Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Curvature-Flux Representation of Local Dirac-Node Topology from Non-Hermitian Zeeman Quantum Geometry
Rongjie Cui, Longjun Xiang, Fuming Xu et al. (+1 more)
Local Dirac-node
topology is usually described by a winding number or Berry phase, whereas
curvature-flux formulations are commonly associated with global band
topology. Here we show that the non-Hermitian Zeeman
quantum geometric tensor (QGT) provides a
curvature-flux representation of local $\pi_1$
topology. Unlike the conventional Hermitian QGT, whose metric and Berry
curvature are fixed respectively by its real symmetric and imaginary antisymmetric parts, the Zeeman QGT must be decomposed according to
symmetry under index exchange. This decomposition yields normal and anomalous metric-
curvature sectors. The normal sector has the same metric-
curvature structure as the conventional Hermitian QGT. The anomalous sector, by contrast, contains two components absent in the conventional QGT: an imaginary symmetric metric-like tensor and a real antisymmetric
curvature-like tensor. In a two-dimensional Dirac system, the anomalous Zeeman
curvature forms a radial flux field Hodge-dual to the tangential winding field of the Dirac node, thereby converting the local winding invariant into a Gauss-type flux invariant. We further show that the four Zeeman-
geometric sectors map one-to-one onto frequency- and
symmetry-resolved gyrotropic conductivity channels, with reciprocal kinetic magnetoelectric response providing a complementary probe. These results establish non-Hermitian Zeeman
quantum geometry as a measurable framework connecting local Dirac-node
topology and transport.
Read the full abstract ▾
All authors Rongjie Cui, Longjun Xiang, Fuming Xu, Jian Wang
Statistical Mechanics
Path-Integral Formulation of Unavoidable Canonical Nonlinearity: Dynamic Discretization Cost over Variable Supports
Koretaka Yuge
In the statistical thermodynamics of classical discrete systems, the map from microscopic interactions to thermodynamic
equilibrium configurations generally exhibits complex nonlinearity, known as "canonical nonlinearity" (CN). While conventionally characterized by the Kullback-Leibler (KL) divergence, this approach inevitably misses intrinsic nonlinearities arising from the discretization of continuous Gaussian families themselves. This intrinsic effect of unavoidable CN (UCN), has recently been quantified within a transport-information-
geometric framework. However, the UCN is fundamentally limited to evaluating the discretization-induced cost for a single continuous distribution. It therefore does not capture the information-
geometric cost between a continuous Gaussian reference and an actual discrete distribution, nor between states with fundamentally different supports, making it conceptually unclear how to decompose the overall CN. To address this limitation, we propose the Path-Integral UCN (PUCN) quantifying the cumulative information-
geometric cost between distinct distributions. The PUCN adopts a path by (i) retaining the canonical distribution as an exponential family via the $e$-mixture (
geometric mean) of the base measure, leading to an arithmetic mixture of the Fisher metric as the CN standard, and (ii) enforcing covariant changes in the discretization
cell through the harmonic mixture of its second-moment
matrix $M$, reflecting the uncertainty in parameter variations on the statistical
manifold. The resulting PUCN provides a flexible measure of the
geometric cost between arbitrary states, including those with essentially different supports. This formulation enables an explicit quantification of CN between different CDOS systems and a natural decomposition of the total CN into the UCN and a residual contribution, which has not been clearly separated in existing approaches.
Read the full abstract ▾
Materials Science
Including sample shape in micromagnetics with 3D periodic boundary conditions
Frederik Laust Durhuus, Andrea Roberto Insinga and Rasmus Bjørk
Periodic boundary conditions (PBCs) for computing
magnetic fields in repeating
magnetic structures, e.g. in micromagnetic simulations, are typically imposed using the quasi periodic macrogeometry approach, where many copies of the simulated domain are introduced. This can be computationally problematic, especially if the simulated domain is incommensurate with the desired sample shape. In this work, we present a formal proof that for sufficiently large
magnetic samples, only the average magnetisation gives non-negligible shape effects. Using this insight, we develop a simple, computationally efficient modification of existing implementations which incorporates shape effects in PBC methods.
Read the full abstract ▾
Materials Science
Pressure-stabilized dual-BCC polymorphism in a rhenium-based high-entropy alloy
Raimundas Sereika, Andrew D. Pope, Hunter Kantelis et al. (+3 more)
Accessing metastable structural states in high-
entropy alloys offers a promising route to tailor material properties, yet the use of high pressure to engineer such states remains underexplored. Here, we report the pressure-driven synthesis of a unique metastable dual-BCC microstructure in a near-equimolar ReNbTiZrHf
alloy. Starting from an ambient two-phase mixture of hexagonal (C14-derived) and body-centered cubic (BCC) phases, compression induces a selective, diffusionless transformation of the hexagonal constituent into a second, crystallographically distinct BCC polymorph, while the original BCC phase remains stable. Upon decompression, the pressure-induced BCC phase is kinetically trapped, yielding a dual-BCC state that is inaccessible via conventional thermal processing. The pressure-stabilized BCC polymorph is Re-enriched and inherits the exceptional stiffness of its hexagonal parent (bulk modulus ~290 GPa), creating a composite microstructure with pronounced elastic and mechanical contrast relative to the softer original BCC
matrix (~180 GPa). These findings demonstrate that pressure can effectively navigate the flat free-energy landscapes of chemically complex
alloys, establishing a robust pathway for polymorph engineering and metastable phase design in refractory HEAs.
Read the full abstract ▾
All authors Raimundas Sereika, Andrew D. Pope, Hunter Kantelis, Caleb M. Knight, Kallol Chakrabarty, Yogesh K. Vohra
Materials Science · Cross-listed from physics.chem-ph
Cryogenic hydrogen embrittlement of 316plus (EN 1.4420) stainless steel at 77 K and 20 K
W. Li, A. Zafra, L. Armendariz et al. (+4 more)
This paper presents the first experimental characterisation of combined hydrogen-temperature effects in 316plus (EN 1.4420), a new austenitic stainless steel for
liquid hydrogen (LH2) storage. Uniaxial tensile tests were conducted at room temperature (RT), 77 K and 20 K on uncharged and hydrogen-precharged specimens, complemented by fractography and EBSD-based quantification of strain-induced martensite (SIM). 316plus exhibited cryogenic strengthening at 77 K and 20 K by enhanced SIM formation. Hydrogen did not influence strength at RT or 77 K and caused a modest decrease (~10%) at 20 K, keeping 316plus at the upper bound of cryogenic strength for 316L. The presence of hydrogen resulted in significant reductions in ductility at all temperatures, being most severe at 77 and 20K (~40-50%). Hydrogen suppressed SIM at 20 K, but SIM fraction did not correlate with ductility reduction. Despite the combined effect of temperature and hydrogen, 316plus retained notable ductility (reduction in area ~30%).
Read the full abstract ▾
All authors W. Li, A. Zafra, L. Armendariz, Z. Wang, W. Bailey, E. Martinez-Pañeda, S. Afshan
Materials Science · Cross-listed from physics.chem-ph
Active Learning for Generalizable Detonation Performance Prediction of Energetic Materials
R. Seaton Ullberg, Megan C. Davis, Jeremy N. Schroeder et al. (+5 more)
The discovery of new energetic materials is critical for advancing technologies from defense to private industry. However, experimental approaches remain slow and expensive while computational alternatives require accurate material property inputs that are often costly to obtain, limiting their ability to efficiently predict detonation performance across a vast chemical space. We address this challenge through an active learning strategy that integrates density functional theory calculations, thermochemical modeling, message-passing neural networks, and
Bayesian optimization. The resulting high-throughput workflow iteratively expands the training
dataset by selecting new molecules in a targeted manner that balances the exploration of broad chemical space with the exploitation of promising high-performing candidates. This approach yields the largest publicly available database of potential CHNO explosives drawn from an initial pool of more than 70 billion candidates and a generalizable surrogate model capable of accurately predicting detonation performance (R$^2$ > 0.98). Feature importance analysis on this largest-to-date
dataset reveals that oxygen balance is the dominant driver of detonation performance, complemented by contributions from local electronic structure, density, and the presence of specific functional groups. Cheminformatics analysis highlights how energetic materials with similar performance metrics tend to cluster in distinct chemical spaces offering a clearer direction for future synthesis studies. Together, the surrogate model, database, and resulting chemical insights provide a valuable foundation for high-throughput screening and targeted discovery of new energetic materials spanning diverse and previously unexplored regions of chemical space.
Read the full abstract ▾
All authors R. Seaton Ullberg, Megan C. Davis, Jeremy N. Schroeder, Andrew H. Salij, M. J. Cawkwell, Christopher J. Snyder, Wilton J. M. Kort-Kamp, Ivana Matanovic
Mesoscale and Nanoscale Physics
Optical spin defect pairs in cubic boron nitride
Josiah E. Hsi, Islay O. Robertson, Abhijit Biswas et al. (+9 more)
Room-temperature optically active solid-state
spin defects are widely known to be useful in
quantum sensing applications, however, only a select range of materials have been found to host such systems. Recent measurements in the van der Waals material hexagonal boron nitride (hBN) have shown optically detected
magnetic resonance (ODMR) with
spin-1/2-like signatures can be explained by a charge transfer mechanism where charges move between adjacent defects forming weakly coupled
spin pairs. Interestingly, these ODMR signatures have been reported in a variety of materials aside from hBN, suggesting the
spin pair model provides a potentially material agnostic approach for enabling ODMR. Here, we test whether the charge transfer mechanism is supported in a different
crystal phase, and report on ODMR signatures in cubic boron nitride (cBN), showing all the characteristic properties identified in hBN are preserved. We consider a selection of different cBN samples of varying size and observe ODMR from a single sub-micron cBN particle, paving the way towards sensing applications. This work further expands understanding of the ubiquity of optical
spin defect pairs, and establishes the potential for exploring
quantum technologies with a wider range of materials.
Read the full abstract ▾
All authors Josiah E. Hsi, Islay O. Robertson, Abhijit Biswas, Jishnu Murukeshan, Valery Khabashesku, Alexander J. Healey, Erin S. Grant, David A. Broadway, Mehran Kianina, Igor Aharonovich, Pulickel M. Ajayan, Jean-Philippe Tetienne
Strongly Correlated Electrons · Cross-listed from hep-lat
Exact SL(2,Z)-Structure of Lattice Maxwell Theory with $\theta$-term in Modified Villain Formulation
Shoto Aoki, Yoshio Kikukawa and Toshinari Takemoto
We study the duality of
lattice Maxwell theory in the modified Villain formulation, employing an ultra-local action with a theta term. Although this action is known to become non ultra-local through the Poisson resummation formula, we show that this non ultra-locality can be removed by incorporating a non-local transformation procedure into the definition of the S-transformation. As a result, the ultra-local action with a theta term exhibits an exact SL(2,Z)-duality. We further analyze the SL(2,Z)-structure of Wilson and 't Hooft loops, demonstrating that they transform properly up to a nontrivial phase factor arising from the nontrivial self-linking of the loops. This effect originates from the non-local transformation procedure in the S-transformation. Remarkably, the resulting SL(2,Z)-structure closely resembles that of non-
spin Maxwell theory.
Read the full abstract ▾
Superconductivity
Annealing-induced grain coarsening and voltage kinks in superconducting NbRe films
Zahra Makhdoumi Kakhaki, Anton O. Pokusinskyi, Francesco Avitabile et al. (+5 more)
NbRe, a non-centrosymmetric
superconductor with a transition temperature $T_\mathrm{c}$ up to 9\,K, attracts interest for its strong antisymmetric
spin-orbit coupling and suitability for single-
photon detection. While bulk and thin-film polycrystalline NbRe are well studied, how superconductivity and
vortex dynamics evolve with increasing grain size in thin films is largely unknown. Here, we investigate as-grown and annealed 20\,nm-thick NbRe films, where annealing increases the average crystallite size from approximately $2$\,nm to $8$\,nm, and study
vortex dynamics via current-voltage ($I$-$V$) measurements over a broad temperature and
magnetic field range. In contrast to as-grown films, where the low-resistive state breaks down due to flux-flow instability, annealed films exhibit multiple voltage kinks in the $I$-$V$ curves. We attribute these kinks to the nucleation and growth of normal domains, as further suggested by time-dependent Ginzburg-Landau simulations. Overall, the annealed films form superconducting networks with
vortex-channeling paths along the grain boundaries, while localized heating and voltage kinks could be harnessed for discrete-resistance switching and sensing.
Read the full abstract ▾
All authors Zahra Makhdoumi Kakhaki, Anton O. Pokusinskyi, Francesco Avitabile, Abhishek Kumar, Francesco Colangelo, Carla Cirillo, Carmine Attanasio, Oleksandr V. Dobrovolskiy
Quantum Gases
Immiscible to miscible quenching instabilities in two-dimensional binary Bose-Einstein condensates
Lauro Tomio, S. Sabari, Arnaldo Gammal et al. (+1 more)
Immiscible to miscible quenching transitions (IMQT) in homogeneous Bose-Einstein condensate are investigated, considering rubidium isotopes $^{85}$Rb and $^{87}$Rb confined in a two-dimensional (2D) circular box, under two different initial configurations. These IMQT instabilities, triggered by sudden reductions in the two-body interspecies scattering length $a_{12}$, are explored under two distinct initialconditions, highlighting the critical role of nonlinear dynamics in their
evolution. The numerical simulations indicate that the instability dynamics are primarily driven by the production of large
vortices and the propagation of sound waves (
phonons), with sound wave excitations prevailing in the long-term
evolution. The compressible and incompressible parts of the kinetic energy spectra, in terms of the wave number $k$, are confronted with the classical Kolmogorov scaling, $k^{-5/3}$ for
turbulence, which is observed in the onset of instabilities. Before reaching the ultraviolet dissipation region at small scales, the IMQT spectra exhibit a bottleneck effect, indicating a clear departure from classical scaling behavior. In the time asymptotic miscible regime, it is observed that the vorticity and sound-wave production remain practically stable. In this regime, for both cases investigated, a linear relation is also recognized between the miscibility parameter and the initial IMQT configuration.
Read the full abstract ▾
All authors Lauro Tomio, S. Sabari, Arnaldo Gammal, R. K. Kumar
Strongly Correlated Electrons
Topological invariant of periodic many body wavefunction from charge pumping simulation
Haoxiang Chen, Yubing Qian, Weiluo Ren et al. (+2 more)
Many-body topological
quantum states host exotic
quantum phenomena and lie at the forefront of developing next-generation
quantum technologies. Recently emerged neural network wavefunction methods have established themselves as a powerful computational framework for accessing these states, enabling the variational machine learning calculation of the system's ground state wavefunction. However, reliable computation of topological invariants remains an open challenge when the whole deterministic energy spectrum is not available. In this work, we introduce a robust approach to determining topological invariant based on simulating the charge pumping process, by monitoring the response of polarization upon flux insertion. By applying this method, we accurately extract the Chern numbers for Abelian fractional Chern
insulators. Our approach also enables the first neural-network-wavefunction-based identification of anomalous composite
Fermi liquid states. Our work resolves a key bottleneck in applying neural network wavefunctions to correlated topological matter, and the method proposed is also generally applicable to other many-body approaches, thereby opening up new avenues for future research in this field.
Read the full abstract ▾
All authors Haoxiang Chen, Yubing Qian, Weiluo Ren, Xiang Li, Ji Chen
Materials Science · Cross-listed from physics.app-ph
Mitigating the contact resistance limitation of cavitated fine line Ag paste by Laser-Enhanced Contact Optimization
Donald Intal, Abasifreke Ebong, Vijay Upadhyaya et al. (+4 more)
Cavitation-assisted Ag paste is a promising route for fine-line, low-silver metallization in silicon
solar cells because it improves paste dispersion, extends shelf life, and reduces Ag consumption, but matching the contact performance of commercial pastes remains a challenge. Here, cavitated paste was evaluated on PERC
solar cells at peak firing temperatures of 720, 740, 750, and 762 C, with and without
laser-enhanced contact optimization (LECO). The results show a clear firing window: 720 and 740 {\deg}C produced high series resistance and reduced fill factor, 750 C gave the best pre-LECO performance, and 762 C showed additional electrical limitations with only limited LECO benefit. LECO selectively recovered the under-activated states, increasing fill factor from 76.8 to 80.2% at 720 C and from 76.7 to 79.8% at 740 C. Electroluminescence and conductive AFM further indicated improved current collection and stronger localized conduction after LECO. These results show that cavitated paste performance is governed primarily by a shifted contact-formation window, and that firing optimization combined with LECO provides a practical route to retain the fine-line advantage while improving electrical performance.
Read the full abstract ▾
All authors Donald Intal, Abasifreke Ebong, Vijay Upadhyaya, Brian Rounsaville, Ajeet Rohatgi, Dana Hankey, Marshall Tibbetts
Materials Science
A metallic CrS$_2$ phase bridging the gap between two- and three-dimensional dichalcogenides
Hicham Moutaabbid, Dario Taverna, Denis Pelloquin et al. (+5 more)
We report on the high-pressure synthesis of a CrS$_2$ phase in the form of single-crystalline nanorods. A structural refinement of Precession Electron Diffraction
Tomography data confirms the nominal CrS$_2$ composition and unveils a ladder-type structure formed by portions of 1T-type CrS$_2$ layers characteristic of two-dimensional (2D) dichalcogenides connected by chains of edge-sharing CrS$_6$ octahedra characteristic of 3D dichalcogenides with marcasite structure. Ab initio density functional theory calculations of the relaxed structure confirm the stability of this structure and indicate a strong overlap of the 3d states of Cr with the 3p states of S, thus suggesting strong covalent Cr-S bonds and metallic behavior. Electrical resistivity, $\varrho$, measurements on single nanorods confirm this behavior and yield $\varrho \sim 2-20$ m$\Omega$ cm at 4 K. The proposed ladder-like structure of CrS$_2$ forms open channels along the chain direction, which may be suitable for ionic conduction.
Read the full abstract ▾
All authors Hicham Moutaabbid, Dario Taverna, Denis Pelloquin, Lorenzo Paulatto, Alexandre Gloter, Sophie Guéron, Alik Kasumov, Andrea Gauzzi
Superconductivity
Bulk-dissociated topological bands without spin-orbit coupling in hetero-dimensional superconducting metamaterials
Joseph J. Cuozzo, Sayed Ali Akbar Ghorashi, Purna P. Paudel et al. (+3 more)
Topological
superconductors (TSCs) in superconducting hybrid
heterostructures, which integrate superconducting and non-superconducting materials, have been intensely investigated with the hope of discovering exotic non-Abelian anyons for fault-tolerant
quantum computing. In this effort, a challenge for hybrid superconducting systems is controlling hybridization, which is often a balance between enhancing the superconducting proximity effect at the cost of suppressing desirable electronic properties such as strong
spin-orbit interactions. Hence, discovering hybrid superconducting systems with topological properties controlled and enhanced by material geometry design without
spin-orbit interactions would be intriguing to explore. In this work, we theoretically study a square superconducting network decorated with
spin-polarized
magnetic adatoms. We find that localized Yu-Shiba-Rusinov bound states at
magnetic adatom sites collectively form a weak topological superconducting phase despite the absence of
spin-orbit interactions. We then demonstrate that by tuning the
Fermi energy of the network, the system can transition from a weak TSC phase to a bulk-dissociated TSC phase where the edge state bands separate from the bulk, giving rise to unexpected features such as nodal lines and co-existing bulk-dissociated edge and corner modes. Moreover, our findings highlight how hetero-dimensional superconducting metamaterials can serve as a useful template for controlling the coupling and dissociation between electronic degrees of freedom of different dimensionalities.
Read the full abstract ▾
All authors Joseph J. Cuozzo, Sayed Ali Akbar Ghorashi, Purna P. Paudel, Dale Huber, Wei Pan, François Léonard
Quantum Gases
An Algorithm for Fast Assembling Large-Scale Defect-Free Atom Arrays
Tao Zhang, Xiaodi Li, Hui Zhai et al. (+1 more)
It is widely believed that tens of thousands of physical
qubits are needed to build a practically useful
quantum computer. Atom arrays formed by optical tweezers are among the most promising platforms for achieving this goal, owing to the excellent scalability and mobility of atomic
qubits. However, assembling a defect-free atom array with ~ 10^4
qubits remains algorithmically challenging, alongside other hardware limitations. This is due to the computationally hard path-planning problems and the time-consuming generation of suffciently smooth trajectories for optical tweezer potentials by spatial light modulators (SLM). Here, we present a unified framework comprising two innovative components to fully address these algorithmic challenges: (1) a path-planning module that employs a supervised learning approach using a graph neural network combined with a modified auction decoder, and (2) a potential-generation module called the phase and profile-aware Weighted Gerchberg-Saxton
algorithm. The inference time for the first module is nearly a size-independent constant overhead of ~ 5 ms, and the second module generates a potential frame with about 0.5 ms, a timescale shorter than the current commercial SLM refresh time. Altogether, our
algorithm enables the assembly of an atom array with 10^4
qubits on a timescale much shorter than the typical
vacuum lifetime of the trapped atoms.
Read the full abstract ▾
All authors Tao Zhang, Xiaodi Li, Hui Zhai, Linghui Chen
Mesoscale and Nanoscale Physics
Fluctuation engineering in cavity quantum materials
Hope M Bretscher, Lorenzo Graziotto, Marios H Michael et al. (+14 more)
Coupling tailored electromagnetic fluctuations to materials provides a resource for controlling correlated
quantum matter. By structuring the frequency, spatial, and modal distribution of fluctuations through a new generation of cavity
quantum materials,
vacuum and thermal spectra can shift phase boundaries and stabilize or suppress orders. This review organizes the field around a fluctuation-focused perspective, surveying a practical design toolbox and recent milestones, and outlining theory-experiment challenges in realistic, multimode, beyond-long-wavelength regimes. We highlight photonic observables and map opportunities for
equilibrium and driven control across superconducting,
magnetic, moire, and topological platforms.
Read the full abstract ▾
All authors Hope M Bretscher, Lorenzo Graziotto, Marios H Michael, Angela Montanaro, I-Te Lu, Andrey Grankin, James W McIver, Jerome Faist, Daniele Fausti, Martin Eckstein, Michael Ruggenthaler, Angel Rubio, DN Basov, Mohammad Hafezi, Martin Claassen, Dante M Kennes, Michael A Sentef
Strongly Correlated Electrons
Nucleation of Sachdev-Ye-Kitaev Clusters in One Spatial Dimension
Hrant Topchyan and Tigran A. Sedrakyan
We study how Sachdev-Ye-Kitaev (SYK) interactions can arise from localized single-particle states on a system that is effectively one dimensional. If a local interaction is projected onto coarse localized orbitals, the resulting couplings do not immediately follow the standard SYK distribution. Instead, they have a finite probability of being exactly zero, a broad non-Gaussian distribution for the nonzero values, and strong correlations coming from the geometry of the localized states. We then show that this changes when each localization volume is resolved into $M>1$ smaller microscopic pieces with random phases. As $M$ increases, the distribution of the nonzero couplings moves toward the complex-Gaussian SYK form. At the same time, the large-$M$ limit is a sparse but asymptotically canonical SYK network: the nonzero couplings create SYK clusters, while the pattern of missing or very weak couplings is still determined by the real-space overlap of the localized orbitals. Finally, we map the interaction tensor to a graph in pair space. This makes it possible to follow the formation, merger, and growth of SYK clusters, which we characterize using connected components and clique/simplex counts. The result is a minimal real-space phenomenological theory of SYK-cluster formation, providing clear experimental criteria.
Read the full abstract ▾
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Geometry-Induced Long-Range Correlations in Recurrent Neural Network Quantum States
Asif Bin Ayub, Amine Mohamed Aboussalah and Mohamed Hibat-Allah
Neural
Quantum States based on autoregressive recurrent neural network (RNN) wave functions enable efficient sampling without Markov-chain autocorrelation, but standard RNN architectures are biased toward finite-length correlations and can fail on states with long-range dependencies. A common response is to adopt
transformer-style self-
attention, but this typically comes with substantially higher computational and
memory overhead. Here we introduce dilated RNN wave functions, where recurrent units access distant sites through dilated connections, injecting an explicit long-range inductive bias while retaining a favorable $\mathcal{O}(N \log N)$ forward pass scaling. We show analytically that dilation changes the correlation geometry and can induce power-law correlation scaling in a simplified linearized and perturbative setting. Numerically, for the critical 1D transverse-field Ising model, dilated RNNs reproduce the expected power-law connected two-point correlations in contrast to the exponential decay typical of conventional RNN ansätze. We further show that the dilated RNN accurately approximates the one-dimensional Cluster state, a paradigmatic example with long-range conditional correlations that has previously been reported to be challenging for RNN-based wave functions. These results highlight dilation as a simple
geometric mechanism for building correlation-aware autoregressive neural
quantum states.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
High-Fidelity Transmon Reset with a Multimode Acoustic Resonator
Andraž Omahen, Simon Storz, Igor Kladarić et al. (+1 more)
Achieving sufficiently low residual excited-state populations remains a key challenge in superconducting
quantum circuits, particularly for protocols operating close to noise limits or requiring repeated
qubit initialization. Existing protocols primarily address this challenge through sophisticated control, engineered dissipation, or feedback mechanisms. Here, we demonstrate an alternative approach in which a superconducting
qubit is reset using a physically distinct, intrinsically colder phononic bath. Specifically, we interface a transmon with a high-overtone bulk acoustic resonator (HBAR), enabling cooling of the
qubit into GHz-frequency modes. Using this approach, we achieve a residual excited-state population of the
qubit below $10^{-4}$, representing an improvement of one to two orders of magnitude compared to existing reset schemes. These results highlight the potential of phononic baths as a resource for high-fidelity
qubit initialization in superconducting
circuits.
Read the full abstract ▾
All authors Andraž Omahen, Simon Storz, Igor Kladarić, Yiwen Chu
Mesoscale and Nanoscale Physics
Mesoscopic transport in a Chern mosaic
Sayak Bhattacharjee, Julian May-Mann, Yves H. Kwan et al. (+2 more)
We analyze mesoscopic electronic transport in a Chern mosaic: a regular pattern of domains whose electronic bands carry differing local Chern numbers. An example platform where a Chern mosaic can arise is a moiré
heterostructure, where variations in the local moiré parameters can produce such domains. We compute resistances at linear response for a variety of domain wall network geometries at zero temperature and
magnetic field. Simple domain configurations can exhibit zero, integer, or fractional multiples of the
quantum of resistance in both the longitudinal and transverse (
Hall) responses. Our simple semi-classical analysis provides a useful computational method and comparative catalog for ongoing experiments in two-dimensional topological materials.
Read the full abstract ▾
All authors Sayak Bhattacharjee, Julian May-Mann, Yves H. Kwan, Trithep Devakul, Aaron Sharpe
Statistical Mechanics
Decoding coherent errors in toric codes on honeycomb and square lattices: duality to Majorana monitored dynamics and symmetry classes
Zhou Yang, Andreas W. W. Ludwig and Chao-Ming Jian
Topological stabilizer codes, such as the toric and surface codes, are leading candidates for fault-tolerant
quantum computation. While their decodability under
stochastic noise has been extensively studied, the effects of coherent errors, which involve
quantum interference, remain less explored. In this work, we study the decodability of toric codes on honeycomb and square
lattices subject to $X$- and $Z$-type coherent errors generated by the $X$- and $Z$-rotations on each
qubit. We establish a duality between these decoding problems and 1+1D monitored dynamics of non-interacting Majorana
fermions. This duality shows that the Altland-Zirnbauer
symmetry class of the dual Majorana dynamics governs the universal structure of the decodability phase diagram. We show that the honeycomb-
lattice toric code (hTC) with $X$-type error is dual to class-DIII dynamics, while the hTC with $Z$-type error and the square-
lattice toric code (sTC) with both error types are dual to class-D dynamics. The key distinction arises from time-reversal
symmetry. In class DIII, the generic transition out of the decodable phase is dual to a measurement-induced transition between dynamical phases with area-law and logarithmic
entanglement scaling. In contrast, in class D, the generic decodability transition corresponds to a transition between two topologically distinct area-law phases. To explore these transitions in microscopic models, we consider hTC and sTC with $X$-type errors as representatives and introduce a minimal two-parameter coherent error model with spatially varying rotation angles. Using analytical and numerical methods, we map out the decodability phase diagrams and characterize the universal behavior of the transitions. We find that the decodability of sTC is more vulnerable to spatially varying coherent errors than uniform ones.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Floquet Engineering of a Quasiequilibrium Superradiant Phase Transition in Landau Polaritons
Wen-Hua Wu, Fuyang Tay, Mengqian Che et al. (+3 more)
Superradiant phase transitions (SRPTs), characterized by
photon condensation and macroscopic matter polarization, are forbidden in
equilibrium for homogeneous fields by no-go
theorems. Here, we show that Floquet driving can circumvent this constraint in a Landau polariton system consisting of a two-dimensional electron gas coupled to a terahertz cavity in a DC
magnetic field. An off-resonant AC
magnetic field modulates the cyclotron frequency and light–matter coupling strength while leaving the diamagnetic term unchanged, generating an additional DC coupling contribution. This drives the system across a critical threshold into a superradiant phase, characterized by
photon condensation and Landau-level polarization in the ground state of the Floquet
Hamiltonian. This quasiequilibrium approach offers a route to SRPTs distinct from driven-dissipative schemes.
Read the full abstract ▾
All authors Wen-Hua Wu, Fuyang Tay, Mengqian Che, Andrey Baydin, Junichiro Kono, David Hagenmüller
Quantum Gases · Cross-listed from physics.optics
Fresnel zone plates for reconfigurable atomic waveguides
A.M. Pike, A. Dorne, L. Pickering et al. (+7 more)
Fresnel zone plates (FZPs), with patterns of $1\,\mu$m resolution, allow the formation of clean, diffraction-limited foci – but have a static phase profile. Spatial light modulators (SLMs) allow dynamic control of spatial beam intensity and phase – but are bulky and currently limited to roughly $10\,\mu$m pixel sizes and $1\,$Mega-pixel formats. Here, we present a new `best-of-both' kind of FZP, scalable to large area rings currently incompatible with direct SLM generation. It is equivalent to a plano-convex donut lens, whereby light's local intensity and global phase at the FZP map directly onto the image plane. The same FZP under different SLM illumination can generate: rings and arcs, double-rings, phase windings and ring
lattices (or dynamic combinations thereof). The smooth and adaptable near-field waveguide this enables will be ideal for Sagnac interferometry with ultracold atoms.
Read the full abstract ▾
All authors A.M. Pike, A. Dorne, L. Pickering, M. Jamieson, I.T. MacCuish, E. Riis, M.Y.H. Johnson, V.A. Henderson, P.F. Griffin, A.S. Arnold
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Dynamical control of non-hermitian coupling between sub-threshold nanolasers enables Q-switched pulse generation
Kristian Seegert, Roberto Gajardo, Guillaume Huyet et al. (+2 more)
Non-Hermitian photonics provides a framework to engineer the gain and loss of optical modes in open systems, enabling control of their spectral and dynamical properties. In particular, the ability to dynamically tune modal losses offers a route to implement functionalities traditionally relying on cavity Q-factor modulation, such as Q-switching, within nanophotonic platforms. Here, we demonstrate the generation of short optical pulses in a pair of phase-coupled photonic
crystal nanolasers exploiting non-Hermitian coupling. Two waveguide-coupled nanocavities are operated below their individual lasing thresholds and subjected to asymmetric optical pumping, such that a transient carrier-induced detuning modifies the interference conditions between them. This dynamically controls the gain and loss of the collective modes, and, upon crossing a resonance condition, leads to the rapid release of stored carrier energy as an optical pulse. A rate-equation model captures the interplay between carrier dynamics and modal coupling and reproduces the observed behavior. Experiments performed on an indium phosphide platform show pulse generation from cavities that do not lase efficiently on their own in continuous-wave operation, with temporal characteristics governed by carrier dynamics. These results indicate that non-Hermitian coupling can be used to control the effective cavity losses in time, providing a route to pulse generation in integrated photonic systems.
Read the full abstract ▾
All authors Kristian Seegert, Roberto Gajardo, Guillaume Huyet, Fabrice Raineri, Guilhem Madiot
Statistical Mechanics · Cross-listed from hep-th
$\mathcal{PT}$-symmetric Field Theories at Finite Temperature
Oleksandr Diatlyk, Andrei Katsevich and Fedor K. Popov
We investigate the thermal properties of $\mathcal{PT}$-symmetric scalar field theories with purely imaginary couplings. The free energy governs the asymptotic density of states, providing an effective measure of the number of degrees of freedom, while thermal masses and one-point functions provide predictions for operator dimensions and three-point functions in the corresponding $d=2$ Conformal Field Theories. Naive finite-temperature perturbation theory near upper critical dimensions is spoiled by infrared divergences. To remove these divergences, we introduce a ”thermal normal-ordering” scheme that resums these contributions and yields a systematic $\epsilon$-expansion. This framework allows us to compute the free energy, thermal masses, and one-point functions in the cubic and quintic $O(N)$ models. We compare the thermal free energy density, thermal masses, and one-point function in two dimensions with exact results derived from the proposed Ginzburg-Landau descriptions of the non-
unitary minimal models $M(2,5)$ and $M(3,8)_D$. Eventually, we employ two-sided Padé extrapolations to obtain estimates for the thermal free energy in $d=3,4,5$.
Read the full abstract ▾
Strongly Correlated Electrons
Revealing the nature of the charge density wave order of ErTe$_3$ via Raman scattering under anisotropic strain
Theotime Freitas, Mattia Udina, Alexandr Alekhin et al. (+7 more)
The nature of the charge density wave (CDW) order of the rare-earth tritelluride ErTe3 is investigated by Raman scattering under anisotropic strain. The CDW state of ErTe3 is unconventional since it is accompanied by an unusual mirror
symmetry breaking, whose origin remains to be understood. Studying the polarization-resolved Raman spectrum of the CDW amplitude mode as a function of strain and temperature, we find that the mirror
symmetry breakings of the CDW state are not independent, arguing against the recently proposed ferro-axial multi-component CDW order. Instead, we show that a single component CDW order parameter with an ordering wavevector tilted away from the principle crystallographic axis can reproduce the observed mirror
symmetry breakings and their manifestation in the Raman spectra.
Read the full abstract ▾
All authors Theotime Freitas, Mattia Udina, Alexandr Alekhin, Niloufar Nilforoushan, Sarah Houver, Alain Sacuto, Benito A. Gonzalez, Ian R. Fisher, Indranil Paul, Yann Gallais
Superconductivity
Three-Dimensional Electronic Structures in Superconducting Ruddlesden-Popper Bilayer Nickelate Films
Yueying Li, Lizhi Xu, Wei Lv et al. (+13 more)
Beyond the quasi-two-dimensional (2D) paradigm of cuprates, the role of the third dimension of the Ruddlesden-Popper
bilayer nickelates is essential to decoding their superconducting mechanism. Here, using angle-resolved photoemission spectroscopy (ARPES) with varied
photon energies, we systematically investigate the electronic band structures in three dimensions for superconducting (La,Pr,Sm)$_3$Ni$_2$O$_7$/SrLaAlO$_4$ thin films (superconducting onset temperature $T_c^{\text{onset}} \sim 48$ K) transferred via a cryogenic ultra-high
vacuum suitcase. We reveal an orbital-dependent dimensionality: while the $d{x^2-y^2}$-dominant bands exhibit a quasi-2D character, the $d{z^2}$-dominant band displays a finite $k_z$ dispersion. Finite energy gaps are identified on all observed bands across multiple high-
symmetry directions. Systematic temperature-dependent analysis characterizes the superconducting nature of the gap on the $d{z^2}$-derived band, revealing a large gap $\Delta\sim 18$ meV and a ratio $2\Delta/k_BT_c\sim 8$ exceeding the weak-coupling BCS limit. The suppression of spectral weight near the
Fermi level persists above the superconducting transition temperature. Ubiquitous waterfall-like spectral features evidence the presence of electron interactions. These results underscore the role of the $d_{z^2}$ orbital and correlations, placing constraints on theoretical models for nickelate superconductivity.
Read the full abstract ▾
All authors Yueying Li, Lizhi Xu, Wei Lv, Zihao Nie, Zechao Wang, Yu Miao, Jianchang Shen, Guangdi Zhou, Wenhua Song, Heng Wang, Haoliang Huang, Junfeng He, Jin-Feng Jia, Peng Li, Qi-Kun Xue, Zhuoyu Chen
Mesoscale and Nanoscale Physics
Light-controlled van der Waals tunnel junctions: mechanisms, architectures, functionalities, and opportunities
Mohamed Shehabeldin, Xuguo Zhou, Ran Li et al. (+4 more)
The phenomenon of electron tunneling has long been central to
quantum transport and continues to provide a powerful framework for understanding and controlling electronic processes in solids. When combined with optical excitation, tunneling becomes a particularly rich platform for experiments, because light can drive nonequilibrium carrier populations and open transport pathways that are inaccessible without optical excitation. The emergence of van der Waals (vdW) materials has greatly expanded this opportunity by enabling atomically thin
heterostructures with clean interfaces, engineered barriers, and highly tunable band
alignment. In this review, we discuss the fundamental mechanisms of photo-assisted transport and the realization of vdW tunnel junctions, and show how they provide electrical access to nonequilibrium dynamics and collective excitations in
quantum materials. We further examine emerging functionalities including photodetection, tunneling-driven light emission, sensing, and
memory. Finally, we present a forward-looking perspective on new opportunities such as
quantum-
geometric probes, twist-resolved spectroscopy, moire ferroelectricity, and scalable architectures for computing and sensing.
Read the full abstract ▾
All authors Mohamed Shehabeldin, Xuguo Zhou, Ran Li, Pablo Jarillo-Herrero, Yuxuan Cosmi Lin, Jian Tang, Qiong Ma
Statistical Mechanics
Harmonic morphisms and dynamical invariants in network renormalization
Francesco Maria Guadagnuolo, Marco Nurisso, Federica Galluzzi et al. (+2 more)
Renormalization of complex networks requires principled criteria for assessing whether a coarse-graining preserves dynamical content. We prove that discrete harmonic morphisms – surjective maps preserving harmonic functions – provide the minimal condition under which random walks on a fine-grained network project exactly onto random walks on its coarse-grained image, through an appropriate random time change. We formalize this via the harmonic degree, a diagnostic quantifying how closely any network coarse-graining approximates a harmonic morphism. Applying this framework to
geometric,
Laplacian, and GNN-based renormalization across real-world networks, we find that each method produces a distinct dynamical fingerprint encoding its underlying physical assumptions. Most strikingly,
Laplacian renormalization spontaneously yields exact harmonic morphisms in several networks, achieving exact preservation of first-exit random-walk transition structure at specific scales, a property that entropic susceptibility fails to detect. Our results identify a discrete analog of
diffusion-preserving conformal maps for irregular network
topologies and provide quantitative tools for designing and evaluating multi-scale network descriptions.
Read the full abstract ▾
All authors Francesco Maria Guadagnuolo, Marco Nurisso, Federica Galluzzi, Antoine Allard, Giovanni Petri
Mesoscale and Nanoscale Physics
Valley-controlled many-body exciton interactions in monolayer WSe$_2$ phototransistors
Daniel Vaquero, Cédric A. Cordero-Silis, Daniel Erkensten et al. (+6 more)
Many-body
exciton interactions shape the optoelectronic response of atomically-thin transition metal dichalcogenides, yet optical control of these interactions remains largely unexplored. To date, modulation of
exciton-
exciton interactions has primarily relied on electrical gating or van der Waals engineering. Here, we demonstrate all-optical control of many-body
exciton interactions in monolayer WSe$_2$ via valley-selective excitation using polarization-resolved pulsed-
laser photocurrent spectroscopy. Circular excitation selectively populates
excitons in a single valley, whereas linear excitation populates both valleys, inducing a valley-dependent nonlinear photoresponse. We observe helicity-dependent
exciton renormalization, alongside a two-fold enhancement of sublinear photocurrent scaling under circular excitation, reflecting single-valley population of interacting
excitons. A microscopic model incorporating intervalley-exchange and
exciton-
exciton annihilation mediated by dark and bright
exciton populations reproduces the nonlinear valley-selective response. These results establish the valley degree of freedom as an all-optical control parameter for tuning many-body excitonic effects and, exploring correlated
exciton states and valleytronic applications in two-dimensional
semiconductors.
Read the full abstract ▾
All authors Daniel Vaquero, Cédric A. Cordero-Silis, Daniel Erkensten, Roberto Rosati, Martijn H. Takens, Kenji Watanabe, Takashi Taniguchi, Ermin Malic, Marcos H. D. Guimarães