Strongly Correlated Electrons
Low temperature Spin freezing and Diffuse Magnetic Correlations in Tb$_{2}$Zr$_{2-x}$Ti$_{x}$O$_{7}$ (x = 0, 0.5)
Sujata Singh, Leon Carstens, M. Duc Le et al. (+2 more)
Structural disorder in the magnetically frustrated pyrochlore system leads to intriguing
magnetic states. We present the thermodynamic behavior and short range
magnetic correlations in Tb$_{2}$Zr$_{2}$O$_{7}$ and Tb$_{2}$Zr$_{1.5}$Ti$_{0.5}$O$_{7}$ compounds. The parent compound Tb$_{2}$Zr$_{2}$O$_{7}$ has defect fluorite structure, which evolves toward the pyrochlore phase on Ti doping at Zr site. There is no long range
magnetic order down to 0.4 K, and a
magnetic field dependent
spin freezing evolves below 1.25 K and 1.05 K for the parent and doped compounds, respectively. The ac susceptibility measurements indicate slow
spin relaxation process below 20 K in these compounds. Inelastic
neutron scattering reveals broad diffuse scattering, indicative of short range correlations at low temperature, owing to local structural distortions and persistent
spin fluctuations. These results suggest a correlated, disorder influenced
magnetic state in Tb$_{2}$Zr$_{2}$O$_{7}$, Tb$_{2}$Zr$_{1.5}$Ti$_{0.5}$O$_{7}$ compounds.
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All authors Sujata Singh, Leon Carstens, M. Duc Le, R. Klingeler, C.S. Yadav
Materials Science · Cross-listed from physics.optics
Breakdown of spallation in multi-pulse ultrafast laser ablation
David Redka, Julian Vollmann, Nicolas Thomae et al. (+2 more)
Ultrashort-pulse
laser ablation of metals near damage threshold is governed by homogeneous spallation, in which tensile unloading releases a nanometre-thin
liquid film whose optical signatures are temporally evolving concentric Newton rings in pump–probe experiments. This well-established picture rests almost exclusively on single-pulse results obtained on ideally flat surfaces, yet application-oriented processing invariably operates in a multi-pulse regime in which each pulse irradiates a surface progressively modified by preceding pulses. Whether homogeneous spallation persists under these conditions has remained an open question. Here we resolve this question using time-resolved pump-probe interferometry applied pulse by pulse to austenitic stainless steel. We show that homogeneous spallation dominates the first pulse, while its contribution is strongly reduced for the second pulse. By the third pulse, Newton rings vanish and sustained surface bulging collapses, with the optical transients fully saturating into a phase-explosion-like signature by the fourth pulse.
Fourier-domain coherence analysis rules out roughness-induced decoherence as an optical artefact. Four independent observables, spanning time-resolved and final-state measurements, converge on the same transition after three to four pulses. Spallation-layer formation, widely invoked to explain ultrashort-pulse ablation of metals, is thus a single-pulse phenomenon rather than a multi-pulse ablation mechanism.
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All authors David Redka, Julian Vollmann, Nicolas Thomae, Maximilian Spellauge, Heinz P. Huber
Statistical Mechanics
First Passage Times for Variable-Order Time-Fractional Diffusion
Wancheng Li and Daniel S. Han
We derive the asymptotic first passage time (FPT) distribution for space-dependent variable-order time-fractional
diffusion, where the fractional exponent $\alpha(x)$ varies with position. On a bounded interval with an absorbing and a reflecting boundary, we show that the survival probability decays as $\Psi(t)\sim C\,t^{-\alpha_*}/[\ln (t/\tau)]^{\nu}$, where $\alpha_*$ is the minimum value of the fractional exponent and $\nu$ is determined by the location and shape of the minimum. The exponent $\nu$ is fixed by the location and order of the minimum, taking the value $1/k$ at a $k$\textsuperscript{th}-order interior minimum, $1$ at the reflecting boundary and $2$ at the absorbing boundary. For a constant fractional exponent, $\nu=0$, so the logarithmic factor distinguishes a continuously varying order field from a homogeneous medium. We recover both exponents from simulated first passage times by a direct linear fit, with no amplitude or
geometric input. We validate the theory against exact Laplace-space solutions and Monte Carlo simulations for linear and nonlinear profiles of $\alpha(x)$.
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Materials Science
On phase separation and crystallization of Ge-rich GeSbTe alloys from atomistic simulations with a machine learning interatomic potential
Omar Abou El Kheir, Dario Baratella and Marco Bernasconi
We developed a machine learning interatomic potential (MLIP) for Ge-rich GeSbTe
alloys of interest for applications in phase change
memories embedded in microcontrollers. The MLIP was generated by fitting with a neural network method a large database of energies and forces computed within density functional theory of elemental, binary, stoichiometric and non-stoichiometric ternary
alloys in the Ge-Sb-Te phase diagram. The MLIP is demonstrated to be highly transferable to large regions of the phase diagram around the compositions included in the
dataset. The MLIP is then exploited to simulate the crystallization with phase separation of three Ge-rich
alloys on the Ge-Sb$_2$Te$_3$ and Ge- Ge$_2$Sb$_2$Te$_5$ tie-lines that correspond to the set process of the
memory cell. The transformation on the ns time scale and at 600 K, comparable to the operation conditions of the
memory, yields crystalline cubic GeTe slightly Sb-doped and amorphous GeSb and Ge. These metastable phases differ from the thermodynamically stable products and form due to kinetics effects on the short time span of the set operation in phase change
memories.
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Soft Condensed Matter
Beads, springs and fields: particle-based vs continuum models in cell biophysics
Valerio Sorichetti, Juraj Májek, Ivan Palaia et al. (+4 more)
Quantitative modeling has become an essential tool in modern biophysics, driven by advances in both experimental techniques and theoretical frameworks. Powerful high-resolution techniques now provide detailed
datasets spanning molecular to tissue scales, allowing to visualize cellular structures with unprecedented detail. In parallel, developments in soft and active matter physics have established a robust theoretical basis for describing biological systems. In this context, two main modeling paradigms have emerged: particle-based models, which explicitly represent discrete components and their interactions, and continuum models, which describe systems through spatially varying fields. We compare these approaches across biological scales, highlighting their respective strengths, limitations, and domains of applicability. To keep our discussion biologically relevant, we focus on five systems of fundamental importance: the cytoskeleton, membranes, chromatin, biomolecular condensates and tissues. With this Review, we thus aim to provide a framework for both theorists and experimentalists to select appropriate modeling strategies, and highlight future directions in biophysical modeling.
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All authors Valerio Sorichetti, Juraj Májek, Ivan Palaia, Fernanda Pérez-Verdugo, Christian Vanhille-Campos, Edouard Hannezo, An{\dj}ela Šarić
Materials Science
Complex surface patterning in homo- and heteroepitaxial contexts: (simultaneous) step bunching and step meandering
Vassil Ivanov, Vesselin Tonchev, Marta A. Chabowska et al. (+2 more)
We confront a meso-scale continuum model, archetypical for the heteroepitaxial context, with an atomistic Vicinal Cellular Automaton (VicCA), built as a homoepitaxial counterpart, to show that in (2+1)D complex surface instabilities are fundamental growth phenomena rather than context-specific artifacts. Our approach is to first construct a Ginzburg-Landau-type model, designed to extend the previously (1+1)D Tersoff-type models to (2+1)D. We complement the continuum approach with a discrete one - the VicCA, in which we use a novel version of the potential landscape for the diffusing particles - a double-well potential located at each step edge. Importantly, this framework also captures both step bunching and step meandering. While these behaviors are rarely treated together in earlier approaches, they naturally coexist in real materials. Thus we establish a cross-context correspondence at the level of obtained morphologies and morphology diagrams and, additionally, a multiscale perspective on the governing parameters, bridging the gap between the mesoscale and atomistic modeling.
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All authors Vassil Ivanov, Vesselin Tonchev, Marta A. Chabowska, Hristina Popova, Magdalena A. Załuska-Kotur
Other Condensed Matter
Phonon drag as a mechanism of delayed terahertz response of metals
Ivan Oladyshkin
We show that electron drag by nonequilibrium
phonons describes the actual waveform and spectrum of terahertz pulses generated during femtosecond
laser irradiation of metals. In contrast to previous models, there is a picosecond delay in the drag force development due to the relatively slow
lattice heating and finite
phonon lifetime. We also predict that, at high pump fluences, a macroscopic deformation wave enhances nonlinearly the drag force and terahertz response. Our results establish the terahertz pulse waveform as a direct probe of ultrafast
lattice dynamics in metals.
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Materials Science · Cross-listed from physics.optics
Non-Hermitian reshaping of high-order Landau modes
Zhihao Wang, Jie Jiang, Yanji Zheng et al. (+6 more)
When charged particles are subjected to strong
magnetic fields, they form discrete energy levels known as Landau levels. The Landau levels consist of a series of degenerate states of Landau modes, making them a promising platform for large-capacity information processing. However, to date, exploiting the high-order Landau modes and control their spatial distributions has remained elusive. Here, we propose to construct
magnetic fields, electric fields, and imaginary momentum simultaneously to reshape high-order Landau modes in non-Hermitian systems. By building a non-Hermitian electric
circuit platform, we experimentally realize pseudomagnetic fields via inhomogeneous coupling and pseudoelectric fields via a gradient on-site potential, while simultaneously introducing an imaginary momentum via non-reciprocal coupling. We directly observe multi-frequency single-peak localization of high-order Landau modes. Our work provides a universal method for manipulating high-order Landau modes and exploring applications in nonHermitian systems, such as frequency multiplexing and wave packet reshaping.
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All authors Zhihao Wang, Jie Jiang, Yanji Zheng, Wen Zhao, Chenyang Wang, Zhiwei Guo, Yong-Chun Liu, Shuang Zhang, Cuicui Lu
Materials Science
Spatial deformation of a ferromagnetic elastic rod
G. R. Krishna Chand Avatar and Vivekanand Dabade
Ferromagnetic elastic slender structures offer the potential for large actuation displacements under modest external
magnetic fields, due to the magneto-mechanical coupling. This paper investigates the phase portraits of the
Hamiltonian governing the three-dimensional deformation of inextensible
ferromagnetic elastic rods subjected to combined terminal tension and twisting moment in the presence of a longitudinal
magnetic field. The total energy functional is formulated by combining the Kirchhoff elastic strain energy with micromagnetic energy contributions appropriate to soft and hard
ferromagnetic materials: magnetostatic (demagnetization) energy for the former, and exchange and Zeeman energies for the latter. Exploiting the circular cross-sectional
symmetry and the integrable structure of the governing equations, conserved Casimir invariants are identified and the
Hamiltonian is reduced to a single-degree-of-freedom system in the Euler polar angle. Analysis of the resulting phase portraits reveals that purely elastic and hard
ferromagnetic rods undergo a supercritical
Hamiltonian Hopf pitchfork bifurcation, whereas soft
ferromagnetic rods exhibit this bifurcation only within a restricted range of the magnetoelastic parameter, $0<\tilde{K}_{dM}<1/8$. Both helical and localized post-buckling configurations are analyzed, and the corresponding load-deformation relationships are systematically characterized across a range of loading scenarios. Localized buckling modes, corresponding to homoclinic orbits in the
Hamiltonian phase space, are constructed numerically. In contrast to the purely elastic case, the localized configurations of soft
ferromagnetic rods exhibit non-collinear extended straight segments, a geometrically distinctive feature arising directly from the magnetoelastic coupling.
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Statistical Mechanics · Cross-listed from math-ph
On Exponentially Long Prethermalization Timescales in Isolated Quantum Systems
Matteo Gallone
We study prethermalization in time-independent
quantum many-body systems on a $d$-dimensional
lattice with an extensive local
Hamiltonian $H=N+\varepsilon P$, in the regime where $\varepsilon \ll 1$. We prove that the prethermal timescale is exponential in $\varepsilon_0/\varepsilon$, where $\varepsilon_0$ is an explicit scale determined by the locality exponent and the local norm of $P$. We also construct two extensive local quasi-conserved quantities whose variation remains exponentially small throughout this time interval.
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Materials Science · Cross-listed from physics.optics
Tuning light-matter interaction of near-infrared nanoplasmonic scintillators
Michał Makowski, Dominik Kowal and Muhammad Danang Birowosuto
Nanoplasmonic modification of scintillation has so far been explored mainly in the weak-coupling regime, where changes in the local density of optical states enhance radiative recombination via Purcell-type rate engineering. By contrast, strong light-matter coupling generates hybrid states that modify emission dynamics beyond simple decay-rate acceleration, but its implications for scintillator nanocrystals (NCs) under ionizing radiation remain poorly understood. All of these effects are beneficial for near-infrared scintillators, which are typically slow and have low brightness. Here, we present a
quantum-optical framework to investigate how near-infrared scintillator NCs coupled to nanoplasmonic
antennas evolve from weak coupling toward strong light-matter coupling. We compare broad- and narrow-
antenna platforms with single and periodic Au nanorods and
benchmark them against conductive plasmonic
antennas based on indium tin
oxide and
graphene. As representative emitters, we consider wide-band PbS NCs and narrow-band cubic Lu2O3:Er3+ scintillators. The calculations show that the onset of strong-coupling signatures is jointly governed by emitter dephasing and the
antenna linewidth, with narrow-band emitters coupled to spectrally narrow
antennas providing the most favorable conditions. Among the platforms considered,
graphene gives the lowest threshold (g = 4 meV) for observable coherent exchange owing to its ultranarrow
antenna linewidth (ąppa} = 3.5 meV). These results identify near-infrared conductive nanoantennas, particularly
graphene-based ones, as promising platforms for accessing hybrid scintillation regimes relevant to radiation detection.
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Materials Science
Anion Ordering and Phase Stability Govern Optical Band Gaps in BaZr(S,Se)3
Erik Fransson, Michael Xu, Prakriti Kayastha et al. (+6 more)
Chalcogenide perovskites have emerged as promising lead free materials for photovoltaic and thermoelectric applications. Among them, BaZrS3 has attracted particular
attention due to its thermal and chemical stability, favorable optoelectronic properties, and low thermal conductivity. Here, we combine molecular dynamics and Monte Carlo simulations based on machine learned interatomic potentials with scanning transmission electron microscopy to investigate mixing thermodynamics and phase stability in the BaZr(S,Se)3 system. We identify an unusual ordered structure that persists at room temperature, most prominently at 33% S, where S and Se atoms form alternating layers within the
crystal. Free energy calculations yield the temperature composition phase diagram, including a nonperovskite delta phase in the Se rich limit and a perovskite phase in the S rich limit, separated by a broad two phase region. Analysis of the dielectric function and the absorption coefficient demonstrates that composition,
crystal structure, and anion ordering jointly control the optical band gap. Selenium alloying enables tuning between approximately 1.6 and 1.9eV, while anion ordering within a given composition reduces the gap by about 0.12eV. Lastly, variations between structural polymorphs give rise to band gap differences of up to 0.4eV.
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All authors Erik Fransson, Michael Xu, Prakriti Kayastha, Kevin Ye, Ida Sadeghi, Rafael Jaramillo, James M. LeBeau, Lucy Whalley, Paul Erhart
Mesoscale and Nanoscale Physics
Spin Qubit Leapfrogging: Dynamics of shuttling electrons on top of another
Nicklas Meineke and Guido Burkard
Spin shuttling has crystalized as a powerful and promising tool for establishing intermediate-range connectivity in
semiconductor spin-
qubit devices. Although experimental demonstrations have performed exceptionally well on different materials platforms, the question of how to handle areas of low valley splitting in silicon during shuttling remains unresolved. In this work, we explore the possibility of utilizing the valley degree of freedom, particularly in regions of low valley splitting, to allow mobile
spin qubits to be shuttled through an occupied stationary
quantum dot, thereby leapfrogging over the stationary electron. This not only grants a more enriched mobility for shuttled electrons, as it opens new possible routing paths, but also enables the implementation of an entangling SWAP$^\gamma$ two-
qubit gate operation in the process. Simulating this process for different sets of parameters, we demonstrate the feasibility of such an operation and offer a unique use case for otherwise precarious regions of a
quantum processor chip and propose a possible extension to the set of possible operations for silicon
spin qubit devices.
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Materials Science
Dynamic Behaviors of Materials Under Angle-Resolved Experiments: A Matrix Framework for Nonlinear Physics
Hongjin Xiong, Zhonghui Xia, Xuan Ye et al. (+1 more)
Matter and external stimuli interact dynamically almost everywhere in nature. Under an applied field, a material seldom stays in the state in which it was characterized, and its properties change with time. Angle-resolved experiments are the standard way to resolve direction-dependent properties, however, current theoretical tools for data analysis are built for static states, leaving dynamic behaviors largely neglected. Here, we develop a generalized “input-coefficient-output” (ICO) approach that constructs spatial operation
matrices and
symmetry-reduced coefficient
matrices across diverse physical systems, as we verify for nonlinear optics, elasticity, electrostriction and magnetostriction, and a Python program is released for convenient application. Using angle-resolved polarized second-harmonic generation (SHG) as an example, we focus on the dynamic modeling of material properties under angle-dependent stimuli, construct dynamic
matrix equations that capture the time-dependent
evolution of material responses, and propose three dynamic models and a point-to-point data fitting method. For the SHG experiments performed on $T_d-$WTe$_2$, the discrete dynamic model captures the asymmetric characteristics of the measured polar pattern with a significantly improved coefficient of determination ($R^2$ increasing from 0.567 to 0.773), whereas conventional static models are constrained to a symmetric curve. The
evolution operator extracted from the dynamic model connects the macroscopic measurement to microscopic intermediate states during their interaction with stimuli. This work provides a practical
matrix framework for dynamic modeling of material properties, paving the way for exploring complex nonlinear physics under realistic experimental conditions.
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All authors Hongjin Xiong, Zhonghui Xia, Xuan Ye, Teng Ma
Strongly Correlated Electrons
Probing the real-space density of spin-entangled electrons
Federico Pisani, Leonie Spitz, Libor Vojáček et al. (+12 more)
On the textbook example of an isolated
antiferromagnetic Heisenberg dimer, we demonstrate that the
magnetic form factor and the
magnetic electron density distribution can be extracted from the momentum-dependence of the inelastic
neutron scattering (INS) intensity of a
magnetic excitation. We measure the three-dimensional (3D)
magnetic structure factor of the singlet-to-triplet excitation in Cu(II) acetate monohydrate with INS. Using a minimal parametrization of the
magnetic electron density, we deduce the real-space density of the
spin-entangled electrons and the transfer of
magnetic electron density between metal and ligand atoms from the experimental data. Density functional theory (DFT) calculations reproduce the measured structure factor quantitatively, providing a direct validation of DFT broken-
symmetry spin densities against full 3D INS data. The quantitative agreement between experiment, parametrization, and theory establishes a robust framework for determining
magnetic form factors and the
magnetic electron density in a broad range of
magnetic materials and demonstrates INS as a probe of the envelope of spatial electronic wavefunctions.
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All authors Federico Pisani, Leonie Spitz, Libor Vojáček, Flaviano José dos Santos, Alberto Carta, Bastien Dalla Piazza, Stanislav E. Nikitin, Karl W. Krämer, Björn Fåk, Taro Nakajima, Daichi Ueta, Hiraku Saito, Jian-Rui Soh, Nicola Marzari, Henrik M. Rønnow
Materials Science · Cross-listed from physics.app-ph
A Variable-Spot-Size and Multi-Frequency Square-Pulsed Source (SPS) Approach for Comprehensive Characterization of Anisotropic Thermal Transport Properties in Multilayered Thin Films
Kexin Zhang, Tao Chen, Jinlong Ma et al. (+1 more)
Multilayered thin-film structures are frequently encountered in industrial applications, where accurate thermal property characterization is essential for performance optimization. These films, typically ranging from nanometers to micrometers in thickness, often exhibit anisotropic thermal conductivity and non-bulk heat capacity, which are challenging to measure. In this study, we introduce a variable-spot-size and multi-frequency square-pulsed source (SPS) method for the simultaneous determination of anisotropic thermal conductivities, heat capacities, and interfacial thermal conductance in multilayered systems. By leveraging a broad modulation frequency range (1 Hz to 10 MHz) and tunable
laser spot sizes, the SPS method enhances sensitivity to different thermal parameters across layers. We validate this approach on a silicon-on-
insulator (SOI) sample comprising a 1.59 um Si layer, 1.03 um SiO2 layer, and a silicon substrate with a 122 nm aluminum (Al) transducer. The SPS method successfully extracts seven key thermal parameters, including the in-plane and cross-plane thermal conductivities and heat capacity of the Si film, the thermal conductivity and heat capacity of the SiO2 layer, the thermal conductivity of the substrate, and the interfacial thermal conductance between Al and Si. Temperature-dependent measurements from 80 to 500 K showed excellent agreement with literature values and first-principles predictions, confirming the method's accuracy and reliability. These results demonstrate the SPS method as a powerful tool for comprehensive thermal characterization of complex multilayered structures, with implications for both fundamental research and practical applications.
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All authors Kexin Zhang, Tao Chen, Jinlong Ma, Puqing Jiang
Materials Science · Cross-listed from physics.app-ph
Universal thermometry of solid-liquid interfacial thermal conductance
Tao Chen and Puqing Jiang
Solid-
liquid interfacial thermal conductance (ITC) critically influences heat transport in microfluidic, electronic, and energy systems, yet most optical thermometry techniques are limited to specific metal-
liquid interfaces. In this work, we introduce a universal broadband square-pulsed thermometry method that enables simultaneous quantification of ITC across a wide range of arbitrary solid-
liquid interfaces, while also providing accurate measurements of nanoscale
liquid-film thickness. To validate the method, we applied it to Al-water interfaces, yielding ITC values in the range of 50-55 MW m^(-2) K^(-1), consistent with prior studies. The technique also reveals markedly lower ITCs for glass-water (9.9 MW m^(-2) K^(-1)) and Si-water (5.7 MW m^(-2) K^(-1)), and further measurements on Al-silicone oil (~10 MW m^(-2) K^(-1)) and PMMA-silicone oil (~0.4 MW m^(-2) K^(-1)) extend the validation to highly viscous nonpolar
liquids and
polymer-
liquid interfaces. These results highlight the capability of the method to capture thermal transport differences across diverse solid-
liquid combinations. Further comparisons with acoustic/diffuse mismatch models and molecular dynamics simulations, together with theoretical analysis, highlight the influence of vibrational mismatch, wettability, and surface condition on interfacial thermal transport. This broadly applicable technique enables rapid, quantitative characterization of solid-
liquid interfacial thermal transport, with broad implications for interfacial heat transfer science and technology.
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Mesoscale and Nanoscale Physics
Nonlinear Circular Dichroism Reveals the Local Berry Curvature
Nele Tornow, Paul Herrmann, Clemens Schneider et al. (+3 more)
Light-matter interactions are governed by conservation laws of energy and momentum. For harmonic generation in crystalline solids, energy conservation imposes that $m$ incoming
photons with energy $\hbar \omega_0$ are combined to form one
photon at energy $m\hbar \omega_0$. Linear momentum conservation governs phase matching, whereas angular momentum conservation connects the angular momentum carried by
photons to the discrete rotational
symmetry of the
crystal lattice. As a consequence, circular harmonic generation exerts a torque on the
lattice and, conversely, a macroscopic rotation of the
crystal induces a nonlinear rotational Doppler shift. These cornerstone laws of nonlinear optics rely on macroscopic
symmetry arguments, and therefore provide little insight into the microscopic origin of angular momentum transfer. Here we uncover a direct connection between angular momentum conservation in nonlinear optics and the electronic
quantum geometry, by proving that the transferred angular momentum from light to the
crystal is proportional to the local Berry
curvature at one optical resonance. This relation is encoded in the nonlinear harmonic circular dichroism, which we measure experimentally in an atomically thin
semiconductor. With this, we extend our understanding of nonlinear optics, and we establish a method for the all-optical control and read-out of the local Berry
curvature.
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All authors Nele Tornow, Paul Herrmann, Clemens Schneider, Ferdinand Evers, Jan Wilhelm, Giancarlo Soavi
Mesoscale and Nanoscale Physics
Charge waves and dynamical signatures of topological phases in Su-Schrieffer-Heeger chains
Tomasz Kwapinski, Marcin Kurzyna and Luis E. F. Foa Torres
We investigate the emergence of charge waves and their temporal dynamics in one-dimensional Su-Schrieffer-Heeger (SSH) topological chains. Contrary to the conventional view that charge oscillations are suppressed in gapped topological systems with preserved
chiral symmetry, we show that such oscillations can indeed occur. The general condition for an arbitrary oscillation period is analysed, and we find that the charge waves propagating along the chain do not depend on its
topology, except at the edges, where both topological phases exhibit essential differences. In chains with inequivalent atoms within the SSH unit
cell, we observe regular long-period sublattice oscillations that appear simultaneously with even-odd charge oscillations. Furthermore, we study the nonequilibrium dynamics in SSH chains. After a quench, the time
evolution of the local density of states and charge occupancies exhibits clear dynamical fingerprints that distinguish topologically trivial and nontrivial phases. Our results establish that transient charge dynamics can distinguish topologically trivial and nontrivial phases in real time by detecting the presence of topologically-protected edge states.
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Mesoscale and Nanoscale Physics
Automatic Charge State Tuning of 300 mm FDSOI Quantum Dots Using Neural Network Segmentation of Charge Stability Diagram
Peter Samaha, Amine Torki, Ysaline Renaud et al. (+4 more)
Tuning of gate-defined
semiconductor quantum dots (QDs) is a major bottleneck for scaling
spin qubit technologies. We present a deep learning (DL) driven, semantic-
segmentation pipeline that performs charge auto-tuning by locating transition lines in full charge stability diagrams (CSDs) and returns gate voltage targets for the single charge regime. We assemble and manually annotate a large, heterogeneous
dataset of 1015 experimental CSDs measured from silicon QD devices, spanning nine design geometries, multiple wafers, and fabrication runs. A U-Net style convolutional neural network (CNN) with a MobileNetV2 encoder is trained and validated through five-fold group cross validation. Our model achieves an overall offline tuning success of 80.0% in locating the single-charge regime, with peak performance exceeding 88% for some designs. We analyze dominant failure modes and propose targeted mitigations. Finally, wide-range diagram
segmentation also naturally enables scalable physic-based feature extraction that can feed back to fabrication and design workflows and outline a roadmap for real-time integration in a cryogenic wafer prober. Overall, our results show that neural network (NN) based wide-diagram
segmentation is a practical step toward automated, high-throughput charge tuning for silicon QD
qubits.
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All authors Peter Samaha, Amine Torki, Ysaline Renaud, Sam Fiette, Emmanuel Chanrion, Pierre-Andre Mortemousque, Yann Beilliard
Mesoscale and Nanoscale Physics
Exciton screening in C$_{60}$ and PTCDA complexes. TDDFT calculations with GGA and hybrid functionals
N.L. Matsko and Mahmoud A. Salem
Photoabsorption in the low-energy region for C$_{60}$ and PTCDA molecular complexes is studied within linear response TDDFT. For the PBE, B3LYP and HSE exchange-correlation (xc) functionals the dependence of the accuracy of the
exciton energy on the electron-hole separation is analyzed. Particular
attention is paid to the charge-transfer (CT)
excitons. The inclusion of non-local exchange using hybrid functionals increases the accuracy of calculations for short-range
excitons, however, the accuracy of hybrid functionals decreases significantly for long-range
excitons. Moreover, as the
exciton radius approaches the "screening length"\ , the simpler PBE functional gives more accurate excitonic energies than the mentioned hybrid functionals.
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Soft Condensed Matter · Cross-listed from physics.chem-ph
Ion-Specific Anomalous Water Diffusion in Aqueous Electrolytes: A Machine-Learned Many-Body Force Field Study with MACE
Massimo Ciacchi, Ilnur Saitov, Nico Di Fonte et al. (+2 more)
The dynamics of water in electrolyte solutions exhibits a striking, ion-specific anomaly: the
diffusion coefficient of water is enhanced relative to the neat
liquid in chaotropic CsI solutions, yet suppressed in kosmotropic NaCl solutions. This phenomenon, long challenging for classical force-field-based molecular dynamics, is studied here using classical molecular dynamics simulations with a many-body machine-learned force field (MLFF) trained within the MACE equivariant graph neural network framework. The force field is trained on energies, forces, and stresses computed at the density functional theory level with the revPBE-D3 exchange–correlation functional, which provides a reliable balance between accuracy and computational efficiency for aqueous systems. Simulations of NaCl and CsI aqueous solutions at ambient conditions over a concentration range of 0.89–3.56 mol/kg reproduce the experimentally observed anomalous
diffusion and show a quantitative improvement over previous results obtained with the DeePMD framework, trained on the same theory, particularly for NaCl solutions. This improvement is traced to a stronger Na$^{+}$–water interaction in the first hydration shell and the non-negligible retarding contribution of the second hydration shell of Na$^{+}$. For CsI solutions, the water acceleration is shown to be primarily driven by the anion I$^{-}$, whose diffuse and weakly structured hydration shell facilitates rapid water exchange with the bulk. These results are rationalised through a shell-decomposition analysis of time-dependent water diffusivities and ion–oxygen potentials of mean force providing a coherent microscopic picture of the acceleration–retardation mechanism in the studied aqueous electrolytes.
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All authors Massimo Ciacchi, Ilnur Saitov, Nico Di Fonte, Isabella Daidone, Carlo Pierleoni
Soft Condensed Matter
Hierarchical Bayesian calibration of mesoscopic models for ultrasound contrast agents from force spectroscopy data
Brieuc Benvegnen, Nikolaos Ntarakas, Tilen Potisk et al. (+2 more)
Ultrasound-guided drug and gene delivery (USDG) is a promising non-invasive approach for targeted therapeutic applications. Mechanical properties of encapsulated microbubbles (EMBs), which serve as contrast
agents, strongly affect their specific interactions with ultrasound and are thus critical to the success and efficiency of USDG. Accurate calibration of high-fidelity particle-based models of EMB capsid mechanics is computationally challenging because direct
Bayesian inference with dissipative particle dynamics (DPD) is prohibitively expensive. We employ a surrogate-accelerated
Bayesian calibration workflow that combines deep neural network (DNN) surrogates, transitional Markov chain Monte Carlo sampling, and hierarchical regularization across EMB diameters. Using this framework, we develop two data-informed DPD models of commercial EMB
agents, i.e., Definity and SonoVue, and perform inference of force field parameters based on published compression experiments for Definity and indentation experiments for SonoVue, each spanning three distinct diameters. The inferred posteriors show that key model parameters, such as the stretching stiffness and bending modulus, are consistently constrained by the available data. The presented methodology can be used to derive bespoke, data-informed models for a wide range of ultrasound contrast
agents, including encapsulated gas vesicles, EMBs with diverse capsids consisting of lipids,
proteins, or
polymers, and functionalized with ligands.
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All authors Brieuc Benvegnen, Nikolaos Ntarakas, Tilen Potisk, Ignacio Pagonabarraga, Matej Praprotnik
Soft Condensed Matter
Ternary liquid crystalline mixture showing broad antiferroelectric smectic C$_A$* and glassy hexatic smectic X$_A$* phases
Aleksandra Deptuch, Anna Drzewicz, Marcin Piwowarczyk et al. (+4 more)
A ternary
liquid crystalline mixture was designed to obtain a tilted hexatic smectic phase in the glassy state. Structural, electro-optic, and dielectric properties of the mixture are investigated, and selected measurements are also performed for its pure components. In particular, the electron density profile perpendicular to smectic layers is determined from the X-ray diffraction data and compared to the results of density functional theory calculations both for the mixture and pure components. Comparison of the experimental smectic layer spacing and tilt angle in the mixture allows us to assess whether molecular dimerization is likely to occur. On the mesoscopic scale, the helical pitch is determined in the SmC$_A$* phase of the mixture, and selective reflection of light is observed under a polarizing microscope in the SmC*, SmC$_A$*, and SmX$_A$* phases. The glass transition in the smectic X$_A$* phase is observed in calorimetric results. At the same time, the dielectric spectra do not directly reveal the primary $\alpha$-process, although the secondary $\beta$- and $\gamma$-processes are detected. Overall, the results show that the ternary mixture stabilizes a broad SmC$_A$* phase and enables vitrification of the hexatic SmX$_A$* phase, while the structural data suggest a change in the molecular organization between the SmC* and SmC$_A$* phases.
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All authors Aleksandra Deptuch, Anna Drzewicz, Marcin Piwowarczyk, Michał Czerwiński, Mateusz Filipow, Mateusz Pączek, Ewa Juszyńska-Gałązka
Strongly Correlated Electrons
The ground ytterbium doublet in h-YbMnO3 and the related low-temperature peculiarities of the compound
S.A. Klimin, N.D. Molchanova, N.N. Kuzmin et al. (+3 more)
We have performed detailed temperature-dependent study of optical f-f transitions of the Yb3+ ions in h-YbMnO3 by means of
Fourier-transform spectroscopy. The splitting of the ground Kramers doublet as a function of temperature, D0(T), for the Yb3+ ion at 4b site was determined. The D0(T) function follows the dynamics of the manganese
magnetic moment below TN = 87 K, indicating, that the ytterbium subsystem is magnetized by the
magnetic field generated by an ordered manganese subsystem, which is consistent with the results of previous studies. Excitation of the upper component of the split ground doublet plays a significant role in low-temperature dynamics of the h-YbMnO3
crystal. Using the D0(T) function we calculated the temperature behavior of the of the Yb(4b)
magnetic moment: it is in clear agreement with the
neutron data [Phys. Rev. B 98, 134413, 2018]. The calculated contribution of Yb(4b) to heat capacity definitely explains the origin of the Schottky anomaly in the CP(T) dependence. A scenario for phase transitions in h-YbMnO3 is proposed in which the energy gain in the ytterbium system plays a key role.
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All authors S.A. Klimin, N.D. Molchanova, N.N. Kuzmin, E.S. Sektarov, Lihua Yin, M.N. Popova
Materials Science · Cross-listed from physics.class-ph
Beyond the dipole approximation: A compact operator form to describe magnetizable many-body systems
Dirk Romeis
To describe the interactions in magnetically soft particle systems either numerical full-field methods or dipole models are used. Whereas the former are computationally challenging, simple dipole interactions are largely underestimating the actual forces when particles get closer. Based on the full 2-body solution, an analytic approximation scheme for many-body full-field interactions is developed. The concept is formulated in terms of an improved operator that is equivalent to the classical dipole form. The full interaction operator allows to describe cluster formation and dispersion among particles in applied
magnetic fields very compactly and highly efficient. In view of its simple 'dipole-like' form, the implementation is straightforward in many areas where magnetically soft objects are used.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Theory of spin qubits and the path to scalability
Z. M. McIntyre, Abhikbrata Sarkar and Daniel Loss
Spin qubits have emerged as a leading platform for
quantum information processing due to their long coherence times, small footprint, and compatibility with the existing
semiconductor industry. We first provide an introduction to the different
qubit implementations currently being investigated, including single electron-
spin qubits, hole-
spin qubits, donor
qubits, and multispin encodings. We discuss how the confinement and strain present in
semiconductor heterostructures produce addressable levels whose
spin degree of freedom can be used to encode a
qubit. A large emphasis is placed on reviewing the theoretical foundations and recent experimental demonstrations of proposed mechanisms for long-range coupling, including hybrid approaches based on
circuit QED and Andreev
qubits, as well as
spin shuttling. Finally, we review a recent proposal for linking
spin qubits using topological
spin textures.
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Materials Science
Strain-Mediated Lattice Reconstruction Enhances Ferromagnetism in Cr2Ge2Te6/WTe2 van der Waals Heterobilayers
Franz Herling, Mireia Torres-Sala, Dorye L. Esteras et al. (+17 more)
Van der Waals (vdW)
heterostructures enable tailored electronic and
magnetic phases by stacking atomically thin layers with pristine interfaces. Here, we investigate fully 2D Cr2Ge2Te6/WTe2
heterostructures and identify a strong enhancement of ferromagnetism in Cr2Ge2Te6 (CGT). Magnetotransport measurements across multiple devices with WTe2 thicknesses ranging from monolayer to bulk reveal a robust anomalous
Hall effect together with a more than twofold increase of the Curie temperature and substantially enhanced coercive fields. Interface microscopy confirms chemically abrupt vdW interfaces with no detectable interdiffusion, while control experiments rule out processing- or stray-field-induced artifacts. Our experiments and theoretical calculations demonstrate that interfacial charge transfer renders CGT conductive and that proximity-induced
lattice distortions in CGT enhance exchange and magnetocrystalline anisotropy. These results establish strain-mediated
lattice reconstruction as a strategy for engineering high-temperature
magnetic order in 2D
heterostructures and clarify that modifications within the
magnetic layer itself can govern proximity effects in vdW stacks.
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All authors Franz Herling, Mireia Torres-Sala, Dorye L. Esteras, Charlotte Evason, Motomi Aoki, Marcos Rosado, Kapil Gupta, Bernat Mundet, Kai Xu, J. Sebastián Reparaz, Kenji Watanabe, Takashi Taniguchi, Dimitre Dimitrov, Vera Marinova, Ivan A. Verzhbitskiy, Goki Eda, José H. Garcia, Stephan Roche, Juan. F. Sierra, Sergio O. Valenzuela
Statistical Mechanics · Cross-listed from physics.optics
Non-Hermitian Exceptional Dynamics in First-Order Heat Transport
Pengfei Zhu
Heat transport exhibits distinct regimes ranging from ballistic propagation to diffusive relaxation, traditionally described by disparate theoretical frameworks. Here, we introduce a unified first-order operator formulation in which temperature and heat flux are treated as a coupled state vector, yielding a minimal dynamical closure of heat transport. The resulting generator is intrinsically non-Hermitian and gives rise to a spectral structure governed by an exceptional point that separates overdamped
diffusion from underdamped wave-like propagation. In this framework,
Fourier law emerges as a singular limit of a
hyperbolic dissipative system, while the Cattaneo equation arises naturally as the minimal hydrodynamic closure of kinetic theory. We show that the exceptional point induces nonanalytic spectral transitions, nonmodal transient dynamics, and a breakdown of conventional modal decomposition. The theory further generalizes to anisotropic media, where direction-dependent exceptional surfaces enable intrinsic steering of heat flow. Our results establish a unified non-Hermitian dynamical framework for heat transport and reveal exceptional-point physics as a fundamental organizing principle underlying thermal dynamics across scales.
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Statistical Mechanics · Cross-listed from physics.flu-dyn
Nonlinear scalings emerge in a linear regime: an observation in electrokinetic flow
Jin'an Pang, Guangyin Jing, Xiaoqiang Feng et al. (+2 more)
In nonlinear systems, small perturbations are conventionally attributed to negligible nonlinearity, justifying linear approximations. Here, we uncover a notable exception to this paradigm in an electrokinetic (EK) flow. Using a novel dual frequency excitation scheme with two high frequency AC electric fields ($> 10^{5}$ Hz), we efficiently excite flow perturbations at a difference frequency ($\Delta f$) four orders of magnitude lower. This approach reveals a strong nonlocal energy transfer mechanism mediated purely by the nonlinearity of the electric body force, enabling precise, clean flow control free from electrode polarization artifacts. Unexpectedly, these small, nominally linear velocity and electric conductivity fluctuations exhibit power law spectra. With increasing electric Rayleigh number, the scaling exponents agree quantitatively with predictions for fully developed EK
turbulence by the Quad cascade process theory. This observation not only implies multiple flow state transitions even at low excitations, but also indicates that intrinsic nonlinearity regulates perturbations even in the linear regime, necessitating a fundamental re examination of linear approximations in electrohydrodynamics and other nonlinear systems.
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All authors Jin'an Pang, Guangyin Jing, Xiaoqiang Feng, Kaige Wang, Wei Zhao