Soft Condensed Matter
Position-dependent friction in protein folding from a GLE derived with a non-stationary localized projection distribution
Salma Salem, Lucas Tepper, Benjamin J. A. Héry et al. (+3 more)
The Generalized Langevin Equation (GLE) is an integro-differential equation of motion for a general observable of a many-body system and is rigorously derived using the projection operator formalism. In the standard derivation, a stationary canonical phase space distribution is used for the projection. Here, we derive a novel class of GLEs using a non-stationary projection distribution that constrains the initial ensemble to a hypersurface in phase space on which the observable has a fixed value $A_0$. As a result, all GLE parameters, and in particular the
memory friction kernel, depend on $A_0$ and can be extracted from short simulations that do not sample the entire phase space. Applying this non-stationary GLE to
protein folding trajectories, we find for villin and an $\alpha$-helical poly-alanine segment that the total friction is higher in the folded state. These results demonstrate that observable-dependent friction effects are non-negligible and can be accounted for using non-stationary GLEs derived by constrained projection schemes.
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All authors Salma Salem, Lucas Tepper, Benjamin J. A. Héry, Henrik Kiefer, David D. Girardier, Roland R. Netz
Materials Science
Achieving 5-angstrom-resolution diffraction contrast with an uncorrected electron probe and nanosized defect characterizations
Yao Li, Austin C. Houston, Ziang Yu et al. (+8 more)
Atomic-resolution micrographs remain limited in application due to small field of view and low numbers of recorded defects. Defect imaging with reliable statistics in transmission electron microscopy (TEM) relies heavily on diffraction contrast. However, with 200-300 kV electrons, low-
curvature Ewald sphere limits diffraction resolution at ~5 nm. Here, we imaged defects with a forbidden condition in TEM and improved the resolution in diffraction contrast from 5 to 0.5 nm. The superiority of our equal-s method is demonstrated by the discovery of a novel phase and dislocation loop structure in steels, which have not been previously reported experimentally or theoretically. Our equal-s can largely replace the classical two-beam condition for defect study.
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All authors Yao Li, Austin C. Houston, Ziang Yu, Zehui Qi, Siwei Chen, Yajie Zhao, Sung Joo Kim, Steven J. Zinkle, Gerd Duscher, Blas P. Uberuaga, Benjamin K. Derby
Mesoscale and Nanoscale Physics
Theory of optical alignment and orientation of excitons in an ensemble of semiconductor nanoplatelets
O. O. Druzhinina and A. V. Rodina
We present the theory of
exciton optical
alignment and optical orientation effects in a single
semiconductor nanoplatelet (NPL) and in an ensemble of NPLs. The theoretical model is developed to take into account the emission from both bright and dark
exciton states in the case of strong electron-hole exchange interaction and an isotropic distribution of in-plane orientations of the NPLs' edges with respect to the linear polarization axis. The conditions for the linear optical response regime on the polarized resonant excitation of the bright
exciton are considered, and the steady-state and time-dependent expressions for polarized photoluminescence are presented for the low temperature case in the Faraday
magnetic field at normal incidence. The
symmetry of the obtained optical response corresponds to the $C_{2}$ point group for the single NPL and the $C_{\infty}$ point group for the NPL ensemble. The bright-to-dark
exciton coupling mechanism allowing one to observe the optical
alignment of the dark
exciton is considered. The example calculations of the effects are presented for the parameters close to those of CdSe/CdS core/shell NPLs. The effect of the fluctuations in the
exciton parameters in the ensemble on the polarization dephasing in the transverse effective
magnetic field is demonstrated.
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Statistical Mechanics · Cross-listed from hep-th
Relational background field formulation of discrete quantum gravity models: The case of $O(N)$ vector models in zero dimensions
Vincent Lahoche, Dine Ousmane Samary and Parham Radpay
In a recent paper arxiv.org/abs/2609.21031, we have introduced the concept of a relational background field as a new approach to the renormalization group (RG) for discrete
quantum gravity models, focusing on random
matrix models. The proposed method offers the dual advantage of preserving the model's gauge
symmetry (typically $U(N)$ or $O(N)$), whose breaking in conventional approaches has remained an open problem, and providing a more satisfactory treatment of the continuum or infrared (IR) limit. In this limit, the theory is described by a non-local field theory in dimension $D = 2k + 3$, where $k$ denotes the number of cuts in the effective spectrum as dictated by random
matrix theory. This pedagogical paper reviews this construction for real random vector models in zero dimensions, with $O(N)$ as the
symmetry group. Following the general strategy of background-field-type formulations, we show, using the BBP (Baik-Ben Arrous-P'ech'e) phase transition, that a partial Hubbard–Stratonovich decomposition of the quartic interaction, involving a
matrix-valued intermediate field, allows a preferred notion of scale to emerge. This scale, in turn, defines an RG flow, whose perturbative structure is analyzed. Our calculation demonstrates the existence of an asymptotic Wilson–Fisher-type fixed point, whose sole relevant critical exponent is in qualitative agreement with the double-scaling critical exponent of these models.
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Mesoscale and Nanoscale Physics
Nonabelian vortices: From topological strings to nonvolatile memory
Chau Dao, Eric Kleinherbers and Yaroslav Tserkovnyak
We investigate the topological classification and properties of nonabelian
vortices that arise in a 2-dimensional film of a two-component condensate. For a repulsive interaction between the condensates, we realize an order parameter in the ordered configuration space of three complex numbers $\mathcal C_3(\mathbb C)$. Analyzing the homotopic properties, we find the emergence of elementary nonabelian
vortex-antivortex pairs connected by energetic strings that are rooted in the repulsive interaction and carry the nonabelian information. Moreover, we predict the existence of Brunnian
vortices, which are textures exhibiting zero net winding of the condensate phases and can only be detected by a higher-order winding number. Finally, to motivate technological applications rooted in nonabelian
vortex transport, we devise a nonvolatile
memory storage device that encodes topologically robust information.
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Mesoscale and Nanoscale Physics
Correlated quasiperiodicity enables efficient thermoelectric energy conversion
Swaraj Biswas and Santanu K. Maiti
We investigate a route to enhanced thermoelectric energy conversion in nanoscale systems by exploiting a correlated quasiperiodic energy landscape in a one-dimensional chain coupled to source and drain reservoirs. The considered modulation generates a highly non-uniform electronic transmission spectrum, providing favorable conditions for achieving a large thermoelectric figure of merit. By systematically tuning the incommensurability parameter, a variety of quasiperiodic configurations are explored, several of which yield high values of the figure of merit exceeding $2$. Electronic transport properties are evaluated within a tight-binding framework using the non-
equilibrium Green's function formalism, while the thermoelectric coefficients, including electrical conductance, Seebeck coefficient, and electronic thermal conductance, are determined through the Landauer approach. The underlying quasiperiodic potential belongs to the Aubry-André-Harper (AAH) family and exhibits a weakly varying spatial profile, leading to transmission characteristics that are favorable for thermoelectric optimization. The influence of
phonon thermal conductance on the overall energy-conversion efficiency is also analyzed in detail. For the sake of completeness, we also critically inspect the effect of conductor to electrode coupling and the coupling asymmetry on $ZT$. We also check the thermoelectric response of conventional AAH system and an elaborate comparison is made with our chosen
quantum system. Our findings highlight the potential of correlated quasiperiodic nanostructures as promising candidates for efficient thermoelectric applications.
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Materials Science
SoLiD26: A First Principles Solid-Liquid Interface Dataset for Machine-learned Interatomic Potentials
Jonas Busk, Emil J. P. Frost, Yogeshwaran Krishnan et al. (+7 more)
Machine-learned interatomic potentials (MLIPs) for solid-
liquid interfaces in advanced materials applications, e.g., electrochemistry, catalysis and corrosion, require training data that samples both
liquid environments, the solid and the interface itself. We present SoLiD26, a curated solid-
liquid interface
dataset, containing 15.4 million first-principles atomic structures with up to 576 atoms and 15 chemical elements for training and evaluating MLIPs. The structures were compiled from density functional theory (DFT) calculations performed in studies of solid-
liquid interfaces, with most configurations originating from ab initio molecular dynamics (AIMD) simulations. Each record contains atomic species, positions, simulation
cell, periodic boundary conditions, potential energy and atomic forces. SoLiD26 includes aqueous coinage metal interfaces, electrode-electrolyte systems, and selected bulk reference structures, calculated with VASP using the PBE functional and D3 dispersion corrections. We describe the data ingestion and preparation pipeline used to construct the
dataset. The application of SoLiD26 for training and evaluating MLIPs is demonstrated with a suite of MACE models on a simple training, validation and test split. The
dataset enables development and benchmarking of MLIPs for structurally and chemically heterogeneous solid-
liquid interfaces.
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All authors Jonas Busk, Emil J. P. Frost, Yogeshwaran Krishnan, Henrik H. Kristoffersen, August E. G. Mikkelsen, Xueping Qin, Xin Yang, Heine A. Hansen, Arghya Bhowmik, Tejs Vegge
Soft Condensed Matter
Insight into ordering at nematic twist-bend interfaces
Szymon Drzazga, Piotr Kubala and Lech Longa
Twist-bend nematics formed by achiral particles support heliconical domains of opposite handedness. Using Monte Carlo and molecular dynamics simulations of repulsive bent particles, we study the interface between two such domains. Rather than a gradually untwisting texture, we find a density-modulated splay-bend-twist structure. The density modulation is along the helix axis with a period of approximately half the bulk pitch, while the twist is locally enhanced in magnitude, alternates in sign, and vanishes only on an undulating surface. An explicit director interpolation shows how gradients along the helix axis and across the interface combine to produce an undulating zero-twist surface.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Quantum Simulation of Si/SiGe Devices with Experimentally Calibrated Micromagnet Effects
Andrii Sokolov, Conor Power, Mathieu Moras et al. (+7 more)
Silicon-based
spin qubits in Si/SiGe
heterostructures are a leading platform for scalable
quantum computing, yet bridging the gap between theoretical computer-aided design(CAD) models and experimental reality remains a significant challenge. Standard simulations often fail to capture critical physical phenomena, such as interface dipoles, parasitic charge accumulation, and the
magnetic hysteresis of on-chip micromagnets. In this work, we present a comprehensive, experimentally calibrated 3D simulation pipeline for a 6-dot Si/SiGe device. We refine the
semiconductor band
alignment and introduce a semi-empirical classical charge screening model to accurately capture the formation of parasitic wells and their suppression of gate lever-arms. Furthermore, we apply the Jiles-Atherton model to account for the hysteresis and pre-magnetization of integrated cobalt micromagnets, successfully reproducing the experimental resonant frequencies across all six
qubits. By coupling these calibrated electrostatic and
magnetic profiles into a time-dependent rotating wave approximation (RWA)
Hamiltonian, we reproduce experimental observables, including microwave power chevrons. This framework provides a robust foundation for predicting device behavior, evaluating microwave line losses, and optimizing future scalable
spin qubit architectures prior to fabrication.
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All authors Andrii Sokolov, Conor Power, Mathieu Moras, Claude Rohrbacher, Brian Malone, Sergey Amitonov, Agostino Apra, Amir Sammak, Nodar Samkharadze, Elena Blokhina
Quantum Gases
Non-Hermitian engineering of superfluidity in a Rashba spin-orbit-coupled Fermi gas
Pingcheng Zhu, Lihong Zhou and Jianxin Zhong
We investigate superfluid pairing in a two-dimensional Rashba
spin-orbit-coupled Fermi gas subject to
spin-selective one-body loss. Within the non-Hermitian mean-field framework, we self- consistently solve the gap and number equations and find that moderate dissipation can significantly enhance the pairing gap, resulting in a pronounced nonmonotonic dependence on the dissipation strength. Dissipation also provides an additional control parameter for driving the system across the BCS-BEC crossover. We further analyze the quasi-particle spectrum and identify two distinct superfluid regimes characterized by one and three exceptional rings, separated by an exceptional spectral transition. Interestingly, dissipation can enhance both pairing channels while simultaneously inducing a momentum-dependent phase twist in the triplet component. These results demonstrate that
spin-selective dissipation provides a versatile non-Hermitian control knob for manipulating superfluid pairing, spectral structure, and crossover physics in
spin-orbit-coupled
quantum gases.
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Other Condensed Matter
Resonantly Enhanced Multiphonon Scattering and Local Orbital-Phonon Coupling in Bulk and Thin Flakes of 2D Single Crystals of Antiferromagnetic (NixFe1-x)2P2S6
Nasaru Khan, Miłosz Rybak, Yuliia Shemerliuk et al. (+5 more)
Orbital degrees of freedom play a pivotal role in shaping the physical properties of two-dimensional (2D) van der Waals
magnetic systems, strongly influencing electron-
phonon coupling and intermediate-state dynamics. In this study, we present a comprehensive temperature and thickness-dependent Raman investigation of the single
crystals of 2D van der Waals antiferromagnetic series (NixFe1-x)2P2S6. Utilizing Raman spectroscopy, we explore the interplay between local orbital excitations and
lattice vibrations, observing higher-order
phonon modes extending up to the fourth order. We observe an anomalously high and weakly temperature-dependent intensity ratio of these higher-order modes relative to low-energy first-order
phonons. Theoretical cluster calculations and Franck-Condon modelling reveal that these features originate from resonantly enhanced multiphonon scattering mediated by localized intermediate Ni 3d8 multiplet excitations. The local orbital occupancy of these intermediate states couples strongly to
lattice coordinates, providing a selective enhancement mechanism for specific
phonon channels. Notably, these higher-order features are absent in the end-member Fe2P2S6. This distinction reflects the charge-transfer character of Ni2P2S6, which places optical transitions in resonance with local multiplet states, contrasted with the Mott-Hubbard
insulator regime in Fe-rich analogues. Our findings clarify the microscopic origin of high-frequency Raman scattering in transition metal thiophosphates and underscore the central role of local orbital-
phonon interactions in 2D correlated magnets.
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All authors Nasaru Khan, Miłosz Rybak, Yuliia Shemerliuk, Sebastian Selter, Bernd Büchner, Saicharan Aswartham, Krzysztof Wohlfeld, Pradeep Kumar
Mesoscale and Nanoscale Physics
Aharonov-Bohm interference probing of chiral Andreev edge states via scanning gate microscopy
S. Maji and M. P. Nowak
We theoretically investigate the spatial response of chiral Andreev edge states at a
quantum Hall-
superconductor interface probed by scanning gate microscopy. Using the Bogoliubov-de Gennes formalism, we demonstrate that the localized potential of the scanning gate tip decouples the chiral Andreev edge states from the
superconductor into independent electron and hole paths. In the $\nu=2$ regime, this local separation forces the quasiparticles to accumulate a relative
magnetic phase in the normal region, resulting in Aharonov-Bohm-type conductance oscillations that are captured by a
geometric analytical model. At higher filling factors (e.g., $\nu=4$), the tip progressively interacts with spatially distinct edge channels, dynamically altering the Andreev-induced mode mixing and modifying the transport resonances. Furthermore, we show that these highly localized interferometric signatures survive in the presence of disorder, even when conventional non-local transport oscillations are masked.
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Statistical Mechanics
Multiscale Entropies as Order Parameters for Nonequilibrium Phase Transitions
Gerhard Jung and Misaki Ozawa
We develop a multiscale
entropy framework based on the wavelet conditional renormalization group that decomposes the total Shannon
entropy into contributions from different spatial scales. Generative modeling enables accurate estimation of these
entropies from configurations or snapshots, even in nonequilibrium systems whose underlying probability distributions are unknown. Applications to the
equilibrium $\varphi^4$ model and nonequilibrium active Model B+ show that multiscale
entropies reveal criticality and spatial organization obscured in the total
entropy. These
entropies serve as scale-dependent order parameters for characterizing phase transitions and pattern formation.
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Materials Science
Direct observation of the electronic structure of even-layer puckered SnTe monolayer films on graphene
Satoru Ichinokura, Shunsuke Tsuda, Kiyohisa Tanaka et al. (+1 more)
We report a direct observation of the electronic structure of monolayer SnTe on
graphene by angle-resolved photoemission spectroscopy. By combining low-energy electron diffraction, momentum microscopy, core-level spectroscopy, and first-principles calculations, we show that the observed monolayer-limit electronic structure is consistent with a puckered even-layer biatomic-layer building block rather than a nonpuckered square-flat structure. The observed band dispersion and its polarization dependence are reproduced by a puckered structure with a substrate-renormalized buckling amplitude. We further show that
graphene actively interacts with ultrathin SnTe by selecting its in-plane orientational texture, renormalizing the buckling amplitude, and modifying the local interfacial electrostatic environment in the monolayer limit. In comparison, multilayer SnTe exhibits a more ringlike momentum-space distribution, interlayer-split valence bands, and a stronger p-type character, revealing the onset of thickness
evolution from an interface-stabilized puckered ultrathin limit toward a more bulklike state.
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All authors Satoru Ichinokura, Shunsuke Tsuda, Kiyohisa Tanaka, Koichiro Yaji
Mesoscale and Nanoscale Physics
Charge and spin qubits in interacting quantum dots coupled to Rashba-active leads
Grazia Di Bello, Fabrizio Pavan, Mattia Trama et al. (+3 more)
We present a unified study of charge and
spin qubits encoded in a single interacting
quantum dot tunnel-coupled to Rashba fermionic leads. The dot is described by an Anderson impurity
Hamiltonian with either repulsive or attractive local interactions and a
magnetic field of arbitrary orientation. In the repulsive regime, a
spin qubit is encoded in the singly occupied
spin sector, whereas in the attractive regime, close to the degeneracy between the empty and doubly occupied configurations, these two states define a charge-
qubit subspace. We combine a weak-coupling Lindblad master equation in the Markovian secular limit with numerically controlled
matrix-product-state simulations of the full dot-reservoir system. In
equilibrium, we identify
magnetic pair breaking in the attractive regime and a weak Rashba-induced
magnetic anisotropy when the
magnetic field is rotated relative to the
spin-orbit axis. In the dynamical regime, relaxation and decoherence are controlled by the energetic gap between the logical
manifold and nearby leakage states, and are further enhanced by Rashba-dependent tunneling. These findings show that even a minimal Anderson-impurity description captures key ingredients for coherent
spin and charge
qubits: the energetic structure of leakage states and
spin-orbit-dependent dot-lead hybridization.
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All authors Grazia Di Bello, Fabrizio Pavan, Mattia Trama, Roberta Citro, Giulio De Filippis, Carmine Antonio Perroni
Strongly Correlated Electrons
Asymmetric magnetoresistance in 3$d$-5$d$ based La$_{0.67}$Ca$_{0.33}$MnO$_3$/SrIrO$_3$ bilayer: The role of unidirectional anisotropy
A. G. A. Rahman, Subham Naskar, R. K. Patel et al. (+4 more)
The complex interplay between
spin-orbit coupling, magnetism, and
magnetic field at the interface of a
heterostructure consisting of ferromagnet (FM) and heavy metal (HM), often exhibit extraordinary
magnetic and electric phenomena where an in-plane Dzyaloshinskii-Moriya (DM) interaction plays a crucial role to stabilize local
spin texture in FM layer. Here, we report detailed
magnetic and magneto-transport behaviour on an epitaxially grown thin
heterostructure with 3$d$ FM La$_{0.67}$Ca$_{0.33}$MnO$_3$ (LCMO) and 5$d$ HM SrIrO$_3$ (SIO).
Magnetic measurements show an unusual development of
magnetic ordering in SrIrO3 around 42 K, which further leads to a Mn/Ir
magnetic coupling at the interface. The magnetoresistance (MR) measurements show an
evolution of its value and shape with the
magnetic state of this bilayer. While MR is negative at high temperature, it shows a positive to negative crossover with stable
magnetic ordering of LCMO, and finally the positive MR exhibits an asymmetry at low temperature with the ordering of SIO. While we ascribe this unusual MR behaviour to interface-driven varying
spin scattering between itinerant and localized electrons, our results shed a light to comprehend the complex but tunable interface behavior on charge transport in a particularly designed
heterostructure, offering valuable insights for future functional material engineering.
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All authors A. G. A. Rahman, Subham Naskar, R. K. Patel, S. Manna, Chandrani Nath, Kranti Kumar, A. K. Pramanik
Materials Science
High-Throughput Photovoltaic Screening and Spacer-Dependent Shift Current in Two-Dimensional Hybrid Perovskites
Vikrant Chaudhary, Fu Li, Yue Zhao et al. (+5 more)
High-throughput first-principles screening of structurally diverse two-dimensional hybrid organic-inorganic perovskites (2D HOIPs) provides a route to systematically explore their photovoltaic properties. Here, we develop a computational workflow with two distinct objectives: spectroscopic limited maximum efficiency (SLME) screening to identify materials with promising photovoltaic potential and nonlinear shift current calculations to characterize their bulk photovoltaic response. Applying this workflow to a curated
dataset of experimentally reported 2D HOIPs, we identify more than 25 compounds with SLME values above 25% and more than 25 compounds exhibiting shift current responses exceeding 10~$\mu$A/V$^2$. We then focus on the Pb-I-based 2D HOIPs with $n=1$ to investigate the influence of spacer chemistry on the shift current response, revealing substantial spacer-dependent variations in both its magnitude and spectral peak position. Overall, these results highlight the potential of high-throughput first-principles calculations to accelerate the discovery of experimentally relevant 2D HOIPs with promising photovoltaic properties while revealing how organic spacer chemistry influences their nonlinear shift photocurrent response.
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All authors Vikrant Chaudhary, Fu Li, Yue Zhao, José A. Márquez, Wei Xie, Claudia Draxl, Zhihua Sun, Hongbin Zhang
Mesoscale and Nanoscale Physics
Observation of the orbital Nernst effect
Yuto Masuda, Takamasa Hirai, Daegeun Jo et al. (+5 more)
The Nernst effect, which converts a temperature gradient into a transverse charge current, is fundamental to thermoelectrics. Its
spin analogue, the
spin Nernst effect, enables thermal generation of transverse
spin currents and is central to
spin caloritronics. Recently, the discovery of orbital currents, the orbital counterpart of
spin currents, has extended angular-momentum transport beyond
spin, leading to the prediction of the orbital Nernst effect, in which a temperature gradient drives a transverse orbital current. However, experimental evidence for this effect has been lacking. Here, we report the observation of the orbital Nernst effect in Ti. Using Ni electrodes on Ti, we detect a thermally induced voltage that depends on the magnetization direction and scales linearly with the temperature gradient. This voltage is strongly suppressed both when Ni is replaced with Ni$_{81}$Fe$_{19}$ and when Ti is replaced with Cr, providing strong evidence that the signal originates from the orbital Nernst effect rather than the anomalous Nernst or
spin Nernst effect. These results establish thermally driven orbital transport, opening a pathway toward orbital caloritronics.
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All authors Yuto Masuda, Takamasa Hirai, Daegeun Jo, Naoki Yano, Peter M. Oppeneer, Hossein Sepehri-Amin, Ken-ichi Uchida, Kazuya Ando
Materials Science
Emergence of Chiral Dynamical Multiferroicity in a Ferroelectric Lattice Nonadiabatically Driven by Ultrafast Achiral Electric Fields
Chuanbao Zhang, Zhizhong Ding, Ping Cui et al. (+1 more)
It has been shown recently that chiral dynamical multiferroicity can be generated on a ferroelectric
lattice whose electric dipoles respond masslessly under chiral optical pumping. Here we demonstrate that, when driven by ultrafast electric pulses, chiral dynamical multiferroicity can also emerge even in situations where the external field is achiral. We reveal this striking phenomenon using a prototypical system of a BaTiO$_3$ moiré ferroelectric
lattice, emphasizing the key factor that its chiral electric dipoles inevitably behave massively upon ultrafast driving. At a deeper level, the massive nature is attributed to the anisotropic and nonadiabatic dipolar responses, as captured by the phase difference between the faster longitudinal and slower transverse components of the ferroelectric polarization. Crucially, such a phase difference naturally also gives rise to dynamical magnetization, which exhibits chiral
magnetic textures with monopole-like
topology coexisting with the ferroelectric chirality. These findings establish the dipolar mass as an enabling and tunable degree of freedom in inducing chiral dynamical multiferroicity, offering new avenues for ultrafast, non-contact
magnetic control using pure electric probes.
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All authors Chuanbao Zhang, Zhizhong Ding, Ping Cui, Zhenyu Zhang
Materials Science
Tough and high-temperature stable nacre-like Bi4Ti3O12-based piezoceramics
Ruxue Yang, Temesgen Tadeyos Zate, Elo Overgaard Mogensen et al. (+2 more)
Bi4Ti3O12-based ceramics are promising candidates for high-temperature piezoelectric devices owing to their high Curie temperature (> 600 {\deg}C). However, their low piezoelectric constants and poor mechanical reliability hinder their use in some engineering applications. Here, we fabricate nacre-like <00l>-textured (f_00l > 94%) Bi3.96Ce0.04Ti2.965W0.0175Nb0.0175O12 (NL-BCWNT) ceramics via a scalable
magnetic-assisted slip casting (MASC) self-assembly process. In addition to crystallographic texture, the final material presents a brick-and-mortar microstructure with micro-sized grains with a median aspect ratio of 15. NL-BCWNT exhibits a high fracture toughness for piezoceramics, with both $K_{IC}$ and $K_J$ reaching 2.2 $\pm$ 0.4 $MPa \cdot m^{0.5}$ and 4.2 $\pm$ 0.4 $MPa \cdot m^{0.5}$, respectively. The toughening originates from deflection and stable crack propagation within the nacre-like structure. The $d_{33}$ is 30 $\pm$ 3 $pC/N$ with a Curie temperature of 661${\deg}C$, and $d_{33}^*$ reaches 46 $\pm$ 3 $pm/V$ at 160 ${\deg} C$ with less remanent strain than random BCWNT. The improvements are attributed to aligned domain along spontaneous polarization direction <h00> with better mobility. NL-BCWNT exhibited excellent ferroelectricity fatigue resistance with higher than 106 cycles without degradation. Furthermore, similar improvements are observed in pure BiT, suggesting the general applicability of this strategy to other BiT-based systems. The nacre-like architecture thus provides a promising addition to the design toolbox for high-performance electromechanical materials.
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All authors Ruxue Yang, Temesgen Tadeyos Zate, Elo Overgaard Mogensen, Astri Bjørnetun Haugen, Florian Bouville
Mesoscale and Nanoscale Physics
Ultrastrong coupling of topologically protected edge and bulk magnetoplasmons without a dedicated cavity
F. Velli, P. Sai, M. Dub et al. (+6 more)
In the ultrastrong light-matter coupling regime, the ability to confine the electric field to subwavelength scales and define an electromagnetic mode is essential. This task is typically achieved through dedicated cavities, such as THz metal resonators. Here, we instead introduce ultrastrong coupling directly between distinct magnetoplasmon excitations, leveraging solely the spatial
symmetry of a confined electronic medium in the presence of a
magnetic field. By patterning an AlGaN/GaN single
quantum well hosting a two-dimensional electron gas into micrometer-scale patches, we tailor the mutual interactions between topologically protected edge and bulk magnetoplasmons, achieving coupling strengths of up to 0.1. The progressive breaking of rotational
symmetry determines the coupling rules and leads to the emergence of energy gaps and unique chiral-mode hybridization. Our results highlight a path towards exploiting the
symmetry class and
topology of the magnetoplasmon wavefunction as a new parameter space for ultrastrong light-matter interaction without a dedicated cavity.
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All authors F. Velli, P. Sai, M. Dub, J. Dzian, F. Le Mardele, M. Mittendorff, M. Orlita, W. Knap, C. Lange
Statistical Mechanics · Cross-listed from quant-ph
Classical Root Systems Reveal Defect-Junction Data in Stabilizer Renyi Entropy
M. A. Rajabpour
Universal information extracted from a critical
quantum state depends on how the state is probed. Spatial
entanglement, participation statistics, and stabilizer Rényi
entropy correspond to different replica geometries and need not isolate the same boundary data. We show that the complete distribution of Pauli magnitudes in critical Ising chains carries an exact
geometric fingerprint of boundary termination, distinguishing
lattice realizations that flow to the same infrared boundary fixed point. This structure is organized by discrete Selberg ensembles associated with the classical root systems $A$, $B$, $C$, and $D$: three open chains sharing the free–free Ising boundary condition retain distinct $B_L$, $C_L$, and $D_L$ trigonometric wall geometries. The standard
symmetry-breaking representatives instead produce rectangular, pinned, and character-inserted $C$ ensembles. Their four boundary moments contain exactly two independent multiplicative combinations invariant under local endpoint normalizations. One of these reduces exactly at finite rank to a moment of the fundamental symplectic character and provides a
lattice target for a defect–measurement-boundary junction amplitude. A conditional Gaussian-character law predicts its values throughout the unlocked phase, while exact-arithmetic finite-rank results at the $\alpha=4$ transition depart sharply from the Gaussian continuation. These results show that the full Pauli spectrum resolves boundary information invisible to the infrared boundary fixed point alone and provide concrete targets for replicated boundary conformal field theory.
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Statistical Mechanics · Cross-listed from quant-ph
Fate of average symmetry-protected topological states under symmetry-preserving quantum operations
Yoshihito Kuno and Takahiro Orito
The fate of average
symmetry-protected topological (ASPT) states based on the one-dimensional cluster state is investigated by using the Choi mapping, namely, the doubled
Hilbert-space formalism. By introducing two effective
spins, $\tau$ and $\eta$, on each doubled rung, we obtain a transparent representation of the ASPT parent
Hamiltonian and systematically identify the conserved stabilizers and the corresponding orders. We further study
symmetry-preserving operations that deform the ASPT by combining qualitative effective-
Hamiltonian and systematic parent-
Hamiltonian analyses with numerical
matrix-product-state filtering calculations. We find that although the ASPT remains robust over a broad range of decoherence strengths, strong-to-weak spontaneous
symmetry breaking (SWSSB) becomes exact in the maximal-decoherence limit. In addition, we consider
symmetry preserving no-click postselection, which removes the exact conservation law supporting the Rényi-2 string order of the ASPT and drives the system toward weak-
symmetry spontaneous
symmetry breaking (WSSB). Again, the ASPT remains robust over a broad range of postselection strengths, with WSSB becoming pronounced only near the projective limit and exact at the limit itself.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Optimal low-rank compression of quantum dynamics
Hugo Mackay, Donghoon Kim, Tan Van Vu et al. (+1 more)
Local
quantum interactions generate dynamics in an exponentially large
Hilbert space, yet locality and
entanglement restrict the information that can spread and accumulate. Bounds on propagation and
entanglement growth, together with tensor networks, exploit these restrictions to discard information unnecessary for describing the
evolution. This leads to a sharper question: how much information must any low-rank representation retain? Here we determine these limits, up to logarithmic factors, for short-range interactions. For time-independent
evolution, the optimal rank obeys $\log D=\widetilde O(t+\sqrt{\log(1/\epsilon)})$, with matching lower bounds fixing the accuracy exponent $1/2$; for arbitrary driving, matching fixed-time bounds instead give $2/3$. Correspondingly, the corresponding dynamical
entanglement spectra exhibit distinct small-$\alpha$ Rényi laws, $\alpha^{-1}$ and $\alpha^{-2}$. In one dimension, the static limit is constructively attained by an explicit MPO
algorithm, with an analogous extension to Liouvillian dynamics. Together, these results determine the irreducible information required to represent local
quantum evolution and uncover distinct
entanglement structures in static and driven dynamics.
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All authors Hugo Mackay, Donghoon Kim, Tan Van Vu, Tomotaka Kuwahara
Materials Science
Spurious spin nutation modes arising from truncated memory effects
Markus Weißenhofer, Ritwik Mondal, M. S. Mrudul et al. (+1 more)
Spin dynamics is conventionally treated as inertia-free. The inertial Landau-Lifshitz-Gilbert equation (iLLG) extends this with a second-order time derivative, predicting a high-frequency nutational mode that recent experiments have claimed to observe and interpreted as direct evidence for
spin inertia. We show that when
spin inertia is generated by eliminating additional dynamical degrees of freedom, the resulting exact
spin-only description is generally non-Markovian. The iLLG is recovered as the low-frequency, second-order truncation of the underlying
memory kernel. Using a minimal
spin–cavity model, we show that the exact eigenfrequencies and those obtained via the iLLG differ and that the
spin nutation mode predicted by the latter is a truncation-induced high-frequency artifact. This raises a broader question of the applicability of the iLLG obtained from analogous low-frequency truncations, which may likewise generate spurious high-frequency roots. Consequently, agreement of a high-frequency spectral feature with the iLLG nutation frequency does not, by itself, establish a physical nutation mode.
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All authors Markus Weißenhofer, Ritwik Mondal, M. S. Mrudul, Peter M. Oppeneer
Materials Science
Investigation of Hopping Conduction and Its Impact on the Subthreshold and Transition Region Transport in Oxide Semiconductor Transistors by Magneto-Transport Measurements
Chen Wang, Liankai Zheng, Kai Jiang et al. (+4 more)
In this work, magneto-transport measurements, including Hall effects and magnetoresistance (MR) at various temperatures, are employed to directly probe the electron transport properties in crystalline indium oxide (In2O3) and amorphous indium-zinc oxide (IZO) transistors. For the first time, we develop a subgap density of states (DOS) extraction method based on the MR measurements at low temperature, considering both the interference and orbital shrinkage effects. The sign and magnitude of MR are used as direct evidence to distinguish the dominating transport mechanisms between hopping conduction and free-electron conduction. It is found that crystalline In2O3 exhibits a subgap DOS more than two orders of magnitude lower than that of amorphous IZO, together with a smaller localization radius of hopping sites. As a result, crystalline In2O3 not only enhances the carrier mobility but also significantly reduces the supply voltage (VDD) because of the smaller transition region enabled by the much-suppressed subgap DOS. This study reveals that structural disorder critically influences the device operation in the subthreshold and transition regions of oxide
semiconductor transistors.
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All authors Chen Wang, Liankai Zheng, Kai Jiang, Jinxiu Zhao, Zhenyu Zhang, Xuefei Li, Mengwei Si
Statistical Mechanics
Uphill and downhill first passage of an active Brownian particle: Asymmetry and exact path reweighting
Mykola Tasinkevych, Xuan My Le and Artem Ryabov
First passage processes in active systems combine
stochastic transport with self-propulsion and orientational persistence, making motion along and against an external bias sensitive to the internal active dynamics. For passive biased
diffusion, opposite exits can have different splitting probabilities while their conditional first passage time distributions remain identical. We study how this relation changes for an active Brownian particle driven by a constant external force between two absorbing boundaries. Self-propulsion breaks the equality of the uphill and downhill first passage time distributions and modifies the splitting probabilities. Nevertheless, the two directional path ensembles remain exactly related by spatial reflection, which pairs downhill and uphill first passage paths of the same duration while preserving their orientational history. The log-ratio of the probabilities of a path and its reflected partner defines a path-dependent asymmetry functional and provides an exact reweighting between the two ensembles. In the symmetric half-weighted representation, the uphill and downhill first passage time distributions coincide for arbitrary orientational persistence. The same path relation also allows rare uphill statistics to be reconstructed from the more frequently sampled downhill trajectories. Numerical simulations confirm the weighted equality across the explored bias and persistence regimes, while perturbative and asymptotic analyses clarify how orientational persistence produces the directional asymmetry of the unweighted statistics. The exact relation between the two directional path ensembles suggests that similar
symmetry-based reconstruction protocols may be found in other nonequilibrium first-passage problems.
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Soft Condensed Matter
Multigeometric Breathing Mode Framework for viruses
Krish Bardhan, Charu Sharma, Shivansh Bhatnagar et al. (+1 more)
The estimation of the breathing mode frequency for viral capsids remains a persistent challenge across literature which spawned various frameworks and methodologies. However, discrepancies were observed between the experimental Low Frequency Raman Scattering (LFRS) and calculated pre-existing values. To solve this discrepancy, we propose a framework which is developed to determine the breathing-mode frequency by modelling the virus as a macroscopic coupled harmonic oscillator. By integrating mass-loading directly into the classical elastodynamic equations, this model yields an analytical expression that couples the system's total inertia with its specific geometry. Moreover, the viruses are segregated according to their geometries into three coordinates to acquire their respective
geometric eigen values. Here we illustrate how the proposed Multigeometric Breathing mode Framework for Virus (MBFV) outperforms prior models by yielding closer values than the pre-existing frameworks upon validating against LFRS.
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All authors Krish Bardhan, Charu Sharma, Shivansh Bhatnagar, Prafulla K Jha
Materials Science
Physics-guided inverse design of Co-based superalloys using machine learning and multi-objective optimization for enhanced $\gamma'$ solvus temperature
Prashil S. Joshi
The discovery of next-generation Co-based superalloys with improved high-temperature stability is hindered by the vast compositional design space and complex interactions among alloying elements governing gamma-
prime phase stability. This study presents a physics-informed machine learning framework for the inverse design of Co-based superalloys with higher gamma-
prime solvus temperature while accounting for
alloy density. Four descriptors representing atomic size mismatch (delta-MV), mixing enthalpy (Delta-Hm), electronegativity mismatch (delta-EN), and valence electron concentration mismatch (delta-VEC) were used to characterize the chemistry governing phase stability. Regression
algorithms were evaluated using leave-one-out cross-validation, with Gaussian Process Regression (GPR) achieving the best performance (R2 = 0.932, RMSE = 34.7 deg C, and MAE = 25.9 deg C). The probabilistic nature of GPR enabled uncertainty-aware
Bayesian optimization for exploring the uncharted composition space. Non-dominated Sorting Genetic
Algorithm II (NSGA-II) and Genetic
Algorithms were used to simultaneously increase gamma-
prime solvus temperature and reduce
alloy density. The optimization generated numerous previously unexplored Co-based
alloy compositions, with predicted gamma-
prime solvus temperatures of 1248-1353 deg C, including candidates approaching or exceeding the maximum value in the experimental
dataset. Descriptor analysis identified atomic size mismatch and mixing enthalpy as key factors governing gamma-
prime stability, while principal component analysis confirmed that the proposed
alloys occupy chemically relevant descriptor regions. This physics-informed inverse design framework provides an efficient route for identifying high-performance Co-based superalloys and can be adapted to other advanced structural
alloys.
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Materials Science
Fractionation as a Tool to Control Mn/Al Site Mixing and Magnetism in CaMn_{2+x}Al_{10-x}
Szymon Królak, Sushma Kumari, Sergey L. Bud'ko et al. (+1 more)
We report single
crystal growth and physical property characterization of CaMn_{2+x}Al_{10-x}
crystals grown using a fractionation approach. Three consecutive batches were obtained from the same initial melt composition, systematically sampling neighboring, narrow regions of the ternary Ca-Mn-Al phase diagram. Single-
crystal X-ray diffraction measurements reveal Mn/Al site mixing, with the excess Mn concentration, x, decreasing systematically with decreasing decanting temperature. A low-temperature upturn in magnetization and a maximum in electrical resistivity both become progressively weaker with decreasing excess Mn content, suggesting that the previously reported
magnetic properties attributed to stoichiometric CaMn_{2}Al_{10} instead arise from an inhomogeneous distribution of excess Mn atoms. More broadly, the results presented in this work demonstrate how fractionation can help distinguish intrinsic
magnetic behavior from disorder-induced effects associated with an inhomogeneous distribution of
magnetic ions in materials with a finite width of formation, particularly when itinerant magnetism is under consideration.
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All authors Szymon Królak, Sushma Kumari, Sergey L. Bud'ko, Paul C. Canfield