PDF Summaries - vdW materials

It is now known that in addition to electrons, other quasi-particles such as phonons and magnons can also generate a thermal Hall signal. Graphite is a semimetal with extremely mobile charge carriers of both signs and a large lattice thermal conductivity. We present a study of the thermal Hall effect in highly oriented pyrolytic graphite (HOPG) samples with electronic, phononic and phonon drag contributions to the thermal Hall signal. The measured thermal Hall conductivity ($\kappa_{xy}$) is two orders of magnitude higher than what is expected by electronic carriers according to the electrical Hall conductivity and the Wiedemann-Franz law, yielding a record Hall Lorenz number of $164.9\times10^{-8}V^2 K^{-2}$ ($\sim$67$L_0$) - the largest ever observed in a metal. The temperature dependence of the thermal Hall conductivity significantly differs from its longitudinal counterpart, ruling out a purely phononic origin of the non-electronic component. Based on the temperature dependence and the amplitudes of the Seebeck and Nernst responses, we demonstrate that ambipolar phonon drag dominates the thermal Hall response of graphite.

Rhombohedral trilayer graphene provides a platform for exploring exotic quantum phases arising from the interplay of electron correlations and band topology. The development of strategies to engineer rhombohedral trilayer graphene with flat bands is important for both fundamental studies of correlated topological states and potential device applications. Here, we demonstrate that a slight rotation of monolayer graphene relative to a bilayer offers an effective approach to achieving this goal. In minimally twisted monolayer-bilayer graphene (mtMBG), significant structural relaxation gives rise to stable, large-scale ABA and ABC domain arrays. When the twist angle falls below a critical threshold, the ABC regions exhibit electronic properties akin to those of rhombohedral trilayer graphene, featuring robust and spatially uniform flat bands with tunable layer polarization. At partial filling, the conduction flat band progressively splits into four sub-bands, driven by electron-electron interactions and indicative of quantum phase transitions between correlated states. Moreover, spectroscopic signatures of electronic polarization and topological edge states at the domain walls separating the ABA and ABC regions are observed. These results establish mtMBG as a versatile platform for investigating emergent flat-band phenomena and related electronic states.

Author(s): Pan Shi, Yao Chen, Jingyi Zhang, Jian Feng, and Jie Yang

Graphene is prone to out-of-plane instabilities, with buckling under compression being the most common example. While tensile loading is generally expected to suppress such effects, recent studies on macroscopic elastic sheets have shown that localized tension can induce transverse buckling and gian…

This work investigates the Floquet dynamics of electrons and excitons (particle-hole pairs) in a Dirac material referred to as Kekul\'e-distorted graphene. Specifically, we examine the role played by a high frequency driving electromagnetic field on the tunneling and blocking by a potential barrier on both the charged single particles as well as the neutral composite particles. We demonstrate that the small effective masses of the electron and hole for the energy spectrum of this Kekul\'e distorted graphene leads to practically almost perfect transmission across a symmetric potential barrier for any angle of incidence of impinging excitons. However, this unexpected Klein paradox for excitons does not hold for the single-particle electrons. The reduced total transmission of electron due to Kekul\'e distortion is more suppressed due to irradiation. Additionally, we calculate and investigate the exciton binding energy since the quantum tunneling of a bound electron-hole pair across a potential barrier is governed by its mass measured in the center of mass and binding energy of the composite pair. Thus, irradiation with circularly polarized light fundamentally modifies exciton formation, coherence and transport properties, thereby producing unusual topological behaviors. These behaviors are unlike conventional Dirac materials. Possible technical applications of the results arising from our investigation include valleytronics due to the folding of the valleys, thereby making intervalley coupling feasible. Other practical applications include optoelectronics due to Floquet tuning of energy spectrum and transport properties.

Van der Waals (vdW) ferroelectric heterostructures provide a versatile platform for exploring interfacial interactions and advanced functionalities. Here, we report a thickness-engineered strategy to modulate the interfacial states and polarization switching in 2H-MoTe2/BaTiO3 (BTO) heterostructures. The interplay among band-alignment-induced charge transfer, polarization field, and defect-related traps governs the interfacial electronic structure. Remarkably, a two-unit-cell (u.c.) thickness variation (from 18 to 20 u.c.) in MoTe2 induces a 0.44 eV work function shift, reversing the band alignments and interfacial doping polarity. This transition triggers a reversal of BTO polarization from Pup to Pdown state, enabling deterministic and nondestructive polarization control. Electrical transport evolves from trap-assisted space-charge-limited conduction and thermionic emission to Fowler-Nordheim tunneling under strong polarization field, yielding robust multilevel nonvolatile memory characteristics. These results highlight thickness-controlled interfacial states as an effective route to tailor ferroelectric switching dynamics for nonvolatile memory and neuromorphic computing applications.

The self-assembly of enzyme proteins on 2D nanomaterials has enabled the construction and functional control of viable biochemical pathways. However, enzymatic cascades, which combine essential components of the photosynthetic and respiratory electron transport chains in tandem, have thus-far remained elusive. Herein, we have investigated a galvanic biohybrid nanosystem coupling photosystem I and cytochrome c oxidase on the surface of graphene oxide nanosheets in colloidal suspension. The oriented immobilization of the enzymes was facilitated by Ni-coordination sites tethered to the carbon basal plane, with negligible parasitic O 2 consumption. Transient absorption and electrochemical measurements provided evidence of electron transfer between donors and acceptors, leading to light-induced O 2 consumption of up to 70 out of 120 O 2 molecules/s/CcO unit. Graphene oxide behaves as an electronic reservoir and as an electroactive support, enabling electron transport, in concert with cytochrome c , as well as small-molecule redox mediators and reductants. This study provides a state-of-the-art approach for the exploration of photoelectron transfer in membrane-free suspensions of nanosurface-anchored photosynthetic–respiratory enzymatic chains.

Neuromorphic vision computing offers a promising solution to machine vision's arithmetic bottleneck. Single devices integrating perception, processing, and memory functions have attracted considerable interest, though maintaining effective hardware‐software coordination remains challenging. In this work, we demonstrate a neuromorphic vision systems (NVS) incorporating photoelectrically modulation neuromorphic devices with in‐device computing capabilities. The system employs a three‐terminal hardware configuration utilizing a 2D WS 2 /PdSe 2 heterostructure, which exhibits a high on/off ratio of ∼10 6 and minimal power consumption of 2.4 pJ per event. It demonstrates multimodal analog synaptic behaviors under electrical modulation, including robust synaptic plasticity and weight updateability. Notably, under photoelectric modulation, the device not only enables multi‐parameter tuning of synaptic behaviors across a broad spectral range (460, 532, and 660 nm) via optical pulses, but also can realize bidirectional weight update (LTP/LTD) modulation with wide spectral ranges through electrical pulses. Based on this, we developed a multi‐channel attention residual network (MAResNet) for neuromorphic computing, which achieves 92.8% recognition accuracy on the CIFAR‐10 dataset with an average AUC exceeding 0.98. Moreover, the model exhibits interpretable spatial responses and channel selectivity, further verifying the effectiveness and robustness of the neuromorphic computing framework inspired by biological vision. This work paves the way toward high‐accuracy NVS.

All-optical control of material phases at the nanoscale enables reconfigurable platforms for sensing and nanophotonics. We present a plasmon-driven strategy to both write and read localized 2H→1T' phase transitions in few-layer MoTe2 using individual Au nanoparticles as dual-function nanoantennas. Their localized surface plasmon resonances concentrate continuous-wave laser excitation to drive the transition via hot carriers and local heating, reducing the threshold power by nearly an order of magnitude, while their dark-field scattering spectra provide in situ optical readout through characteristic redshift-then-blueshift behavior. Raman spectroscopy confirms formation of the 1T' phase. The Au NP/1T'-MoTe2 system shows a strong temperature-dependent scattering response, enabling nanoscale optical thermal sensing. In an Au/MoTe2/MoS2 vertical heterostructure, plasmon-induced 2H→1T' conversion reconfigures the band alignment, turning a photoluminescence-quenched OFF state into a trion-dominated ON state. This establishes a general route for all-optical, nanoscale phase engineering of 2D materials for active thermal and excitonic control.

Author(s): Fei Gao, Nikhil Dhale, Ling-Fang Lin, Keith M. Taddei, Yang Zhang, Clarina Dela Cruz, Elbio Dagotto, and Bing Lv

We report the canted antiferromagnetic (AFM) structure together with a spin reorientation in a single chain quasi-one-dimensional (Q-1D) iron chalcogenide ${\mathrm{Ba}}_{2}{\mathrm{FeSe}}_{3}$. ${\mathrm{Ba}}_{2}{\mathrm{FeSe}}_{3}$ crystallizes in Pnma (No. 62) orthorhombic structure with linear s…

Chiral boundary states with perfect conducting channels are essential characteristics of magnetic topological materials. Prominent examples include the one-dimensional (1D) chiral edge and 2D chiral surface states found in 2D and 3D quantum Hall materials under magnetic fields, respectively. However, these boundary states are restricted to specific fixed dimensions, so they hardly facilitate cross-dimensional energy and information transport. Here, we fabricate a unique 3D photonic antiferromagnetic topological insulator with net zero magnetization that can simultaneously support different-dimensional hinge states and unpaired surface Dirac cones on neighboring facets. Owing to the chiral anomaly present in a finite-size sample, the gapless surface Dirac cone, neighbored by facets with surface Dirac masses of opposite signs, is further converted, exhibiting 2D planar one-way propagation. In conjunction with 1D hinge states, we experimentally observe a closed chiral loop for nonreciprocal hinge–surface transport across dimensions in topological photonics, similar to that theoretically proposed in 3D quantum anomalous Hall materials. Our findings enrich the chiral boundary features of 3D magnetic topological insulators and offer a topological strategy for exploring ideal cross-dimensional devices.

We introduce a linear-scaling real-space methodology to compute time-resolved electrical responses of materials driven far-from-equilibrium, with energy relaxation and disorder treated on equal footing. Applying this approach to AB-stacked (Bernal) bilayer graphene, driven by a circularly polarized optical pulse, we observe the generation of a finite Hall conductivity. This Hall signal oscillates during optical driving and remains sizable after the light is switched off before relaxing toward equilibrium. Remarkably, this dynamical Hall response is robust in the presence of realistic descriptions of disorder, suggesting that disorder and relaxation dynamics can be leveraged as design parameters rather than being limitations. More broadly, our new methodology enables the investigation of electrical responses in driven, complex disordered quantum materials and highlights how engineered energy transfer pathways can enable ultrafast optoelectronic functionality.

Optimizing the interfaces in perovskite solar cells (PSCs) is essential for enhancing their performance, improving their stability, and making them commercially viable for large-scale deployment in solar energy harvesting applications. Point defects, like vacancies, have a dual role, as they can inherently provide a proper doping, but they can also reduce the collected current by trap-assisted recombination. Moreover, they can play an active role in ion migration and degradation. Using {\it ab initio} density functional theory (DFT) calculations we investigate the changes in the band alignment induced by interfacial vacancy defects in a TiO$_2$/MAPI/Cu$_2$O based PSC. Depending on the type of the vacancy (Ti, Cu, O, Pb, I) in the oxide and perovskite materials, additional doping is superimposed on the already existing background. Their effect on the performance of the PSCs becomes visible, as shown by SCAPS simulations. The most significant impact is observed for $p$ type doping of TiO$_2$ and $n$ type doping of Cu$_2$O, while the effective doping of the perovskite layer affects one of the two interfaces. We discuss these results based on modifications of the band structure near the active interfaces and provide further insights concerning the optimization of electron and hole collection.

Small, EarlyView.

Magnetic topological insulators have received significant interest due to their dissipationless edge states, which promise advances in energy-efficient electronic transport. However, the magnetic topological insulator state has typically been found in ferromagnets (FMs) that suffer from low magnetic ordering temperatures and stray fields. Identifying an antiferromagnetic topological insulator that exhibits the quantum anomalous Hall effect (QAHE) with a relatively high N\'eel temperature has been a longstanding challenge. Here, we focus on the recently discovered van der Waals (vdW) antiferromagnet (AFM) UOTe, which not only features a high N\'eel temperature (\(\sim\)150K) but also exhibits intriguing Kondo interaction and topological characteristics. Our systematic analysis of the layer-dependent topological phases based on \textit{ab} initio computations predicts the two-layer UOTe film to be an ideal 2D AFM Chern insulator in which the Hall conductivity is quantized with a fully compensated spin magnetization. By applying an in-plane strain or electric field, we show how the itinerancy of U-5f electrons can be manipulated to trigger a transition between the nontrivial ($C = 1$) and trivial ($C = 0$) phases. Interestingly, the 3-layer UOTe film is found to have zero charge conductance but it hosts a quantized spin Hall conductivity (SHC) with finite magneto-electric coupling, suggesting the presence of an axion insulator-like state. The unique magnetic structure of UOTe supports a layer-tunable topology in which films with an odd number of layers are axion-like insulators, while films with an even number of layers are Chern insulators, and the bulk material is a Dirac semimetal. Our study offers a new intrinsic AFM materials platform for realizing correlated topological phases for next-generation spintronics applications and fundamental science studies.

We investigate the dynamics of active nematic liquid crystals on deformable membranes, focusing on the interplay between active stress and anisotropic curvature coupling. Using a minimal model, we simulate the coupled evolution of the nematic order parameter and membrane height. We demonstrate a continuous transition from a curvature-dominated regime, where topological defects are trapped by local deformation, to an activity-dominated regime exhibiting active turbulence. A scaling analysis reveals that the critical activity threshold $\zeta_c$ scales as $\alpha^2/\kappa$, where $\alpha$ and $\kappa$ are the coupling constant and bending stiffness, respectively; this relationship is confirmed by our numerical results. Furthermore, we find that significant correlations between the orientational pattern and membrane geometry persist even in the turbulent regime. Specifically, we identify that "walls" in the director field induce characteristic wave-like curvature profiles, providing a mechanism for dynamic coupling between order and shape. These results offer a physical framework for understanding defect-mediated deformation in nonequilibrium biological membranes.

We investigate the thermoelectric properties of two newly synthesized columnar double halide perovskites Cs$_2$AgPdCl$_5$ and Cs$_2$AgPtCl$_5$. These materials accommodate a distorted local polyhedral architecture with tetrahedral symmetry compared to traditional double halide perovskites. By employing density functional theory along with the semiclassical transport model, we have analyzed the electronic and transport properties of these materials. Our results show that at 800 K, the largest figure of merit ($zT$) is 1.30 (0.86) for p-type (n-type) Cs$_2$AgPdCl$_5$ and 0.87 for n-type Cs$_2$AgPtCl$_5$ at doping concentrations of $1.94 \times 10^{20}$ ($3.76 \times 10^{19}$) cm$^{-3}$ and $3.52 \times 10^{19}$ cm$^{-3}$, respectively. Remarkably, a very low doping concentration is required to achieve a high $zT$, setting these materials apart from others in this field. Our calculations demonstrate that Cs$_2$AgPdCl$_5$ benefits from the presence of conduction and valence band valleys near the band edges; however, the flat bands present in the valence band of Cs$_2$AgPtCl$_5$ do not improve its thermoelectric performance. Among these systems, hole doping in Cs$_2$AgPdCl$_5$ has shown remarkable thermoelectric performance. Interestingly, the local octahedral distortions present in these perovskites contribute to a marked reduction in the lattice thermal conductivity to 0.27 W/mK in Cs$_2$AgPtCl$_5$ and 0.20 W/mK in Cs$_2$AgPdCl$_5$ by causing enhanced phonon scattering, further improving the thermoelectric figure of merit. This drop in thermal conductivity, combined with the favorable electronic properties, underscores the potential use of these materials for applications in highly efficient thermoelectric devices.

Topological spin textures are hallmark manifestations of competing interactions in magnetic matter. Their effective description by nonlinear field theories reflects an energetic frustration that destabilizes uniform order while selecting finite-size, topologically nontrivial configurations as stationary states. Among the most extreme realizations are atomically-sharp domain wall excitations, namely one-dimensional (1D) magnetic solitons, which represent the ultimate scaling limit of magnetic textures. Such solitons may emerge in magnetic systems where effective exchange interactions compete directly with uniaxial magnetic anisotropy. Here we show that the square-net rare earth compound EuRhAl$_{4}$Si$_{2}$ realizes a very susceptible regime where the magnetic anisotropy competes with highly frustrated exchange interactions stabilizing a rare ferrimagnetic $\uparrow\uparrow\downarrow$ state that, under applied magnetic field, supports the formation of atomically-sharp soliton defects. We confirm the bulk response of the 1D magnetic solitons via magnetization and electrical transport measurements. We establish both the zero- and in-field $\uparrow\uparrow\downarrow$ order via neutron diffraction, while magnetic force microscopy visualizes its real-space evolution into a stripe-like array. To elucidate the microscopic origin of the soliton, we relate the Ruderman-Kittel-Kasuya-Yosida (RKKY)-driven exchange interactions and the magnetic anisotropy through density functional theory, and we construct an effective 1D $J_{1}$-$J_{2}$-$K$ model whose atomistic spin dynamics simulations reproduce the observed soliton states as a function of external field. Our results demonstrate that EuRhAl$_{4}$Si$_{2}$ hosts atomically-sharp, field-driven 1D magnetic solitons, providing a new platform for studying 1D topological excitations at the atomic length scale.

Rechargeable aqueous zinc-ion batteries (RAZIBs) attract considerable scientific and commercial interest for deployment in grid-scale energy storage due to higher safety and lower manufacturing cost when compared to lithium-ion batteries. However, currently studied cathode materials suffer from severe capacity fade when cycling at rates appropriate for grid-scale applications ($$ C/2), which hampers the commercialization of RAZIBs. To address the present limitation on cathode material availability, more than 2000 previously synthesized oxides, chalcogenides, Prussian blue analogues, and polyanion materials were computationally screened for the discovery of highly stable RAZIB cathode materials. The structural, electrochemical, and chemical properties of the materials were respectively evaluated through an investigation of the available Zn$^{2+}$ percolation paths in the crystal structure, the stability of the material in aqueous media under RAZIB operation conditions, and the attained transition metal oxidation state during cycling. The transition metal oxidation state and intercalating ion coordination environment were determined to govern the magnitude of the calculated intercalation potential, with this finding directly supporting the development of batteries with high operation potentials. Finally, 10 previously unexplored materials were identified with leading metrics for operation as RAZIB cathode materials, such as high Zn$^{2+}$ (de)intercalation potential, electrochemical stability, theoretical gravimetric capacity, and energy density, being here proposed for experimental testing. The materials identified in this study demonstrate a guide for advancing the available cathode materials for RAZIB, and help expedite the establishment of RAZIB as a commercially viable technology for grid-scale energy storage.

Fractional quantum Hall (FQH) states and superconductors typically require contrasting conditions, yet recent experiments have observed them in the same device. A natural explanation is that mobile anyons give rise to superconductivity; however, this mechanism requires binding of minimally charged anyons to establish an unusual energy hierarchy. This scenario has mostly been studied with effective theories, leaving open the question of how anyon superconductivity can arise from repulsive interactions. Here, we show that such an energy hierarchy of anyons arises naturally in fractional Chern insulators (FCIs) at fillings $\nu = 2/(4p \mp 1)$ when they are driven toward a quantum phase transition into a ``semion crystal'' -- an exotic charge-density-wave (CDW) insulator with semion topological order. Near the transition, Cooper-pair correlations are enhanced, so that a conventional charge-2e superconductor appears with doping. Guided by these insights, we analyze a microscopic realization in a repulsive Hubbard-Hofstadter model. Tensor network simulations at $\nu = 2/3$ reveal a robust FCI that, with increasing interactions, transitions into the semion crystal. Finding a stable semion crystal in such a minimal model highlights it as a viable state competing with conventional CDW and FQH states. In the vicinity of this transition, we find markedly enhanced Cooper pairing, consistent with our theory that the 2e/3 anyon is cheaper than a pair of isolated e/3 anyons. Doping near the transition should in general lead to doping Cooper pairs and charge-2e superconductivity, with chiral edge modes of alternating central charge $c = \pm2$, which can coexist with translation symmetry breaking. Our framework unifies recent approaches to anyon superconductivity, reconciles it with strong repulsion and provides guidance for flat band moir\'e materials such as recent experiments in twisted MoTe$_2$.

Due to their high kinetic inductance, highly disordered superconducting thin films are a potential hardware for the realization of compact, low-noise elements in cryoelectronic applications. However, high disorder typically results in structural defects that cause spatial inhomogeneity of the superconducting order parameter, thereby impairing the film's properties. Here, we employ scanning tunneling microscopy to demonstrate that NbN thin films fabricated by plasma-enhanced atomic layer deposition (PE-ALD) exhibit unusual spatial homogeneity, even at thicknesses approaching the superconductor-insulator transition. Tunneling spectra acquired across the sample surface show only small variations of the order parameter with a standard deviation of 2-3%, on length scales that significantly exceed the film's grain size. At the same time, the films achieve a relatively high sheet resistance (up to 1400 Ohm) and, consequently, a high sheet kinetic inductance (up to approximately 200 pH), making them well-suited for applications.

We study the localization properties of the low-lying Dirac eigenmodes in QCD near the crossover temperature, using staggered fermions on the lattice. We find that localized low modes, absent at low temperature, appear at a temperature $T_{\mathrm{loc}}$ in the range $155\,\mathrm{MeV}\le T_{\mathrm{loc}}\le 158\,\mathrm{MeV}$, in excellent agreement with the pseudocritical crossover temperature as determined from the chiral condensate and from the light-quark susceptibility.

The sublattice-symmetry breaking in the $\alpha-T_3$ lattice leads to a bandgap opening. A defect line in the substrate on which the $\alpha-T_3$ lattice is deposited can be viewed as a topological change in the substrate that induces translational in-plane symmetry breaking, resulting in mid-gap states. These topologically protected states are confined along the defect line and exhibit preferential directional motion, with different signs for the different Dirac valleys. Within this context, we investigate how these unidirectional interface chiral states are affected in the presence of a perpendicular magnetic field and how they can be tuned by varying the controlling system parameter $\alpha$. The latter tunes the $\alpha-T_3$ structure from a honeycomb-like lattice ($\alpha=0$) to a dice lattice ($\alpha=1$). Our theoretical framework is based on the continuum approximation described by a $3\times 3$ matrix Hamiltonian with a sublattice symmetry-breaking term given by $\Delta(x) diag(1,\quad -1,\quad 1)$, assuming $\Delta(x)$ as a kink-like mass potential profile. Results for dispersion relations and wavefunction distributions for different $\alpha$ parameters and magnetic field amplitudes are discussed. We demonstrate lifting of Landau levels degeneracy and of valley degeneracy. Our findings pave the way for proposing valley filter devices based on any evolutionary stage between the honeycomb-like and dice lattice structures of the $\alpha-T_3$ phase, controlled by external fields.

Cavity quantum electrodynamics (cQED) provides strong light-matter interactions that can be used for manipulating and detecting quantum states. The interaction can be enhanced by increasing the resonator's impedance, while approaching the quantum impedance ($h/e^2$) remains challenging. Edge plasmons emergent as chiral bosonic modes in the quantum Hall channels provide high quantized impedance of $h/ \nu e^2$ that can exceed 10 k$\Omega$ for the Landau-level filling factor $\nu \leq 2$, well beyond the impedance of free space. Here, we apply such a high-impedance plasmon mode in a quantum-Hall plasmon resonator to demonstrate dispersive detection of a nearby charge qubit formed in a double quantum dot. The phase shift in microwave transmission through the plasmon resonator follows the dispersive shift associated with the qubit state in agreement with the cQED theory. The high impedance allows us to perform dispersive detection of qubit spectroscopy with a plasmon resonator having a broad bandwidth. Leveraging these topological edge modes, our results establish two-dimensional topological insulators as a new platform of cQED.

Author(s): Roger Brunner, Titus Neupert, and Glenn Wagner

We study a spinful, time-reversal symmetric lowest Landau level model for a flatband quantum spin Hall system at total filling fraction ${ν}_{\mathrm{T}}=2/3$. Such models are relevant, e.g., for spin-valley locked moiré transition metal dichalcogenides. The opposite Chern number of the two spins hi…

We present a simple methodology to compute the anomalous Hall conductivity (AHC) as a function of the canting angles in ferromagnets and altermagnets, starting from a nonmagnetic Hamiltonian obtained from first-principles calculations that preserves the full symmetry of the crystal structure. Magnetism is introduced by including on-site spin splitting, spin-orbit coupling, and spin-canting angles. As a representative material, we study SrRuO$_3$, which supports spin canting and exhibits a sign change of the AHC. In the ferromagnetic phase, the low-energy AHC is found to be close to zero at the Fermi level, in agreement with experimental observations. We show that the dependence of the AHC on the relevant physical parameters is most pronounced in the central region of the electronic bandwidth. We determine the symmetry-allowed components of the AHC for different magnetic orders in the large family of transition-metal perovskite ABO$_3$ compounds with space group $62$, including the spontaneous in-plane anomalous Hall effect. Within density functional theory, we evaluate the range of spin-canting angles in SrRuO$_3$ and demonstrate that it is suppressed as electronic correlations increase. By analyzing the AHC as a function of the canting angle, we find that the collinear magnetic configurations contribute most to the AHC, while spin canting plays a secondary role in determining its magnitude in non-collinear ferromagnets and altermagnets. However, canting can become relevant and induce a sign change of the AHC when the collinear magnetic state exhibits an AHC close to zero. Finally, we investigate the locations of Weyl points in the Brillouin zone and their evolution as a function of the canting angle.

A family of ferrimagnets (CoV2O4, GdCo, TbCo) exhibits out-of-plane magnetic anisotropy when strained compressively and in-plane magnetic anisotropy when strained expansively (or vice versa). If such a ferrimagnetic thin film is placed on top of a topological insulator (TI) thin film and its magnetic anisotropy is modulated with strain, then interfacial exchange coupling between the ferrimagnet (FM) and the underlying TI will modulate the surface current flowing through the latter. If the strain is varied continuously, the current will also vary continuously and if the strain alternates in time, the current will also alternate with the frequency of the strain modulation, as long as the frequency is not so high that the period is smaller than the switching time of the FM. If the strain is generated with a gate voltage by integrating a piezoelectric underneath the FM/TI stack, then that can implement a transconductance amplifier or a synapse for neuromorphic computation.

Author(s): S. E. Shafraniuk

An obstacle to utilizing the entangled photons nowadays is the low efficiency of their creation. As a solution, we consider the generation of coherent photons using coupled graphene quantum dot (GQD) lasers activated with a short voltage pulse. To illustrate the method, we analyze the terahertz (THz…

arXiv:2509.07099v2 Announce Type: replace-cross Abstract: We present a general framework for constructing quantum cellular automata (QCA) from topological quantum field theories (TQFT) and invertible subalgebras (ISA) using the cup-product formalism. This approach explicitly realizes all $\mathbb{Z}_2$ and $\mathbb{Z}_p$ Clifford QCAs (for prime $p$) in all admissible dimensions, in precise agreement with the classification predicted by algebraic $L$-theory. We determine the orders of these QCAs by explicitly showing that finite powers reduce to the identity up to finite-depth quantum circuits (FDQC) and lattice translations. In particular, we demonstrate that the $\mathbb{Z}_2$ Clifford QCAs in $(4l{+}1)$ spatial dimensions can be disentangled by non-Clifford FDQCs. Our construction applies beyond cubic lattices, allowing $\mathbb{Z}_2$ QCAs to be defined on arbitrary cellulations. Furthermore, we explicitly construct invertible subalgebras in higher dimensions, obtaining $\mathbb{Z}_2$ ISAs in $2l$ spatial dimensions and $\mathbb{Z}_p$ ISAs in $(4l{-}2)$ spatial dimensions. These ISAs give rise to $\mathbb{Z}_2$ QCAs in $(2l{+}1)$ dimensions and $\mathbb{Z}_p$ QCAs in $(4l{-}1)$ dimensions. We further prove that the QCAs in $3$ spatial dimensions constructed via TQFTs and ISAs are equivalent by identifying their boundary algebras, and show that this approach extends to higher dimensions. Together, these results establish a unified and dimension-periodic framework for Clifford QCAs, connecting their explicit lattice realizations to field theories.

arXiv:2503.06665v3 Announce Type: replace-cross Abstract: Quantum many-body scars have received much recent attention for being both intriguing non-ergodic states in otherwise quantum chaotic systems and promising candidates to encode quantum information efficiently. So far, these studies have mostly been restricted to Hermitian systems. Here, we study many-body scars in many-body quantum chaotic systems coupled to a Markovian bath, which we term Lindblad many-body scars. They are defined as simultaneous eigenvectors of the Hamiltonian and dissipative parts of the vectorized Liouvillian. Importantly, because their eigenvalues are purely real, they are not related to revivals. The number and nature of the scars depend on both the symmetry of the Hamiltonian and the choice of jump operators. For a dissipative four-body Sachdev-Ye-Kitaev (SYK) model with $N$ fermions, either Majorana or complex, we construct analytically some of these Lindblad scars while others could only be obtained numerically. As an example of the former, we identify $N/2+1$ scars for complex fermions due to the $U(1)$ symmetry of the model and two scars for Majorana fermions as a consequence of the parity symmetry. Similar results are obtained for a dissipative XXZ spin chain. We also characterize the physical properties of Lindblad scars. First, the operator size is independent of the disorder realization and has a vanishing variance. By contrast, the operator size for non-scarred states, believed to be quantum chaotic, is well described by a distribution centered around a specific size and a finite variance, which could be relevant for a precise definition of the eigenstate thermalization hypothesis in dissipative quantum chaos. Moreover, the entanglement entropy of these scars has distinct features such as a strong dependence on the partition choice and, in certain cases, a large entanglement.

$\alpha$-RuCl$_3$ is a leading material for proximate Kitaev magnetism. We address the origin of the broad, $\Gamma$-point centered excitation continuum observed by inelastic neutron scattering at elevated temperatures in this compound. Using stochastic Landau-Lifshitz dynamics augmented with quantum-equivalent corrections, we reproduce the temperature-dependent dynamical spin structure factor across both the correlated and conventional paramagnetic regimes. A meta-analysis of 38 published exchange parameter sets identifies those most consistent with the full temperature evolution. A Bayesian optimization procedure is used to derive parameters that capture the low-energy star-like momentum dependence and the overall bandwidth of the continuum. Rescaling temperatures by the Curie--Weiss scale produces a collapse of spectral measures, demonstrating that the high-$T$ dynamics are governed by correlated paramagnetism below $\theta_{\mathrm{CW}}$ rather than by the Kitaev crossover to fractionalized excitations. Complementary 24-site exact diagonalization clarifies finite-size systematics at low temperature and the proximity to zigzag/incommensurate ordering. Beyond $\alpha$-RuCl$_3$, our simulation pipeline provides a reproducible, data-driven framework to infer effective spin models in magnets that exhibit broad continua.

We investigate the Multiple Equilibria phase of generalized Lotka-Volterra dynamics with random, non-reciprocal interactions. We compute the topological complexity of equilibria, which quantifies how rapidly the number of equilibria of the dynamical equations grows with the total number of species. We perform the calculation for arbitrary degree of non-reciprocity in the interactions, distinguishing between configurations that are dynamically stable to invasions by species absent from the equilibrium, and those that are not. We characterize the properties of typical (i.e., most numerous) equilibria at a given diversity, including their average abundance, mutual similarity, and internal stability. This analysis reveals the existence of two distinct ME phases, which differ in how internally stable equilibria behave under invasions by absent species. We discuss the implications of this finding for the system's dynamical behavior.