Optical vortex beams are a type of topological light characterized by their inherent orbital angular momentum (OAM), leading to the propagation of a spiral-shaped wavefront. In this study, we focus on two-dimensional electrons with Rashba and Dresselhaus spin-orbit interactions and examine how they respond to pulsed vortex beams in the terahertz frequency band. Spin-orbital interactions play a vital role in transferring the OAM of light to electron systems and generating spatiotemporal spin textures. We show that the spatiotemporal spin polarization of electrons reflects OAM carried by optical vortex pulses. These findings demonstrate how optical vortices facilitate ultrafast spin manipulation in spin-orbit-coupled electrons. Our results can be straightforwardly extended to the case of higher-frequency vortex beams for other two-dimensional metals with a larger Fermi energy.

Coherent quantum state transfer over macroscopic distances between non-neighboring elements in quantum circuits is a crucial component to increase connectivity and simplify quantum information processing. To facilitate such transfers, an efficient and easily controllable quantum pump would be highly beneficial. In this work, we demonstrate such a quantum pump based on a one-dimensional quasicrystal Fibonacci chain (FC). In particular, we utilize the unique properties of quasicrystals to pump the edge-localized winding states between the two distant ends of the chain by only minimal manipulation of the FC at its end points. We establish the necessary conditions for successful state transfer within a fully time-dependent picture and also demonstrate robustness of the transfer protocol against disorder. We then couple external qubits to each end of the FC and establish highly adaptable functionality as a quantum bus with both on-demand switching of the qubit states and generation of maximally entangled Bell states between the qubits. Thanks to the minimal control parameters, the setup is well-suited for implementation across diverse experimental platforms, thus establishing quasicrystals as an efficient platform for versatile quantum information processing.

The Anderson model in one dimension is a quantum particle on a discrete chain of sites with nearest-neighbor hopping and random on-site potentials. It is a progenitor of many further models of disordered systems, and it has spurred numerous developments in various branches of physics. The literature does not readily provide, however, practical analytic tools for computing the density of states of this model when the distribution of the on-site potentials is arbitrary. Here, supersymmetry-based techniques are employed to give an explicit linear integral equation whose solutions control the density of states. The output of this analytic procedure is in perfect agreement with numerical sampling. By the Thouless formula, these results immediately provide analytic control over the localization length.

We report on the enhancement of the spin coherence time $\left(T_2\right)$ by almost an order of magnitude in exciton-polariton condensates through driven spin precession resonance. Using a rotating optical trap formed by a bichromatic laser excitation we synchronize the trap's stirring frequency with the condensate's intrinsic Larmor precession, achieving a substantial increase in spin coherence. By tuning the optical trap profile via the excitation laser intensity, we precisely control the resonance width. Here, we present a theoretical model that explains our experimental results in terms of the mutual synchronization of the condensate circular polarization components. Our findings underpin the potential of polariton condensates for spinoptronic devices and quantum technologies.

Ternary potassium copper chalcogenides $\mathrm{KCu}X$ ($X=$ Se, Te) crystallizing in the hexagonal space group $P{6}_3/mmc$, are investigated for their topological phonon characteristics using ab initio techniques. The computed phonon dispersion relations exhibit multiple symmetry-enforced features, including high-degeneracy points and a nodal plane at the Brillouin zone boundary, consistent with the nonsymmorphic nature of the space group. Furthermore, a network of phononic nodal lines is identified, originating from the band crossings along high-symmetry paths and planes. These nodal lines are protected by crystalline symmetries such as mirror and rotational operations. To explore the topological consequences of these bulk features, we compute the surface phonon spectra, revealing the emergence of drumheadlike surface states that span the projections of the bulk nodal lines onto the surface Brillouin zone. These states indicate the nontrivial topological nature of the phonon bands. Our findings establish $\mathrm{KCu}X$ ($X=$ Se, Te) compounds as promising candidates for emergent topological phonon phases beyond the usual topology of the electronic structure.

We present a systematic framework for Floquet prethermalization under strong resonant driving, emphasizing the pivotal role of dynamical space-time symmetries. Our approach demonstrates how dynamical space-time symmetries map onto the projective static symmetry group of the prethermal Hamiltonian governing the prethermal regime. We introduce techniques for detecting dynamical symmetries through the time evolution of local observables, facilitating a detailed analysis of micromotion within each period and surpassing the limitations of conventional stroboscopic Floquet prethermal dynamics. To implement this framework, we present a prethermal protocol that preserves order-2 dynamical symmetry in a spin-ladder model, confirming the predicted relationships between the expectation values of local observables at distinct temporal points in the Floquet cycle, linked by this symmetry.

Non-Abelian gauge offers a powerful route to engineer novel topological phenomena. Here, we systematically investigate a two-dimensional non-Hermitian Hatano-Nelson model incorporating an SU(2) non-Abelian gauge, demonstrating the emergence of Hopf-link bulk braiding topology in the complex energy spectrum solely with $x$-direction nearest-neighbor couplings. Given that the limitations of exceptional point topology in fully capturing the rich non-Hermitian skin effect (NHSE) under non-Abelian influence, we introduce a polarization parameter derived from the generalized Brillouin zone. This parameter quantitatively discerns left-, right-, and notably, both-side skin modes, with its accuracy corroborated by directly encoding real-space eigenstate. Our findings reveal that non-Abelian gauge provides unprecedented influence over NHSE, compared with Abelian gauge and without gauge cases. Furthermore, we uncover the pronounced clustering and size-effect-independent bipolar localization behavior of the eigenstates at the topological boundaries, as characterized by dynamics evolution and inverse participation ratio. This work establishes a paradigm for synthesizing and manipulating non-Hermitian topological phases driven by non-Abelian structures, opening avenues for topological engineering and holding promise for experimental realization in synthetic platforms.

We employ the diagrammatic Monte Carlo method with a lattice path-integral formulation for both electron and phonon degrees of freedom to investigate the formation and properties of bond polarons and bipolarons on a two-dimensional triangular lattice. In the deep adiabatic regime ($\omega /t<1.0$), single polarons remain light with a small effective mass, while bipolarons remain compact and lightweight, resulting in a high superfluid transition temperature $T_c$. We systematically study the dependence of $T_c$ on electron-phonon coupling strength and on-site interaction in the bond bipolaron model. Our results show that a moderate on-site repulsion enhances $T_c$ by stabilizing compact yet lightweight bipolarons, leading to high-$T_c$ superconductivity in the dilute limit. Notably, the triangular lattice sustains relatively high $T_c$ across a wide range of phonon frequencies, outperforming square lattice geometry. This enhancement arises from the higher coordination number and the bond-centered nature of the electron-phonon coupling. These findings suggest that triangular lattice geometry offers a promising platform for realizing high-$T_c$ bipolaronic superconductivity.

We report the synthesis of single crystals of ${\mathrm{Ce}}_2{\mathrm{SnS}}_5$ through a two-stage chemical vapor transport method. The ${\mathrm{Ce}}_2{\mathrm{SnS}}_5$ system is a member of the orthorhombic Pbam (No. 55) space group and realizes a distorted trigonal tricapped prism (TTP) crystal field around each cerium site. We characterized the sample through orientation-dependent magnetization and heat capacity measurements to probe the magnetic anisotropy in the system characteristic of XY-like anisotropic Heisenberg model behavior. ${\mathrm{Ce}}_2{\mathrm{SnS}}_5$ furthermore enters a zero-field ordered phase under $T_N=2.4\text{K}$; powder neutron diffraction measurements reveal incommensurate magnetic order near $T_N$. The system then locks into a commensurate, two-$q$ magnetic structure below approximately $1.2\text{K}$. This commensurate structure belongs to the Shubnikov group $P{b}^{\prime }{a}^{\prime }{m}^{\prime }\left(\mathrm{MSG}55.359\right)$ and realizes the propagation vectors $\vec{q}=(1/3,0,0)$ and $\vec{q}=(0,0,0)$.

Kagome magnets naturally hosting Dirac points and flat bands exhibit novel topological phases, enabling rich interplays between interactions and topologies. The discovery of two-dimensional (2D) magnets generally coexisting with different types of magnetic interactions poses a challenge for topological magnonic manipulation. Here we investigate the topological magnon phases of 2D kagome ferromagnet with multiple magnetic anisotropic interactions, i.e., Dzyaloshinskii-Moriya interaction (DMI) and pseudodipolar interaction (PDI). It is found that the different sole magnetic anisotropic interactions introduce completely distinct topological phase diagrams and topological states. The multiple topological magnon phases with high Chern number emerge due to the distinct anisotropic interactions. Moreover, the interplay of the multiple anisotropic DMI and PDI interactions involved with Dirac and flat bands controls a variety of topological phase transitions, implying greater manipulation potential. In addition, the sign reversal of thermal Hall and Nernst conductivities induced by temperature is found in particular topological phase regions, namely topological origin, relating to the energy gap and Berry curvature (Chern number) in the vicinity of magnetic phase transition from the thermal fluctuations, providing a possible explanation for the experimental puzzles. All these results demonstrate that the novel topological magnonic properties in kagome magnet with multiple magnetic anisotropic interactions can realize a potential platform for magnonic devices and quantum computing.

The square-net ferromagnet ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$ has attracted significant attention owing to its zero-field skyrmionic bubbles at room temperature and the associated intriguing topological transport phenomena. Compared with the other members of the $R{\mathrm{Mn}}_2{\mathrm{Ge}}_2$ family ($R$ = rare-earth elements), this compound exhibits a notably more complex and diverse magnetic structure. In this work, we present a systematic investigation of the magnetic properties of ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$. The magnetism predominantly arises from the Mn sublattice across a broad temperature range, with Nd moments becoming significant only at lower temperatures. With increasing external magnetic field applied along the $c$ axis, the ferromagnetic transition temperature $T_{\mathrm{c}}$ shifts to higher temperatures, whereas the spin reorientation temperature $T_{\mathrm{SR}}$ decreases. Based on these observations, we construct a detailed magnetic phase diagram and interpret the field-induced evolution of the topological magnetic states from an energetic standpoint. Critical exponents extracted from isothermal magnetization curves reveal that the magnetic exchange interaction decays as $J\left(r\right)\sim r^{-4.59}$, placing it between short-range and long-range interaction regimes. This intermediate range suggests the coexistence of both interaction types, which may underpin the formation of skyrmionic bubbles in ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$. Furthermore, ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$ exhibits a maximum magnetic entropy change of $4.16\mathrm{J}{\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$ and a relative cooling power of $218\mathrm{J}{\mathrm{kg}}^{-1}$ at 70 kOe near room temperature. Our results provide a deeper understanding of the magnetic interactions in ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$ and shed light on the relationship between its complex magnetic behavior and emergent topological spin textures.

The on-site potentials may break the symmetry of a system, resulting in the loss of its original topology protected by the symmetry. In this work, we study the counteracting effect of non-Hermitian terms on real potentials, resulting in dynamically stable topological edge states. We show exactly for a class of systems that the spectrum remains unchanged in the presence of balanced perturbations. As a demonstration, we investigate an extended non-Hermitian Su-Schrieffer-Heeger (SSH) ladder. We find that the bulk-boundary correspondence still holds, and the zero-energy edge states become coalescing states. In comparison to the original SSH chain, such edge states are robust not only against local perturbations but also in the time domain. As a result, a trivial initial state can always evolve to a stable edge state. Our results provide insights for the application of time-domain stable topological quantum devices.

We explore the robustness of Hall conductivity quantization in several insulating systems, exhibiting one scenario where the quantization is not preserved. Specifically, we apply the Kubo formula to topological models with the Hatsugai-Kohmoto interaction. Starting from the many-body degeneracy induced by this interaction in the topological Kane-Mele model, we consider Zeeman fields to select specific states within the ground-state manifold that reveal a nonquantized Hall response, precisely for the case with a Zeeman field diagonal in the bands of the Kane-Mele model. From a physical point of view, this term may mimic a ferromagnetic order that arises naturally when couplings beyond the Hatsugai-Kohmoto interaction are taken into account.

To study the spin-Peierls transition at finite temperatures, we use path integral molecular dynamics (PIMD) in combination with stochastic series expansion or exact diagonalization to sample the quantum Boltzmann distribution of the spin-phonon-coupled one-dimensional isotropic Heisenberg chains. The use of PIMD in this context has apparently been overlooked up to now and offers several advantages over other approaches, including no restriction on the functional forms of the phonon potential or the exchange coupling. This approach allows us to study the spin-spin correlation in such systems in detail. Looking at $S=1/2$, we find that it exhibits algebraic decay in the undimerized phase and exponential decay in the dimerized phase, but with many nuanced trends present. The decay exponentials in all cases roughly obey the scaling of ${(g^2/\left(m{\omega }_{\pi }^2\right))}^{\gamma }$, where $g$ is the spin-phonon coupling constant, $m$ is mass, and ${\omega }_{\pi }$ is the frequency of the $k=\pi$ phonon.

We introduce a generic method for computing groundstates that is applicable to a wide range of spatially anisotropic 2D many-body quantum systems. By representing the 2D system using a low-energy 1D basis set, we obtain an effective 1D Hamiltonian that only has quasilocal interactions, at the price of a large local Hilbert space. We apply our new method to three specific 2D systems of weakly coupled chains: hardcore bosons, a spin-$1/2$ Heisenberg, and spinful fermions with repulsive interactions. In particular, we showcase a nontrivial application of the energy expansion framework, to the anisotropic triangular Heisenberg lattice, a highly challenging model related to 2D spin liquids. Treating lattices of unprecedented size, we provide evidence for the existence of a quasi-1D gapless spin liquid state in this system. We also demonstrate the energy expansion framework to perform well where external validation is possible. For the fermionic benchmark in particular, we showcase the energy expansion framework's ability to provide results of comparable quality at a small fraction of the resources required for previous computational efforts.

A minimal chain of two quantum dots (QDs) connected via a superconductor has been predicted to host perfectly localized zero-energy states, known as poor man's Majoranas (PMMs). These states are expected to be related to Majorana bound states (MBSs) in longer chains and that the tunable nature of this setup makes it a promising platform to study MBSs. However, realistic systems can only host highly, but not perfectly, localized near-zero-energy states, called imperfect PMMs. These imperfect PMMs have been shown to evolve into trivial states unrelated to MBSs when the chain is extended. Such states are called false PMMs, whereas PMMs that evolve into MBSs in long chains are called true PMMs. Here, using a microscopic model of QD-superconductor arrays, we consider properties of false PMMs and the circumstances under which they appear. In two-site systems, we find that the origin of many false PMMs can be related to zero-energy states occurring in the absence of superconductivity, and we use this analytic understanding to characterize the false PMMs that are typical for different regions of parameter space. In three-site systems, we show that false PMMs can occur via the same mechanism as for two-site systems, but we also find them in regions of parameter space where they are not predicted to exist, thus hinting that the physics of false PMMs can be richer in longer chains. Finally, we demonstrate that the PMMs most stable to perturbations in chemical potential and with the largest excitation gaps appear in a region of parameter space that also has a large ratio of false to true PMMs.

The rapid evolution of quantum computing hardware opens up new avenues in the simulation of energy materials. Today's quantum annealers are able to tackle complex combinatorial optimization problems. A formidable challenge of this type is posed by materials with site-occupational disorder for which atomic arrangements with a low, or lowest, energy must be found. In this article, a method is presented for the identification of the correlated ground-state distribution of both lithium ions and redox electrons in lithium iron phosphate (LFP), a widely employed cathode material in lithium-ion batteries. The point-charge Coulomb energy model employed correctly reproduces the LFP charging characteristics. As is shown, grand-canonical transformation of the energy cost function makes the combinatorial distribution problem solvable on quantum annealing (QA) hardware. The QA output statistics follow a pseudothermal behavior characterized by a problem-dependent effective sampling temperature, which has bearings on the estimated scaling of the QA performance with system size. This work demonstrates the potential of quantum computation for the joint simulation of the electronic and ionic structure in energy materials.

Topological insulators host robust, symmetry-protected localized states at their boundaries, whose existence is dictated by bulk topological invariants. However, the number or spatial positions of these states are typically fixed by lattice geometry, limiting their tunability for practical applications. Here, we propose a synthetic band winding mechanism enabled by inserting additional lattice sites into a generalized Aubry-André-Harper (AAH) model. This design allows independent control over the number and eigenfrequency of localized states. These newly introduced states hybridize with original edge bands, giving rise to multiple windings in the parameter-dependent band dispersion. Under time modulation, we uncover delayed and directional energy transfer processes enabled by these multiband windings, including novel Landau-Zener type pathways in finite systems. Extending this construction to two dimensions leads to a hierarchy of tunable corner and edge states. By permitting the additional sites to be inserted at arbitrary locations, the spatial positioning of localized modes also becomes fully programmable. Our framework offers a highly reconfigurable platform for engineered localization, with promising implications for topological photonic devices, multimode energy transport, and programmable waveguides.

A general hyperelastic constitutive model for hexagonal two-dimensional (2D) materials is presented, wherein the strain energy density is expressed in terms of the invariants of the Green–St. Venant strain tensor. The functional dependence of the strain energy density on the strain tensor is elucidated through the introduction of new invariants that capture the contributions of dilatational, deviatoric, and strain-induced anisotropy effects. The strain energy density is formulated in terms of these new invariants and the corresponding second Piola-Kirchhoff stress tensor is obtained. A specific form of the constitutive model, characterized by seven elastic constants, is presented and a methodology for systematically evaluating the elastic constants is provided. A general expression for the tangent stiffness tensor is provided based on the new invariants. Additionally, the constitutive model is linearized for infinitesimal deformations and expressions for the Young's modulus, Poisson's ratio, and shear modulus are derived. Expressions for the layer modulus and speed of sound of hexagonal 2D materials are presented in terms of the linearized elastic properties. The nonlinear elastic behavior of graphene and molybdenum disulfide is investigated using the proposed approach. The constitutive model is validated using density functional theory data and the linearized elastic properties of graphene and molybdenum disulfide are compared with values reported in the literature. The proposed constitutive model accurately captures the nonlinear elastic response of graphene and molybdenum disulfide and can be adapted to study other 2D materials of hexagonal symmetry.