Strongly Correlated Electrons
Diversifying time evolution of matrix product states using BUGs
Kornél Kapás, Dominik Sulz, Charlotte Verhoeven et al. (+3 more)
Time
evolution of tensor-network states is a central tool for studying nonequilibrium dynamics in strongly correlated
quantum systems. In the past decade, using the time-dependent variational principle (TDVP) discretized by projector-splitting has become the gold standard for evolving
matrix product states (MPS) with long-range
Hamiltonians. More recently, a conceptually different class of discretizations of the TDVP, the class of Basis Update and Galerkin (BUG) integrators, has been developed within the framework of dynamical low-rank approximation, offering an alternative, more flexible approach. In this work, we formulate two BUG integrators explicitly for MPS. The BUG integrators result in "single-site" MPS integrators that are robust with respect to small singular values, avoid backward-in-time substeps, and naturally allow for the adaptive choice of bond dimensions. We consider the augmented BUG integrator of first order and the midpoint BUG integrator of second order and clarify their relation to the projector-splitting discretization of the TDVP. Using representative models of strongly correlated
quantum systems, like the XY
spin model with long-range interaction and two-dimensional
lattice models of
fermions and
spins of various lengths, we perform a systematic numerical comparison between BUG and projector-splitting time discretizations of the continuous-time TDVP, focusing on scalability, numerical complexity, and accuracy. We find that BUG integrators, due to their reduced numerical cost and the flexibility of the concept, provide a competitive and, in certain regimes, advantageous alternative to the well-established time-stepping by projector-splitting in TDVP, especially in models with large local dimensions, and in cases where observables are extracted with high temporal resolution.
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All authors Kornél Kapás, Dominik Sulz, Charlotte Verhoeven, Miklós Antal Werner, Örs Legeza, Christian Lubich
Materials Science
Ultrastrong Au-Te bonding drives disorder in monolayer ZrTe$_5$ on gold
Konrád Kandrai, Zoltán Tajkov, Péter Kun et al. (+3 more)
Monolayer ZrTe$_5$ is predicted to host a large-gap
quantum spin Hall phase, motivating efforts to isolate single layers of the material. Gold-assisted exfoliation produces clean monolayers of many chalcogen-terminated van der Waals
crystals, but the strong Te-Au bond may compete with the bonding network of the ZrTe$_5$ layer itself. Across tens of samples, low-temperature scanning tunneling microscopy on gold-exfoliated flakes shows a disordered monolayer surface in the overwhelming majority of cases, while thicker flakes preserve the characteristic quasi-one-dimensional chain structure. Ab initio calculations of the ZrTe$_5$/Au(111) interface reproduce this asymmetry and resolve its mechanism: the Te atoms facing the gold chemisorb, rupturing the weak zigzag Te-Te bonds that cross-link the ZrTe$_3$ chains, turning the discrete bond-length spectrum of the
crystal into a continuous one, while the chains persist as distorted units. Charge analysis shows the signature of covalent Te-Au bonding with a modest transfer that hole-dopes the monolayer; in the bilayer, the distortion and the doping stay confined to the layer contacting the gold, and the chemisorption and disorder each preclude the predicted
quantum spin Hall phase. The same quasi-covalent Te-Au bond may perturb the contact layer of other gold-exfoliated Te-terminated
crystals, particularly those with weakly connected intralayer networks.
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All authors Konrád Kandrai, Zoltán Tajkov, Péter Kun, Levente Tapasztó, János Koltai, Péter Nemes-Incze
Mesoscale and Nanoscale Physics
Superfluorescence in CdS/CdSe/CdS Spherical Quantum Wells Modulated by Excitation Geometry
Chunzheng Bai, Qihao Sun, Yiying Zhu et al. (+6 more)
Superfluorescence (SF) originates from the spontaneous buildup of macroscopic coherence among initially incoherent emitters. Its formation is highly sensitive to dephasing and collective coupling in the system. Here, we observe room-temperature SF in CdS/CdSe/CdS spherical
quantum wells. With increasing excitation fluence, the peak emission intensity shows a nearly quadratic increase, while the emission delay and pulse width decrease. Burnham-Chiao ringing is also observed, revealing the characteristic collective radiation dynamics of SF. Further experiments with stripe excitation show that shortening the excitation length L changes the dominant fast emission from amplified spontaneous emission to SF. More importantly, the threshold for SF under stripe excitation is only about 1/30 of that under spot excitation. This large reduction indicates that the propagating radiation field provided by spatially extended excitation favors the buildup of cooperative coherence. These findings provide direct experimental evidence for understanding ultrafast many-body coherence dynamics and offer a route to actively control collective emission at room temperature.
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All authors Chunzheng Bai, Qihao Sun, Yiying Zhu, Ruilin Xu, Bin Gu, Jinsong Qi, Fengrui Hu, Xiaoyong Wang, Jiayu Zhang
Quantum Gases · Cross-listed from math-ph
Random field approximation and local counting statistics for the weakly interacting thermal Bose gas
Andreas Deuchert, Marcin Napiórkowski and Błażej Ruba
We study weakly interacting
bosons on the three-dimensional
torus at temperatures proportional to the critical temperature for Bose–Einstein condensation. We show that, as the expected particle number tends to infinity, the grand canonical Gibbs state is asymptotically described by the coherent state quantization of a random field that converges to a novel Bogoliubov random field. Moreover, the point process associated with the Gibbs state can be approximated by a Cox process. These results are based on and extend the approximation of the Gibbs state recently obtained by the first two authors and Nam. Using these approximations, we compute limiting distributions of the number of particles outside the condensate, the joint occupation statistics of finitely many momentum modes, and particle-number fluctuations in macroscopic subsets of the
torus, all governed by the Bogoliubov field. We further prove convergence of the empirical measure of the associated point process to the uniform measure and convergence of the microscopic particle-number statistics to the
boson point process. The latter result establishes the universality of particle-number statistics on microscopic length scales.
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Materials Science
Agent-authored deposition recipes for X-ray multilayer mirrors: schema-bound LLM control of a magnetron sputtering system with reflectivity-verified outcomes
Oleksiy V. Penkov, Haoyu Fu, Yueying Zhan et al. (+2 more)
Periodic multilayer mirrors for X-rays require a layer period controlled to about 0.1 nm, set by deposition rates held in the laboratory's own notebook. A supervising model session gave a large
language model
agent a target multilayer specification and calibration constants derived from a laboratory archive. The
agent authored recipes in the magnetron sputtering system's native recipe
language and submitted them through a Model Context Protocol bridge of 17 tools in three tiers, with enforcement in the control application. The target was a 30-bilayer Ru/C multilayer with a period of 6.85 nm, a pair chosen because each period is fitted as two layers. The
agent could read and write only its own working project, so it could alter neither the calibration record nor the measurements that scored it. We scored mirrors by X-ray reflectivity and fixed the 3% acceptance threshold on relative period difference before deposition. Across four scored depositions, the relative period difference fell from 20% on the calibration as given to 2.26% after one measured-feedback iteration and 0.79% after a second. We identified sixteen failure modes of the
agent-facing interface. The result is bounded to the period, pair, and chamber observed.
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All authors Oleksiy V. Penkov, Haoyu Fu, Yueying Zhan, Pengyuan Wu, Jiong Jin
Materials Science · Cross-listed from physics.optics
Interplay between growth conditions and formation of localized light emitters in epitaxial AlN thin films
Meysam Saeedi, Duc V. Dinh, Andrey N. Anisimov et al. (+3 more)
AlN is a promising material for integrated
quantum photonics due to its broad transparency window, its compatibility with CMOS technology, and the possibility to host localized light emitters acting as single
photon sources. However, little is understood yet about the microscopic nature and formation mechanisms of these light emitters. In this contribution, we demonstrate that their formation efficiency depends significantly on the growth conditions of the AlN thin film. We reveal that localized light emitters with distinct zero-
phonon lines in the 600–800~nm range can be efficiently formed in epitaxial AlN thin films grown under N-rich conditions by exposing the AlN to a post-growth treatment consisting in a
proton irradiation followed by an annealing process. In contrast, the density of light emitters formed in AlN grown under Al-rich conditions remains low, even after the thin films have been exposed to the post-growth treatment. These results open a pathway toward a better understanding of the microscopic nature of these light emission centers, as well as their engineered integration as
quantum light sources in AlN-based optomechanical platforms.
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All authors Meysam Saeedi, Duc V. Dinh, Andrey N. Anisimov, Mingyun Yuan, Georgy V. Astakhov, Alberto Hernández-Mínguez
Materials Science
Crack propagation threshold in single-crystal silicon: a cleavage plane-crackons model
Faming Gao
Experiments revealed the discontinuities in the dependence of the crack speeds on the crack driving force. Despite great efforts, until now, previous theoretical methods, such as linear elastic fracture mechanics and molecular dynamics calculations, failed to elucidate the issue of speed gap. Herein, the cleavage plane-crackons model for crack propagation has been proposed. The normalized crack propagation speed of silicon is proportional to the one-fourth power of the
quantum numbers. This motion equation is consistent with experimental results of silicon. It clarifies the underlying mechanism of the long-standing issue of the speed gap. The relationship between
quantum numbers and the roughness of the surface of the cracks has been established. The critical
quantum number for the onset of unstable crack propagation in single-
crystal silicon has been determined. The correspondence between the critical
quantum number and fracture toughness has been discovered. This methodology lead to insights into the underlying mechanism of the fracture processes. It is not limited to silicon and can be extended to other crystalline material to understand and predict the fracture behaviors.
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Strongly Correlated Electrons · Cross-listed from hep-th
Superstrip Algebras and Nonperturbative Spectra in Fermionic Theories
Jin Chen, Zhihao Duan, Qiang Jia et al. (+1 more)
This is an extended version of arXiv:2511.22129. We develop a general construction of the superstrip
algebra $\mathbf{sStr}_{\mathscr C}(\mathcal M)$, the fermionic counterpart of the strip
algebra, for a gapped $(1+1)$-dimensional system with a fermionic superfusion category $\mathscr C$ and the
vacuum structure described by the supermodule category $\mathcal M$. As illustrations, we work out the superstrip
algebra for two simple examples: the fermionic variant of the Fibonacci fusion category and the q-type $\mathbb{Z}_2$
symmetry. We then apply the framework to the gapped IR phases of the $\mathcal N=2$ and $\mathcal N=1$ superconformal minimal models deformed by their least relevant operator and compute the Witten indices. We explain how the particle and
soliton spectra, together with their
fermion parity, are organized into representations of the corresponding superstrip
algebras. A mixed 't Hooft anomaly between the spontaneously broken
symmetry and the unbroken
fermion parity $(-1)^F$ further forces each $\mathcal N =2$
soliton to carry a fractional
fermion number. Finally, we set up the boundary SymTFT for fermionic systems and reproduce the results in several examples studied in this paper.
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All authors Jin Chen, Zhihao Duan, Qiang Jia, Sungjay Lee
Mesoscale and Nanoscale Physics
In-plane anomalous and third-harmonic Hall response in an easy-plane trigonal magnet
Arnab Das and Soumik Mukhopadhyay
We report the emergence of an in-plane anomalous Hall effect (IPAHE) and a pronounced third-harmonic Hall response in an easy-plane trigonal
magnetic system achieved via tuning of
magnetic anisotropy. Angle-dependent Hall measurements reveal a clear departure from conventional sinusoidal behavior, revealing a strong sin(3{\theta}) component at elevated fields, which increases as the
magnetic anisotropy is reduced, accompanied by a finite in-plane Hall signal. Consistently, the observed nonlinear Hall signal exhibits a cubic field dependence, indicative of a leading third-order contribution to the transverse conductivity. The enhancement of the third harmonic reflects the
evolution toward coherent in-plane magnetization and
symmetry-governed nonlinear transport. These observations support an intrinsic,
symmetry-controlled transport mechanism enabled by reduced
magnetic anisotropy and establish a direct link between anisotropy,
crystal symmetry, and higher-order Hall response.
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Statistical Mechanics · Cross-listed from quant-ph
Synchronized Spin Trajectories under Collective Weak Measurements
Yiwen Han, Konghao Sun, Wei Yi et al. (+1 more)
We consider locally driven-dissipative
quantum spins that undergo a continuous weak measurement of their collective
spin. We show that such a system can exhibit full
spin-synchronization in trajectories corresponding to the same measurement record. Mathematically, we demonstrate that this is a general consequence of the irreducibility of the
quantum Markov semigroup generated by the Lindbladian, in combination with a transitive
symmetry, in particular
spin-permutation
symmetry. When breaking the irreducibility, e.g. in the absence of local dissipation, the system can exhibit a weaker form of partial synchronization. Given the general origin, this measurement-induced phenomenon arises in a broad class of many-body systems.
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All authors Yiwen Han, Konghao Sun, Wei Yi, Johannes Schachenmayer
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Diffusion Enhancement and Directional Suppression Induced by Reciprocal Flows
Yuki Koyano, Hiroyuki Kitahata and Takeshi Ooshida
Reciprocal flows repeatedly return fluid elements to their initial positions, producing no net advective transport on time average. Nevertheless, their interplay with
diffusion gives rise to nontrivial transport. To describe this phenomenon, we develop a general theory of effective
diffusion under two-dimensional linear flows with arbitrary time dependence. By analyzing the advection-
diffusion equation, we derive exact expressions for the mean square displacement and the effective
diffusion coefficients for extensional, simple shear, and rotational flows within a single framework. We show that the reciprocal flows universally induce
diffusion enhancement. The
diffusion tensor exhibits pronounced anisotropy, which can result in directional
diffusion suppression in spite of the direction-averaged
diffusion enhancement. Our results provide a general framework for
diffusion control by time-dependent flows and can provide new strategies for transport manipulation in microfluidic and biological systems.
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Statistical Mechanics · Cross-listed from hep-th
Conformal defects of general dimensions at finite temperature
Yucheng Li, Haruki Nakayama and Tatsuma Nishioka
We consider defect conformal field theories (DCFTs) at finite temperature, where a $p$-dimensional conformal defect wraps the thermal circle. Extending the previous study of line defects to defects of general dimensions, we determine the general forms of the thermal one-point functions of bulk scalars, conserved currents and the stress tensor by imposing the residual
symmetry and the conservation laws. The low temperature expansion of the thermal one-point functions is shown to be reproduced by the bulk-defect operator expansion, allowing us to read off the thermal one-point coefficients of defect operators. We examine the general results in four classes of examples with free bulk theories: the trivial defect, free scalar and
fermion theories with a boundary, the free scalar theory with a localized $\phi$ deformation in $d=2\,p+2$ dimensions and the free $\mathrm{O}(N)$ model with a localized $\phi^2$ deformation in $d=p+2-\epsilon$ dimensions. In the last example with $\epsilon = 1$, where the defect becomes an interface, we find that the thermal one-point functions coincide with those of the free scalar theory with the Dirichlet boundary condition, in accordance with the conjectured factorization of an interface CFT into two decoupled boundary CFTs.
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Materials Science
Inferring Dislocation Microstructures from X-ray Diffraction via Cross-Modal Contrastive Learning
Benjamin Udofia, Nicolas Bertin and Markus Stricker
Understanding and inferring dislocation microstructures from diffraction patterns remains an open challenge in materials characterization, as diffraction measurements provide only indirect information about the underlying dislocation structure. In this work, a cross-modal learning framework is developed to enable the prediction of 3D dislocation structures directly from diffraction data. Dislocation density fields generated from discrete dislocation dynamics simulations are paired with corresponding virtual X-ray diffraction patterns and embedded into a shared 2D latent space using contrastive learning. The
alignment between structural and diffraction representations of dislocation structures is evaluated directly in the learned latent space using correlations between corresponding latent features. To estimate the role of
dataset size for this approach, farthest point sampling is employed to construct representative and diverse training subsets of varying sizes. The results show strong cross-modal
alignment and that model performance improves rapidly with increasing
dataset size. Near-saturation is achieved with approximately 500 representative observations from a
dataset of 10,000 observations, enabling accurate prediction of dislocation density fields from previously unseen diffraction data of the same distribution. Qualitative comparisons confirm that the predicted structures capture the dominant spatial features of the underlying dislocation microstructures. These findings demonstrate an efficient approach for learning structure-diffraction relationships and highlight the potential for inferring structural characteristics of dislocation networks directly from diffraction patterns, providing a pathway toward diffraction-based structural analysis and future extension to experimental data.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Emergent universality in Kraus maps of quantum chaotic many-body dynamics
Qi Camm Huang, Wai-Keong Mok, Tobias Haug et al. (+1 more)
Recent studies of "deep thermalization" have revealed universal physics in
quantum many-body dynamics beyond equilibration towards Gibbs states: maximally random
quantum state ensembles can emerge on local subsystems, generated by measurements on their complement. In this work, we further identify a new form of universality exhibited in the "finer fingerprints" of
quantum dynamics for local subsystems, induced by global
unitary time-
evolution. Specifically, we consider the projected Kraus ensemble, an ensemble of Kraus operators obtained by unraveling the
quantum channel on a small subsystem with respect to knowledge of the classical configurations of its complement. Our central result is a one-parameter random
matrix Ansatz that captures the ensemble's emergent statistical behavior along particular spacetime scalings, valid for generic 1D
circuit dynamics without conservation laws: the ensemble is described by the product of a complex Ginibre random
matrix and an independent log-normal random real scalar. The former encodes scrambling within the subsystem, captured by rotational invariance of the Ginibre measure, whereas the latter encodes fluctuations in the Born probabilities, arising from locality of the underlying dynamics. Our Ansatz can be established in the special cases of dynamics generated by global Haar random
unitaries and dual-
unitary circuits, while we motivate it for generic
circuits using arguments of spacetime duality and the multiplicative ergodic
theorem on long products of spatial transfer
matrices. Extensive numerical simulations for random and Floquet
circuit models verify these predictions. This universality in Kraus operators also provides a microscopic mechanism for deep thermalization in generic 1D
quantum circuit dynamics, and has implications for local
quantum information recoverability involving classical side information tied to knowledge of the bath.
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All authors Qi Camm Huang, Wai-Keong Mok, Tobias Haug, Wen Wei Ho
Statistical Mechanics
Chirality enhances diffusion in disordered environments
Joshua Uhlig, Jan Wójcik, Ralf Metzler et al. (+1 more)
Chirality, a systematic rotational bias in the motion of a particle, arises in a wide range of physical and biological systems, from charged colloids in
magnetic fields to swimming bacteria near surfaces. While its effects in homogeneous environments are well understood, the interplay between chirality and structural disorder has remained largely unexplored. Here we investigate the chiral random walk on two-dimensional percolation clusters above the percolation threshold, combining numerical simulations with an analytically tractable annealed-disorder approximation. We find that the long-time
diffusion coefficient depends non-monotonically on both the chirality parameter and the obstacle density: for every obstacle density above the percolation threshold, there exists an optimal chirality that enhances
diffusion relative to the achiral walk. We show that the optimal chirality is set by an edge-adhering mechanism: maximum
diffusion is achieved when the persistence length of the wall-adhering motion matches half the typical obstacle cluster perimeter. This yields a closed-form prediction for the optimal chirality in terms of
geometric properties of the medium alone, which we verify across the full range of obstacle densities studied. The enhancement extends to first-passage statistics, where chirality shortens typical search times at strong disorder while lengthening them at weak disorder, with direct implications for biological navigation in disordered environments.
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All authors Joshua Uhlig, Jan Wójcik, Ralf Metzler, Erik Kalz
Disordered Systems and Neural Networks
On non-phononic modes and glassy dynamics
Felix C. Mocanu, Dmytro Khomenko, Matteo Paoluzzi et al. (+4 more)
The relationship between vibrational modes and glassy dynamics has been an important and controversial topic of study for many decades. We introduce a family of glass-forming model potentials that have identical molecular and swap dynamics but different low-frequency vibrational modes. In sufficiently small systems low frequency modes do not hybridize with
phonons, and this enables us to study their statistical properties independently. We investigate i) the role of the optimization
algorithm used to find a minimum; ii) that of the finite-size effects; iii) that of the truncation of the interaction potential; and, iv) that of the parent temperature. We find that models with identical supercooled
liquid structure and dynamics can have dramatically different non-phononic vibrational modes at low frequency, based on how the potential is truncated. These findings challenge ideas relating the low-frequency non-phononic vibrational modes with the slow supercooled
liquid relaxation.
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All authors Felix C. Mocanu, Dmytro Khomenko, Matteo Paoluzzi, Giancarlo Ruocco, Walter Schirmacher, Grzegorz Szamel, Francesco Zamponi
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Design and Finite-Element Analysis of a New Inclined Blade-Electrode Architecture for Trapped-Ion Quantum Information Processing
Nahiyan Archa, Abhinand P, Ahammed Shabeeb et al. (+1 more)
The development of scalable
quantum technologies requires ion-trap architectures that provide strong and stable confinement while minimizing motional heating caused by electric-field noise. Trapped-ion systems offer long coherence times and high-fidelity
quantum control; however, anomalous motional heating from electrode surfaces can limit their performance. This study presents a finite-element analysis of a novel inclined ion-trap architecture, focusing on the effects of electrode geometry and blade separation on confinement strength, secular frequencies, motional heating, thermal response, and RF stability. Five trap inclinations were investigated using three-dimensional electrostatic simulations for blade separations of 5 to 35 um. The RF electric-field distribution was used to determine the effective pseudopotential, trap depth, secular frequencies, and normal modes. An empirical electric-field-noise model was then used to estimate the motional heating rate for frequency-noise exponents alpha = 3, 3.5, and 4. The results reveal a trade-off between confinement strength and ion-electrode distance. Blade separations of approximately 25 to 35 um provide a favorable design regime. At 25 um, the predicted heating rate is approximately 127 to 135 quanta per second for alpha = 3, but the RF stability margin is lower (qmax approximately 1.9). At 35 um, the stability is substantially improved (qmax approximately 0.52), while the heating rate increases to approximately 1570 to 1820 quanta per second. These results provide design guidelines for optimizing inclined ion traps for future trapped-ion
quantum-information architectures.
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All authors Nahiyan Archa, Abhinand P, Ahammed Shabeeb, Nikhil Kumar
Strongly Correlated Electrons
Nonequilibrium Broken-Symmetry States from Retained Observables
Sankha Subhra Bakshi and Gia-Wei Chern
In
equilibrium, broken-
symmetry states are selected by the competition between energy and
entropy. Out of
equilibrium, slowly relaxing observables retain information about the preparation and may reshape this competition, allowing orders that are not thermally favored. Identifying such states ordinarily requires following slow, protocol-dependent dynamics. Here we recast this dynamical selection as a static constrained variational problem. A small set of experimentally measurable or numerically accessible quantities-particle number, energy, and slow observables-defines a constraint space. The underlying dynamics determines where the system lies in this space, while
entropy maximization over both quasiparticle occupations and a prescribed class of candidate orders determines which order is selected. Restricting the variational states to the Gaussian
manifold yields a computationally inexpensive constrained Hartree-Fock implementation. For photoexcited Hubbard models, the approach reproduces the long-time TDHF suppression of square-
lattice antiferromagnetism and identifies incommensurate spiral order in place of the
equilibrium $120^\circ$ state on the triangular
lattice. For a continuously driven ferromagnetic double-exchange model, evaluating the constrained order map at the stationary NESS energy reveals a restricted region in which Neel order is favored. The framework therefore turns the search for nonequilibrium broken-
symmetry states into a practical static screening problem, without requiring simulations of every preparation protocol.
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Mesoscale and Nanoscale Physics
Fluctuation-induced antiparallel spin polarization near the boundaries of chiral metals
Kosuke Yoshimi, Yusuke Kato, Yuta Suzuki et al. (+4 more)
The
spin response of chiral conductors to nonequilibrium electrical fluctuations remains largely unexplored. We develop a low-frequency semiclassical Boltzmann theory coupled to Gauss's law for a chiral metal with
spin-orbit coupling of hedgehog type, treating impurity scattering beyond the conventional relaxation-time approximation. We first determine the quadratic response to a local ac current and its frequency dependence, and then show that zero-mean stationary current fluctuation and electric-field fluctuation near boundaries generate finite time-averaged
spin polarizations in the two boundary regions of the chiral metal. The polarizations are normal to the boundaries and antiparallel: for one chirality they point inward at both boundaries, and for the other they point outward. Within this model, the dominant contribution arises from the linear Edelstein effect driven by a quadratic effective electric field localized near each boundary. This picture may provide a qualitative explanation for CISS-related
spin polarization reported in the absence of an applied bias. More broadly, we expect other externally maintained
stochastic drives to induce
spin polarization through the same mechanism.
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All authors Kosuke Yoshimi, Yusuke Kato, Yuta Suzuki, Shuntaro Sumita, Takuro Sato, Hiroshi M. Yamamoto, Yoshihiko Togawa
Materials Science
Direct observation of reversible ionic polarization at a buried solid-state battery interface
Giovanni Ceccio, Romana Miksova, Jiri Vacik et al. (+5 more)
Electric fields control ionic distributions at solid-solid interfaces. However, whether buried interfaces possess an intrinsic ionic reversibility has remained experimentally unresolved. Here, we directly observe reversible ionic polarization at the buried amorphous LiCoO2/Li1.5Al0.5Ge1.5P3O12 electrolyte interface. By combining the Elastic Recoil Detection Analysis (ERDA) method, utilizing time-of-flight (ToF) measurements and nanometer-scale resolution, with the
Neutron Depth Profiling (NDP) method for the absolute quantification of lithium, we show that an applied bias of +-1 V results in a reversible redistribution of approximately 9.3% of lithium in the interface region, while conserving its total content. Upon polarity reversal, the lithium redistribution is completely reversed, indicating reversible interfacial ionic polarization rather than irreversible lithium loss or permanent interphase formation. These results demonstrate that buried interfaces in solidelectrolyte systems can behave as electrically reconfigurable ionic regions with an intrinsic reversible freedom for ion motion, thereby providing direct microscopic insight into the physics of space-charge formation and low-voltage interfacial response in solid-state electrochemical systems.
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All authors Giovanni Ceccio, Romana Miksova, Jiri Vacik, Zoltan Szaraz, Josef Dobrovodsky, Pavlina Zavadilová, Pavol Noga, Ivan Mastronardo
Strongly Correlated Electrons
Magnetically activated optical visibility of many-body excitons in NiPS$_3$
Shuta Matsuura, Shohei Imai and Naoto Tsuji
NiPS$_3$ is a layered van der Waals magnet that provides a unique platform for exploring the interplay between
excitons and
magnetic order. In its antiferromagnetic phase, strong many-body interactions give rise to a many-body
exciton, which manifests itself as an exceptionally sharp resonance near $1.47 \, \mathrm{eV}$ in optical absorption spectra and photoluminescence. Previous theoretical studies have assigned the local ground state and the many-body
exciton to
spin-triplet and
spin-singlet states, respectively, both with even parity. This picture, however, cannot account for the observed optical visibility of the many-body
exciton because one-
photon transitions between these states are forbidden by
spin and parity selection rules. Here, using group-theoretical analysis and exact diagonalization of single- and two-cluster models, we show that zigzag antiferromagnetic order breaks the relevant
symmetries and activates the otherwise forbidden transition. We further find that trigonal distortion of the local ligand environment and the inter-cluster exchange interaction relax additional spatial and
spin constraints on the transition, producing an
exciton signal in the optical conductivity that is distinguishable from the spectral background. These results provide a microscopic explanation for the optical visibility of the many-body
exciton and its connection to antiferromagnetic order in NiPS$_3$.
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Soft Condensed Matter
Confinement-Induced Pumping of Chiral Active Fluids
Joscha Mecke, Yongxiang Gao and Marisol Ripoll
Chiral active fluids, composed of continuously rotating active constituents, exhibit a wealth of nonequilibrium phenomena arising from the interplay of activity, hydrodynamic interactions, and broken mirror
symmetry. While these systems naturally generate circulating flows and active
turbulence, converting their microscopic rotational motion into directed macroscopic transport remains an open challenge. By means of mesoscale hydrodynamic simulations, here we show that channels with an intrinsic asymmetry result in the spontaneous formation of a persistent net flux in the absence of externally imposed pressure gradients or body forces. Our results can be extrapolated to various
geometric confinement strategies providing efficient and versatile strategies for transforming chiral activity into autonomous fluid transport, such that they can be utilized as a promising platform for self-powered microfluidic pumping.
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Statistical Mechanics
Certifying Hidden Dissipation from Observed Current Fluctuations
Ahmed Roman
A single-molecule experiment on a driven enzyme or motor resolves only a few of the transitions the machine makes, yet one would like to know how much free energy it dissipates in total, including on the steps that stay hidden. The mean and the fluctuations of the currents on the watched transitions are shown to certify this hidden dissipation, with no knowledge of the transition rates and no access to the hidden transitions: when the watched transitions span the cycles of the network, the observed-current covariance recovers the full density-contracted quadratic current geometry, including the contribution of transitions that are never seen. The mechanism is that fluctuations are set by the dynamical activity, or traffic, the symmetric partner of the current. Contracting the large-deviation cost of empirical currents over density fluctuations identifies the observed-current covariance with a traffic-weighted metric, and turns partial observation into a minimum-energy completion problem over the unseen cycles, whose solution is the certified hidden cost. Existing current-fluctuation uncertainty relations bound dissipation from chosen currents but do not say when partial observation fixes the hidden contribution; the cycle-observability condition derived here does. The statements concern long-time means and fluctuations; finite-time estimates require separate error control.
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Mesoscale and Nanoscale Physics
Cryogenic wafer probing below one Kelvin: Characterization of normal-metal Coulomb blockade thermometers at wafer scale
Lassi Lehtisyrjä, Renan P. Loreto, Juho Luomahaara et al. (+11 more)
Coulomb blockade thermometers (CBTs) have attracted more interest in recent years, as the demand for sub-one Kelvin thermometry has increased, especially due to the prevalence of dilution refrigerators in research and applications in
quantum technology. CBTs can be operated both as a primary thermometer, requiring no prior calibration, or as a simple resistance thermometer in the secondary mode after calibration. As new scalable fabrication processes for
quantum devices and cryogenic electronics are being developed, cryogenic wafer characterization methods must also scale up to provide statistical data on device parameters. Currently, characterization throughput of cryogenic devices is limited by the turnover time and sample capacity of traditional cryostats, where a measurement cycle for only a few devices can take several days. In this work, we demonstrate wafer-scale cryogenic characterization of a recently developed TiW/Al-AlOx/TiW normal-metal tunnel junction technology using CBTs. Measurements performed in a 300 mm cryogenic wafer prober (CWP) show on-chip electron temperatures below 700 mK across a full 150 mm wafer, as determined by primary thermometry. These results establish wafer-level testing below 1 K as a viable approach for large-scale cryogenic characterization of electrical devices, opening a pathway toward high-throughput screening of
quantum devices and direct wafer-scale characterization of aluminum-based superconducting
circuits.
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All authors Lassi Lehtisyrjä, Renan P. Loreto, Juho Luomahaara, Jarno Järvinen, Tuure Rantanen, Juha Vikstedt, Janne S. Lehtinen, Matti Remes, Timo Salminen, Juuso Helander, Aki Junes, Pasi Aaltonen, Vesa Henttonen, Mika Prunnila
Superconductivity
Nonequilibrium Quasiparticle Effects on Domain Wall Dynamics in Superconductors
Takuma Kanakubo, Taira Kawamura and Yusuke Kato
We study the dynamics of a domain wall (DW) in a type-II
superconductor connected to two heat reservoirs. We employ a generalized time-dependent Ginzburg–Landau framework in which the superconducting order parameter and the nonequilibrium quasiparticle distribution are treated as coupled dynamical variables. Within this framework, the effect of the thermal bias is imposed through boundary conditions on the quasiparticle distribution, which are set by the reservoir temperatures. We show, both numerically and within linear response, that the DW moves toward the hotter boundary. From the local momentum-balance relation implied by the model, we identify a viscous force and a force arising from the coupling between the order parameter and the nonequilibrium distribution function. The nonequilibrium distribution separates exactly into a boundary-driven part and a part generated by the motion of the DW itself. The former sets the sign of the DW velocity, whereas the latter renormalizes the relaxation of the order parameter. These results provide a microscopic basis for the phenomenological local-temperature description developed in our previous work.
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Statistical Mechanics
Persistence of BKT phase transition in the 2D nonanalytic XY model
Sihan Hu, Xianzhi Pan, Kun Chen et al. (+2 more)
We study the two-dimensional XY model with the nonanalytic pair potential $2[(1-\cos\delta)/2]^{p}$, whose small-angle law $\propto|\delta|^{2p}$ carries a cusp for $p<1$ and a flat bottom for $p>1$, invalidating the harmonic
spin-wave expansion. Two questions arise: the nature of the low-temperature ($T$) phase and of the phase transition. A naive energetic argument would predict genuine long-range order and an enhanced transition temperature for $p<1$, and no transition at all for $p>1$. Large-scale Monte Carlo simulations contradict both: for every $p>0$ the \dengrevxxi{low-$T$ phase} is quasi-long-range ordered, with anomalous dimension $\eta(T)\propto T^{1/p}$, and terminates at a Berezinskii–Kosterlitz–Thouless transition. Using a
vortex-free noncompact
lattice-field description and utilizing a duality transformation, we show that coarse-graining drives the height-difference distribution onto a single Gaussian fixed point, renormalizing the cusp and flatness into a finite harmonic stiffness that restores the
spin-wave description and the BKT scenario for all $p>0$.
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All authors Sihan Hu, Xianzhi Pan, Kun Chen, Yi Jiang, Youjin Deng
Soft Condensed Matter
Interfacial Packing of DNA Nanostars Regulates Dynamics on Synthetic Cell Membranes
Kazutoshi Masuda, Takahiro Yokoyama, Miho Yanagisawa et al. (+1 more)
DNA nanostructures are emerging as programmable components for engineering synthetic
cell membranes, yet how their collective packing and deformability regulate molecular dynamics at membrane interfaces remains poorly understood. Here, we investigate the packing and mobility of DNA nanostars with tunable stiffness on lipid-coated droplets. The negatively charged nanostars spontaneously adsorb onto cationic membranes, and their interfacial packing is changed by the bulk DNA concentration and droplet size, which together determine the number of encapsulated nanostars. Combining fluorescence recovery after photobleaching experiments with coarse-grained simulations, we reveal distinct packing-dynamics relationships for rigid and soft nanostars. For rigid nanostars,
diffusion first decreases gradually and then drops sharply with increasing interfacial packing, approaching a dynamically arrested state consistent with jamming-like behavior. In contrast, at equivalent experimental conditions, soft nanostars systematically reach lower interfacial packing fractions and show a weaker decrease in apparent mobility. This behavior is consistent with their weaker membrane affinity, which facilitates adsorption-desorption with the bulk. When this exchange is suppressed in simulations, crowding reduces the lateral
diffusion of both nanostar types, but produces distinct dense configurations: soft nanostars become strongly deformed, whereas rigid nanostars largely retain their shape and form interlocked, gear-like arrangements. Nanostar adsorption also impedes lipid
diffusion, while differences in membrane affinity result in distinct lipid mobile fractions. These findings reveal how the interplay between nanostar packing and deformability regulates molecular transport at membrane interfaces, providing a physical design principle for tuning lateral fluidity and crowding in artificial
cells.
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All authors Kazutoshi Masuda, Takahiro Yokoyama, Miho Yanagisawa, Arash Nikoubashman
Statistical Mechanics
Efficient kinetic Monte Carlo simulations with long-range electrostatic interactions
Roya Ebrahimi Viand, Bat-Amgalan Bat-Erdene, Karsten Reuter et al. (+1 more)
Charge transport in solid-state materials is often governed by charge carrier hopping processes in the presence of long-range electrostatic interactions. Kinetic Monte Carlo (kMC) simulations provide a framework for describing such rare-event dynamics over extended timescales. However, the efficient treatment of long-range interactions remains a major computational challenge, since each particle jump modifies the energy landscape globally and, in principle, requires updating all transition rates after every carrier motion. We present an efficient and generally applicable update process for these transition rates in the presence of long-range electrostatic interactions. To illustrate the method, we study charge
diffusion on a simple cubic host
lattice under an external electric field. The transport behavior is investigated in high states of charge (SOC), and the influence of temperature, electric field strength, and SOC is examined. Our simulations show strongly suppressed transport at 100\,% SOC (50\,% occupation) caused by a freezing of the charge carriers into a Coulomb superlattice. Slight deviations from this reference in terms of charge carrier concentration lead to a rapid increase in conductivity. A deeper analysis reveals that this behavior can be rationalized as transport of non-interacting defects in the Coulomb superlattice. These results demonstrate the capability of the proposed update procedure to efficiently capture non-
equilibrium transport phenomena in interacting charged systems and provide a foundation for simulations of more complex charge
diffusion problems.
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All authors Roya Ebrahimi Viand, Bat-Amgalan Bat-Erdene, Karsten Reuter, Sebastian Matera
Mesoscale and Nanoscale Physics
Efficient non-volatile electric control of magnetosensing in CrSBr
Bálint Fülöp, Yeonsu Jeong, Sofia Ferreira-Teixeira et al. (+10 more)
In two-dimensional
crystals, electrostatic gating can modulate the charge carrier density, thereby tuning their electrical properties. In
magnetic materials such as CrSBr, this approach can also enable direct electrical control of magnetoresistance. Non-volatile gating is particularly attractive since it allows the carrier density to be maintained at a desired level without the need for a continuous gate bias, offering significant advantages for technological applications. Here, we demonstrate a simple device architecture in which a solution-processed ferroelectric P(VDF-TrFE) layer is integrated directly onto a CrSBr channel, enabling non-volatile control of its magnetoresistance. We investigate the magnetotransport response over a broad temperature range and demonstrate a reproducible and robust gate dependence. Notably, the ferroelectric gate achieves a gating efficiency approximately one order of magnitude higher than that of a conventional SiO$_2$ dielectric, highlighting the potential of ferroelectric gating for electrical control of 2D
magnetic materials.
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All authors Bálint Fülöp, Yeonsu Jeong, Sofia Ferreira-Teixeira, Covadonga Álvarez-García, Tamás Prok, Xiaomin Guo, Endre Tóvári, Jong Hoon Jung, Luis Hueso, Paolo Samori, Marco Gobbi, Péter Makk, Szabolcs Csonka
Superconductivity
Universal transverse diode effects in superconducting unconventional magnet hybrids
Pei-Hao Fu, Luca Chirolli and Jorge Cayao
We demonstrate that superconducting unconventional magnet junctions harbor transverse
spin and charge diode effects with perfect rectification efficiencies. This nonreciprocal transverse transport is governed by the interplay of mirror reflections and
spin rotation with respect to the Néel vector, a mechanism that is universally applicable to all unconventional magnets. Interestingly, the transverse
spin diode features pure
spin currents, while the charge diode yields
spin-polarized charge currents, both exhibiting highly controllable rectification functionalities at vanishing net magnetization. Our results position superconducting unconventional magnets at the forefront of orthogonal engineering in next-generation transverse superconducting spintronics.
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