Mesoscale and Nanoscale Physics · Cross-listed from physics.acc-ph
Discrete Electron Emission
Arnar Jonsson, Kristinn Torfason, Andrei Manolescu et al. (+1 more)
Analysis of space-charge effects on electron emission typically makes some assumption of continuity and smoothness, whether this is continuity of charge as in the classical derivation of the Child-Langmuir current, or the mean-field approximation used in particle-in-
cell simulations. However, when studying the physics of electron emission and propagation at the mesoscale it becomes necessary to consider the discrete nature of electronic charge to account for the space-charge effect of each individual point charge. In this paper we give an extensive analysis of some previous work on the distribution of electrons under space-charge limited conditions. We examine the spacing of electrons as they are emitted from a planar surface, We present simplified models for analysis of such conditions to derive scaling laws for emission and compare them to computer simulations.
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All authors Arnar Jonsson, Kristinn Torfason, Andrei Manolescu, Agust Valfells
Mesoscale and Nanoscale Physics
Nonlocal and nonlinear plasmonics in atomically thin heterostructures
Line Jelver and Joel D. Cox
Plasmons in atomically thin materials offer a compelling route to trigger nonlinear light-matter interactions through extreme optical confinement in the two-dimensional (2D) limit. However, optical nonlocality in plasmons is typically associated with losses in the linear response regime. Here, we show that nonlocal effects mediate strong plasmon-assisted optical nonlinearity in electrically reconfigurable 2D
heterostructures. Using atomistic simulations that capture
quantum finite-size and nonlocal effects in the nonlinear plasmonic response of
graphene and phosphorene nanoribbon dimers, we reveal how
symmetry and inter-ribbon coupling shape harmonic generation processes in perturbative and high-harmonic regimes. Independent tuning of geometry and carrier density in nanoribbon
heterostructures is shown to induce inter-ribbon plasmon hybridization, impacting inversion
symmetry governing even-ordered nonlinear processes like second-harmonic generation. These results reveal design principles for active and passive tuning of nonlinear plasmonic effects and enable selective enhancement of specific harmonic processes, establishing 2D
heterostructures as a versatile platform for nonlinear nanophotonics.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Full Quantum Work Statistics for Non-Homogeneous Many-Body Systems
Antonio Palamara, Francesco Plastina, Antonello Sindona et al. (+1 more)
The nonequilibrium thermodynamics of interacting
quantum many-body systems is investigated within the framework of thermal time-dependent density functional theory using a generalized linear-response formulation for the full
quantum work statistics. A first-principles route is established to reconstruct the relaxation function that underlies linear-response theory, thereby moving beyond phenomenological descriptions and enabling a consistent evaluation of all moments of the dissipated-work distribution in interacting systems. The predictive power of the approach is demonstrated for the Hubbard model subject to a staggered external potential, where the
evolution of the relaxation dynamics during the Mott-to-band-
insulator crossover reveals how distinct many-body phases shape the out-of-
equilibrium thermodynamic response. These results provide a microscopic and transferable framework for
quantum thermodynamics in correlated systems, bridging thermal density functional theory and nonequilibrium work statistics.
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All authors Antonio Palamara, Francesco Plastina, Antonello Sindona, Irene D'Amico
Materials Science
On the origin of energy gaps in quasicrystalline potentials
Emmanuel Gottlob, David Gröters and Ulrich Schneider
Quasicrystals, structures that are ordered yet aperiodic, defy conventional band theory, confining most studies to finite-size real-space numerics. We overcome this limitation with a configuration-space framework that predicts and explains the positions and origins of energy gaps in quasicrystalline potentials. We find that a hierarchy of gaps stems from resonant hybridization between increasingly distant neighboring sites, pinning the integrated density of states below these gaps to specific irrational areas in configuration space. Large-scale simulations of a lowest-band tight-binding model built from localized Wannier functions show excellent agreement with these predictions. By moving beyond finite-size numerics, this study advances the understanding of quasicrystalline potentials, paving the way for new explorations of their
quantum properties in the infinite-size limit.
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Soft Condensed Matter
Machine-Learned Many-Body Potentials for Charged Colloids reveal Gas-Liquid Spinodal Instabilities only in the strong-coupling regime of Primitive Models
Thijs ter Rele, René van Roij and Marjolein Dijkstra
Past experimental observations of gas-
liquid and gas-
crystal coexistence in low-salinity suspensions of highly charged colloids have suggested the existence of like-charge attraction. Evidence for this phenomenon was also observed in primitive-model simulations of (asymmetric) electrolytes and of low-charge nanoparticle dispersions. These results from low-valency simulations have often been extrapolated to experimental parameter regimes of high colloid valency where like-charge attraction between colloids has been reported. However, direct simulations of highly charged colloids remain computationally demanding. To circumvent slow equilibration, we employ a machine-learning (ML) framework to construct ML potentials that accurately describe the effective colloid interactions. Our ML potentials enable fast simulations of dispersions and successfully reproduce the gas-
liquid and gas-solid phase separation observed in primitive-model simulations at low charge numbers. Extending the ML-based simulations to higher valencies, where primitive-model simulations become prohibitively slow, also reveals like-charge attractions and gas-
liquid spinodal instabilities, however only in the regime of strongly coupled electrostatic interactions and not in the weakly coupled Poisson-Boltzmann regime of the experimental observations of colloidal like-charge attractions.
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Materials Science
Anomalous Hysteresis Behavior in Sputter-deposited Ultrathin Films of Amorphous- CoFeB Alloy
Baisali Ghadai, Kirti Kirti, Abinash Mishra et al. (+1 more)
Thin amorphous-CoFeB (a-CFB) is deposited by rf-magnetron sputtering on a self-oxidized Si (100) substrate with different film thicknesses ranging from 0.7 nm to 20 nm. The 5-nm-thick a-CFB film is capped with a W layer for comparison. The surface morphology is investigated by using the atomic force microscopy technique. The low roughness of all the surface of the film indicates uniformity, moderate corrosion resistance, and good structural quality. The X-ray diffraction spectra reveal the amorphous nature of the CFB layer, while the W capping is of mixed phase in the experimental thickness regime. In-plane and out-of-plane hysteresis loops obtained from the vibrating sample magnetometry technique show a transition from an upright S to nearly rectangular shape via a completely inverted profile. A self-sustained tilted
magnetic anisotropy is stabilized in a seed-free environment based on the direct substrate-to-magnet interaction. The interface anisotropy is estimated to be 0.06 erg/cm2. The complex anisotropic behavior originates from the interplay between interface anisotropy, conventional shape anisotropy, growth-induced anisotropies, and inhomogeneity-induced anisotropies. In essence, effective anisotropy is responsible for the anomalous hysteresis behavior observed in these films, and this work might provide valuable insights to improve the functionalities of amorphous soft
magnetic alloys.
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All authors Baisali Ghadai, Kirti Kirti, Abinash Mishra, Sucheta Mondal
Statistical Mechanics · Cross-listed from math-ph
From entropic constraints to reinforced processes: a probabilistic origin of multiscale measures
Francesco Camilli, Pierluigi Contucci and Emanuele Mingione
We study multiscale measures, defined by a hierarchy of partial Gibbs
equilibria, from variational and probabilistic perspectives. We first show that they are the unique solutions of a generalized maximum-
entropy principle in which conditional
entropies at different levels carry different weights. We then construct a hierarchical reinforced multinomial process proving a large-deviation principle for its empirical measure. The
stochastic process leaves the typical empirical distribution unchanged but modifies the exponential cost of its fluctuations. The resulting rate function is a weighted sum of conditional Kullback-Leibler divergences, establishing a direct link with the entropic principle above. The relation between the reinforcement and Poisson-Dirichlet processes is discussed.
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Materials Science · Cross-listed from math.DG
The chiral gyrating H'-T surface family: construction from the dual qtz–qzd nets and existence proof using a toroidal Weierstrass method
Hao Chen, Shashank G. Markande, Matthias Saba et al. (+2 more)
This paper provides a construction and existence proof for a 1-parameter family of
chiral unbalanced triply-periodic minimal surfaces of genus 4. We name these {gyrating H'-T surfaces, because they are related to Schoen's H'-T surfaces in a similar way as the Gyroid is to the Primitive surface. Their chirality is manifest in a screw
symmetry of order six. The two labyrinthine domains on either side of the surface are not congruent, rather one representing the quartz net (qtz) and the other one the dual of the quartz net (qzd). The family tends to the Scherk saddle tower in one limit and to the doubly periodic Scherk surface in the other. The motivation for the construction was to construct a
chiral tunable unbalanced surface family, originally as a template for photonic materials. The numeric construction is based on reverse-engineering of the tubular surface of two suitably chosen dual nets, using the Surface Evolver} to minimize area or
curvature variations. The existence is proved using Weierstrass parametrizations defined on the branched
torus.
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All authors Hao Chen, Shashank G. Markande, Matthias Saba, Gerd E. Schröder-Turk, Elisabetta A. Matsumoto
Statistical Mechanics
Entropy of full covering of the kagome lattice by straight trimers
Deepak Dhar, Tiago J. Oliveira, R. Rajesh et al. (+1 more)
We consider the number of ways all the sites of a kagome
lattice can be covered by non-overlapping linear rigid rods where each rod covers 3 sites. We establish a 2-to-1 correspondence between the configurations of trimers on the kagome
lattice to the covering by dimers of a related hexagonal
lattice to show that
entropy of coverings per trimer $s_{\text{tri,kag}}$ equals the
entropy per dimer $ s_{\text{dim,hex}} $, and is given by $ s_{\text{tri,kag}} = s_{\text{dim,hex}} = \frac{1}{2 \pi} \int_0^{ 2 \pi/3} \log( 2 + 2 \cos k) dk \approx 0.323065947\ldots$.
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All authors Deepak Dhar, Tiago J. Oliveira, R. Rajesh, Jürgen F. Stilck
Materials Science · Cross-listed from physics.optics
Controlling Ultrafast Excitations in Germanium:The Role of Pump-Pulse Parameters and Multi-Photon Resonances
Amir Eskandari-asl and Adolfo Avella
We employ the Dynamical Projective Operatorial Approach (DPOA) to investigate the ultrafast optical excitations of germanium under intense, ultrashort pump pulses. The method has very low resource demand relative to many other available approaches and enables detailed calculation of the residual electron and hole populations induced by the pump pulse. It provides direct access to the energy distribution of excited carriers and to the total energy transferred to the system. By decomposing the response into contributions from different multi-
photon resonant processes, we systematically study the dependence of excited-carrier density and absorbed energy on key pump-pulse parameters: duration, amplitude, and
photon energy. Our results reveal a complex interplay between these parameters, governed by resonant Rabi-like dynamics and competition between different multi-
photon absorption channels. For the studied germanium setup, we find that two-
photon processes are generally dominant, while one- and three-
photon channels become significant under specific conditions of pump-pulse frequency, duration, and intensity. This comprehensive analysis offers practical insights for optimizing ultrafast optical control in
semiconductors by targeting specific multi-
photon pathways.
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Mesoscale and Nanoscale Physics
Solution of Wave Acceleration and Non-Hermitian Jump in Nonreciprocal Lattices
Sayan Jana, Bertin Many Manda, Vassos Achilleos et al. (+2 more)
The time
evolution of initially localized wavepackets in the discrete Hatano-Nelson
lattice displays a rich dynamical structure shaped by the interplay between dispersion and nonreciprocity. Our analysis reveals a characteristic
evolution of the wave-packet center of mass, which undergoes an initial acceleration, subsequently slows down, and ultimately enters a regime of uniform motion, accompanied throughout by exponential amplification of the wave-packet amplitude. To capture this behavior, we develop a continuum approximation that incorporates higher-order dispersive and nonreciprocal effects and provides accurate analytical predictions across all relevant time scales. Building on this framework, we then demonstrate the existence of a non-Hermiticity-induced jump - an abrupt spatial shift of the wave-packet center even in the absence of disorder - and derive its underlying analytical foundation. The analytical predictions are in excellent agreement with direct numerical simulations of the Hatano-Nelson chain. Our results elucidate the interplay between dispersion and nonreciprocity in generating unconventional transport phenomena, and pave the way for controlling wave dynamics in nonreciprocal and non-Hermitian metamaterials.
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All authors Sayan Jana, Bertin Many Manda, Vassos Achilleos, Dimitrios J. Frantzeskakis, Lea Sirota
Statistical Mechanics
Current reversals in driven lattice gases and Brownian motion
Moritz Wolf, Sören Schweers and Philipp Maass
Particle currents flowing against an external driving are a fascinating phenomenon in both single-particle and interacting many-particle systems. Underlying physical mechanisms of such current reversals are not fully understood yet. Predicting their appearance is difficult, in particular for interaction-induced ones that emerge upon changes of the particle density. We here derive conditions on external time-dependent drivings, under which current reversals occur in
lattice gases with arbitrary pair interactions. Our derivation is based on particle-hole
symmetry and shows that current reversals must emerge if the time-varying driving potential changes sign after a translation in time and/or space. Our treatment includes nonstationary dynamics and time-dependent spatially averaged currents in nonequilibrium steady states. It gives insight also into possible occurrences of current reversals in continuous-space dynamics, which we demonstrate for hardcore interacting particles driven across a periodic potential by a traveling wave.
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Soft Condensed Matter · Cross-listed from math.NA
Hybrid multiscale method for polymer melts: analysis and simulations
Ranajay Datta, Mária Lukáčová-Medviďová, Andreas Schömer et al. (+1 more)
We model the flow behaviour of dense melts of flexible and semiflexible ring
polymers in the presence of walls using a hybrid multiscale approach. Specifically, we perform molecular dynamics simulations and apply the Irving-Kirkwood formula to determine an averaged stress tensor for a macroscopic model. For the latter, we choose a Cahn-Hilliard-Navier-Stokes system with dynamic and no-slip boundary conditions. We present numerical simulations of the macroscopic flow that are based on a finite element method. In particular, we present detailed proofs of the solvability and the energy stability of our numerical scheme. Phase segregation under flow between flexible and semiflexible rings, as observed in the microscopic simulations, can be replicated in the macroscopic model by introducing effective attractive forces.
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All authors Ranajay Datta, Mária Lukáčová-Medviďová, Andreas Schömer, Peter Virnau
Materials Science
First-principles study of magnetic and spin-dependent transport properties of Mn2VZ (Z = Al, Ga) with negative spin polarization using a disordered local moment approach at finite temperatures
Shogo Yamashita, Esita Pandey, Gerhard H. Fecher et al. (+2 more)
First-principles studies were performed on two Mn-based ferrimagnetic Heusler compounds with L21 and B2 structures, that is, Mn2VZ (Z = Al or Ga). The aim was to investigate their
magnetic properties, electronic structures, and
spin-resolved longitudinal conductivity at finite temperatures. Density functional theory (DFT) and functional integral theory were used. This approach incorporates transverse
spin fluctuations through a disordered local moment method and the coherent potential approximation. In all cases, the calculated theoretical Curie temperatures were lower than the experimental values.
Alloys with a B2 structures exhibit higher Curie temperatures compared to compounds with an L21 structures. Calculations of the temperature dependence of the density of states (DOS) indicate that the half-metallic electronic structure collapses owing to the renormalization of transverse
spin fluctuations at a finite temperatures. However, the
spin-resolved longitudinal conductivities demonstrated an improved
spin polarization, particularly for Mn2VGa with an L21 structure. This result contradicts predictions based on the temperature-dependent DOS. The competition between the metallic transitions, which are caused by a modification of the DOS, and scattering coming from
spin-disorder explains this phenomenon. Both of these effects are induced by transverse
spin fluctuations. Additionally, the results show that half-
metallicity, as defined by the DOS or conductivity, is inconsistent at finite temperatures. Finally, the total energy landscape of the paramagnetic state was calculated using the fixed
spin moment method to investigate the strength of the longitudinal
spin fluctuations. These results suggest that the
alloys may exhibit strong longitudinal
spin fluctuations.
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All authors Shogo Yamashita, Esita Pandey, Gerhard H. Fecher, Claudia Felser, Atsufumi Hirohata
Materials Science
Parameter-free prediction of irradiation defect structures in tungsten at room temperature using stochastic cluster dynamics
Sicong He, Brandon Schwendeman, George Tynan et al. (+1 more)
The foundations of irradiation damage theory were laid in the 1950s and 60s within the framework of chemical reaction kinetics. While helpful to analyze qualitative aspects of irradiation damage, the theory contained gaps that delayed its implementation and applicability as a predictive tool. The advent of computer simulations with atomistic resolution in the 80s and 90s revealed a series of mechanisms that have proved essential to understand key aspects of irradiation damage in crystalline solids. However, we still lack a comprehensive model that can connect atomic-level defect physics with experimental measurements of quantitative features of the irradiated microstructure. In this work, we present a mesoscale model that draws from our improved understanding of irradiation damage processes collected over the last few decades, bridging knowledge gained from our most sophisticated atomistic simulations with defect kinetics taking place over time scales many orders of magnitude larger than atomic interaction times. Importantly, the model contains no adjustable parameters and combines several essential pieces of irradiation damage physics: each playing an irreplaceable role in the context of the full model but of limited utility if considered in isolation. Crucially, we carry out a set of experiments carefully designed to isolate the key irradiation damage variables and facilitate validation. Using tungsten as a model material, we find exceptionally good agreement between our numerical predictions and experimental measurements of defect densities and defect cluster sizes.
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All authors Sicong He, Brandon Schwendeman, George Tynan, Jaime Marian
Materials Science
Multi-Functional Properties of Manganese Pnictides: A First-Principles Study on Magneto-Optics and Magnetocaloric Properties
Jayendran S, Abhishek K G, Suresh R et al. (+2 more)
Magnetic refrigeration presents an energy-efficient and environmentally benign alternative to traditional vapour-compression cooling technologies. It relies on the magnetocaloric effect, in which the temperature of a
magnetic material changes in response to variations in an applied
magnetic field. Optimal magnetocaloric materials are characterized by a significant change in
magnetic entropy under moderate
magnetic field. In this study, we systematically investigated the inter-atomic exchange interactions,
magnetic anisotropy energy and magnetocaloric properties of MnX (X = N, P, As, Sb, Bi) using a combination of density functional theory and Monte-Carlo simulations. Additionally, the magneto-optical Kerr and Faraday spectra were computed using the all-electron, fully relativistic, full-potential linearized muffin-tin orbital method. The largest Kerr effect observed in MnBi can be inferred as a combined effect of maximal exchange splitting of Mn 3d states and the large
spin-orbit coupling of Bi. To extract site-projected
spin and orbital moments,
spin-orbit coupling and orbital polarization correction are accounted in the present calculation, which shows good agreement between the moment obtained from the X-ray
magnetic circular dichroism sum rule analysis,
spin-polarized calculation, and experimental studies. The
magnetic transition temperatures predicted through Monte-Carlo simulations were in good agreement with the corresponding experimental values. Our results provide a unified microscopic understanding of magnetocaloric performance and magneto-optical activity in Mn-based pnictides and establish a reliable computational framework for designing next-generation
magnetic refrigeration materials.
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All authors Jayendran S, Abhishek K G, Suresh R, Helmer Fjellvåg, Ravindran P
Materials Science
CrystalFormer-CSP: Thinking Fast and Slow for Crystal Structure Prediction
Zhendong Cao, Shigang Ou and Lei Wang
Crystal structure prediction is a fundamental problem in materials science. We present CrystalFormer-CSP, an efficient framework that unifies data-driven heuristic and physics-driven optimization approaches to predict stable
crystal structures for given chemical compositions. The approach combines pretrained generative models for space-group-informed structure generation and a universal machine learning force field for energy minimization. Reinforcement fine-tuning can be employed to further boost the accuracy of the framework. We demonstrate the effectiveness of CrystalFormer-CSP on
benchmark problems and showcase its usage via web interface and
language model integration.
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Materials Science · Cross-listed from physics.chem-ph
Super-Poissonian Squeezed Light in the Ground State of Strongly Coupled Light-matter Systems
Cankut Tasci, Mohammad Hassan, Leon Orlov-Sullivan et al. (+2 more)
Strong light-matter coupling enables hybrid states in which photonic and electronic degrees of freedom become correlated even in the ground state. While many-body effects in long-range dispersion interactions are known to reshape electronic properties under such conditions, their impact on
quantum-optical observables remains largely unexplored. Here, we address this problem using
quantum electrodynamical density-functional theory (QEDFT) combined with the recently developed
photon-many-body dispersion (pMBD) functional, which can capture higher-order electron-
photon correlations and multi-
photon processes. We compute ground-state photonic observables including
photon number fluctuations, second-order correlations, and quadrature variances, and find squeezing and super-Poissonian
photon statistics emerging from light-matter interactions in the strong coupling regime. Our results demonstrate that capturing the full hierarchy of many-body, electron-
photon and multi-
photon correlations is essential for a consistent description of
quantum-optical properties in strongly coupled molecular systems, establishing QEDFT as a first-principles framework for predicting nonclassical photonic features in the ground state of complex systems.
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All authors Cankut Tasci, Mohammad Hassan, Leon Orlov-Sullivan, Leonardo A. Cunha, Johannes Flick
Materials Science
Symmetry breaking transforms strong to normal correlation and false metals to true insulators
Alex Zunger, Jia-Xin Xiong and John P. Perdew
Material scientists and condensed matter physicists have long been divided on the issue of choosing the conceptual framework for explaining why open-shell transition-metal
oxides tend to be
insulators, whereas otherwise successful theories such as DFT often predict them to be (false) metals. Strong correlation becomes the recommended medicine. We point out that strong correlation can be mitigated by allowing DFT to lower the energy by breaking structural,
magnetic or dipolar
symmetries. Such local motifs are observed experimentally by local probes beyond the 'average structure' determined by X-Ray diffraction. Observed broken
symmetries can arise from slow fluctuations that persist over the observation time or longer. The surprising fact is that when
symmetry breaking motifs are used as input to electronic structure calculations, false metals are converted into real
insulators without the recommended medicine of strong correlation. Consistently, DFT calculations that show energy lowering
symmetry breaking correct most cases where DFT, even with advanced exchange-correlation functionals, previously missed the correct metal vs
insulator designation. Total energy calculations distinguish systems that support energy-lowering
symmetry breaking from those that do not. This approach distinguishes between paramagnetic insulating and metallic phases and shows mass enhancement in Mott metals. The reason is that
symmetry breaking removes many of the degeneracies that exist in a
symmetry-unbroken system, reducing significantly the need for strong correlation. If one chooses to ignore
symmetry breaking, the persistent degeneracies often call for strong correlation treatment. Thus,
symmetry breaking transforms strong to normal correlation and false metals to true
insulators. This view sheds light on the historic controversy between Mott and Slater that still reverberates today.
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Strongly Correlated Electrons
Electronic Phonons in a Moiré Electron Crystal
Yan Zhao, Yuhang Hou, Xiangbin Cai et al. (+12 more)
Collective
quantum phenomena, such as the excitation of composite
fermions1,
spin waves2, and
exciton condensation3,4, can emerge in strongly correlated systems like the fractional
quantum Hall states5,
spin liquids6, or excitonic
insulators7. Two-dimensional (2D) moiré superlattices have emerged as a powerful platform for exploring such correlated phases and their associated collective excitations8,9. Specifically, electron
crystals stabilized by longrange Coulomb interactions may host collective vibrational excitations emerging from electron correlations10, termed electronic
phonons, which are fundamentally distinct from atomic
lattice phonons. Despite theoretical prediction of their existence in moiré electron
crystals11, direct experimental evidence has remained elusive. Here we report the observation of electronic
phonons in the Mott insulating and stripe phases of a WS2/WSe2 moiré superlattice, achieved through light scattering measurements. The
phonon energies, temperature and filling factor dependencies, along with theoretical modeling, corroborate their origin as collective vibrations of a correlated electron
crystal. Polarization-resolved measurements further indicate rotational
symmetry breaking in the Mott state. Notably, these electronic
phonons exhibit strong tunability in energy, intensity, and polarization under external electric or
magnetic fields, highlighting rich and controllable
lattice dynamics of the electron
crystal. These findings provide direct spectroscopic evidence for the electronic crystalline nature of correlated phases, opening avenues for probing and manipulating collective excitations in correlated electron systems.
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All authors Yan Zhao, Yuhang Hou, Xiangbin Cai, Shihao Ru, Shunshun Yang, Yan Zhang, Xuran Dai, Qiuyu Shang, Abdullah Rasmita, Haiyang Pan, Kenji Watanabe, Takashi Taniguchi, Hongbin Cai, Hongyi Yu, Weibo Gao
Materials Science
Unusual strain relaxation and Dirac semimetallic behavior in epitaxial antiperovskite nitrides
Ting Cui, Zihan Xu, Qinghua Zhang et al. (+13 more)
Antiperovskite nitrides (X3AN) are the structural analogues to perovskite
oxides, while their epitaxial growth and electronic properties remain largely unexplored. We report the successful synthesis of Ni3InN thin films on substrates with different
lattice constants. First-principles
phonon calculations confirm the dynamical stability of cubic phase Ni3InN, providing the basis for epitaxial synthesis. High-resolution scanning transmission electron microscopy reveals coherent (001)-oriented interfaces when Ni3InN is grown on LaAlO3 and SrTiO3, while an unexpected (011)-orientation forms on DyScO3, aligning with surface-energy predictions. Transport measurements highlight a strain-controlled
Fermi-
liquid behavior, correlated with variations in the Ni-3d bandwidth and hybridization. Band structure calculations reveal a dual character near the
Fermi level: a high-mobility Dirac-like band and a Ni-3d
manifold that drives strange-metal transport with a reduced slope compared to
oxide perovskites. The formal Ni valence (+2/3) places Ni3InN in an overdoped correlated-metal regime, distinguishing from most perovskite
oxides. This positions antiperovskite nitrides as a promising platform for investigating overdoped
Fermi liquids and strange-metal behavior.
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All authors Ting Cui, Zihan Xu, Qinghua Zhang, Xiaodong Zhang, Qianying Wang, Dongke Rong, Songhee Choi, Axin Xie, Hongyun Ji, Can Wang, Chen Ge, Hongjian Feng, Shanmin Wang, Kuijuan Jin, Liang Si, Er-Jia Guo
Materials Science
Observation of square-like moire lattice and quasicrystalline order in twisted rock-salt nitrides
Dongke Rong, Qinghua Zhang, Ting Cui et al. (+10 more)
Twistronics, which exploits moire modulation of
lattice and electronic structures in twisted
bilayers, has emerged as a powerful approach to engineer novel
quantum states. Recent efforts have expanded beyond two dimensional van der Waals (vdWs)
crystals to more complex, strongly correlated materials, where interfacial moire effects can dominate physical properties. Here we demonstrate a generalizable route to fabricate twisted
bilayers of transition metal nitrides with vdWs like interfaces, using freestanding CrN membranes as a model system. Twisted
bilayer CrN (tCrN) is realized by employing cubic alkaline earth metal monoxides as sacrificial layers, enabling the assembly of clean, controllable interfaces. Electron ptychography reveals well defined, periodic square moire superlattices in tCrN. For a twist angle of 16.3 degree, we identify a nearly commensurate moire
lattice with coincident Cr columns, whereas at 45 degree we uncover localized octagonal quasicrystalline order with clear self-similarity. These results establish a practical platform for twisted TMNs and open avenues to explore moire-induced atomic configurations and emergent correlated phenomena in nitride based
heterostructures.
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All authors Dongke Rong, Qinghua Zhang, Ting Cui, Qianying Wang, Hongyun Ji, Axin Xie, Songhee Choi, Qiao Jin, Chen Ge, Can Wang, Shanmin Wang, Kuijuan Jin, Er-Jia Guo
Materials Science
High-Entropy Oxide Nanostructures for Rapid and Sustainable Nitrophenol Reduction
Anjali Varshney, Aishwery J. Verma, Ritesh Dubey et al. (+3 more)
High-
entropy materials have emerged as a promising class of catalysts, driven by their high configurational
entropy originating from structural disorder in single-phase multicomponent systems. Despite their potential, the catalytic performance of high-
entropy oxides (HEOs) remains relatively underexplored. In this study, we present a simple solution-based combustion route to synthesize two low-cost, transition metal-rich multicationic
oxides positioned in the medium-
entropy (HEO-4) and high-
entropy (HEO-5) regimes. Rietveld refinement of powder X-ray diffraction data confirmed single-phase formation with a face-centered cubic (fcc)
crystal structure for both nanostructures. The morphology, particle size, and multicationic elemental distribution were investigated using scanning and transmission electron microscopy. The catalytic performance of the synthesized HEOs was evaluated in the hydrogenation of a series of nitrophenol derivatives. Notably, HEO-5 exhibited significantly enhanced catalytic activity ($k_{\mathrm{app}} \approx 0.5~\mathrm{min^{-1}}$, TOF $= 2.1 \times 10^{-3}~\mathrm{mol\,g^{-1}\,s^{-1}}$), achieving rapid conversion of p-nitrophenol compared to the medium-
entropy oxide nanostructures ($k_{\mathrm{app}} \approx 0.02~\mathrm{min^{-1}}$, TOF $= 7.2 \times 10^{-4}~\mathrm{mol\,g^{-1}\,s^{-1}}$). Furthermore, the kinetic and thermodynamic parameters of the reaction, including the activation energy ($E_a$), enthalpy of activation ($\Delta H^{\ddagger}$), Gibbs free energy of activation ($\Delta G^{\ddagger}$), and
entropy of activation ($\Delta S^{\ddagger}$), were determined to gain mechanistic insight into the reduction process. This study opens new avenues for the rational design and facile synthesis of high-
entropy oxide catalysts, highlighting their potential for efficient and sustainable large-scale amine production.
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All authors Anjali Varshney, Aishwery J. Verma, Ritesh Dubey, Sushil Kumar, Tapas Goswami, Samar Layek
Superconductivity · Cross-listed from quant-ph
Superconducting qubit decoherence correlated with detected radiation events
A. R. Castelli, K. M. Beck, L. D. H. Alegria et al. (+6 more)
Most
quantum error correction (QEC) protocols for superconducting
qubits assume spatially and temporally uncorrelated decoherence events; however, recent evidence suggests that
cosmic radiation induces spatially correlated errors. We present a platform that sandwiches a superconducting transmon
qubit between two microwave kinetic inductance detector (MKID) arrays, enabling real-time detection of radiation-induced
phonon bursts. By synchronizing MKID event detection with single-shot measurements of
qubit energy relaxation ($T_1$) and phase coherence ($T_2$), we observe statistically significant reductions in both $T_1$ and $T_2$-up to 30.5%-immediately following dual MKID events attributed to penetrating
muons. Our findings directly link radiating events to correlated
qubit decoherence. Furthermore, our experimental platform provides a foundation for systematic studies of radiation effects, the development of shielding and mitigation techniques, and the refinement of error-correction
algorithms tailored to correlated noise sources.
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All authors A. R. Castelli, K. M. Beck, L. D. H. Alegria, L. A. Martinez, K. R. Chaves, S. R. O'Kelley, N. Materise, J. L DuBois, Y. J. Rosen
Soft Condensed Matter
Dehydration-Driven Ion Aggregation and the Onset of Gelation in ZnCl$_2$ Solution
Alexei V. Tkachenko, Chuntian Cao, Amy C. Marschilok et al. (+1 more)
A minimal model of ionic aggregation in concentrated ZnCl$_2$ is developed, guided by molecular dynamics simulations with a machine-learned potential. It explicitly incorporates solvent-site depletion, correlated chloride binding, and allows for loops within Zn-Cl clusters. Dehydration is shown to drive ion binding through two sharp transitions set by the Zn coordination number $Z$: a crossover at $Z=2$ from isolated ions to Cl-bridged clusters, and gelation near $Z\approx 3$. The model agrees quantitatively with MD results, and the critical exponent of the cluster-size distribution matches percolation theory.
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All authors Alexei V. Tkachenko, Chuntian Cao, Amy C. Marschilok, Deyu Lu
Materials Science · Cross-listed from quant-ph
Lattice-Renormalized Tunneling Models for Superconducting Qubit Materials
P. G. Pritchard and James M. Rondinelli
We present a
lattice-renormalized formalism for configurational tunneling two-level systems (TLS) that overcomes limitations of minimum-energy-path and light-particle models. Derived from the
nuclear Hamiltonian, our formulation introduces composite
phonon coordinates to capture
lattice distortions between degenerate potential wells. This approach resolves deficiencies in prior models and enables accurate computation of tunnel splittings and excitation spectra for hydrogen-based TLS in bcc Nb. Our results bound experimental tunnel splittings and reveal strong anharmonic couplings between tunneling atoms and
lattice phonons, establishing a direct link between TLS dynamics and
phonon-mediated strain interactions. The formalism further generalizes to multi-level systems (MLS), providing insight into defect-induced decoherence in superconducting
qubits and guiding strategies for materials design to suppress TLS-related loss.
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Statistical Mechanics
Estimating Solvation Free Energies with Boltzmann Generators
Maximilian Schebek, Nikolas M. Froböse, Bettina G. Keller et al. (+1 more)
Accurate calculations of solvation free energies remain a central challenge in molecular simulations, often requiring extensive sampling and numerous alchemical intermediates to ensure sufficient overlap between phase-space distributions of a solute in the gas phase and in solution. Here, we introduce a computational framework based on normalizing flows that directly maps solvent configurations between solutes of different sizes, and compare the accuracy and efficiency to conventional free energy estimates. For a Lennard-Jones solvent, we demonstrate that this approach yields acceptable accuracy in estimating free energy differences for challenging transformations, such as solute growth or increased solute-solute separation, which typically demand multiple intermediate simulation steps along the transformation. Analysis of radial distribution functions indicates that the flow generates physically meaningful solvent rearrangements, substantially enhancing configurational overlap between states in configuration space. These results suggest flow-based models as a promising alternative to traditional free energy estimation methods.
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All authors Maximilian Schebek, Nikolas M. Froböse, Bettina G. Keller, Jutta Rogal