Statistical Mechanics · Cross-listed from cs.LG
Dropout Neural Network Training Viewed from a Percolation Perspective
Finley Devlin and Jaron Sanders
In this work, we investigate the existence and effect of percolation in training deep Neural Networks (NNs) with dropout. Dropout methods are regularisation techniques for training NNs, first introduced by G. Hinton et al. (2012). These methods temporarily remove connections in the NN, randomly at each stage of training, and update the remaining subnetwork with
Stochastic Gradient Descent (SGD). The process of removing connections from a network at random is similar to percolation, a paradigm model of statistical physics. If dropout were to remove enough connections such that there is no path between the input and output of the NN, then the NN could not make predictions informed by the data. We study new percolation models that mimic dropout in NNs and characterise the relationship between network
topology and this path problem. The theory shows the existence of a percolative effect in dropout. We also show that this percolative effect can cause a breakdown when training NNs without biases with dropout; and we argue heuristically that this breakdown extends to NNs with biases.
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Quantum Gases
Quasiparticle projection method for dynamically unstable Bose-Einstein condensates
Asier Izquierdo, Maria Arazo, Sofía Martínez-Garaot et al. (+1 more)
We present a general formalism for performing a time-dependent Bogoliubov analysis of a dynamically unstable Bose-Einstein condensate, which extends the quasiparticle projection method of Morgan et al. [Phys. Rev. A 57, 3818 (1998)] to cases with a complex spectrum. By introducing the proper left eigenvectors associated with each regime, we construct a biorthogonal basis. While the usual Bogoliubov normalization $\langle u | u \rangle - \langle v | v \rangle = 1$ may not hold in this basis, it still allows for a complete mode decomposition and an accurate reconstruction of arbitrary perturbations over time. This approach extends the applicability of the Bogoliubov framework beyond the stable regime, providing a consistent analysis of the time
evolution of unstable condensates. As a proof of concept, we apply the method to a one-dimensional condensate with attractive interactions, which is dynamically unstable and evolves into nonstationary localized structures seeded by small perturbations. Overall, the present method provides a complete and robust mode expansion that remains meaningful beyond the linear regime and useful for characterizing the macroscopic development of instabilities.
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All authors Asier Izquierdo, Maria Arazo, Sofía Martínez-Garaot, Michele Modugno
Materials Science
CrSe_2 and CrTe_2 Monolayers as Efficient Air Pollutants Nanosensors
Hakkim Vovusha, Puspamitra Panigrahi, Yash Pal et al. (+4 more)
Nanosensors are critical in environmental monitoring, industrial safety, and public health by detecting specific hazardous gases like CO, NO, SO_2, and CH_4 at trace levels. This study uses density functional theory (DFT) calculations to examine the gas-sensing capabilities of chromium diselenide (CrSe_2) and chromium ditelluride (CrTe_2) monolayers through their structural and electronic responses to gas adsorption. Adsorption energy analysis shows that Te vacancy-induced CrTe_2 (VTe-CrTe_2) exhibits the strongest binding with energies of -1.52, -1.79, and -1.61 eV for CO, NO, and SO_2, respectively. Similarly, CrSe_2 has its values of -1.13, -1.17, -0.90, and -1.12 eV for CO, NO, SO_2, and CH_2, respectively, indicating suitability for reversible sensing. This study also investigates how substitutional doping of Ge, Sb, and Sn influences the sensing mechanism of CrSe_2 and CrTe_2 monolayers. Density of states (DOS) analysis highlights notable electronic changes around the
Fermi level, especially in VTe-CrTe_2 and Sb/Sn-doped CrTe_2, confirming their enhanced sensing abilities. Charge density difference analysis shows significant charge redistribution, with CrTe_2 experiencing stronger charge transfer effects than CrSe_2. Variations in electrostatic potential and work function further demonstrate the higher sensitivity of CrTe_2, particularly in its defective and doped forms, confirming its status as a superior material for gas sensing applications.
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All authors Hakkim Vovusha, Puspamitra Panigrahi, Yash Pal, Muhammad J. A. Shiddiky, Massimiliano Di Ventra, Hoonkyung Lee, Tanveer Hussain
Quantum Gases
From Bose glass to many-body localization in a one-dimensional disordered Bose gas
Vincent Grison and Nicolas Dupuis
We determine the finite-temperature phase diagram of a one-dimensional disordered Bose gas using bosonization and the nonperturbative functional renormalization group (RG). We discuss two different scenarios, based on distinct truncations of the effective action. In the first scenario, the Bose glass is destabilized at any finite temperature, giving rise to a normal fluid. Nevertheless, one can distinguish a low-temperature glassy regime, where disorder plays an important role on intermediate length and time scales, from a high-temperature regime, where disorder becomes irrelevant. In the second scenario, below a temperature $T_c$, the RG flow exhibits a singularity at a finite value of the RG momentum scale. We propose that this singularity signals a lack of thermalization and the existence of a localized phase for $T<T_c$. We provide a description of this low-temperature localized phase within a droplet picture and highlight a number of possible similarities with characteristics of many-body localized phases, including non-thermal behavior, avalanche instabilities and many-body resonances, the structure of the many-body spectrum, and slow dynamics in the ergodic phase. The normal fluid above $T_c$, and below a crossover temperature $T_g$, exhibits glassy properties on intermediate scales.
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Materials Science
Reproducible container solutions for codes and workflows in materials science
Dylan Bissuel, Léo Orveillon, Benjamin Arrondeau et al. (+15 more)
A computing solution combining the GNU Guix functional package manager with the Apptainer container system is presented. This approach provides fully declarative and reproducible software environments suitable for computational materials science. Its versatility and performance enable the construction of complete frameworks integrating workflow managers such as AiiDA, and Ewoks that can be deployed on HPC infrastructures. The efficiency of the solution is illustrated through several examples: (i) AiiDA workflows for automated
dataset construction and analysis as well as path-integral molecular dynamics based on ab initio calculations; (ii) workflows for the training of machine-learning interatomic potentials; and (iii) an Ewoks workflow for the automated analysis of coherent X-ray diffraction data in large-scale synchrotron facilities. These examples demonstrate that the proposed environment provides a reliable and reproducible basis for computational and data-driven research in materials science.
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All authors Dylan Bissuel, Léo Orveillon, Benjamin Arrondeau, Paulo Almeida De Mendonça, Irina Piazza, Martin Uhrin, Étienne Polack, Akshay Krishna Ammothum Kandy, David Martin-Calle, Jonathan Chapignac, Aadhityan Arivazhagan, Lorenzo Paulatto, Pierre-Antoine Bouttier, M.-I Richard, Thierry Deutsch, David Rodney, A M Saitta, Nöel Jakse
Disordered Systems and Neural Networks
Machine learning Majorana topology using unsupervised and supervised learning
Jacob Taylor, Haining Pan and Sankar Das Sarma
In unsupervised learning, the training data for deep learning does not come with any labels, thus forcing the
algorithm to discover hidden patterns in the data for discerning useful information. This, in principle, could be a powerful tool in identifying topological order since
topology does not always manifest in obvious physical ways (e.g., topological superconductivity) for its decisive confirmation. The problem, however, is that unsupervised learning is a difficult challenge, necessitating huge computing resources, which may not always work. In the current work, we combine unsupervised and supervised learning to establish that unlabeled (simulated) data in the Majorana splitting in realistic short disordered nanowires may enable not only a distinction between `topological' and `trivial', but also where their crossover happens in the relevant parameter space. This may be a useful tool in identifying
topology in experimental Majorana nanowires.
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Strongly Correlated Electrons · Cross-listed from hep-lat
Algorithmic Aspects of Gauged Gaussian Fermionic PEPS: Gauge Fixing and Translation Invariance
Itay Gomelski, Jonathan Elyovich, Ariel Kelman et al. (+2 more)
Lattice gauge theories (LGTs) provide a powerful framework for studying non-perturbative phenomena in gauge theories. However, conventional approaches such as Monte Carlo (MC) simulations in imaginary time are limited, as they do not allow real time
evolution and suffer from a sign problem in many important cases. Using Gauged Gaussian fermionic projected entangled pair states (GGFPEPS) as a variational ground state ansatz offers an alternative for studying LGTs through a sign-problem-free variational MC. As this method is extended to larger and more complex systems, understanding its numerical behavior becomes essential. While conventional action based MC has been extensively studied, the performance and characteristics of non-action-based MC within the GGFPEPS framework are far less explored. In this work, we investigate these algorithmic aspects, identifying an optimal update size for GGFPEPS-based MC simulations for $\mathbb{Z}_2$ in $2+1$ dimensions. We show that gauge fixing generally slows convergence, and demonstrate that not exploiting the translation-invariance can, in some cases, improve the computational time scaling of error convergence. We expect that these improvements will allow advancing the simulation to larger and more complex systems.
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All authors Itay Gomelski, Jonathan Elyovich, Ariel Kelman, Erez Zohar, Patrick Emonts
Statistical Mechanics · Cross-listed from quant-ph
Universal Statistics of Measurement-Induced Entanglement in Tomonaga-Luttinger liquids
Kabir Khanna and Romain Vasseur
We study the statistics of measurement-induced
entanglement (MIE) after partial measurement on a class of one-dimensional
quantum critical states described by Tomonaga-Luttinger
liquids at low energies. Using a replica trick to average over measurement outcomes in the charge basis and tools from conformal field theory (CFT), we derive closed-form expressions for the cumulants of MIE. We show that exact Born-averaging over microscopic measurement outcomes becomes equivalent at low energy to averaging over conformal boundary conditions weighted by their corresponding partition functions. Our results yield distinctive critical behavior across all cumulants in the regime where the unmeasured parts of the system are maximally separated. We also obtain the full distribution of MIE, finding that it is generically bimodal and exhibits fat-tails. We corroborate our analytical predictions by numerical calculations and find good agreement between them.
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Superconductivity
Chiral topological superconductivity in hole-doped Sn/Si(111)
Matthew Bunney, Lucca Marchetti, Domenico Di Sante et al. (+2 more)
A third monolayer of tin atoms on the
semiconductor substrate Si(111) has been shown to become superconducting upon six to ten percent hole doping. Experiments have reported promising results hinting at a superconducting
chiral $d$-wave order parameter. Here we examine Sn/Si(111) by combining most recent ab initio results, quasi-particle interference calculations, state-of-the-art truncated-unity functional renormalization group simulations and Bogoliubov-de Gennes analysis. We show remarkable agreement between experimental and theoretical quasi-particle interference data both in the metallic and superconducting regimes. The interacting phase diagram reveals that the superconductivity is indeed
chiral $d$-wave with Chern number $C=4$. Surprisingly, magnetically ordered phases are absent, instead we find charge density wave order, as observed in related compounds, as a competing phase. Our results demonstrate that Sn/Si(111) is an outstanding candidate material for
chiral topological superconductivity.
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All authors Matthew Bunney, Lucca Marchetti, Domenico Di Sante, Carsten Honerkamp, Stephan Rachel
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Freeness Reined in by a Single Qubit
Alexander Altland, Francisco Divi, Tobias Micklitz et al. (+1 more)
Free probability provides a framework for describing correlations between non-commuting observables in complex
quantum systems whose
Hilbert-space states follow maximum-
entropy distributions. We examine the robustness of this framework under a minimal deviation from freeness: the coupling of a single ancilla
qubit to a Haar-distributed
quantum circuit of dimension $D0 \gg 1$. We find that, even in this setting, the correlation functions predicted by free probability theory receive corrections of order $O(1)$. These modifications persist at long times, when the dynamics of the coupled system is already ergodic. We trace their origin to non-uniformly distributed stationary
quantum states, which we characterize analytically and confirm numerically.
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All authors Alexander Altland, Francisco Divi, Tobias Micklitz, Maedeh Rezaei
Statistical Mechanics · Cross-listed from hep-th
Non-hermitian Density Matrices from Time-like Entanglement and Wormholes
Jonathan Harper, Taishi Kawamoto, Ryota Maeda et al. (+2 more)
We extensively explore the connections between time-like
entanglement and non-hermitian density
matrices in
quantum many-body systems. We classify setups where we encounter non-hermitian density
matrices into two types: one is due to causal influences under
unitary evolutions, and the other is due to non-
unitary evolutions in non-hermitian systems. We provide various examples of these setups including interacting harmonic oscillators, two dimensional conformal field theories and
holographic dualities. In them, we compute the time-like
entanglement entropy and imagitivity, which measures how much density
matrices are non-hermitian. In both two classes, typical
holographic examples are given by traversable AdS wormholes. We explain how causal influences in a wormhole dual to a pair of non-hermitian
quantum systems is possible even without interactions between them. We argue that to realize a traversable wormhole we need not only ordinary
quantum entanglement but also time-like
entanglement.
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All authors Jonathan Harper, Taishi Kawamoto, Ryota Maeda, Nanami Nakamura, Tadashi Takayanagi
Quantum Gases
Interferometric probe for the zeros of the many-body wavefunction
Wayne J. Chetcuti, Anna Minguzzi, Juan Polo et al. (+1 more)
The nodal surfaces of the many-body wavefunction are fundamental
geometric features that encode critical information regarding particle statistics and their interaction. Directly probing these structures, particularly in correlated
quantum systems, remains a significant experimental challenge. Here, we provide rigorous results on the structure of the many-body wavefunction and propose to use an interferometric technique to probe its zeros in ultra-cold atomic systems. Specifically, we refer to the so-called heterodyne interferometric reconstruction of the phase of the many-body wavefunction. We prove that the sought nodal surfaces show up as specific discontinuities in the interference fringes. Following Leggett, both `
symmetry-dictated' nodal surfaces, due to particle statistics, and `non-
symmetry dictated' nodal surfaces emerging from interaction effects, can be probed. We demonstrate how the
spin degrees of freedom, effectively modifying the structure of the nodal surfaces of the many-body wavefunction, leave distinct fingerprints in the resulting interference pattern. Our work addresses important features of the structure of the many-body wavefunction that are broadly relevant for
quantum science ranging from conceptual aspects to computational questions of extended systems and
quantum simulation.
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All authors Wayne J. Chetcuti, Anna Minguzzi, Juan Polo, Luigi Amico
Strongly Correlated Electrons
Magnetism and superconductivity in bilayer nickelate
Hui Yang and Ya-Hui Zhang
The discovery of high-temperature superconductivity in
bilayer nickelate La$_{3}$Ni$_{2}$O$_{7}$ necessitates a minimal theoretical model that unifies the superconducting phase with the
spin-density-wave (SDW) phase without external pressure or strain. We propose a model where half-filled $d_{z^{2}}$ local moments interact with itinerant $d_{x^{2}-y^{2}}$ electrons via strong Hund's coupling $J_H$, which reduces to a
bilayer type-II t-J model in the large $J_H$ limit. Using iDMRG calculations on an $L_y=4, L_z=2$ cylinder, we demonstrate that the competition between double-exchange ferromagnetism and in-plane superexchange generates period-4 stripe-like SDW order-a feature absent in one-orbital t-J model with only $d_{x^2-y^2}$ orbital. Furthermore, increasing the interlayer exchange coupling suppresses
magnetic order and stabilizes interlayer s-wave superconductivity. These results identify the type-II t-J model as a minimal framework for capturing the interplay of magnetism and superconductivity in
bilayer nickelates.
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Strongly Correlated Electrons
False Vacuum Decay in Flat-Band Ferromagnets: Role of Quantum Geometry and Chiral Edge States
Fabian Pichler, Clemens Kuhlenkamp and Michael Knap
Dynamical control of
quantum matter is a challenging, yet promising direction for probing strongly correlated states. Motivated by recent experiments in twisted MoTe$_2$ that demonstrated optical control of magnetization, we propose a protocol for probing magnetization dynamics in flat-band ferromagnets. We investigate the nucleation and dynamical growth of
magnetic bubbles prepared on top of a false vaccum in both itinerant ferromagnets and
spin-polarized Chern
insulators. For
ferromagnetic metals, we emphasize the crucial role of a non-trivial
quantum geometry in the magnetization dynamics, which in turn also provides a probe for the
quantum metric. Furthermore, for
quantum Hall ferromagnets, we show how properties of
chiral edge modes localized at domain-wall boundaries can be dynamically accessed. Our work demonstrates the potential for nonequilibrium protocols to control and probe strongly correlated phases, with particular relevance for twisted MoTe$_2$ and
graphene-based flat-band ferromagnets.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Constant-Depth Clifford-Hierarchy Gates via Non-Abelian Surface Codes
Alison Warman and Sakura Schafer-Nameki
We present an entirely 2D constant-depth realization of topologically protected phase gates at any level of the Clifford hierarchy, and beyond, using non-Abelian surface codes. Our construction encodes a logical
qubit in the
quantum double $D(G)$ of a non-Abelian group $G$ on a triangular spatial patch. The logical gate is implemented by a constant-depth
circuit constructed from stacking on the spatial region a
symmetry-protected topological (SPT) phase specified by a group 2-cocycle and boundary counter-terms. The Bravyi-König
theorem limits the
unitary gates implementable by constant-depth
quantum circuits on Pauli stabilizer codes in $D$ dimensions to the $D$-th level of the Clifford hierarchy. We bypass this limitation, by constructing constant-depth
unitary gates at arbitrary levels of the Clifford hierarchy purely in 2D, without sacrificing locality or fault tolerance, at the cost of using the
quantum double of a non-Abelian group $G$. Specifically, for $G = D_{4N}$, the dihedral group of order $8N$, we realize the phase gate $T^{1/N} = \mathrm{diag}(1, e^{i\pi/(4N)})$ in the logical $\overline{Z}$ basis. In this context, we propose a non-abelian stabilizer group formalism, which we work out for dihedral groups. For $8N = 2^n$, the logical gate lies at the $n$-th level of the Clifford hierarchy and, importantly, has a
qubit-only realization: we show that it can be constructed in terms of Clifford-hierarchy stabilizers for a code with $n$ physical
qubits on each edge of the
lattice. We also discuss code-switching to the double surface-code $D(\mathbb{Z}_2\times\mathbb{Z}_2)$, to complete a universal gate-set in this setup.
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Quantum Gases · Cross-listed from quant-ph
Quantum simulation using Trotterized disorder Hamiltonians in a single-mode optical cavity
Rahel Lea Baumgartner, Pietro Pelliconi, Soumik Bandyopadhyay et al. (+4 more)
All-to-all interacting and disordered many-body systems are notoriously hard to simulate on
quantum platforms, as interactions are commonly mediated by auxiliary degrees of freedom that lower the amount of disorder, introducing undesired correlations. In this work, we show how a Trotterization scheme can be effectively utilized to densify the disorder of the model. In particular, we study the statistical properties of the resulting model, as well as Trotterization errors in the simulation that affect the time
evolution and dynamical observables. As a concrete example, we propose an implementation via a single-mode cavity QED platform of the complex Sachdev-Ye-Kitaev model. We analyze several features of the effective model, such as the distribution of the effective couplings, the number of interacting sites, state preparation, and the behavior of
quantum chaos probes. We conclude this work with a detailed investigation of the robustness of our findings against dissipation, both analytically and numerically.
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All authors Rahel Lea Baumgartner, Pietro Pelliconi, Soumik Bandyopadhyay, Francesca Orsi, Philipp Hauke, Jean-Philippe Brantut, Julian Sonner
Statistical Mechanics
Monte Carlo study of phase transitions in model orthonickelate
V. S. Ryumshin
The results of numerical simulation using a classical Monte Carlo method with a kinematic accounting of the
bosons concentration for a pseudospin model of orthonickelates are presented. Type of the phase transitions of the model orthonickelates is investigated.
Materials Science
Nucleation suppression by charge screening on grain boundaries: a kinetic model for bulk imprint in polycrystalline ferroelectric thin films
Huanhuan Tian, Jianguo Yang and Ming Liu
The imprint effect, a significant reliability challenge in ferroelectric
memories, manifests as a shift in the coercive field during retention and endurance tests, ultimately degrading the usable
memory window. \rv{While traditional models attribute imprint primarily to charge screening at the interface between the dead layer and the ferroelectric film, the contribution from grain boundaries has been largely overlooked. This work advances a bulk imprint mechanism by establishing a phase-field model, which demonstrates that the tuning of domain
nuclei near grain boundaries via charge screening consistently explains the imprint process and aligns with key experimental trends.} These findings provide novel insights into the imprint process and advance the understanding of reliability issues in ferroelectric
memory devices.
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Materials Science · Cross-listed from cs.CE
Probabilistic Predictions of Process-Induced Deformation in Carbon/Epoxy Composites Using a Deep Operator Network
Elham Kiyani, Amit Makarand Deshpande, Madhura Limaye et al. (+7 more)
Fiber reinforcement and
polymer matrix respond differently to manufacturing conditions due to mismatch in coefficient of thermal expansion and
matrix shrinkage during curing of thermosets. These heterogeneities generate residual stresses over multiple length scales, whose partial release leads to process-induced deformation (PID), requiring accurate prediction and mitigation via optimized non-isothermal cure cycles. This study considers a unidirectional AS4 carbon fiber/amine bi-functional epoxy prepreg and models PID using a two-mechanism framework that accounts for thermal expansion/shrinkage and cure shrinkage. The model is validated against manufacturing trials to identify initial and boundary conditions, then used to generate PID responses for a diverse set of non-isothermal cure cycles (time-temperature profiles). Building on this physics-based foundation, we develop a data-driven surrogate based on Deep Operator Networks (DeepONets). A DeepONet is trained on a
dataset combining high-fidelity simulations with targeted experimental measurements of PID. We extend this to a Feature-wise Linear Modulation (FiLM) DeepONet, where branch-network features are modulated by external parameters, including the initial degree of cure, enabling prediction of time histories of degree of cure, viscosity, and deformation. Because experimental data are available only at limited time instances (for example, final deformation), we use transfer learning: simulation-trained trunk and branch networks are fixed and only the final layer is updated using measured final deformation. Finally, we augment the framework with Ensemble Kalman Inversion (EKI) to quantify uncertainty under experimental conditions and to support optimization of cure schedules for reduced PID in composites.
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All authors Elham Kiyani, Amit Makarand Deshpande, Madhura Limaye, Zhiwei Gao, Zongren Zou, Sai Aditya Pradeep, Srikanth Pilla, Gang Li, Zhen Li, George Em Karniadakis
Materials Science
Nonreciprocal Transport with Quantum Geometric Origin in Layered Hybrid Perovskite
Zihan Zhang, Sihan Chen, Mingfeng Chen et al. (+14 more)
Quantum geometry quantifies how the electron wavefunction evolves distinctly from conventional transport theory. In noncentrosymmetric materials, nonreciprocal transport with
quantum geometric origin remains prominent with localized charge independent of vanished group velocity. The discovery of such nonreciprocal and nonlinear responses was realized by recent advances in two-dimensional materials. As a promising candidate, the electronic structure and
symmetry of layered hybrid perovskites can be deliberately designed and manipulated by incorporating selected organic ligands. Despite the observation of exotic photogalvanic effects and
chiral optical effects, the underlying mechanism how these nonlinear responses are enabled in the multi-
quantum well structures remained unclear. Here we demonstrated the
quantum geometric origin for interlayer spontaneous photocurrent in (PEA)2PbI4. Contrary to assumptions that charge transport across the 2D planes is limited, we observed a spontaneous photocurrent along this crystalline orientation. Theoretical analysis using a tight-binding model identifies shift current as the microscopic origin. This
quantum geometric effect is enabled by ionic displacements from centrosymmetric coordinates and enhanced by multiband transition high-density bands of the layered hybrid
crystal. We anticipate that such unique low-dimensional systems with structure can provide fertile ground for discovering novel optoelectronic functionalities.
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All authors Zihan Zhang, Sihan Chen, Mingfeng Chen, Jee Yung Park, Gang Shi, Kaitai Xiao, Swati Chaudhary, Alejandro T. Busto, Kenji Watanabe, Takashi Taniguchi, Peng Xiong, Xiao-Xiao Zhang, Efstratios Manousakis, Letian Dou, Xi Wang, Cyprian Lewandowski, Hanwei Gao
Strongly Correlated Electrons · Cross-listed from quant-ph
Quantum Integrability of Hamiltonians with Time-Dependent Interaction Strengths and the Renormalization Group Flow
Parameshwar R. Pasnoori
In this paper we consider
quantum Hamiltonians with time-dependent interaction strengths, and following the recently formulated generalized Bethe ansatz framework [P. R. Pasnoori, Phys. Rev. B 112, L060409 (2025)], we show that constraints imposed by integrability take the same form as the renormalization group flow equations corresponding to the respective
Hamiltonians with constant interaction strengths. As a concrete example, we consider the anisotropic time-dependent Kondo model characterized by the time-dependent interaction strengths $J_{\parallel}(t)$ and $J_{\perp}(t)$. We construct an exact solution to the time-dependent Schrodinger equation and by applying appropriate boundary conditions on the
fermion fields we obtain a set of
matrix difference equations called the
quantum Knizhnik-Zamolodchikov (qKZ) equations corresponding to the XXZ R-
matrix. The consistency of these equations imposes constraints on the time-dependent interaction strengths $J_{\parallel}(t)$ and $J_{\perp}(t)$, such that the system is integrable. Remarkably, the resulting temporal trajectories of the couplings are shown to coincide exactly with the RG flow trajectories of the static Kondo model, establishing a direct and universal correspondence between integrability and renormalization-group flow in time-dependent
quantum systems.
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Materials Science
Rapid synthesis of dual-element isotope-enriched alpha-MoO3 crystals by reactive vapor transport
Ryan W. Spangler, Jacob M. Shusterman, Anton V. Ievlev et al. (+3 more)
In this work, we develop a rapid reactive vapor transport technique to efficiently utilize limited isotopically pure precursors, particularly gaseous 18O2, and synthesize mm-scale, high-quality
crystals within few-minute growth durations. We unlock this capability by using metallic molybdenum precursors with high source temperatures (900 C) and total pressures (1 atm) to maximize precursor efficiency and yield. Subsequently, we grow MoO3 single
crystals with high and uniform enrichment levels of 98Mo and 18O isotopes in several different permutations. As probed by Raman spectroscopy, modest and significant
phonon energy
redshifts occur following 98Mo and 18O enrichment, respectively. By demonstrating control over both molybdenum and oxygen isotopic fractions, we establish a powerful tool to advance nanophotonics and thermal management goals using MoO3. This work is motivated by the possibility to enhance and engineer
lattice vibrational mode phenomena including thermal conduction and
hyperbolic phonon polariton (HPhP) dispersion, with particular interest in comparing the effects of light and heavy element enrichment.
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All authors Ryan W. Spangler, Jacob M. Shusterman, Anton V. Ievlev, Patrick E. Hopkins, Joshua D. Caldwell, Jon-Paul Maria
Materials Science
Transition from population- to coherence-dominated nondiffusive thermal transport
Laurenz Kremeyer, Bradley J. Siwick and Samuel Huberman
Deviations from diffusive heat transport in high thermal conductivity crystalline
insulators are generally understood within the framework of the
phonon Boltzmann Transport Equation. However, for low thermal conductivity materials with large primitive
cells or strong anharmonicity, the recently developed Wigner Transport Equation is more appropriate as it includes tunnelling between overlapping
phonon bands. In this work, via solutions to the Wigner Transport Equation, we develop a scheme to obtain the dynamics of the
phonon populations and coherences as a function of an arbitrary heat source. The approach is applied to predict size effects and dynamical thermal conductivities in CsPbBr$_\text{3}$ and La$_\text{2}$Zr$_\text{2}$O$_\text{7}$ using first-principles data as input. We predict significant deviations from the bulk thermal conductivity in these materials at length scales on the order of hundreds of nanometers to a few microns at room temperature, well within the reach of direct observation using current experimental techniques.
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Strongly Correlated Electrons
CrFe2Ge2: Investigation of novel ferromagnetic material of Fe13Ge8-type crystal
P.L.S. Cambalame, B.J.C. Vieira, J.C. Waerenborgh et al. (+2 more)
We successfully synthesized a novel intermetallic compound $\rm CrFe_2Ge_2$ with the $\rm Fe_{13}Ge_{8}$-type
crystal structure. A structural study is presented combining single-
crystal X-ray diffraction and Mössbauer spectroscopy analysis, confirming the presence of two distinct Fe sublattices. $\rm CrFe_2Ge_2$ exhibits a metallic
ferromagnetic state with $T_C \approx \rm 200~K$. This material does not follow the usual $M^2 \propto H/M$ Arrott law, rather a modified Arrott law is obeyed in this material. The critical exponents determined from detailed analysis of modified Arrott plots were found to be $\beta = 0.392$, $\gamma = 1.309$ and $\delta = 4.26$ obtained from the critical isotherm at $ T_{\rm C} =\rm 200~K$. Self-consistency and reliability of the critical exponent analysis were verified by the Widom scaling law and scaling equations. Using the results from renormalization group calculation, the critical behavior of $\rm CrFe_2Ge_2$ is akin to that of a $d=3, n=3$ ferromagnet in which the
magnetic exhange distance is found to decay as $J(r) \approx r^{-4.86}$ with long-range
magnetic coupling. The evaluated Rhodes-Wohlfarth ratio of $\sim 3$ points to an itinerant
ferromagnetic ground state. Low-temperature measurements of resistivity, $p(T)$, and specific heat, $C_P(T)$, reveal a pronounced contribution from electron-
magnon scattering.
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All authors P.L.S. Cambalame, B.J.C. Vieira, J.C. Waerenborgh, P.S.P. da Silva, J.A. Paixão
Materials Science · Cross-listed from physics.optics
Thermoplasmonics under optically coupled regime: A Numerical Study of Dimers, Nanolenses, and Switchable Clusters
José Luis Montaño Priede and Marek Grzelczak
The management of thermal effects in plasmonic nanostructures is frequently viewed as a detrimental waste rather than a useful, controllable entity. We show that optical coupling of plasmonic nanoparticles enables precise spatiotemporal control over nanoscale heating. Through numerical investigation of experimentally-achievable systems from individual nanoparticles and dimers to nanolenses and switchable clusters, we demonstrate how plasmon hybridization and near-field coupling dictate the magnitude and spatial distribution of temperature. Our results highlight the critical role of polarization and gap distance in tuning the thermal output of dimers, the ability of a trimer nanolens to focus heat into a sub-diffraction volume, and the pronounced thermal difference in a switchable nanoparticle cluster. This work establishes a framework for designing advanced thermoplasmonic systems where heat is not merely a detriment, but a dynamically controllable element for applications in catalysis, health, or active photonic devices.
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Superconductivity
Nonreciprocal Transport in chiral Mo3Al2C Near the Superconducting to Normal Transition
Jeongsoo Park, Sang-Wook Cheong and Xianghan Xu
We investigate nonreciprocal electrical transport in bulk single-crystalline Mo3Al2C, a material known to host crystallographic chirality, a polar charge-density-wave instability, and a superconducting transition near 8 K. Using AC transport measurements to analyze the first-harmonic and second-harmonic resistance responses, we observe a distinct nonreciprocal second-harmonic signal that is significantly enhanced near the boundary of the normal and superconducting phases. Phenomenologically, this response arises from direction-dependent coupling between the external
magnetic field and the current-induced intrinsic magnetization within the
chiral lattice. Furthermore, a persistent nonreciprocal response observed under perpendicular
magnetic fields suggests a toroidal-induced effect linked to the electric polarization emerging from the charge-density-wave phase. These results demonstrate that bulk Mo3Al2C serves as an intrinsic platform for tunable nonreciprocal transport rooted in the interplay of chirality, polarity, and superconductivity.
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Superconductivity
Vortex core spectroscopy links pseudogap and Lifshitz critical point in a cuprate superconductor
Tejas Parasram Singar, Ivan Maggio-Aprile, Genda Gu et al. (+1 more)
Understanding how superconductivity competes with other electronic phases in cuprates requires direct access to the hidden non-superconducting low temperature phase, for which Abrikosov
vortices provide a unique local probe. We map the doping- and field-dependent
evolution of
vortex-core states in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ across a broad doping range spanning the
Fermi-surface Lifshitz transition. High-resolution scanning tunneling spectroscopy reveals a striking transformation of the
vortex-core spectrum from unconventional, pseudogap-like signatures at moderate doping to more BCS-like behavior beyond a critical doping $p^* \approx 0.21$. This crossover aligns with the pseudogap endpoint and the onset of
Fermi-surface reconstruction, indicating a direct link between pseudogap physics and
vortex electronic structure. Our findings highlight the
vortex core as a sensitive local probe of the cuprate ground state.
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All authors Tejas Parasram Singar, Ivan Maggio-Aprile, Genda Gu, Christoph Renner
Materials Science
I. I. Gimazov, D. E. Zhelezniakova, R. B. Zaripov et al. (+7 more)
We report results of electron
spin resonance (ESR) measurements in single
crystals of EuSn$_2$As$_2$. In the temperature range of
antiferromagnetic (AFM) ordering of Eu atoms, $T \leq T_N\approx 24$\,K, the ESR signal splits into two resonance lines, one of which, at high-field (or low-frequency), is the conventional acoustic AFM resonance mode that occurs at temperatures below $T_N$. The lower-field (high-frequency) line, as we have proven here, is the
ferromagnetic resonance associated with the presence in the layered AFM
crystal of a small amount ($\sim 3\%$) of planar nanodefects with a non-zero
ferromagnetic (FM) moment. The existence of
ferromagnetic nano-inclusions in the bulk of the
antiferromagnetic compound makes EuSn$_2$As$_2$ a peculiar example of a natural
magnetic metamaterial. We believe that the planar FM nanodefects are also inherent in other layered AFM compounds, which explains often observed increase in their
magnetic susceptibility upon cooling at $T< T_N\rightarrow 0$.
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All authors I. I. Gimazov, D. E. Zhelezniakova, R. B. Zaripov, Yu. I. Talanov, A. Yu. Levakhova, A. V. Sadakov, K. S. Pervakov, V. A. Vlasenko, A. L. Vasiliev, V. M. Pudalov
Materials Science
Electronic and optical properties of native point defects in CuInS$_2$ and CuGaS$_2$
Henry Phillip Fried, Daniel Barragan-Yani and Ludger Wirtz
We present a detailed study of common intrinsic defects in CuInS$_2$ and CuGaS$_2$ using the Heyd, Scuseria and Ernzerhof (HSE) hybrid functional scheme. The impact of the two HSE parameters, $\alpha$ and $\omega$ on the band gap and compliance with the generalized Koopmans'
theorem is investigated. Using the formation energy formalism and calculated thermodynamic charge-transition levels, we assess the electronic properties of the defects and explore the connection of charge-transition levels with optical-transition levels. Calculated Franck-Condon shifts for emission highlight the importance of
lattice relaxation for the attribution of defects to luminescence peaks. Our results show that once these effects are included, predictions become closer to photoluminescence measurements available in literature.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Three-qubit entangling gates with simultaneous exchange controls in spin qubit systems
Miguel G. Rodriguez and Yun-Pil Shim
Pairwise exchange couplings have long been the standard mechanism for entangling
spin qubits in
semiconductor systems. However, implementing
quantum circuits based on pairwise exchange gates often requires a lengthy sequence of elementary gate operations. In this work, we present an alternative approach: multi-
qubit entangling gate operations that simultaneously drive the exchange couplings between multiple pairs of
spin qubits. We explore three
spin qubit systems in linear or triangular configurations. We derive analytical expressions for these multi-exchange entangling operations and demonstrate how to use the resulting three-
qubit gates to construct
quantum circuits capable of generating standard entangled states such as GHZ and W states, and the Toffoli gate, by optimizing control parameters. Our results show that this multi-
qubit strategy significantly reduces the number of required operations, offering a pathway to more efficient, shallower, and more coherent
circuits for
spin-
qubit processors.
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