Quantum Geometry of Altermagnetic Magnons Probed by Light

Authors: Rundong Yuan, Wojciech J. Jankowski, Ka Shen, Robert-Jan Slager

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.02781v1 Announce Type: new Abstract: Magnons with momentum-dependent chirality are a key signature of altermagnets. We identify bicircular light as a smoking-gun optical probe for chiral altermagnetic magnons, selectively targeting their quantum geometry induced by an alteration of magnonic chirality. We show that in $d$-wave altermagnets, under a canting magnetic field, the altermagnetic magnons realize a nontrivial quantum geometry, resulting in an enhancement of the nonlinear second-order light-magnon interactions. We find that the scattering of bicircular pulses probes the present magnon quantum geometry, even if the magnonic topology is trivial. Hence, our findings establish bicircular Raman response as an optical effect of choice to identify altermagnetic magnons. As such, we propose a universal experimental protocol to distinguish altermagnets from antiferromagnets by detecting their magnon chirality patterns with light, independently of the underlying magnon topology.

Signatures of quantum chaos and complexity in the Ising model on random graphs

Authors: GJ Sreejith, Sandipan Manna

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.02819v1 Announce Type: new Abstract: We investigate signatures of quantum chaos and complexity in the quantum annealing Ising model on random Erd\H{o}s-R\'enyi graphs. By tuning the connectivity of the graph, the dynamics can be driven from a localized phase through a chaotic regime to an integrable limit. While this dynamical transition reflects in the spectral characteristics, we pursue a broader suite of quantum chaos indicators,some of which can be measured on near-term quantum devices. We study deep thermalization of a quantum state ensemble obtained from a natural unraveling of the subsystem density matrix as an indicator of chaotic dynamics. This extends the analysis of quantum chaos to the ensemble of quantum states. Furthermore, we analyze the eigenstate and eigenvalue correlations through the partial spectral form factor of subsystems and observe distinct signatures of the onset of chaos and its system size dependence, providing experimentally measurable indicators of the localization-to-chaos transition. As a locality-independent probe, we show that the Krylov complexity of operators is also maximized in the chaotic regime, providing a link between graph topology and information scrambling. Finally, we investigate a quantum analogue of the Mpemba effect, where initially "hotter" states can thermalize anomalously fast, a phenomenon most cleanly observed within the chaotic phase. However, away from the chaotic regime, the system is distinguished by multiple crossings across connectivity in its distance from the thermal ensemble with time. Collectively, this work presents a broad characterization of chaos, providing insight beyond spectral analysis and practical indicators for benchmarking near-term quantum devices.

Role of nanoparticle shape on the critical size for quasi-uniform ordering: from spheres to cubes through superballs

Authors: Iago L\'opez-V\'azquez, David Serantes, \`Oscar Iglesias

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.02838v1 Announce Type: new Abstract: The equilibrium magnetic states of single-domain magnetite nanoparticles (NPs) result from a subtle interplay between size, geometry, and magnetocrystalline anisotropy. In this work, we present a micromagnetic study of shape-controlled magnetite NPs using the superball geometry, which provides a continuous interpolation between spheres and cubes. By isolating the influence of shape, we analyze the transition from quasi-uniform (single-domain) to vortex-like states as particle size increases, revealing critical sizes that depend on the superball exponent. Our simulations show that faceted geometries promote the stabilization of vortex states at larger sizes, with marked distortions in the vortex core structure. The inclusion of cubic magnetocrystalline anisotropy, representative of magnetite, further lowers the critical size and introduces preferential alignment along the [111] easy axes. In contrast, the presence of slight particle elongation increases the critical size and induces another preferential alignment direction. These results demonstrate that even small deviations from sphericity or aspect ratio significantly alter the magnetic ordering and stability of equilibrium magnetic states.

Impeded Bloch Oscillation and Nonreciprocal Landau-Zener Tunneling of Bose-Einstein Quantum Droplets in Optical Lattices

Authors: Szu-Cheng Cheng, Yu-Wen Wang, Wen-Hsuan Kuan

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.02852v1 Announce Type: new Abstract: We investigate the nonlinear Bloch dynamics and Landau-Zener tunneling of quantum droplets in optical lattices, where the interplay between mean-field repulsion and beyond-mean-field attraction from Lee-Huang-Yang corrections introduces a localization impedance that inhibits dynamical dispersion. This self-stabilizing mechanism is crucial to droplet mobility and nonlinear dephasing under external driving. In the deep-lattice regime, simulation in tight-binding reduction reveals breathing modes, self-trapping, and nonlinear Bloch oscillations. In the shallow-lattice regime, we reformulate the problem in momentum space and map the dynamics onto a nonlinear two-level model with time-dependent detuning. The adiabatic spectrum features looped bands and multiple fixed points, parallelly captured by the phase-space structure through a classical Josephson analogy. Applying Hamilton-Jacobi theory, we quantify the tunneling probabilities and demonstrate nonreciprocal Landau-Zener tunneling. The transition probability from the lower to upper band differs from that of the reverse process, even under the same sweeping protocol. This asymmetry arises from nonlinearly induced band gap modulation, highlighting rich dynamical behavior beyond the linear and adiabatic regimes.

Self-assembled fluorescent nanodiamond layers for quantum imaging

Authors: Katherine Chea, Erin S. Grant, Kevin J. Rietwyk, Hiroshi Abe, Takeshi Ohshima, David A. Broadway, Jean-Philippe Tetienne, Gary Bryant, Philipp Reineck

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03028v1 Announce Type: new Abstract: The nitrogen-vacancy (NV) center in diamond is emerging as a powerful tool for imaging magnetic and electric signals at the microscale and below. However, most imaging demonstrations thus far have relied on costly, millimeter-sized bulk diamond substrates, which cannot be easily scaled or integrated with other materials. Here, we report a scalable method for fabricating NV-containing dense and homogenous fluorescent nanodiamond (FND) layers through electrostatic self-assembly and demonstrate the utility of the FND layers for magnetic imaging. We investigate the effect of FND concentration in suspension, substrate immersion time, and solvent pH on the FND density on the substrate. We identify optimized self-assembly conditions that maximize the FND density while minimizing aggregation. Using FND layers on a quartz substrate, we demonstrate magnetic field and magnetic noise imaging at the microscale, based on NV optically detected magnetic resonance magnetometry and T$_1$ relaxometry, respectively. Our results provide a direction for the development of cost-effective and scalable FND layers and surface coatings. This paves the way for on-demand quantum sensing and imaging on a broad range of surfaces based on NV centers and other diamond quantum emitters.

Dichotomy of flat bands in the van der Waals ferromagnet Fe$_5$GeTe$_2$

Authors: Han Wu, Jianwei Huang, Chaowei Hu, Lei Chen, Yiqing Hao, Yue Shi, Paul Malinowski, Yucheng Guo, Bo Gyu Jang, Jian-Xin Zhu, Andrew F. May, Siqi Wang, Xiang Chen, Yaofeng Xie, Bin Gao, Yichen Zhang, Ziqin Yue, Zheng Ren, Makoto Hashimoto, Donghui Lu, Alexei Fedorov, Sung-Kwan Mo, Junichiro Kono, Yu He, Robert J. Birgeneau, Pengcheng Dai, Xiaodong Xu, Huibo Cao, Qimiao Si, Jiun-Haw Chu, Ming Yi

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03029v1 Announce Type: new Abstract: Quantum materials with bands of narrow bandwidth near the Fermi level represent a promising platform for exploring a diverse range of fascinating physical phenomena, as the high density of states within the small energy window often enables the emergence of many-body physics. On one hand, flat bands can arise from strong Coulomb interactions that localize atomic orbitals. On the other hand, quantum destructive interference can quench the electronic kinetic energy. Although both have a narrow bandwidth, the two types of flat bands should exhibit very distinct spectral properties arising from their distinctive origins. So far, the two types of flat bands have only been realized in very different material settings and chemical environments, preventing a direct comparison. Here, we report the observation of the two types of flat bands within the same material system--an above-room-temperature van der Waals ferromagnet, Fe$_{5-x}$GeTe$_2$, distinguishable by a switchable iron site order. The contrasting nature of the flat bands is also identified by the remarkably distinctive temperature-evolution of the spectral features, indicating that one arises from electron correlations in the Fe(1) site-disordered phase, while the other geometrical frustration in the Fe(1) site-ordered phase. Our results therefore provide a direct juxtaposition of the distinct formation mechanism of flat bands in quantum materials, and an avenue for understanding the distinctive roles flat bands play in the presence of magnetism, topology, and lattice geometrical frustration, utilizing sublattice ordering as a key control parameter.

Observation of Embedded Topology in a Trivial Bulk via Projective Crystal Symmetry

Authors: Hau Tian Teo, Yang Long, Hong-yu Zou, Kailin Song, Haoran Xue, Yong Ge, Shou-qi Yuan, Hong-xiang Sun, Baile Zhang

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03033v1 Announce Type: new Abstract: Bulk-boundary correspondence is the foundational principle of topological physics, first established in the quantum Hall effect, where a $D$-dimensional topologically nontrivial bulk gives rise to $(D-1)$-dimensional boundary states. The advent of higher-order topology has generalized this principle to a hierarchical chain, enabling topological states to appear at $(D-2)$ or even lower-dimensional boundaries. To date, all known realizations of topological systems must require a topologically nontrivial bulk to initiate the chain of action for bulk-boundary correspondence. Here, in an acoustic crystal platform, we experimentally demonstrate an exception to this paradigm--embedded topology in a trivial bulk--where the bulk-boundary correspondence originates from a trivial bulk. Rather than relying on global symmetries, we employ projective crystal symmetry, which induces nontrivial topology not at the outset in the $D$-dimensional bulk, but midway through the correspondence hierarchy in lower-dimensional boundaries. We further realize a three-dimensional system exhibiting embedded topology that supports zero-dimensional topological states, achieving the longest possible chain of action for such an unconventional bulk-boundary correspondence in physical space. Our work experimentally establishes a new form of bulk-boundary correspondence initiated from a trivial bulk, opening additional degrees of freedom for the design of robust topological devices.

Dielectric Substrate Dependence of Thermoelectric Transport in BLG-GaAs-BLG Heterostructures

Authors: Vo Van Tai, Truong Van Tuan, Tran Trong Tai, Le Tri Dat, Nguyen Duy Vy

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03035v1 Announce Type: new Abstract: We theoretically study the thermoelectric transport S in a double-layer bilayer graphene (BLG-GaAs-BLG) system on dielectric substrates (h-BN, Al2O3, HfO2). Electrons interact with GaAs acoustic phonons via both the deformation potential (acDP) and piezoelectric (acPE) scattering. Results show that piezoelectric scattering dominates the total transport, especially at low carrier density and high dielectric constant. Substrate dielectric constant significantly influences thermopower S, and the thermopower of the materials is in the order of HfO2 > Al2O3 > h-BN. When densities on two BLG layers are unequal, the contribution from acDP scattering Sd decreases (increases) at low (high) densities versus equal densities, while acPE scattering Sg remains stable, making S largely Sg-dependent. Increasing interlayer distance d enhances S, while higher temperature boosts Sd (notably at low densities) with minimal effect on Sg. These insights and substrate-dependent trends demonstrate substrate engineering as a key parameter for optimizing BLG thermoelectric devices

Electronic ordering driven by flat band nesting in a van der Waals magnet Fe5GeTe2

Authors: Qiang Gao, Gabriele Berruto, Khanh Duy Nguyen, Chaowei Hu, Haoran Lin, Beomjoon Goh, Bo Gyu Jang, Xiaodong Xu, Peter Littlewood, Jiun-Haw Chu, Shuolong Yang

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03116v1 Announce Type: new Abstract: Solid-state systems with flat electronic bands have a theoretical propensity to form electronic orders such as superconductivity and charge-density waves. However, for many flat-band systems such as Kagome and Clover lattices, the flat bands do not naturally appear at the Fermi level, hence not driving the low-energy electronic ordering. Here we demonstrate the concurrent formation of flat bands at the Fermi level and a $\sqrt{3} \times \sqrt{3}\, R30^\circ$ charge order in a van der Waals magnet Fe5GeTe2 using high-resolution angle-resolved photoemission spectroscopy. This charge order is manifested by clear band structure folding below 100 K, yet the band folding is limited to 30 meV below the Fermi level where the flat bands reside. The nesting vector in the reciprocal space connects segments of Fermi surfaces where pronounced flat bands are discovered. Taken together with calculations of the Lindhard response function, our results establish Fe5GeTe2 as a model system where flat bands promote inter-band nesting and electronic ordering. The appearance of the flat band at the Fermi level is reminiscent of the Kondo lattice effect, yet we point out that the flat bands may originate from the abundance of vacancies in the Fe(1) sublattice, where the vacancies induce flat dispersions via destructive charge or spin interactions.

Observation of Anomalous Hall Effect in Bulk Single Crystals of n-type Cr-doped Sb$_{2}$Te$_{3}$ Magnetic Topological Insulator

Authors: Ali Sarikhani (Material Research Center, Missouri University of Science and Technology, Rolla, MO), Mathew Pollard (Department of Physics, Missouri University of Science and Technology, Rolla, MO), Jacob Cook (Department of Physics and Astronomy, University of Missouri, Columbia, MO), Sheng Qiu (Department of Physics, Missouri University of Science and Technology, Rolla, MO), Seng Huat Lee (Department of Physics, Missouri University of Science and Technology, Rolla, MO), Laleh Avazpour (Department of Physics, Missouri University of Science and Technology, Rolla, MO), Jack Crewse (Department of Physics, Missouri University of Science and Technology, Rolla, MO), William Fahrenholtz (Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO), Guang Bian (Department of Physics and Astronomy, University of Missouri, Columbia, MO), Yew San Hor (Department of Physics, Missouri University of Science and Technology, Rolla, MO)

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03141v1 Announce Type: new Abstract: The exploration of topological Dirac surface states is significant in the realms of condensed matter physics and future technological innovations. Among the materials garnering attention is Sb$_{2}$Te$_{3}$, a compound that theoretically exhibits topological insulating properties. However, its inherent p-type nature prevents the direct experimental verification of its Dirac surface state due to the Fermi level alignment with the valence band. In this study, by doping Cr atoms into Sb$_{2}$Te$_{3}$, n-type behavior is observed in the Hall resistance measurements. Remarkably, the Cr-doped Sb$_{2}$Te$_{3}$ not only shows ferromagnetism with a high transition temperature of approximately 170 K but also exhibits an anomalous Hall effect (AHE). The Cr doping also allows for a controlled method for Fermi level tuning into the band gap. These properties spotlight its potential as an n-type magnetic topological insulator (MTI) as well as a material candidate for the quantum anomalous Hall effect (QAHE), opening new avenues for applications in spintronics and quantum devices.

Topological band insulators without translational symmetry

Authors: Shuo Wang, Jing-Run Lin, Zheng-Wei Zuo

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03208v1 Announce Type: new Abstract: In the research of the topological band phases, the conventional wisdom is to start from the crystalline translational symmetry systems. Nevertheless, the translational symmetry is not always a necessary condition for the energy bands. Here we propose a systematic method of constructing the topological band insulators without translational symmetry in the amorphous systems. By way of the isospectral reduction approach from spectral graph theory, we reduce the structural-disordered systems formed by different multi-atomic cells into the isospectral effective periodic systems with the energy-dependent hoppings and potentials. We identify the topological band insulating phases with extended bulk states and topological in-gap edge states by the topological invariants of the reduced systems, density of states, and the commutation of the transfer matrix. In addition, when the building blocks of the two multi-atomic cells have different number of the lattice sites, our numerical calculations demonstrate that the existences of the flat band and the macroscopic bound states in the continuum in the amorphous systems. Our findings uncover a new arena for the exploration of the topological band states beyond translational symmetry systems paradigm.

Organic altermagnets based in two-dimensional nanographene frameworks

Authors: Ricardo Ortiz, Karol Struty\'nski, Manuel Melle-Franco

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03234v1 Announce Type: new Abstract: Altermagnetism stands as a third type of collinear magnetic order, whose band structure combines a net zero magnetization with a non-relativistic spin-splitting caused by a broken time reversal symmetry. So far, the strategy to design platforms displaying altermagnetism has relied mostly on inorganic crystals with d-metals as spin centers, where a representative example is the two-dimensional square lattice with antiparallel D2h magnetic blocks related by a pi/2 rotation. Despite the fact that there is no strong requirement for the magnetic atoms to be metals, the construction of an altermagnetic framework with light elements like carbon is challenging due to symmetric constrictions. We show how it is possible to overcome this by including non-alternant rings in pi-conjugated nanographenes. More specifically, dibenzo[ef,kl]heptalene, an S = 1 pi-conjugated hydrocarbon consisting of a graph of two fused heptagons and hexagons, represents a suitable building block for an altermagnetic 2D crystal. In this work, we confirm this hypothesis with DFT calculations of the spin polarized band structure, presenting a spin compensated ground state with broken time reversal symmetry, and a d-wave symmetry of the first valence and conduction bands. Consistent results are obtained for covalent organic frameworks based on dibenzo[ef,kl]heptalene units connected by linkers, paving the way for the realization of organic altermagnetic materials.

Multiscale Coupled Polarization and BKT Transitions in Tow-Dimensional Hybrid Organic-Inorganic Perovskites

Authors: Weijie Wu, Zehua Li, Yu Wang

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03285v1 Announce Type: new Abstract: We present an extended two-dimensional XY rotor model specifically designed to capture the polarization dynamics of hybrid organic-inorganic perovskite monolayers. This framework integrates nearest and next-nearest neighbor couplings, crystalline anisotropy inherent to perovskite lattice symmetries, external bias fields, and long-range dipolar interactions that are prominent in layered perovskite architectures. Through a combination of analytical coarse-graining and large-scale Monte Carlo simulations on 64*64 lattices, we identify two distinct thermodynamic regimes: a low-temperature quasi-ferroelectric state characterized by finite polarization and domain wall formation, and a higher-temperature Berezinskii-Kosterlitz-Thouless (BKT) crossover associated with vortex-antivortex unbinding and the suppression of long-range order. Our results reproduce key experimental signatures observed in quasi-two-dimensional perovskites, including dual peaks in dielectric susceptibility, enhanced vortex density near the transition, multistable polarization hysteresis under applied fields, and the scaling behavior of domain wall widths. This minimal yet realistic model provides a unifying perspective on how topological transitions and ferroelectric ordering coexist in layered perovskite systems, offering quantitative guidance for interpreting the emergent polar vortex lattices and complex phase behavior recently reported in hybrid perovskite thin films.

Berry Curvature of Low-Energy Excitons in Rhombohedral Graphene

Authors: Henry Davenport, Frank Schindler, Johannes Knolle

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03290v1 Announce Type: new Abstract: We investigate low energy excitons in rhombohedral pentalayer graphene encapsulated by hexagonal boron nitride (hBN/R5G/hBN), focusing on the regime at the experimental twist angle $\theta = 0.77^\circ$ and with an applied electric field. We introduce a new low-energy two-band model of rhombohedral graphene that captures the band structure more accurately than previous models while keeping the number of parameters low. Using this model, we show that the centres of the exciton Wannier functions are displaced from the moir\'e unit cell origin by a quantised amount -- they are instead localised at $C_3$-symmetric points on the boundary. We also find that the exciton shift is electrically tunable: by varying the electric field strength, the exciton Wannier centre can be exchanged between inequivalent corners of the moir\'e unit cell. Our results suggest the possibility of detecting excitonic corner or edge modes, as well as novel excitonic crystal defect responses in hBN/R5G/hBN. Lastly, we find that the excitons in hBN/R5G/hBN inherit excitonic Berry curvature from the underlying electronic bands, enriching their semiclassical transport properties. Our results position rhombohedral graphene as a compelling tunable platform for probing exciton topology in moir\'e materials.

From Wye-Delta to Cross-Square Recursion Configurations in Graphene-Based Quantum Hall Arrays

Authors: Ngoc Thanh Mai Tran, Marta Musso, Dominick S. Scaletta, Wei-Chen Lin, Valery Ortiz Jimenez, Dean G. Jarrett, Massimo Ortolano, Curt A. Richter, Chi-Te Liang, David B. Newell, Albert F. Rigosi

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03347v1 Announce Type: new Abstract: In electrical metrology, the quantum Hall effect is accessed at the Landau level filling factor {\nu} = 2 plateau to define and disseminate the unit of electrical resistance (ohm). The robustness of the plateau is only exhibited at this Landau level filling factor and thus places a constraint on the quantized resistances that are accessible when constructing quantized Hall array resistance standards (QHARS) using epitaxial graphene on SiC. To overcome devices constrained by using Hall elements in series or in parallel, this work approaches the fabrication of a cross-square network configuration, which is similar to but departs slightly from conventional wye-delta designs and achieves significantly higher effective quantized resistance outputs. Furthermore, the use of pseudofractal-like recursion amplifies the ability to reach high resistances. QHARS devices designed as the ones here are shown to achieve an effective resistance of 55.81 M$\Omega$ in one configuration and 27.61 G$\Omega$ in another, with a hypothetically projected 317.95 T$\Omega$ that could be accessed with more specialized equipment. Teraohmmeter measurements reveal the limits of conventional wet cryogenic systems due to resistance leakage. Ultimately, this work builds on the capability of realizing exceptionally high-value quantum resistance standards.

Engineering subgap states in superconductors by altermagnetism

Authors: Bo Lu, Phillip Mercebach, Pablo Burset, Keiji Yada, Jorge Cayao, Yukio Tanaka, Yuri Fukaya

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03364v1 Announce Type: new Abstract: We investigate the realization and control of subgap states by tailored altermagnetic fields on unconventional superconductors. When the symmetries of altermagnetism and unconventional superconductivity align, we demonstrate the emergence of bulk zero-energy flat bands, giving rise to a zero-bias conductance peak. The symmetry and strength of $d$- and $g$-wave altermagnets strongly affect the surface Andreev states from $d$-wave and chiral $d$- and $p$-wave superconductors. As a result, distinct types of subgap states are realized, including curved and flat bands, that can be detected by tunneling spectroscopy. Furthermore, we find that the altermagnetism-induced subgap states give rise to a large spin conductance at zero net magnetization which helps identify the strength of the underlying altermagnetism and superconductivity. Our results offer a solid route for designing and manipulating subgap states in superconducting systems, which can be useful for functionalizing superconducting spintronic devices.

Symmetry-breaking-induced topology in FeSe

Authors: Mikel Garc\'ia-D\'iez, Jonas B. Profe, Augustin Davignon, Steffen Backes, Roser Valent\'i, Maia G. Vergniory

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03427v1 Announce Type: new Abstract: FeSe has been one of the most intensively studied iron-based superconductors over the past two decades, exhibiting a wide range of phenomena such as unconventional superconductivity, nematic order, magnetism, orbital-selective correlations, and structural phase transitions. While topologically non-trivial phases have been identified in certain cases - such as Te-doped FeSe and monolayer FeSe - topology in bulk FeSe has largely remained unexplored. In this work, we propose a new route to realize topological phases directly in bulk FeSe. We demonstrate that breaking the in-plane $C_4$ rotational symmetry, thereby lowering the crystal symmetry, can drive FeSe into a strong topological insulating phase. To support this, we perform density functional theory calculations and analyze the band structure using topological quantum chemistry and symmetry-based indicators. Our results show that both uniaxial strain and the structural transition to the orthorhombic low-temperature phase lead to non-trivial band topology. Moreover, incorporating electronic correlations through dynamical mean field theory reveals that the topological characteristics near the Fermi level remain robust, as the relevant bands experience only moderate renormalization. These findings highlight strain as a promising mechanism to induce topological phases in FeSe.

Oxide Interface-Based Polymorphic Electronic Devices for Neuromorphic Computing

Authors: Soumen Pradhan (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Lehrstuhl f\"urTechnische Physik, Germany), Kirill Miller (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Lehrstuhl f\"urTechnische Physik, Germany), Fabian Hartmann (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Lehrstuhl f\"urTechnische Physik, Germany), Merit Spring (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Experimentelle Physik 4, Germany), Judith Gabel (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Experimentelle Physik 4, Germany), Berengar Leikert (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Experimentelle Physik 4, Germany), Silke Kuhn (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Lehrstuhl f\"urTechnische Physik, Germany), Martin Kamp (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Lehrstuhl f\"urTechnische Physik, Germany), Victor Lopez-Richard (Universidade Federal de S\~ao Carlos, Departamento de F\'isica, Brazil), Michael Sing (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Experimentelle Physik 4, Germany), Ralph Claessen (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Experimentelle Physik 4, Germany), Sven H\"ofling (Julius-Maximilians-Universit\"at W\"urzburg, Physikalisches Institut and W\"urzburg-Dresden Cluster of Excellence ct.qmat, Lehrstuhl f\"urTechnische Physik, Germany)

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03515v1 Announce Type: new Abstract: Aside from recent advances in artificial intelligence (AI) models, specialized AI hardware is crucial to address large volumes of unstructured and dynamic data. Hardware-based AI, built on conventional complementary metal-oxidesemiconductor (CMOS)-technology, faces several critical challenges including scaling limitation of devices [1, 2], separation of computation and memory units [3] and most importantly, overall system energy efficiency [4]. While numerous materials with emergent functionalities have been proposed to overcome these limitations, scalability, reproducibility, and compatibility remain critical obstacles [5, 6]. Here, we demonstrate oxide-interface based polymorphic electronic devices with programmable transistor, memristor, and memcapacitor functionalities by manipulating the quasi-two-dimensional electron gas in LaAlO3/SrTiO3 heterostructures [7, 8] using lateral gates. A circuit utilizing two polymorphic functionalities of transistor and memcapacitor exhibits nonlinearity and short-term memory, enabling implementation in physical reservoir computing. An integrated circuit incorporating transistor and memristor functionalities is utilized for the transition from short- to long-term synaptic plasticity and for logic operations, along with in-situ logic output storage. The same circuit with advanced reconfigurable synaptic logic operations presents high-level multi-input decision-making tasks, such as patient-monitoring in healthcare applications. Our findings pave the way for oxide-based monolithic integrated circuits in a scalable, silicon compatible, energy efficient single platform, advancing both the polymorphic and neuromorphic computings.

Quantum Spin Hall Effect with Extended Topologically Protected Features in Altermangetic Multilayers

Authors: Zhiyu Chen, Fangyang Zhan, Da-Shuai Ma, Dong-Hui Xu, Rui Wang

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03580v1 Announce Type: new Abstract: Conventional topological classification theory dictates that time-reversal symmetry confines the quantum spin Hall (QSH) effect to a $\mathbb{Z}_2$ classification, permitting only a single pair of gapless helical edge states. Here, we utilize the recently discovered altermagnetism to circumvent this fundamental constraint. We demonstrate the realization of a unique QSH phase possessing multiple pairs of gapless helical edge states in altermagnetic multilayers. This exotic QSH phase, characterized by a mirror-spin Chern number, emerges from the interplay of spin-orbit coupling and $d$-wave altermagnetic ordering. Moreover, using first-principles calculations, we identify altermagnetic Fe$_2$Se$_2$O multilayers as promising material candidates, in which the number of gapless helical edge states scales linearly with the number of layers, leading to a correspondingly large, exactly quantized, and experimentally accessible spin-Hall conductance. Our findings unveil a new mechanism for stabilizing multiple pairs of gapless helical edge states, significantly expanding the scope of QSH effects, and provide a blueprint for utilizing altermagnetism to engineer desired topological phases.

High-temperature and high-pressure study on columbite structured ZnNb2O6

Authors: A. Tyagi, P. Botella, A. B. Garg, J. Sanchez-Martin, D. Diaz-Anichtchenko, R. Turnbull, S. Anzellini, C. Popescu, D. Errandonea

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03658v1 Announce Type: new Abstract: High-temperature and high-pressure experiments were conducted on columbite-type ZnNb2O6, reaching temperatures up to 873 K at ambient pressure and pressures up to 30 GPa at ambient temperature, respectively. Through systematic analysis employing synchrotron powder X-ray diffraction and Raman spectroscopy, we examined the crystal structure and phonon behavior. Within the specified temperature range, the orthorhombic phase of ZnNb2O6 (space group: Pbcn) demonstrated notable phase stability, with a thermal expansion coefficient similar to that of isomorphic compounds. Notably, a reversible phase transition was observed under compression at 10 GPa, with diffraction experiments indicating a shift to a monoclinic structure (space group P2/a), which remained stable up to 30 GPa. Changes in Raman modes, lattice parameters, and the unit-cell volume were monitored. A significant 2.5% discontinuity in the unit-cell volume at the phase transition pressure from orthorhombic to monoclinic suggests a first-order phase transition. The bulk moduli of the orthorhombic and monoclinic phases were estimated as 165(7) GPa and 230(9) GPa, respectively- We also found that both phases exhibit an anisotropic response to pressure. Furthermore, first-principles calculations support consistently with experimental observations.

A noninvasive and nonadiabatic quantum Maxwell demon

Authors: Lucas Trigal, Rafael S\'anchez

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03659v1 Announce Type: new Abstract: A quantum mechanical Maxwell demon is proposed in a quantum dot setting. The demon avoids continuous-measurement induced decoherence by exploiting an undetailed charge detector. The control of coherent tunneling via Landau-Zener-St\"uckelberg-Majorana driving allows for efficient feedback operations with no work invested. The local violation of the second law achieves simultaneous power generation and cooling. We discuss the response current fluctuations, and the demon backaction deriving from failures, finding optimal performance in the nonadiabatic regime.

Ising spin ladders of orthopyroxene CoGeO$_3$

Authors: Pavel A. Maksimov, Andrey F. Gubkin, Alexey V. Ushakov, Alexander I. Kolesnikov, Matthew S. Cook, Michael A. McGuire, G\"unther J. Redhammer, Andrey Podlesnyak, Sergey V. Streltsov

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03664v1 Announce Type: new Abstract: We present thermodynamic and spectroscopic measurements for an orthopyroxene CoGeO$_3$ with magnetic Co$^{2+}$ ions that form quasi-one-dimensional ladders. We show that non-collinear magnetic order below $T_N$=32 K can be stabilized by a strong local easy-axis anisotropy of $j_\text{eff}=1/2$ moments, which is induced by ligand octahedra distortions. Extraction of a magnetic Hamiltonian from inelastic neutron scattering measurements supports this interpretation and allows us to establish an effective magnetic model. The resulting exchange Hamiltonian justifies CoGeO$_3$ as a realization of an Ising spin ladder compound.

Strong electron-electron interactions in a dilute weakly-localized metal near a metal-to-insulator transition

Authors: Nicol\`o D'Anna, Jamie Bragg, Aidan G. McConnell, Procopios C. Constantinou, Juerong Li, Taylor J. Z. Stock, Steven R. Schofield, Neil J. Curson, Y. Soh, Marek Bartkowiak, Simon Gerber, Markus M\"uller, Guy Matmon, Gabriel Aeppli

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.02793v1 Announce Type: cross Abstract: Because it is easily switched from insulator to metal either via chemical doping or electrical gating, silicon is at the core of modern information technology and remains a candidate platform for quantum computing. The metal-to-insulator transition in this material has therefore been one of the most studied phenomena in condensed matter physics, and has been revisited with considerable profit each time a new fabrication technology has been introduced. Here we take advantage of recent advances in creating ultra-thin layers of Bohr-atom-like dopants to realize the two-dimensional disordered Hubbard model at half-filling and its metal-to-insulator transition (MIT) as a function of mean distance between atoms. We use gas-phase dosing of dopant precursor molecules on silicon to create arsenic and phosphorus $\delta$-layers as thin as 0.4~nm and as dilute as 10$^{13}$~cm$^{-2}$. On approaching the insulating state, the conventional weak localization effects, prevalent at high dopant densities and due to orbital motion of the electrons in the plane, become dominated by electron-electron interaction contributions which obey a paramagnetic Zeeman scaling law. The latter make a negative contribution to the conductance, and thus cannot be interpreted in terms of an emergent Kondo regime near the MIT.

Intermediate-temperature topological Uhlmann phase on IBM quantum computers

Authors: Christopher Mastandrea, Costin Iancu, Hao Guo, Chih-Chun Chien

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.02915v1 Announce Type: cross Abstract: A spin-1 system can exhibit an intermediate-temperature topological regime with a quantized Uhlmann phase sandwiched by topologically trivial low- and high-temperature regimes. We present a quantum circuit consisting of system and ancilla qubits plus a probe qubit which prepares an initial state corresponding to the purified state of a spin-1 system at finite temperature, evolves the system according to the Uhlmann process, and measures the Uhlmann phase via expectation values of the probe qubit. Although classical simulations suggest the quantized Uhlmann phase is observable on IBM's noisy intermediate-scale quantum (NISQ) computers, an implementation of the circuit without any optimization exceeds the gate count for the error budget and results in unresolved signals. Through a series of optimization with Qiskit and BQSQit, the gate count can be substantially reduced, making the jumps of the Uhlmann phase more visible. A recent hardware upgrade of IBM quantum computers further improves the signals and leads to a clearer demonstration of interesting finite-temperature topological phenomena on NISQ hardware.

Simultaneous photonic and phononic bandgaps in a hexagonal lattice geometry with gradually transforming circular-to-triangular air gap holes

Authors: Suhas Bharadwaj, Adarsh Ganesan

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03045v1 Announce Type: cross Abstract: The integration of photonic and phononic bandgaps within a single scalable architecture promises transformative advances in optomechanical and acousto-optic devices. Here, we design and simulate a two-dimensional hexagonal lattice in silicon with air-gap holes that transition smoothly from circular to triangular via tuneable geometrical parameters R and l. This transformation enables suppression of both electromagnetic and elastic wave modes through Bragg scattering and symmetry modulation. We demonstrate that systematic variation of R and l allows tuning of photonic and phononic bandgaps by 18% and 21% respectively. This possibility of geometrical tuning of bandgaps provide strong foundations for applications in Bragg filters, sensors etc. without the need for complex defects and exotic materials.

Integrable multispecies totally asymmetric stochastic interacting particle systems with homogeneous rates

Authors: Eunghyun Lee, Temirlan Raimbekov

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03157v1 Announce Type: cross Abstract: We study one dimensional stochastic particle systems with exclusion interaction that each site can be occupied by at most one particle, and homogeneous jumping rates. Alimohammadi and Ahmadi previously classified 28 Yang-Baxter integrable two-particle interaction rules for the two species models with homogeneous rates. In this work, we show that 7 of these 28 cases can be naturally extended to integrable models with an arbitrary number of species $N \geq 2$. Moreover, we discover new integrable models with one or two parameters that generalize these 7 cases. For 8 of the remaining 21 cases, we propose an alternative extension scheme that yields integrable $N$ species models.

Topological invariants and topological charges in photonic systems

Authors: Kristian Arjas, Grazia Salerno, P\"aivi T\"orm\"a

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03302v1 Announce Type: cross Abstract: Topology in photonics comes in two distinct flavors: global and local. Global topology considers invariants that are obtained by integrating over the energy band, whereas local topology considers defects, typically vortices, in the far-field emission. These topologies are described by a wide range of models built in both real and momentum space, which are connected only by computationally expensive numerical methods that lack physical intuition. Here we propose a general framework based on a real-space Hamiltonian capable of describing electric field as a vector in both near- and far fields, allowing us to bridge between topological defects in the far-field and global topological invariants. The proposed Hamiltonian is constructed from the symmetry-representations of the lattice, is deformable to both atomic localized-mode (tight-binding) and photonic delocalized-mode (long-range) limits, and allows for independent control over the energies of eigenmodes of different symmetries at high-symmetry points of the Brillouin zone. This symmetry-based approach enables the design of structures with almost arbitrary topological properties and is not limited to photonic systems, but could apply to any system with engineered real-space couplings.

All Photonic Isolator using Atomically Thin (2D) Bismuth Telluride (Bi2Te3)

Authors: Saswata Goswami, Bruno Ipaves, Juan Gomez Quispe, Caique Campos de Oliveira, Surbhi Slathia, Abhijith M. B, Varinder Pal, Christiano J. S. de Matos, Samit K. Ray, Douglas S. Galvao, Pedro A. S. Autreto, Chandra Sekhar Tiwary

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03319v1 Announce Type: cross Abstract: This study demonstrates that two-dimensional (2D) Bi2Te3 exhibits strong light-matter interaction, enabling a broadband Kerr nonlinear optical response. This characteristic is advantageous for nonreciprocal light propagation in passive photonic isolators. Using Spatial Self-Phase Modulation (SSPM) spectroscopy, self-induced diffraction patterns in the far field were observed at excitation wavelengths of 650 nm, 532 nm, and 405 nm to calculate the nonlinear refractive index (n2) and the third-order nonlinear optical susceptibility (chi^(3)) of the synthesized 2D Bi2Te3. The results show that 2D Bi2Te3 possesses a significantly higher nonlinear refractive index than graphene. The laser-induced hole coherence effect is responsible for the large magnitude of the third-order nonlinear susceptibility. Surface engineering techniques were also employed to enhance the response speed of the photonic system. Complementary ab initio simulations were performed to gain further insight into the observed nonlinear behavior. Leveraging the strong Kerr nonlinearity of 2D Bi2Te3, a nonlinear photonic isolator that breaks time-reversal symmetry and enables unidirectional light propagation was demonstrated. This work establishes Bi2Te3 as a novel 2D material for nonlinear photonics, expanding its potential applications in detectors, modulators, and optical switches.

Comments on QED$_3$ in a Magnetic Field

Authors: Thomas T. Dumitrescu, Juan Maldacena

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03532v1 Announce Type: cross Abstract: We discuss the low-energy dynamics of massless Dirac fermions interacting with a propagating, relativistic photon in 2+1 spacetime dimensions, when we turn on a uniform magnetic field. This problem can be solved when the magnetic field is sufficiently strong. As observed previously, we find that the vacuum spontaneously breaks some of the global symmetries. We also determine the spectrum of excitations around this vacuum, and compute the resulting low-energy effective action. We use techniques that were previously developed for quantum Hall ferromagnets in condensed matter physics.

Frequency conversion in topological plasmonic THz photo-mixer

Authors: Hamid Javadi

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2508.03592v1 Announce Type: cross Abstract: We propose an alternative explanation for the observed coherent down-conversion in a laser-enabled plasmonic photo-mixer involving infrared, millimeter-wave, microwave photons. We will offer a path toward full experimental characterization of the device.

Stochastic thermodynamics of computation

Authors: David H. Wolpert

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:1905.05669v3 Announce Type: replace Abstract: One of the major resource requirements of computers - ranging from biological cells to human brains to high-performance (engineered) computers - is the energy used to run them. Those costs of performing a computation have long been a focus of research in physics, going back to the early work of Landauer. One of the most prominent aspects of computers is that they are inherently nonequilibrium systems. However, the early research was done when nonequilibrium statistical physics was in its infancy, which meant the work was formulated in terms of equilibrium statistical physics. Since then there have been major breakthroughs in nonequilibrium statistical physics, which are allowing us to investigate the myriad aspects of the relationship between statistical physics and computation, extending well beyond the issue of how much work is required to erase a bit. In this paper I review some of this recent work on the `stochastic thermodynamics of computation'. After reviewing the salient parts of information theory, computer science theory, and stochastic thermodynamics, I summarize what has been learned about the entropic costs of performing a broad range of computations, extending from bit erasure to loop-free circuits to logically reversible circuits to information ratchets to Turing machines. These results reveal new, challenging engineering problems for how to design computers to have minimal thermodynamic costs. They also allow us to start to combine computer science theory and stochastic thermodynamics at a foundational level, thereby expanding both.

Condensation Completion and Defects in 2+1D Topological Orders

Authors: Gen Yue, Longye Wang, Tian Lan

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2402.19253v3 Announce Type: replace Abstract: We review the condensation completion of a modular tensor category $\mathcal{C}$, which yields a fusion 2-category $\Sigma\mathcal{C}$ of separable algebras, bimodules over algebras and bimodule maps in $\mathcal{C}$. Physically, $\Sigma\mathcal{C}$ is the fusion 2-category of codimension-1 defects, codimension-2 defects and instantons in the $2+1$D topological order $\mathcal{C}$. We realize the rough-rough wall and $e$-$m$ exchange wall in Toric Code model on the lattice by deforming the Hamiltonian based on the corresponding algebraic data. We apply condensation completion to Toric Code, $3\mathbf{F}$, two-laryer semion and $\mathbb{Z}_4$ topological orders, and explicitly enumerate their $1$d and $0$d defects along with fusion rules. We also mention other applications of condensation completion: alternative interpretations of condensation completion of a braided fusion category; condensation completion of the category of symmetry charges and its correspondence to gapped phases with symmetry; for a topological order $\mathcal{C}$, one can find all gapped boundaries of the stacking of $\mathcal{C}$ with its time-reversal conjugate through computing the condensation completion of $\mathcal{C}$.

Spin transport revealed by the spin quantum geometry

Authors: Longjun Xiang, Hao Jin, Jian Wang

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2406.02257v3 Announce Type: replace Abstract: We present the framework of \textit{spin quantum geometry}, which is fundamentally linked to the spin degree of freedom of Bloch electrons and incorporates both the spin quantum geometric tensor (QGT) and the recently introduced Zeeman QGT, to elucidate the spin transport. We show that the spin and Zeeman QGTs, respectively, provide a unified framework for revealing known spin currents, such as the intrinsic spin Hall effect, and spin magnetization, such as the Edelstein effect, of Bloch electrons under an electric field. In addition, we predict the linear displacement spin Hall effect, wherein an AC electric field induces a transverse spin current in insulating systems. Furthermore, we propose two novel nonlinear spin responses: the nonlinear Drude spin current (NDSC) and the nonlinear Drude spin magnetization (NDSM), both of which exhibit a quadratic dependence on the relaxation time, like the nonlinear Drude charge current, and are governed by the \textit{spin quantum geometry}. Finally, we evaluate the NDSC and NDSM with Dirac models of topological insulators and find that, in the moderately dirty regime, the NDSC and NDSM can exceed their respective nonlinear intrinsic counterparts, which have recently garnered significant interest in spintronics.

Topological Chiral Superconductivity Mediated by Intervalley Antiferromagnetic Fluctuations in Twisted Bilayer WSe$_2$

Authors: Wei Qin, Wen-Xuan Qiu, Fengcheng Wu

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2409.16114v2 Announce Type: replace Abstract: Motivated by the recent observations of superconductivity in twisted bilayer WSe$_2$ (tWSe$_2$), we theoretically investigate the superconductivity driven by electronic mechanism. We first demonstrate that the multi-band screened Coulomb interaction within the random phase approximation is insufficient to induce observable pairing instability. Nevertheless, by further including the intervalley antiferromagnetic fluctuations, the pairing interaction is substantially enhanced, yielding superconductivity with critical temperature $T_c$ of hundreds of millikelvin at van Hove singularities. The predicted $T_c$ increases with increasing the displacement field and corresponds to a doubly-degenerate $d$-wave-like pairing, which evolves into topological chiral $d \pm id$ superconductor below $T_c$. The interplay between superconductivity and intervalley antiferromagnetism results in a phase diagram consistent with experimental observations.These findings establish intervalley fluctuations as the primary pairing glue in tWSe$_2$.

Voltage-tunable spin supercurrent nonreciprocity reaching 100% efficiency

Authors: Chi Sun, Johanne Bratland Tjernshaugen, Jacob Linder

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2410.07337v2 Announce Type: replace Abstract: The superconducting version of a diode effect has been the subject of extensive research in the past few years. So far, the focus has almost exclusively been on charge transport, but a natural question is whether it is possible to obtain nonreciprocal spin transport without dissipation. Here, we demonstrate that it is possible to generate electrically tunable nonreciprocal spin transport carried by a supercurrent using superconductor/ferromagnet multilayers. The nonreciprocal spin supercurrent reaches an ideal efficiency of 100%, meaning that the spin-polarization of the critical current is finite in one flow direction whereas it vanishes in the other direction. We explain the underlying physics generating this phenomenon. This result provides a way to integrate nonreciprocal supercurrents with spin-polarization, offering new functionality in quantum technologies based on Josephson junctions.

Double sine-Gordon class of universal coarsening dynamics in a spin-1 Bose gas

Authors: Ido Siovitz, Anna-Maria E. Gl\"uck, Yannick Deller, Alexander Schmutz, Felix Klein, Helmut Strobel, Markus K. Oberthaler, Thomas Gasenzer

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2412.13986v3 Announce Type: replace Abstract: Far from equilibrium, universal dynamics prevails in many different situations, from pattern coarsening to turbulence. A central longstanding problem concerns the development of a theory of coarsening that rests on the microscopic properties of the system and allows identifying the interaction mechanisms underlying a possible overarching universality class of the associated scaling dynamics. In quantum systems, this is complicated by the existence of nonlinear and topological excitations due to the compact nature of phase degrees of freedom. We show that the double sine-Gordon model as a noncompact low-energy effective model of the spin-1 Bose gas accounts for subdiffusive coarsening dynamics, identifying field configurations spread over multiple wells of the sinusoidal potential as a precondition for the slow scaling. This is in contrast to diffusion-type scaling which the model is known to exhibit as well, where field configurations are seen to not extend over more than two wells. Experimental observations of a spinor BEC support these characteristics, thus constituting a platform for the investigation of sine-Gordon dynamics. Our results point to a path towards a classification of pattern coarsening in many-body systems on the basis of microscopic models.

Interplay between altermagnetism and topological superconductivity on an unconventional superconducting platform

Authors: Pritam Chatterjee, Vladimir Juri\v{c}i\'c

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2501.05451v2 Announce Type: replace Abstract: We propose a theoretical model to investigate the interplay between altermagnetism and $p$-wave superconductivity, with a particular focus on topological phase transitions in a two-dimensional (2D) $p$-wave superconductor, considering both chiral and helical phases. Our study reveals that the emergence of helical and chiral Majorana states can be tuned by the amplitude of a $d-$wave altermagnetic order parameter, with the outcome depending on the nature of the superconducting state. In the helical superconductor, such an altermagnet can induce a topological phase transition into a gapless topological superconductor hosting Majorana flat edge modes. On the other hand, in the chiral superconductor, the topological transition takes place between a topologically nontrivial gapped phase and a gapless nodal-line superconductor, where the Bogoliubov quasiparticle bands intersect at an isolated line in momentum space. Remarkably, we show that when such an altermagnet is coupled to a mixed-pairing superconductor, with both chiral and helical components, a hybrid topological phase emerges, featuring dispersive Majorana edge modes that coexist with nearly flat Majorana edge states. Our findings therefore establish a novel platform for controlling and manipulating Majorana modes in unconventional superconductors with vanishing total magnetization.

Non-commutative effective field theory of the lowest Landau level superfluid

Authors: Nandagopal Manoj

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2502.03528v2 Announce Type: replace Abstract: A 2+1D superfluid in a rapidly rotating trap forms an array of vortices, with collective excitations called Tkachenko modes. Du et al. (2024) argued from an effective field theory viewpoint that these excitations are described by a field theory living on a non-commutative space. We elucidate the microscopic origin of these non-commutative fields, and present a novel derivation of the effective field theory for this superfluid using a lowest Landau level projected coherent state path integral approach. Besides conceptual clarity, this approach makes quantitative predictions about the long-wavelength, low-energy behavior in terms of the microscopic parameters of the short-range interacting lowest Landau level superfluid -- relevant to trapped Bose-Einstein condensate experiments.

Topological magnons and domain walls in twisted bilayer MoTe$_2$

Authors: Wen-Xuan Qiu, Fengcheng Wu

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2502.11010v2 Announce Type: replace Abstract: We theoretically investigate the magnetic excitations in the quantum anomalous Hall insulator phase of twisted bilayer MoTe$_2$ at a hole filling factor of $\nu=1$, focusing on magnon and domain wall excitations. Using a generalized interacting Kane-Mele model, we obtain the quantum anomalous Hall insualtor ground state with spin polarization. The magnon spectrum is then computed via the Bethe-Salpeter equation, revealing two low-energy topological magnon bands with opposite Chern numbers. To further explore the magnon topology, we construct a tight-binding model for the magnon bands, which is analogous to the Haldane model. We also calculate the energy cost of domain walls that separate regions with opposite Chern numbers and bind chiral edge states. Finally, we propose an effective spin model that describes both magnon and domain wall excitations, incorporating Heisenberg spin interactions and Dzyaloshinskii-Moriya interactions. The coupling constants in this model are determined from the numerical results for magnons and domain walls. This model accounts for the Ising anisotropy of the system, captures the magnon topology, and allows for the estimation of the magnetic ordering temperature. Our findings provide a comprehensive analysis of magnetic excitations in twisted MoTe$_2$ and offer new insights into collective excitations in moir\'e systems.

Energy profile and hopping barriers for small electron polarons at ferroelectric domain walls in bismuth ferrite from first principles

Authors: Sabine K\"orbel

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2503.04394v2 Announce Type: replace Abstract: Evidence from first-principles calculations indicates that excess electrons in BiFeO$_3$ form small polarons with energy levels deep inside the electronic band gap. Hence, $n$-type electronic transport could occur by hopping of small electron polarons rather than by band-like transport. Here, by means of first-principles calculations, small electron polaron hopping in BiFeO$_3$ is investigated. Both bulk BiFeO$_3$ and a typical ferroelectric domain wall, the neutral 71{\deg} domain wall, are considered. The latter is included to account for experimental observations of electrical conductivity at domain walls in otherwise insulating ferroelectrics. The object of this study is to shed light on the intrinsic electron conduction in rhombohedral BiFeO$_3$ and the effect of pristine neutral ferroelectric domain walls. The computed energy barriers for small electron polaron hopping are near 0.2 eV, similar to other perovskite oxides, both in the bulk and within the neutral 71\deg\ domain wall. Trapping energies of small electron polarons at the three prevalent domain walls, the 71\deg, the 109\deg, and the 180\deg\ wall, were determined. The domain walls are found to act as two-dimensional traps for small electron polarons, with a trap depth of about two times the thermal energy at room temperature. Based on these findings, the intrinsic $n$-type mobility and the diffusion constant in BiFeO$_3$ at room temperature are estimated, and experimental conductivity data for BiFeO$_3$ are discussed.

Trivalent network model for d$^3$ transition metal dichalcogenides in the 1T structure: Holography from local constraints

Authors: Ashland Knowles, R. Ganesh

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2505.01510v2 Announce Type: replace Abstract: Dimer models are well known as prototypes for locally constrained physics. They describe systems in which every site on a lattice must be attached to one dimer. Loop models are an extension of this idea, with the constraint that two dimers must touch at each site. Here, we present a further generalization where every site must have three dimers attached -- a trivalent network model. As concrete physical realizations, we discuss d$^3$ transition metal dichalcogenides in the 1T structure -- materials with the structural formula MX$_2$ (M = Tc, Re) or AM$'$X$_2$ (A = Li or Na; M$'$ = Mo, W), where X is a chalcogen atom. These materials have a triangular layer of transition metal atoms, each with three valence electrons in $t_{2g}$ orbitals. Each atom forms valence bonds with three of its nearest neighbours. The geometry of the 1T structure imbues each bond with sharp orbital character. We argue that this enforces a ``bending constraint'' so that two dimers attached to the same site cannot be parallel. This leads to a highly structured space of configurations, with alternating bonds along each line of the underlying triangular lattice. There is no dynamics, as constraints forbid local rearrangements of dimers. We construct a phase diagram, identifying configurations that minimize potential energy. We find a rhombus-stripe phase that explains a distortion pattern seen across several materials. Remarkably, the local constraints in this model lead to a simple example of holography. The bonding configuration in the bulk is completely determined by the configuration at the boundary. We recast the model in terms of three Ising chains that are defined on the boundaries of a triangular cluster. As a testable prediction, we propose that a single impurity will generate long-ranged domain walls.

Phase domain walls in coherently driven Bose-Einstein condensates

Authors: S. S. Gavrilov

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2505.09553v3 Announce Type: replace Abstract: We consider coherent states of weakly interacting bosons under the conditions of external resonant excitation, with a focus on a two-dimensional polariton fluid driven by a plane electromagnetic wave near the ground state. The coherent driving breaks the U(1) symmetry explicitly, which prevents the occurrence of quantum vortices in a uniform scalar condensate. Surprisingly, a spinor (two-component) system of the same kind admits topological excitations, such as domain walls of relative phase or confined half-vortex molecules, typical of a freely evolving spinor Bose system. Opposite-phase domains arise from the spontaneous breakdown of the spin symmetry $(\mathbb{Z}_2)$. Domain walls form with time even when the initial state of the system is uniform or completely disordered; they fall into different topological types distinguished by the total phase variation in the transverse direction.

A many-body marker for three-dimensional topological insulators with inversion symmetry

Authors: Federico Becca, Alberto Parola

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2505.19204v3 Announce Type: replace Abstract: We extend the previously defined many-body marker for two-dimensional $\mathbb{Z}_2$ topological insulators [I. Gilardoni {\it et al.}, Phys. Rev. B {\bf 106}, L161106 (2022)] to distinguish trivial, weak-, and strong-topological insulators in three dimensions, in presence of the inversion symmetry. The marker is written in term of ground-state expectation values of position operators and can be employed to detect topological phases of interacting systems beyond mean-field approximations, e.g., within quantum Monte Carlo techniques. Here, we show that the correct results of the non-interacting limit are reproduced by the many-body marker.

Magnetic Moir\'e Systems: a review

Authors: Paula Mellado

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2506.05620v2 Announce Type: replace Abstract: This review synthesizes recent advancements in the study of moir\'e magnetism. This emerging field, at the intersection of twistronics, topology, and strongly correlated systems, explores novel phenomena that arise when moir\'e potentials influence the magnetism of two-dimensional systems. The manuscript presents recent advances highlighting the interfacial incongruity as a novel mechanism for regulating the magnetism of two-dimensional materials and for the manifestation of various phenomena in twisted and mismatched magnetic two-dimensional interfaces. The manuscript addresses seminal and recent experimental and theoretical advances associated with both small- and large-period magnetic moir\'e lattices, including novel magnetic phases, low-energy and topological magnetic excitations, magnetic and electronic transport, optical properties, phase transitions, and prospective applications of these materials. Moir\'e magnetism signifies a promising frontier for manipulating complex quantum states in quantum matter. The ongoing advances in this field are poised to impact condensed matter physics, materials science, and quantum information science.

Proximate integrability and exact revivals in staggered Rydberg ladders

Authors: Mainak Pal, Tista Banerjee

Published: Wed, 06 Aug 2025 00:00:00 -0400

arXiv:2504.15230v2 Announce Type: replace-cross Abstract: Cold Rydberg atoms trapped in an array of optical tweezers can be manipulated using laser light. We investigate the fate of out-of-equilibrium quantum dynamics in a model of Rydberg atoms arranged in a square ladder geometry within the strong blockade regime, with a detuning profile staggered along the longer direction. As the staggering strength is tuned, the model exhibits a wide class of dynamical phenomena, ranging from quantum many-body scars, integrability-induced slow dynamics and approximate Krylov fractures. Furthermore, by leveraging the chiral nature of the spectrum, we design Floquet protocols which result in dynamical signatures reminiscent of discrete-time-crystalline order and exact Floquet-flat-bands.

Scientists need a break too

Authors: No author

Published: 2025-08-05

Nature Reviews Physics, Published online: 05 August 2025; doi:10.1038/s42254-025-00862-0

As the Northern Hemisphere heads into summer holiday season, we encourage all our readers to properly switch off from work for a while.

Magnon-mediated switching of perpendicular magnetization by the topological crystalline insulator SnTe with high spin Hall conductivity

Authors: Pengnan Zhao, Guoyi Shi, Wentian Lu, Lihuan Yang, Hui Ru Tan, Kaiwei Guo, Jia-Min Lai, Zhonghai Yu, Anjan Soumyanarayanan, Zhe Yuan, Fei Wang, Xiaohong Xu, and Hyunsoo Yang

Published: 2025-08-05T10:00:00+00:00

Author(s): Pengnan Zhao, Guoyi Shi, Wentian Lu, Lihuan Yang, Hui Ru Tan, Kaiwei Guo, Jia-Min Lai, Zhonghai Yu, Anjan Soumyanarayanan, Zhe Yuan, Fei Wang, Xiaohong Xu, and Hyunsoo Yang

Magnons possess the ability to transport spin angular momentum in insulating magnetic materials, a characteristic that sets them apart from traditional electronics where power consumption arises from the movement of electrons. However, the practical application of magnon devices demands room-tempera…

[Phys. Rev. B 112, 054413] Published Tue Aug 05, 2025

Moiré fractional Chern insulators. III. Hartree-Fock phase diagram, magic angle regime for Chern insulator states, role of moiré potential, and Goldstone gaps in rhombohedral graphene superlattices

Authors: Yves H. Kwan, Jiabin Yu, Jonah Herzog-Arbeitman, Dmitri K. Efetov, Nicolas Regnault, and B. Andrei Bernevig

Published: 2025-08-05T10:00:00+00:00

Author(s): Yves H. Kwan, Jiabin Yu, Jonah Herzog-Arbeitman, Dmitri K. Efetov, Nicolas Regnault, and B. Andrei Bernevig

We investigate in detail the $ν=+1$ displacement-field-tuned interacting phase diagram of $L=3,4,5,6,7$ layer rhombohedral graphene aligned to hBN ($\mathrm{R}L\mathrm{G}$/hBN). Our calculations account for the 3D nature of the Coulomb interaction, the inequivalent stacking orientations $ξ=0,1$, the…

[Phys. Rev. B 112, 075109] Published Tue Aug 05, 2025

Moiré fractional Chern insulators. IV. Fluctuation-driven collapse in multiband exact diagonalization calculations on rhombohedral graphene

Authors: Jiabin Yu, Jonah Herzog-Arbeitman, Yves H. Kwan, Nicolas Regnault, and B. Andrei Bernevig

Published: 2025-08-05T10:00:00+00:00

Author(s): Jiabin Yu, Jonah Herzog-Arbeitman, Yves H. Kwan, Nicolas Regnault, and B. Andrei Bernevig

The fractional Chern insulators (FCIs) observed in pentalayer rhombohedral graphene/hexagonal boron nitride superlattices have a unique origin contrary to theoretical expectations: their noninteracting band structure is gapless, unlike standard FCIs and the Landau level. Hartree-Fock (HF) calculatio…

[Phys. Rev. B 112, 075110] Published Tue Aug 05, 2025

Spin-triplet polarization of Majorana zero modes in a one-dimensional chiral nanowire

Authors: Lei Yang, Zhikuan Wang, Quan Gao, Jinming Dong, Dongmei Li, Bing Huang, Desheng Liu, and Bin Cui

Published: 2025-08-05T10:00:00+00:00

Author(s): Lei Yang, Zhikuan Wang, Quan Gao, Jinming Dong, Dongmei Li, Bing Huang, Desheng Liu, and Bin Cui

Majorana zero modes (MZMs) at the boundary of topological superconductors (TSC) have garnered significant attention for their application in quantum computation. In this study, we demonstrate that in heterostructures composed of the one-dimensional (1D) chiral nanowire and a superconductor, structur…

[Phys. Rev. B 112, 075405] Published Tue Aug 05, 2025

Topological charge excitations and Green's function zeros in paramagnetic Mott insulators

Authors: Emile Pangburn, Catherine Pépin, and Anurag Banerjee

Published: 2025-08-05T10:00:00+00:00

Author(s): Emile Pangburn, Catherine Pépin, and Anurag Banerjee

We investigate the emergence of topological features in the charge excitations of Mott insulators in the Chern-Hubbard model. In the strong correlation regime, treating electrons as the sum of holons and doublons excitation, we compute the topological phase diagram of Mott insulators at half-filling…

[Phys. Rev. B 112, 085105] Published Tue Aug 05, 2025

Shift current response in twisted double bilayer graphene

Authors: Takaaki V. Joya, Takuto Kawakami, and Mikito Koshino

Published: 2025-08-05T10:00:00+00:00

Author(s): Takaaki V. Joya, Takuto Kawakami, and Mikito Koshino

We calculate the shift current response in twisted double bilayer graphenes (TDBG) by applying the perturbative approach to the effective continuum Hamiltonian. We have performed a systematic study of the shift current in AB-AB and AB-BA stacked TDBG, where we have investigated the dependence of the…

[Phys. Rev. B 112, 085407] Published Tue Aug 05, 2025

Nonequilibrium critical dynamics with emergent supersymmetry

Authors: Zhi Zeng, Yin-Kai Yu, Zi-Xiang Li, and Shuai Yin

Published: 2025-08-05T10:00:00+00:00

Author(s): Zhi Zeng, Yin-Kai Yu, Zi-Xiang Li, and Shuai Yin

Proposed as an elegant symmetry relating bosons and fermions, spacetime supersymmetry (SUSY) has been actively pursued in both particle physics and emergent phenomena in quantum critical points (QCPs) of topological quantum materials. However, how SUSY casts the light on nonequilibrium dynamics rema…

[Phys. Rev. B 112, L060301] Published Tue Aug 05, 2025

Shot noise from which-path detection in a chiral Majorana interferometer

Authors: C. W. J. Beenakker

Published: 2025-08-05T10:00:00+00:00

Author(s): C. W. J. Beenakker

We calculate the full counting statistics of charge transfer in a chiral Majorana interferometer—a setup where a Dirac mode (an electron-hole mode) is split into two Majorana modes that encircle a number of $h/2e$ vortices in a topological superconductor. Without any coupling to the environment it i…

[Phys. Rev. B 112, L081402] Published Tue Aug 05, 2025

Quasiparticle picture of topological phase transitions induced by interactions

Authors: S. S. Krishtopenko, A. V. Ikonnikov, F. Hartmann, S. Höfling, B. Jouault, and F. Teppe

Published: 2025-08-04T10:00:00+00:00

Author(s): S. S. Krishtopenko, A. V. Ikonnikov, F. Hartmann, S. Höfling, B. Jouault, and F. Teppe

We present a general recipe to describe topological phase transitions in condensed matter systems with interactions. We show that topological invariants in the presence of interactions can be efficiently calculated by means of a non-Hermitian quasiparticle Hamiltonian introduced on the basis of the …

[Phys. Rev. Research 7, 033116] Published Mon Aug 04, 2025

Experimental qudit state estimation via point tomography

Authors: D. Martínez, L. Pereira, K. Sawada, P. González, J. Cariñe, M. Muñoz, A. Delgado, E. S. Gómez, S. P. Walborn, and G. Lima

Published: 2025-08-04T10:00:00+00:00

Author(s): D. Martínez, L. Pereira, K. Sawada, P. González, J. Cariñe, M. Muñoz, A. Delgado, E. S. Gómez, S. P. Walborn, and G. Lima

Point tomography is an approach to the problem of state estimation, which is arguably the most efficient and simple method for modern high-precision quantum information experiments. In this scenario, the experimenter knows the target state that their device should prepare, except that intrinsic syst…

[Phys. Rev. Research 7, 033119] Published Mon Aug 04, 2025

Ultrasensitive detection of amlodipine using plasmonic optical fiber sensors enhanced with graphene oxide and chitosan nanocomposite

Authors: Fidan T. Sedeeq, Hassan Nasiri, Karim Abbasian, Hadi Khodaei

Published: 2025-08-06

Scientific Reports, Published online: 06 August 2025; doi:10.1038/s41598-025-13980-7

Ultrasensitive detection of amlodipine using plasmonic optical fiber sensors enhanced with graphene oxide and chitosan nanocomposite

Author Correction: Topology meets time-reversal symmetry breaking in FeSe1−xTex superconductors

Authors: No author

Published: Tue, 5 Aug 2025 00:00:00 +0000

Sub-nanosecond polarization switching with anomalous kinetics in vdW ferroelectric WTe2

Authors: No author

Published: Tue, 5 Aug 2025 00:00:00 +0000

Universal quantum computation using Ising anyons from a non-semisimple topological quantum field theory

Authors: No author

Published: Tue, 5 Aug 2025 00:00:00 +0000

A quasi-solid-state high-rate lithium sulfur positive electrode incorporating Li₁₀GeP₂S₁₂

Authors: Boyi Pang, Huanxin Li, Yiming Guo, Bochen Li, Feiran Li, Huw C. W. Parks, Liam R. Bird, Thomas S. Miller, Paul R. Shearing, Rhodri Jervis, James B. Robinson

Published: 2025-08-05

Communications Materials, Published online: 05 August 2025; doi:10.1038/s43246-025-00901-4

As the demand for efficient energy storage systems grows, lithium-sulfur batteries face challenges like the polysulfide shuttle effect and sluggish performance. Here, a high-rate quasi-solid-state sulfur positive electrode incorporating Li10GeP2S12 enhances lithium-ion transport, achieving stable, high-capacity performance.

Interface‐Engineered 2H‐MoS2/MXene Heterostructures for High‐Performance Ammonium‐Ion Hybrid Supercapacitors

Authors: Xiaofeng Zhang, Zihua Wang, Jiakun Luo, Salamat Ali, Yu Xie, Yuhang Zhao, Peiao Lu, Muhammad Sufyan Javed, Awais Ahmad, Ammar M. Tighezza, Kui‐Qing Peng, Weihua Han

Published: Mon, 04 Aug 2025 06:20:23 -0700

Small, EarlyView.

Graphitized Biochar Derived from Agricultural Wastes Enhances Methanogenesis via Conductivity‐Driven Direct Interspecies Electron Transfer

Authors: Caiyun Yang, Zhen Liu, Weiguo Liu, Yuxin Qiu, Shuai Zhang, Xinke Zhang, Mengyi Wang, Heng Wu, Hongyi Lyu, Jinzhi Huang, Jia Liu, Yirong Wang, Siying He, Dongze Gu, Xiaohui Guo, Xuanmin Yang, Teng Xie, Heyu Chen, Yiqing Yao

Published: Mon, 04 Aug 2025 02:39:02 -0700

Advanced Science, EarlyView.

Endothelial‐Derived CCL7 Promotes Macrophage Polarization and Aggravates Septic Acute Lung Injury via CCR1‐Mediated STAT1 Succinylation

Authors: Xue Li, Yuqin Long, Yunxi Zhu, Jiahui Gu, Ping Zhou, Changhong Miao

Published: Mon, 04 Aug 2025 02:37:36 -0700

Advanced Science, EarlyView.

Ultrafast Self‐Driven WSe2 Photodetectors with Bottom Schottky Contacts

Authors: Jian Li, Zhihao Wang, Jialing Jian, Zhengjin Weng, Qianqian Wu, Xingyu Zhou, Liangliang Lin, Xiaofeng Gu, Peng Xiao, Haiyan Nan, Shaoqing Xiao

Published: Mon, 04 Aug 2025 02:18:40 -0700

Advanced Science, EarlyView.

Detachable Fluorinated Phthalocyanine Aggregates for Carrier‐Free PDT: Effect of Axial Symmetry on Dynamic Morphological Adjustment and Photodynamic Efficiency

Authors: Shunhu Zhang, Nailin Yang, Haitao Zhao, Shumin Sun, Peidong Chen, Chaowei Cheng, Chunjie Wang, Weiwei He, Lifen Zhang, Liang Cheng, Zhenping Cheng

Published: Tue, 05 Aug 2025 01:11:44 -0700

Advanced Functional Materials, EarlyView.