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Physics Condensed Matter

cond-mat Watch Condensed Matter

Thursday 4 June

Strongly Correlated Electrons

Odd-parity magnons in the Haldane-Hubbard model from topological exciton condensation

Rintaro Eto and Johannes Knolle

Odd-wave magnets are the counterparts to even-wave altermagnets realizing odd-parity spin splitting. Normally discussed for noncollinear systems, they have recently been shown to appear in collinear magnetic states in the presence of loop currents. Here we study collective excitations of the paramagnetic and magnetic phase of the seminal Haldane-Hubbard model. We identify the existence topological excitons in the paramagnetic phase, and their condensation as the driving mechanism into the collinear Néel state. The latter realizes an odd-wave magnet with odd-parity magnons displaying a characteristic $f$-wave splitting. We further uncover that an electron bandgap closing ensures magnon bandgap closing causing a change in odd-parity magnon topology, as well as a drastically enlarged spin splitting. Our results establish the presence of topological excitons and odd-parity magnons in the Haldane-Hubbard, with potential realizations in Floquet-driven materials and cold atomic gases.
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Strongly Correlated Electrons

Study on the validity of IPT+parquet method as an impurity solver in DMFT focusing on orbital fluctuations

Aira Yamada, Ryota Mizuno, Masayuki Ochi et al. (+2 more)

A breakdown of calculations with exact impurity solvers in the dynamical mean field theory in multiband systems easily occurs due to the expensive numerical cost. To overcome this practical difficulty, three of the present authors developed an inexpensive and reliable impurity solver by combining the iterative perturbation theory (IPT) and parquet equation, and named it IPT+parquet [R. Mizuno, et al., Phys. Rev. B 104, 035160 (2021).]. In this study, we validate IPT+parquet focusing on the orbital fluctuation by comparing the numerically exact impurity solvers. We confirm that IPT+parquet can capture competition between orbital fluctuation channels, which the conventional IPT cannot capture.
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All authors Aira Yamada, Ryota Mizuno, Masayuki Ochi, Kazuhiko Kuroki, Takuma Ohashi

Superconductivity

Strongly nonlinear regime of Josephson transmission lines revealed by two-tone spectroscopy

A. S. Averkin, A. A. Kopasov, I. E. Pologov et al. (+5 more)

We present experimental and theoretical studies of the off-resonant and strongly nonlinear regime of Josephson transmission lines (JTLs) with galvanically-coupled nonlinear elements. The transition from the weakly to the strongly nonlinear regime of a JTL induced by increasing the input power of the pump is probed via two-tone spectroscopy. Measurements of the phase of the transmission coefficient for a weak probe signal reveal a large increase and pronounced oscillations in the phase length variation as a function of the microwave power of the pump. Experimental observations are explained on the basis of the developed theoretical approach suitable for the description of the nonlinear response of strongly driven JTLs. Using the derived nonlinear wave equation, we show that the behavior of the phase length variation is associated with the oscillatory dependence of the Josephson inductances on the microwave power. It is demonstrated that the dissipation-induced propagation losses increase in the strongly nonlinear regime and also lead to smearing out the phase length oscillations. The developed theoretical analysis is in good agreement with experimental observations.
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All authors A. S. Averkin, A. A. Kopasov, I. E. Pologov, Aleksey N. Bolgar, Daria A. Kalacheva, Viktor B. Lubsanov, M. V. Fistul, A. Karpov

Materials Science

Strong Optical-Optical Avoided Crossings Suppress Thermal Conductivity in Ga-Substituted TlInTe$_2$

Sayan Paul and Swapan K Pati

In crystalline solids, avoided crossing between acoustic and optical phonons is widely recognized as an effective mechanism for suppressing lattice thermal conductivity ($\kappa_l$). However, the role of avoided crossings among optical phonons remains largely unexplored due to their weak contribution to heat transport. Here, using first-principles calculations combined with the linearized Wigner transport equation (LWTE), we demonstrate that optical-optical avoided crossings can effectively reduce ($\kappa_l$) in TlIn$_{0.5}$Ga$_{0.5}$Te$_2$. Pristine TlInTe$_2$ exhibits strong optical phonon-dominated heat transport, where optical phonons contribute nearly 63% of $\kappa_l$. The phonon dispersion of TlInTe$_2$ shows several crossing points in the optical region, which evolve into avoided crossings after 50% Ga substitution. Irreducible representation analysis reveals that the crossing phonon branches in TlInTe$_2$ belong to different symmetry representations, whereas the corresponding branches in TlIn$_{0.5}$Ga$_{0.5}$Te$_2$ possess the same symmetry representation, which enables phonon modes to couple and results in gap opening at the crossing points. These avoided crossings significantly suppress the optical phonon group velocity, thereby reducing the optical phonon contribution from 63% to 44% and lowering $\kappa_l$ from 0.568 to 0.482 Wm$^{-1}$K$^{-1}$ at 300 K. Mode-averaged transport analysis further confirms that the suppression of $\kappa_l$ is primarily governed by reduced phonon group velocity ($v_g$), while enhanced anharmonic scattering provides an additional secondary contribution. Our results establish symmetry-modified optical-optical avoided crossing as an effective route to suppress optical phonon transport and reduce $\kappa_l$ in systems where optical phonons significantly contribute to heat transport.
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Other Condensed Matter

Beyond Critical Minerals Targets: Digital Rock Physics as Infrastructure for Secure and Circular Supply Chains

Hannah P. Menke, Alessio Scanziani and Maja Rücker

The United Kingdom and Europe are moving rapidly from critical minerals target-setting to implementation. The EU Critical Raw Materials Act and the UK's Vision 2035 create ambitious benchmarks for domestic extraction, processing, recycling, circularity, and supply-chain resilience, but many prospective regional resources remain complex, under-explored, historically worked, or economically marginal. This paper argues that implementation will depend not only on permitting reform and project designation, but also on pre-competitive measurement, modelling, and data infrastructure capable of determining which ores, brines, waste streams, and recycling feedstocks can be processed viably and with lower environmental impact. Digital Rock Physics (DRP) should therefore be understood as enabling infrastructure for resource policy rather than as a specialist laboratory method alone. By combining three-dimensional imaging, correlative chemistry, AI-enabled image analysis, and pore-scale modelling, DRP can connect mineral texture and reactive pathways to decisions about ore characterisation, liberation prediction, leaching, Direct Lithium Extraction, mine-waste valorisation, and battery recycling. The paper sets out a UK-European policy agenda built around translational demonstrators, cross-disciplinary training, a Digital Ore Passport standard, a federated Digital Ore Database, and integrated geo-reactive end stations. Treated as shared implementation infrastructure, DRP could help turn critical minerals strategies into practical routes for supply security, resource efficiency, circularity, and more environmentally responsible development.
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Disordered Systems and Neural Networks · Cross-listed from physics.app-ph

Electrolyte Bonding Engineering for Highly Uniform GeTe-based CBRAM and Parallel Hebbian Learning in Selector-free Hopfield Networks

Jiin Bang, Jingyeong Hwang, Unhyeon Kang et al. (+10 more)

Hopfield networks offer a hardware-friendly framework for energy-efficient associative memory, yet their practical realization in memristor crossbar arrays is critically hindered by device-to-device (D2D) variability, which prevents reliable parallel programming. Here, we address this bottleneck through systematic composition engineering of the Ge-Te solid electrolyte in conductive bridge random access memory (CBRAM) devices. By varying the Ge:Te ratio, we identify Ge3.5Te1 as an optimal electrolyte composition that suppresses stochastic resistance variation by approximately three orders of magnitude compared to GeSe-based devices. Raman spectroscopy reveals that this dramatic improvement originates from a bonding network dominated by asymmetric-stretching GeTe4 tetrahedral units, which form interconnected free-volume channels that confine and stabilize Cu+ ion migration pathways. Leveraging this enhanced uniformity, we fabricate a selector-less 16x16 Cu/Ge3.5Te1 CBRAM crossbar array and demonstrate a 4x4 Hopfield associative network capable of learning and recalling binary pattern pairs via fully parallel programming using a half-selection scheme. Successful pattern recall is achieved for up to two stored associations despite the absence of selector elements, establishing a proof-of-concept for selector-free hardware implementations of associative memory. These results highlight the critical role of electrolyte bonding structure in determining memristor uniformity and provide a materials-driven pathway toward scalable, parallel neuromorphic computing systems.
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All authors Jiin Bang, Jingyeong Hwang, Unhyeon Kang, Seungmin Oh, Kyungmin Lee, Jaehyun Park, Younghyun Lee, Hyun Jae Jang, Seongsik Park, YeonJoo Jeong, Inho Kim, Jong Keuk Park, Suyoun Lee

Strongly Correlated Electrons · Cross-listed from hep-th

Detecting Topological Transitions and Anisotropy through Multipartite Entanglement in Holographic Weyl Semimetals

Xiantong Chen, Xuanting Ji, Wen-Peng Li et al. (+1 more)

We study multipartite entanglement structures in the zero-temperature holographic Weyl semimetal, focusing on tripartite and four-partite structures. For strip regions, we compute the conditional mutual information, the entanglement wedge cross section, tripartite measures $\kappa$ and the Markov gap, multi-EWCS, and two multi-EWCS based four-partite signals $\Delta$ and $g$. These quantities are studied as functions of the strip width $l$ and the tuning parameter across the topological transition. At large $l$, their $l$ dependence takes a power-law form governed by the IR scaling of the system. At fixed large $l$, all these entanglement quantities develop clear features near the critical point, showing that tripartite and four-partite entanglement structures can diagnose the topological quantum phase transition. We further study strips pointing in different directions to probe the anisotropy of the system. The anisotropic large l behavior distinguishes the nontrivial phase from the trivial phase. These results establish multipartite holographic entanglement as a sensitive, nonlocal probe of topological phase transitions and anisotropic IR physics.
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All authors Xiantong Chen, Xuanting Ji, Wen-Peng Li, Ya-Wen Sun

Mesoscale and Nanoscale Physics

Majorana-like fermion physics: Emergence of topologically protected vortical states in graphene interacting with an electromagnetic field

H. V. Grushevskaya and George Krylov

Within the framework of a quasi-relativistic model of graphene that admits topologically nontrivial Majorana-like quasiparticle excitations, appearance of such vortex states in the frequency dependencies of the complex dielectric permittivity of the system subjected to an external electromagnetic field has been examined. The vortex graphene states possess topological charges (flavours ) being nonzero Zak phases. Interaction effects of Majorana-like modes have been qualitatively related to the formation of Fano resonances in the optical response. The constructed topological model of graphene may be considered as a toy model of three-flavour mass-neutrino oscillations.
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Superconductivity

BCS-BEC crossover driven by small Fermi pockets of a high-Tc cuprate superconductor

Junhyeok Jeong, Yamato Enomoto, Yoshimitsu Kohama et al. (+16 more)

Fermi arcs observed in underdoped cuprates have sparked debate over whether they represent segments of a large Fermi surface or small Fermi pockets. This ambiguity has long hindered their classification as either the conventional Bardeen-Cooper-Schrieffer (BCS) regime or the strongly coupled Bose-Einstein condensation (BEC) crossover limit. Here, using angle-resolved photoemission spectroscopy and quantum oscillations, we demonstrate the coexistence of a small Fermi pocket and a large superconducting gap in the clean inner CuO2 layers of the four-layer cuprate Ba2Ca3Cu4O8(F,O)2. This coexistence constitutes a hallmark of the BCS-BEC crossover and has remained elusive for decades. Despite the presence of antiferromagnetic (AF) order, the superconducting gap in the small pocket is remarkably large, yielding a gap-to-Fermi-energy ratio (Delta_pocket/e_F ~ 0.6) and a critical-to-Fermi-temperature ratio (Tc/TF ~ 1.3) that reach the theoretical upper bound for two-dimensional superconductivity. Unexpectedly, this BCS-BEC crossover emerges not as the carrier density decreases but as it increases, abruptly within a narrow doping range of less than 1%. These results provide a long-sought microscopic foundation for the d-wave pairing mechanism in doped AF-Mott insulators.
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All authors Junhyeok Jeong, Yamato Enomoto, Yoshimitsu Kohama, Tomotaka Nakayama, Kotaro Ando, Kifu Kurokawa, Soonsang Huh, Zhuo Yang, Toshihiro Nomura, Matthew D. Watson, Timur K. Kim, Cephise Cacho, Chun Lin, Makoto Hashimoto, Donghui Lu, Shiro Sakai, Takami Tohyama, Kazuyasu Tokiwa, Takeshi Kondo

Materials Science · Cross-listed from physics.app-ph

HVPE Growth of Si-Doped $\beta$-Ga$_2$O$_3$ on Sapphire: Influence of Substrate Offcut on Structural and Electrical Properties

Sourav Sarker, Saleh Ahmed Khan, Ahmed Ibreljic et al. (+1 more)

Si-doped $\beta$-Ga$_2$O$_3$ films were heteroepitaxially grown on sapphire substrates using HVPE. The influence of sapphire offcut on growth kinetics, surface morphology, crystalline quality, and electrical transport properties was systematically investigated. Growth kinetics studies revealed a strong dependence of deposition rate on HCl flow, growth pressure, and source-to-substrate distance, with growth rates reaching up to 30 $\mu$m/hr. Increasing sapphire offcut angle from 0$^\circ$ to 8$^\circ$ promoted a transition from multidirectional growth to highly aligned terrace-dominated surfaces, reducing the surface roughness from 14.69 to 2.74 nm. The improved surface morphology was accompanied by enhanced crystalline quality, with phase-pure (-201)-oriented $\beta$-Ga$_2$O$_3$ growth and a reduction in the rocking-curve full width at half maximum from 994 to 414 arcsec as the sapphire offcut increased. Electrical characterization of films grown on 6$^\circ$ offcut substrates yielded carrier concentrations ranging from $1.0\times10^{17}$ to $3.4\times10^{18}$ cm$^{-3}$. A maximum room-temperature electron mobility of 100cm$^2$/V$\cdot$s was achieved at a carrier concentration of $1.0\times10^{17}$cm$^{-3}$, representing the highest reported room-temperature mobility for HVPE-grown $\beta$-Ga$_2$O$_3$ on a foreign substrate. Analysis of the temperature-dependent transport characteristics yielded donor activation energies of 35 and 90 meV together with a low acceptor concentration of $3\times10^{15}$ cm$^{-3}$, consistent with the improved crystalline quality achieved on the offcut sapphire substrates. These results demonstrate that HVPE is capable of producing high-quality $\beta$-Ga$_2$O$_3$ heteroepitaxial layers with good crystalline quality and carrier transport characteristics, providing a promising pathway for scalable $\beta$-Ga$_2$O$_3$ epitaxy on low-cost foreign substrates.
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All authors Sourav Sarker, Saleh Ahmed Khan, Ahmed Ibreljic, Anhar Bhuiyan

Statistical Mechanics · Cross-listed from math-ph

Thermalization with Gaussian Quantum Cellular Automata

Roman Geiko and Jake Gerenraich

We study the long-time dynamics of many-body bosonic lattice systems under translation-invariant Gaussian quantum cellular automata. We formulate two sets of conditions on GQCAs which separately guarantee thermalization of any state on the local Weyl algebra to the infinite temperature state, whenever the state is locally normal and has uniformly bounded particle density. Our main intermediate result is a quantum many-body generalization of the classic Riemann-Lebesgue lemma which is a bound on expectation values of local Weyl operators involving their support and the state's particle density.
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Soft Condensed Matter · Cross-listed from physics.chem-ph

Methods for Inferring Interaction Potentials from Cross-Linking Mass Spectrometry Data

Börries von Seggern and Mohsen Sadeghi

Cross-linking mass spectrometry (XL-MS) has emerged as a powerful quantitative technique for probing intra-protein structural information as well as protein-protein interactions at an unprecedented scale. XL-MS data yield information on the pairwise spatial proximity of proteins through inter-molecular linkers. However, systematic methods for adapting such data for coarse-grained interacting particle models remain limited. Predominant focus is put on directly fitting radial distribution functions (RDFs), while numerous observables, e.g. coordination numbers, which are functionals of the RDF, cannot be uniquely inverted. In this work, we develop a framework for parameterizing interaction potentials from such observables in potentially phase-separated mixtures, as encountered in XL-MS results. We establish a connection between this problem and the inverse Henderson problem and adapt algorithms such as Iterative Boltzmann Inversion and Iterative Monte Carlo to its numerical solution. We derive exact and low-density limit gradient approximations and propose two new algorithms based on an adaptation of the predictor-corrector~framework. In total, we evaluate several optimization algorithms on biologically realistic ten-component test systems. We demonstrate that for homogeneous fluids, all methods achieve exceptional efficiency and accuracy. Critically, we further demonstrate successful parametrization in a challenging three-phase system. Here, three algorithms, namely Adam and gradient descent employing the low-density derivative as well as Newton's method with the exact gradient, reliably recover the correct parameters. These results establish a clear pathway from XL-MS experiments to coarse-grained protein models for systems where phase separation governs biological function, potentially enabling new investigations of biomolecular condensates and protein aggregation.
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Wednesday 3 June

Quantum Gases

A universal and efficient hybrid digital-analog fermionic quantum simulator

Hao-Tian Wei and Kaden R. A. Hazzard

We present a universal framework to harness fermionic ultracold atom platforms for quantum simulation, showing how variational algorithms on existing hardware can simulate many-body systems well beyond the hardware's native Hamiltonian. Our analysis provides evidence that one can quantum simulate the ground-state properties of a broad class of gapless target Hamiltonians of local observables in a quantum evolution time that grows polynomially with the inverse relative error, $T\sim O(\mathrm{poly}(1/\epsilon))$ up to logarithmic corrections, offering an exponential speedup over naïve classical algorithms such as exact diagonalization. We provide numerical evidence and theoretical argument that this holds for energy density, density-density, and spin-spin correlations in three qualitatively distinct models – the repulsive Hubbard model; a Hubbard model augmented with nearest-neighbor attractive interactions, which introduces the phenomenon of pairing; and the Hofstadter-Hubbard model, which introduces a gauge field and fractional quantum Hall physics. This work demonstrates quantum simulation using current fermionic platforms far beyond the models natively implemented in the hardware.
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Strongly Correlated Electrons

Complexity of the Laughlin wave function from the Dyson-orbital perspective

J. M. Zhang and Y. Liu

The Fermi sea is a simple and common concept in physics. However, a related and equally simple concept – the Dyson orbital – is far less discussed in physics, especially in textbooks. Yet, Dyson orbitals offer a valuable tool for characterizing the complexity of a fermionic wave functions, particularly in distinguishing between Fermi-sea-like and non-Fermi-sea-like states. As a preliminary application, we examine the Laughlin wave function and find the fortunate fact that the Dyson orbitals can be determined analytically. Further numerical data provides quantitative evidence that the Laughlin wave function describes a strongly correlated, non-Fermi liquid state.
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Statistical Mechanics

Dissipation-coherence tradeoff for stochastic oscillations

Jie Gu

Autonomous noisy oscillations in biochemical and mesoscopic systems require nonequilibrium driving and therefore dissipation. A striking conjecture by Oberreiter, Barato, and Seifert (OBS) proposes a universal lower bound on the entropy produced per oscillation period in terms of the coherence number of the slowest oscillatory mode. Here we derive a weaker but rigorous lower bound that preserves the OBS structure while introducing a mode-uniformity factor that quantifies how evenly the oscillatory eigenmode is distributed across states in the steady-state inner product. The result makes explicit that an eigenvalue-only prefactor can fail when the dominant oscillatory mode is localized. We also outline a proof-of-principle route for estimating this factor from low-dimensional data under single-mode dominance and sufficiently informative measurements, and derive an eigenvector-free corollary using only the smallest stationary probability. Translation-invariant Markov jump processes on a ring provide a symmetry-protected class with $\eta=1$, so the refinement reduces to the OBS form; the drift–diffusion limit on a circle saturates the bound.
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Strongly Correlated Electrons

Ideal Quantum Geometry for Fractional Chern Insulators

Jennifer Cano and Jie Wang

Quantum geometry plays a fundamental role in many aspects of condensed matter physics. Among its central objects are the Berry curvature and the quantum metric – quantities that, while distinct, are intertwined through geometric constraints. In this article, we survey recent progress in understanding when and how this bound is saturated, with particular emphasis on the emergence of momentum-space holomorphicity of Bloch states. These developments highlight a profound connection between certain ideal Bloch bands and the Hilbert space structure of the lowest Landau level. We elucidate this relationship through a review of quantum Hall physics in both homogeneous and spatially varying magnetic fields, and conclude by exploring its implications for the search for fractionalized phases in emerging platforms, including moiré materials.
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Mesoscale and Nanoscale Physics

Realistic quantum device data synthesized by consumer AI and how to identify it

S. M. Frolov and O. V. Kravchenko

With the advance of generative artificial intelligence (AI) synthetic texts and images have become commonplace. These capabilities offer clear benefits, but have also raised a number of ethical concerns that often have to do with misrepresenting AI outputs as genuine material. A lesser known capability of generative AI is to perform the basic analysis, processing and even synthesis of numerical data. This raises the question of whether AI can be used to imitate experimental data that an expert would consider scientifically meaningful and on par with data in the figures of peer-reviewed manuscripts? In this paper, we focus on synthesizing data inspired by well-known experiments done frequently on quantum electronic devices. This field is related to information technologies such as spintronics and quantum computing, and is considered data-rich and data-driven. We demonstrate that it is possible to generate dramatic signals associated with iconic effects such as quantum bit control, Majorana fermions, Josephson effects, quantum dots and wires using widely available ChatGPT. We find that because some of the clearest data from quantum devices can be expressed in terms of relatively basic mathematical models, AI does not need to learn on the specialized body of data. Instead, knowledge of the physics equations and of the basic features of experimental signals can go a long way towards building a realistic dataset. We also demonstrate that real data can be augmented by AI, and that AI can mimic the noise of common scientific instruments. To help assure that published data come from experiments and are not synthesized by AI, we recommend sharing large volumes of the primary data. While it is straightforward for AI to mimic a few sets of data, consistently generating long measured sequences poses sufficient barriers to the proliferation of undisclosed synthetic data.
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Materials Science

Interplay of non-local transport and local scattering during electron thermalization and spatial equilibration in laser-excited metals

Markus Uehlein, Tobias Held, Christopher Seibel et al. (+2 more)

Ultrafast laser excitation of metals induces electronic nonequilibrium both in space and locally in the energy distribution. The subsequent dynamics are governed by the interplay between non-local transport and local scattering of hot electrons, yet combined microscopic descriptions of these processes remain sparse. Here, we disentangle the influence of these processes on thermalization using a reformulation of the Boltzmann transport equation in energy space that consistently describes both spatial equilibration and scattering through full collision integrals. Our results reveal that transport accelerates the apparent thermalization observed at the irradiated surface by removing athermal carriers, while the same spatial redistribution delays complete equilibration of the full electron system. We analyze the experimentally accessible energy-dependent dynamics at the front and back surface and find that the dominant process varies, depending on both position and on the energetic window. Overall, our work improves the understanding of the interplay of electronic nonequilibrium processes occurring in optically thick laser-driven systems with relevant implications for future electronic applications.
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All authors Markus Uehlein, Tobias Held, Christopher Seibel, Sebastian T. Weber, Baerbel Rethfeld

Statistical Mechanics · Cross-listed from physics.comp-ph

Newton's Identity in Finite-Bead Fermionic Partition Function

A. Chaudhary and J. Valenzuela

For non-interacting fermions in a harmonic trap, the partition function at any discrete number of imaginary time slices (or beads) and for any choice of short-time propagator admits an exact recursion relation derived directly from the contracted determinant form of the path integral. This finite-bead recursion is distinct from earlier continuum-limit recursions, which do not apply to the discrete time partition functions. By identifying a direct correspondence between this recursion and Newton's identity, application of a closed-form result from the theory of partitions provides an exact expression for the one-dimensional $n$-fermion finite-bead partition function. From this, the Thermodynamic and Hamiltonian energies and specific heats are analytically calculated for any $n$, $N$, $\tau$, and propagator choice.
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Mesoscale and Nanoscale Physics

A nanoscale magnetic spectrum analyzer based on qubit dressed states

Jan Rueschkamp, Shantam Ravan, Daniel Fernandez et al. (+6 more)

Magnetic field fluctuations on nanometer length scales manifest in a diverse range of phenomena – electron and spin dynamics in materials and devices, quantum many-body systems, and molecular chemistry. Measuring these phenomena requires sensors with a challenging combination of broad spectral bandwidth, high sensitivity, and nanoscale spatial resolution. Nitrogen-vacancy (NV) centers, atom-like quantum sensors in diamond, possess the requisite sensitivity and nanoscale sensing volume, but are typically limited in bandwidth by the practical speed of the applied quantum control sequence. Here, we overcome this limitation by exposing the NV qubit to a microwave dressing field during a dynamical decoupling sequence, which both amplifies and frequency-mixes target signals at arbitrary frequencies into the detection band of the dynamical decoupling protocol. We demonstrate this approach by using NV centers to detect both coherent and noisy nanoscale spin wave dynamics in a magnetic yttrium-iron-garnet (YIG) thin film over a broad frequency range. Our technique generalizes to other qubit platforms, providing a versatile framework for nanoscale spectroscopy across diverse physical and chemical systems.
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All authors Jan Rueschkamp, Shantam Ravan, Daniel Fernandez, Nazar Delegan, F. Joseph Heremans, David D. Awschalom, Ronald L. Walsworth, Nikola Maksimovic, Amir Yacoby

Superconductivity

Fermiology and the Candidate Chiral Superconductor in Rhombohedral Tetralayer Graphene

Sandesh S. Kalantre, Ben H. Alexander, Julian May-Mann et al. (+11 more)

Chiral superconductivity, in which the phase of the superconducting order parameter winds in momentum space, has long been sought for its close link to topological superconductivity. Recent work reported a superconductor in rhombohedral multilayer graphene emerging from a time-reversal symmetry broken normal state, suggesting that it could be a chiral superconductor. However, the possibility of chirality depends on the symmetry and structure of the normal-state Fermi surface, which have not been directly measured. Here we measure quantum oscillations in rhombohedral tetralayer graphene over a broad range of the phase diagram, including the superconducting region. At densities well above the onset of superconductivity, we reproduce previously-reported oscillations consistent with a spin- and valley-polarized quarter metal with a single simply-connected Fermi pocket. As the carrier density is reduced, we find a transition to a complex "multitone" state that persists through the superconducting region. This state's spectrum of quantum oscillations is incompatible with a simply-connected quarter metal. The next-simplest candidate normal states suggested by our microscopic modeling (fully-polarized annular, nematic, and three-pocket states) are inconsistent with our measurements, albeit difficult to rule out entirely. The normal state is thus seen to be richer than previously envisaged, reshaping the search for the superconducting mechanism and the possible chirality of the pairing channel.
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All authors Sandesh S. Kalantre, Ben H. Alexander, Julian May-Mann, Jonah Herzog-Arbeitman, Marisa Hocking, Qingrui Cao, Kenji Watanabe, Takashi Taniguchi, David Goldhaber-Gordon, Andrew J. Mannix, Trithep Devakul, Yves H. Kwan, Daniel E. Parker, Aaron Sharpe

Statistical Mechanics

Opinion dynamics on social proximity disordered networks

Fellipe Aranha, Giuliano G. Porciúncula, Adauto J. F. de Souza et al. (+2 more)

Understanding how local social pressure shapes collective opinion formation is essential in modern society, with implications in sociology, politics, finance, and technology. Complex networks are a powerful framework for investigating these processes and for representing social interactions in emergent phenomena, and canonical models such as random, scale-free, and small-world networks remain most relevant when Euclidean geometric proximity and contiguous interactions are not the dominant organizing factors. Our investigation explores the effects of Gabriel graphs, a spatially embedded network that utilizes proximity-based interactions, on social opinion dynamics. Using a geometric disorder parameter that randomly displaces agent coordinates, we transition from square lattices of social interactions to spatial random networks that preserve local constraints while introducing strong topological heterogeneity. Opinion dynamics operate through social pressure, with a level of nonconformity that affects dissent among opinions. We analyze magnetization, susceptibility, and Binder's fourth-order cumulant to characterize the emergence and breakdown of global social consensus. The model exhibits second-order phase transitions whose behavior depends on both geometric disorder and nonconformity levels. We use volumetric scaling and provide a reference frame appropriate for characterizing criticality in regular and heterogeneous interaction topologies. We find that the standard critical exponents remain compatible with the two-dimensional Ising universality class. Furthermore, the results suggest that spatially constrained, planar, and globally connected interaction topologies preserve the dimensionality of space in critical dynamics analysis.
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All authors Fellipe Aranha, Giuliano G. Porciúncula, Adauto J. F. de Souza, Paulo R. A. Campos, André L. M. Vilela

Other Condensed Matter · Cross-listed from physics.ins-det

The MuFusE Large-Volume Diamond Anvil Cell for Exploring Muon-Catalyzed Fusion at Higher Pressures and Temperatures

J.D. Kalow, J.T. Hinchen, G. Harris et al. (+45 more)

A new large-volume diamond anvil cell (DAC) has been developed for the Muon-catalyzed Fusion ($\mu$CF) Experiment (MuFusE), enabling the compression and heating of deuterium-tritium (d-t) mixtures to pressures and temperatures needed to advance $\mu$CF research. The MuFusE DAC achieves the large sample volumes necessary for high-precision fusion measurements while integrating cryogenic loading, all-metal sealing, and flexible bellows to maintain a secure environment during cell compression. Combined with remote pneumatic actuation and secondary containment, the DAC safely managed a 25 Ci tritium inventory while providing a clear optical path for in situ measurements of sample pressure and composition via laser spectroscopy. Utilizing 5 mm diameter diamond anvils oriented in the path of a high-intensity muon beam, the apparatus achieved a stable sample volume of 19.2 mm$^3$ at liquid density, pressures up to 933 MPa and temperatures up to 400 K - benchmarks that significantly exceed previously reported limits for static d-t targets.
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All authors J.D. Kalow, J.T. Hinchen, G. Harris, E. Koukina, D.M. Harrington, P.C. McDaniel, N.J. Brennan, A. Golossanov, I.D. Spool, D. Zajac, M. Mundt, S. Varner, M. Russell, S. Bull, K. McCormack, D. Mayer, L.E. Knaian, M. Khandaker, W. Stadolnik, W.R. Cutler, A. Sampat, K. Lau, J. Betances, C. Fagan, C.R. Shmayda, M. Koch, K. Payne, N.J.L. MacFadden, J. Simon, K. Peterson, A. Gami, S. Machavarapu, A. Tejeda, J. Katz, J.A. Allen, R. Chaney, K. Kem, I. Kiniti, E. Garcia Badaracco, K.R. Lynch, P. Gandhi, C.J. Johnstone, E. Niner, C.C. Petitjean, A. Antognini, W.T. Shmayda, S.O. Newburg, A.N. Knaian

Materials Science

Hydrogen-induced lattice cohesion weakening favors atomic displacement

Liang Gao, Yiran Mao, Markus Wilde et al. (+9 more)

Atomic displacement – the fundamental process underlying diverse deformation and damage phenomena in metals, from irradiation defect production to stress-driven dislocation motion – is governed by interatomic cohesion strength. Here, lattice-dissolved hydrogen (LDH) occurring in metals under direct hydrogen exposure is identified to effectively weaken lattice cohesion, and thereby facilitating atomic displacement and dislocation movement upon plastic deformation in sub-threshold stress regime. This atomic-scale insight provides a physically transparent mechanism for hydrogen-enhanced localized plasticity implicated in hydrogen embrittlement. We quantitatively verify the hydrogen-induced lattice cohesion weakening effect on metal surfaces exposed to low-energy hydrogen plasma, where massive defects are generated despite the absence of sufficient ion momentum for direct displacement damage. By unprecedentedly quantifying the cohesion-weakening effect of LDH independently from defect-trapped H, we establish a new paradigm to understand hydrogen embrittlement.
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All authors Liang Gao, Yiran Mao, Markus Wilde, Xiaoou Yi, Cong Li, Shiwei Wang, Thomas Schwarz-Selinger, Jan Coenen, Richard Kembleton, Sebastijan Brezinsek, Christian Linsmeier, Guanghong Lu

2606.05325 · 3 Jun · We reveal here the exact role of diffusive lattice-dissolved hydrogen (LDH) favoring kink pair nucleation and accelerating dislocation movement, unlocking the underlying nature of the HELP (Hydrogen-Enhanced Localized Plasticity) mechanism. Main text 17 pages, 4 figures; Supplementary Materials 9 pages, 2 figures

Abstract PDF $LATT ×4$PLSM ×1

Strongly Correlated Electrons · Cross-listed from hep-th

Krylov Complexity: Flat bands and Carroll breaking deformations

Aritra Banerjee, Arpan Bhattacharyya, Rudranil Basu et al. (+1 more)

Systems with flat band structures, when written in the language of Compact Localised States (CLS), have been shown to be explicitly invariant under supertranslation symmetries, making Carrollian symmetries inherently important for such systems. In this work, we explore the state dynamics of these systems, focusing on quenches induced by Carroll breaking perturbations, through the probe of Krylov (spread) Complexity. We specialise to Fermionic ladder Hamiltonians with all bands flat (ABF) scenario, augmented by a supertranslation preserving interaction, and discuss Krylov state complexity for quenches across critical lines. We further discuss how the growth of Krylov complexity sharply resolves the phase-dependent resilience of Carrollian sectors against delocalising perturbations. This is augmented by a complementary mechanism for Krylov growth in a continuum Carroll scalar field theory with a gradient deformation, which exhibits strong ultraviolet sensitivity (UV/IR mixing).
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All authors Aritra Banerjee, Arpan Bhattacharyya, Rudranil Basu, Sayan Das

Superconductivity

Magnetochiral anisotropy in strained superconducting transition metal dichalcogenides

Joaquim Telles de Miranda, Maxim Khodas and Alex Levchenko

We present a theoretical study of nonreciprocal charge transport in two-dimensional noncentrosymmetric superconductors, taking the transition-metal dichalcogenide MoS$_2$ as a representative example. In the normal state, the magnetochiral anisotropy vanishes within the minimal band model of MoS$_2$, appearing only at subleading order in the symmetry-breaking perturbations set by trigonal warping, Ising spin-orbit coupling, and the Zeeman field. Superconductivity changes this picture qualitatively: in the vicinity of the transition, the magnetochiral anisotropy is strongly enhanced by pairing fluctuations. We evaluate the nonreciprocal current density arising from order-parameter fluctuations and quantum-interference processes – the Aslamazov-Larkin and Maki-Thompson channels – and show that both are governed by cubic Lifshitz invariants of the Ginzburg-Landau free energy, generically allowed once inversion and time-reversal symmetries are broken. These invariants are derived microscopically from the band model, including the effects of disorder: in the diffusive limit the warping-induced invariant is suppressed, yet the resulting response remains sizable. Strain is shown to enable additional vector components of the nonlinear current, activating the Maki-Thompson channel. Finally, invoking Onsager reciprocity, we identify kinetic Lifshitz invariants, nonreciprocal corrections to the order-parameter relaxation rate, locked to the Langevin noise by the fluctuation-dissipation theorem, and demonstrate that their contribution to the magnetochiral anisotropy is parametrically subleading near the transition.
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Statistical Mechanics · Cross-listed from quant-ph

Isospectrality and Operator Complexity

Pradip Kattel, Yicheng Tang and Natan Andrei

We study a pair of exactly solvable, isospectral fermion chains, one strongly interacting and one quadratic, that nevertheless display remarkably different phase structures and operator dynamics. A nonlocal nonlinear unitary transformation maps one onto the other while preserving the entire many-body spectrum and converting local fermion operators into extended many-body strings. Thus, operators that evolve within a closed linear subspace in the quadratic model become interacting operators that generate increasingly higher-body terms and exhibit asymptotic Lanczos growth $b_n\propto\sqrt n$. Despite their identical spectra, the two models realize distinct phases and sharply different notions of operator complexity. Our results demonstrate that free many-body spectra and interacting operator dynamics are fundamentally compatible.
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Strongly Correlated Electrons

Thermalization Dynamics in the Two-Dimensional Hubbard Model with Neural-Network Quantum States

Alessandro Sinibaldi, Luciano Loris Viteritti, Riccardo Rende et al. (+2 more)

Thermalization in strongly correlated fermionic systems remains a central open problem in quantum many-body physics. In this work, we investigate the real-time dynamics and the approach to thermalization in the two-dimensional Hubbard model, a paradigmatic framework for correlated electrons, relevant to high-temperature superconductivity and ultracold quantum simulation. Focusing on the half-filled square lattice, we monitor the time evolution of the double occupancy following a quench in the on-site interaction $U$, and assess whether its long-time value is captured by a canonical thermal ensemble. We employ time-dependent variational Monte Carlo methods combined with transformer-based Neural-Network Quantum States to accurately describe the nonequilibrium dynamics of fermions, especially for the behavior at long times, thereby accessing regimes that were previously inaccessible to numerical simulations. Our results reveal two dynamical behaviors: for weak to intermediate interactions, the double occupancy rapidly approaches the thermal prediction, consistent with ergodic evolution; beyond a critical interaction $U_{C}$, the dynamics remains distinct from the thermal expectation on the timescales investigated, revealing signatures of a prethermal plateau delaying fast relaxation. These results establish numerical simulation as a powerful tool to probe nonequilibrium quantum phenomena in correlated fermionic matter.
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All authors Alessandro Sinibaldi, Luciano Loris Viteritti, Riccardo Rende, Fakher F. Assaad, Giuseppe Carleo

Statistical Mechanics · Cross-listed from quant-ph

Emergent Self-Similar Quantum Revivals in Spiral Drives

Xin-Chi Zhou, Liang-Hong Mo, Hongzheng Zhao et al. (+1 more)

We uncover a distinct form of nonequilibrium temporal order: self-similar quantum revivals in a many-body system driven by quasiperiodic spiral kicks, where the system recurrently returns close to its initial state at a hierarchically nested sequence of times. We demonstrate that both the fidelity and entanglement entropy exhibit this self-similar temporal structure. It originates from an emergent dynamical attractor, which we identify, such that all momentum modes eventually fall into the same closed orbits at self-similar times. We analytically justify this behavior and show that, for special momentum modes, this attractor arises as a consequence of a generalized spin echo process, and more generally we prove its existence using quasiperiodic SU(2) cocycles. Interestingly, the dynamics between consecutive revivals supports either volume- or area-law entanglement scaling, tunable via the driving parameters. In the presence of integrability-breaking perturbations, the system eventually heats up, but a long-lived prethermal regime with algebraically tunable lifetime occurs before heating sets in. Our results establish self-similar quantum revivals as a new paradigm for nonequilibrium quantum matter and provide a realistic route for its observation in current quantum simulators.
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All authors Xin-Chi Zhou, Liang-Hong Mo, Hongzheng Zhao, Bastien Lapierre

Strongly Correlated Electrons · Cross-listed from hep-th

Hypergroup Symmetry in Relative Quantum Field Theories and Chiral Algebras

Terry Gannon and Brandon C. Rayhaun

A QFT is said to be relative if it lives at the boundary of a topological QFT in one higher dimension. We develop a general framework for working with noninvertible symmetries of relative theories in two spacetime dimensions, extending several well-known results for absolute QFTs. We emphasize various new features which arise in the relative setting, including the role of topological surfaces of the bulk, and the appearance of hypergroups and certain generalizations of tube algebras known as dome algebras. Our formalism is particularly well-suited for studying rational chiral algebras, where it predicts that finite symmetries are in explicit one-to-one correspondence with conformal embeddings of finite index. We describe several implications of our framework for absolute theories. First, we explain how to "glue" together symmetries of the left- and right-moving chiral algebras of a 2D CFT to produce topological line defects of the full theory. Second, we derive a precise correspondence between boundary conditions of a 2D CFT and symmetries of its chiral algebra. This correspondence has several structural corollaries: in diagonal rational CFTs, we demonstrate that the topological line defects of the theory act transitively on its boundary conditions, and further that the identity Cardy state has the smallest $g$-function amongst all boundary conditions, including those which only preserve Virasoro symmetry. We conclude by illustrating our results in a variety of examples. For instance, we show that, if there exists a rational chiral algebra with central charge $c=8$ whose modular tensor category is the Drinfeld center of the Haagerup fusion category, then it must arise as the fixed points of a rank-2 hypergroup acting on the $SU(3)_1\otimes (E_{6})_1$ chiral algebra.
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