicit expression for the
chiral edge states and find that their low-energy dispersion scales cubically with momentum, $E(k)\propto k^3$. Numerical diagonalization of the corresponding tight-binding ribbon confirms the analytical prediction. Our results demonstrate that unconventional bulk band structures can produce qualitatively different boundary excitations, providing a route to engineering nonstandard
chiral edge dynamics in topological materials and synthetic
quantum systems.
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All authors Marta García Olmos, David Martín Tejedor, Mario Amado, Yuriko Baba, Rafael A. Molina
Materials Science
Energy dissipation at the atomic scale explains how fracture energy depends on crack velocity in silica glass
Marthe Grønlie Guren, Sigbjørn Løland Bore, François Renard et al. (+1 more)
The fracture energy of brittle materials rises with crack velocity, and this effect is typically attributed to surface roughening from path instabilities. Here we show, using molecular dynamics simulations of silica glass with a first-principles machine learned interatomic potential, that the structural fracture energy rises by up to 33 % already below the branching threshold, showing that fracture energy is not a constant material property. This rise in fracture energy is roughly equally partitioned between an increase in the intrinsic surface energy density and nanoscale roughening that increases the real fracture surface area. Results demonstrate that dynamic fracture in silica glass increases the fracture energy not merely by creating more apparent surface, but also by creating a fundamentally different surface at the nanoscale.
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All authors Marthe Grønlie Guren, Sigbjørn Løland Bore, François Renard, Henrik Andersen Sveinsson
Soft Condensed Matter
Dynamic properties in a collisional model of a confined quasi-two-dimensional granular fluid driven by a stochastic bath with friction
David González Méndez, Rubén Gómez González and Vicente Garzó
This paper investigates the dynamic properties of a confined quasi-two-dimensional granular fluid at moderate densities, modeled within the framework of the Enskog kinetic equation. The confinement is not treated explicitly at the geometrical level; instead, it is incorporated in an effective way through the so-called $\Delta$-model (a collisional model that includes energy injection through modified collision rules). The referred model is extended in this paper to account for the influence of an interstitial gas via a viscous drag force and a
stochastic Langevin-like term. By applying the Chapman–Enskog method, the Navier–Stokes transport coefficients and the cooling rate are derived analytically considering the leading terms in a Sonine
polynomial expansion. The study focuses on steady-state conditions and examines how the combined effects of inelastic collisions and external driving influence transport properties such as the viscosity and the thermal conductivity. Theoretical predictions for the steady temperature and the kurtosis are validated against direct simulation Monte Carlo (DSMC) results, showing excellent agreement. The findings reveal that the external driving significantly alters the transport coefficients compared to dry (no gas phase) granular systems, challenging previous assumptions that neglected these effects. Additionally, a linear stability analysis demonstrates that the homogeneous steady state is stable across the explored parameter space.
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Strongly Correlated Electrons
Single-stripe magnetic order and bilayer spin dynamics in single-crystalline La3Ni2O7
Lixing Chen, Enkang Zhang, Yiqing Hao et al. (+10 more)
High-temperature superconductivity in pressurized and thin-film nickelates has generated intense interest, yet magnetism in their ambient-pressure parent phases remains poorly understood, despite its potentially crucial role in pairing. Progress has been limited by the lack of large single
crystals suitable for
neutron spectroscopy. Here we overcome this limitation and map the
spin order and excitations of single-crystalline La3Ni2O7. We find single-stripe
magnetic order with a finite
spin gap, anisotropic in-plane excitations and pronounced
bilayer modulation revealing
antiferromagnetic interlayer coupling. The dispersion is captured by a
bilayer Heisenberg-type model with strong interlayer exchange and competing in-plane couplings. Absolute normalization reveals that, although the
spin-wave bandwidth is only about 25% of that in cuprates, the local dynamic susceptibility at comparable energies is enhanced, yielding a comparable total fluctuating moment. These results highlight intense mid-energy
spin excitations rooted in substantial electronic correlations, establishing a
magnetic framework distinct from cuprates and relevant to superconductivity in nickelates.
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All authors Lixing Chen, Enkang Zhang, Yiqing Hao, Yinghao Zhu, Bingkun Cui, Douglas L. Abernathy, Travis J. Williams, Yoichi Ikeda, Hao Zhang, Feiyang Liu, Wenbin Wang, Qisi Wang, Jun Zhao
Materials Science
Coupled phase transitions in crystalline solids with extreme chemical disorder
Subha Dey, Rukma Nevgi, Suresh Chandra Joshi et al. (+13 more)
Structural phase transitions often couple to
magnetic and electronic degrees of freedom, enabling emergent phenomena in solids. In high-
entropy oxides (HEOs), which typically stabilize in highly symmetric cubic phases, such transitions are considered rare due to the extreme chemical disorder-analogous to the behavior observed in high-
entropy alloys. This raises a fundamental question: can the rich physics of coupled phase transitions persist in such disordered systems? Here, we show that targeted design of compositionally complex
oxides (CCOs) can trigger
symmetry-lowering transitions, with spinel-type materials serving as a representative case. For instance, [Mn$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$Zn$_{0.2}$]Cr$_2$O$_4$, having two Jahn-Teller (J-T) active ions, undergoes two successive coupled structural transitions upon cooling: an orbital-driven transition at 100 K and a magnetism-driven transition at 40 K. Systematic substitution of $A$-site cations reveals that both Ni and Cu are essential for these transitions. Element specific local structure investigations uncover distinct and opposing local distortions around Ni and Cu, while Mn, Co, and Zn remain largely undistorted. These results establish that CCOs can host coupled phase transitions through `cooperation via competition' among local distortions in a chemically disordered
lattice. This discovery expands the design principles for complex
oxides, introducing a new paradigm for tuning structural and functional properties in high-
entropy systems beyond conventional
symmetry constraints.
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All authors Subha Dey, Rukma Nevgi, Suresh Chandra Joshi, Sourav Chowdhury, Nandana Bhattacharya, Kashish Kapoor, Tinku Dan, Subhadip Chowdhury, Sabyasachi Karmakar, S. D. Kaushik, Shibabrata Nandi, Christoph Klewe, Manuel Valvidares, Moritz Hoesch, George E. Sterbinsky, Srimanta Middey
Soft Condensed Matter
Sparkling bubbles in chiral active fluids
Alessandro Petrini, Raphaël Maire, Umberto Marini Bettolo Marconi et al. (+1 more)
We study an inertial
chiral active fluid, formed by repulsive particles that transfer angular momentum through odd interactions, i.e. transverse forces. Chirality induces an inhomogeneous phase, consisting of rotating bubbles, whose formation is favored at an optimal packing fraction. In this regime, we discover that bubbles may be dynamically unstable, breaking up and reforming in the steady state, thereby showing a spontaneous sparkling-like behavior reminiscent of supersaturated
liquids. Bubbles and sparkling bubbles are predicted by a coarse-grained hydrodynamic theory, revealing the intrinsic non-linearity of these collective phenomena, and call for experimental verifications in granular spinners or spinning colloids.
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All authors Alessandro Petrini, Raphaël Maire, Umberto Marini Bettolo Marconi, Lorenzo Caprini