We reconstruct the spectral pairing theories to enable analytical descriptions of eigenstate spatiotemporal orders in translation-invariant system without prethermal conditions. It is shown that the strong Ising interactions and drivings alone stabilize a class of “cat scar” eigenstates with tunable patterns, which lead to local discrete time-crystal (DTC) dynamics. They exhibit Fock space localization and long-range correlations robust against generic perturbations in a disorder-free scenario. In particular, we introduce a symmetry indicator method to enumerate cat scars, with which a set of unexpected inhomogeneous scar patterns are identified in addition to the ferromagnetic scars found before. These scars enforce DTC dynamics with rigid inhomogeneous patterns, offering a viable way to verify underlying eigenstate properties experimentally. Further, we prove rigorously that the strong Ising interactions enforces a selection rule for perturbations of different orders, which imposes an exponential suppression of spin fluctuations for Floquet eigenstates. Based on this property, three analytical scaling relations are proved to characterize the amplitudes, Fock space localization, and lifetime for DTC dynamics associated with cat scars. We further provide two practical methods to check whether certain DTC phenomena are dominated by single-spin dynamics or due to genuine interaction effects.

Magnetic skyrmions are topological spin structures that arise in chiral magnetic systems which exhibit broken inversion symmetry and high spin-orbit coupling resulting in a sizable Dzyaloshinskii-Moriya interaction. Understanding the local spin texture of skyrmions is a vital metrological step in the development of skyrmionic technologies required for novel logic or storage devices in addition to providing fundamental insight into the nanoscale chiral interactions inherent to these systems. Here, we propose that there exists a radially dependent stray field signature that emanates from magnetic skyrmions. We employ quantitative magnetic force microscopy to experimentally explore this stray field signature. To corroborate the experimental observations a semianalytical model is developed which is validated against micromagnetic simulations. This unique approach provides a route to understand the unique radially dependent field signature from skyrmions, which allows an understanding of the underlying local magnetization profile to be obtained. From a practical standpoint, our results provide a rapid approach to validate outputs from numerical or micromagnetic simulations. This approach could be employed to optimize the complex matrix of magnetic parameters required for fabricating and modeling skyrmionic systems, in turn accelerating the technology readiness level of skyrmionic based devices.

The exploration of nontrivial transport phenomena associated with the interplay between magnetic order and spin-orbit coupling (SOC), particularly in van der Waals (vdW) systems, has gained a resurgence of interest due to their easy exfoliation, ideal for two-dimensional (2D) spintronics. We report the near room temperature quasi-2D ferromagnet, ${\mathrm{Fe}}_4{\mathrm{GeTe}}_2$ from the iron-based vdW family (${\mathrm{Fe}}_n{\mathrm{GeTe}}_2, n=3$,4,5), exhibiting a large anomalous Hall conductivity (AHC), ${\sigma }_{xy}^A\sim 490{\mathrm{\Omega }}^{-1}{\text{cm}}^{-1}$ at 2 K. The near quadratic behavior of anomalous Hall resistivity (${\rho }_{xy}^A$) with the longitudinal resistivity (${\rho }_{xx}$) suggests that a dominant AHC contribution is coming from an intrinsic Berry curvature (BC) mechanism. Concomitantly, the electronic structure calculations reveal a large BC arising from SOC induced gapped nodal lines around the Fermi level, governing such large AHC property. Moreover, we also report an exceptionally large anomalous Hall angle ($\simeq 10.6$%) and Hall factor ($\simeq 0.22 {\mathrm{V}}^{-1}$) values which, so far, are the largest in compared to those for other members in this vdW family.

The recently discovered vanadium-based Kagome metals $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ ($A=\text{K,}\text{Rb,}\text{Cs}$) are of great interest with the interplay of charge density wave (CDW) order, band topology and superconductivity. In this paper, by identifying elementary band representations (EBRs), we construct a two-EBR graphene-Kagome model to capture the two low-energy van-Hove-singularity dispersions and, more importantly, the nontrivial band topology in these Kagome metals. This model consists of $A_g@3g$ ($\text{V}\text{−}{d}_{x^2-y^2/z^2}$, Kagome sites) and $A_2^{″}@2d$ EBRs (Sb1-$p_z$, honeycomb sites). We have investigated the Fermi surface instability by calculating the electronic susceptibility $\chi \left(\mathit{q}\right)$. Prominent Fermi-surface nesting peaks are obtained at three L points, where the $z$ component of the nesting vector shows an intimate relationship with the anticrossing point along M-L. The nesting peaks at L are consistent with the $2\times 2\times 2$ CDW reconstruction in these compounds. In addition, the sublattice-resolved bare susceptibility is calculated and similar sharp peaks are observed at the L points, indicating a strong antiferromagnetic fluctuation. Assuming a bulk $s$-wave superconducting pairing, the helical surface states and nontrivial superconducting gap are obtained on the (001) surface. Analogous to the ${\mathrm{FeTe}}_{1-x}{\mathrm{Se}}_x$ superconductor, our results establish another material realization of a stoichiometric superconductor with nontrivial band topology, providing a promising platform for studying exotic Majorana physics in condensed matter.

We demonstrate that magnetoresistance of creeping charge-density waves in the quasi-one-dimensional conductor $o\text{−}{\mathrm{TaS}}_3$ changes its character from a negative parabolic at $T\gtrsim 10$ K, where it obeys the $1/T^2$ law to a weakly temperature-dependent negative nearly linear one at lower temperatures. The dominant contribution into the negative parabolic magnetoresistance comes from magnetic field induced splitting of the CDW order parameter. The linear magnetoresistance arises due to CDW quantum interference, similar to the scenario of negative linear magnetoresistance in single-electron systems.

We present a study of the self-interstitial point defect formation energies in silicon using a range of quantum chemical theories, including the coupled cluster (CC) method within a periodic supercell approach. We study the formation energies of the X, T, H, and C3V self-interstitials and the vacancy V. Our results are compared to findings obtained using different ab initio methods published in the literature and partly to experimental data. In order to achieve computational results that are converged with respect to the system size and basis set, we employ the recently proposed finite-size error corrections and basis set incompleteness error corrections. Our coupled cluster with singles, doubles, and perturbative triples [CCSD(T)] calculations yield an order of stability of the X, H, and T self-interstitials, which agrees both with quantum Monte Carlo results and with predictions obtained using the random-phase approximation as well as using screened hybrid functionals. Compared to quantum Monte Carlo results with backflow corrections, the CCSD(T) formation energies of X and H are only slightly larger by about $100\mathrm{meV}$. However, in the case of the T self-interstitial, we find significant disagreement with all other theoretical predictions. Compared to quantum Monte Carlo calculations, CCSD(T) overestimates the formation energy of the T self-interstitial by $1.2\mathrm{eV}$. Although this can partly be attributed to strong correlation effects, more accurate electronic structure theories are needed to understand these findings.

We consider nondissipative drag between Bose-condensed exciton polaritons in optical microcavity and embedded superconductors. This effect consists of induction of a nondissipative electric current in the superconductor by motion of polariton Bose condensate due to electron-polariton interaction, or vice versa. Using many-body theory, we calculate the drag density, characterizing magnitude of this effect, with taking into account dynamical screening of the interaction. Hoping to diminish the interaction screening and microcavity photon absorption, we consider atomically thin superconductors (both conventional $s$-wave and copper-oxide $d$-wave) of planar and nanoribbon shapes. Our estimates show that in realistic conditions the drag effect could be rather weak but observable in accurate experiments in the case of dipolar interlayer excitons in transition metal dichalcogenide bilayers. Use of spatially direct excitons, semiconductor quantum wells as the host for excitons, or thin films of bulk metallic superconductors considerably lowers the drag density.

As a three-dimensional (3D) analog of graphene, the cadmium arsenide $\left({\mathrm{Cd}}_3{\mathrm{As}}_2\right)$ based topological Dirac semimetal has attracted enormous research interest recently. In this work, the temperature-dependent terahertz (THz) properties of ${\mathrm{Cd}}_3{\mathrm{As}}_2$ prepared epitaxially are investigated by using THz time-domain spectroscopy. In the regime of $1.5\sim 300$ K, we obtain the optical conductivity of ${\mathrm{Cd}}_3{\mathrm{As}}_2$ and observe a remarkable phonon absorption peak in the range of $1.7\sim 1.8$ THz. More importantly, it is demonstrated that the effects of weak electronic confinement and optical-phonon-limited behavior of carriers are dominated below and above $\sim 60$ K, respectively. The weak electronic confinement can be attributed to the diffusive restoring current in polycrystalline grains of ${\mathrm{Cd}}_3{\mathrm{As}}_2$. Based on the Drude-Lorentz formula and the modified Drude-Smith formula, the temperature dependencies of the characteristic parameters are extracted to describe the carrier and phonon behaviors. These results not only can provide detailed knowledge of the THz response of epitaxially grown ${\mathrm{Cd}}_3{\mathrm{As}}_2$ depending on temperature but also may find applications in optoelectronic devices based on 3D Dirac semimetals.

This paper presents the second harmonic generation (SHG) behavior of a dolmen-type Au nanostructure under surface plasmon (SP) resonance conditions. The SP-enhanced optical fields of the plasmonic metal nanoparticles are suitable for nonlinear wave mixing at the nanoscale. However, the SP-enhanced fields alone are insufficient for second-order nonlinear optics, including the SHG effect. As in traditional nonlinear optics, it is helpful to prepare the metal nanoparticles in a noncentrosymmetric shape to obtain the large SHG signals in the far fields. The dolmen-type Au nanostructure consists of three centrosymmetric rectangular Au nanorods (AuNRs), two of which are arranged in parallel and the third is perpendicular. The U-shaped arrangement breaks the centrosymmetry in this complex nanostructure. The noncentrosymmetric dolmen-type AuNRs exhibited $\sim 25$ times higher SHG signals than the reference single AuNR. According to the numerically mapped surface charges and near fields, the enhanced SHG signals were related to the hybridized bonding state between the dipolar plasmon of the monomer moiety and the quadrupolar plasmon of the dimer moiety. The far-field SHG signals are attributed to the intense near field, which was not centrosymmetric in the nanogap region between the monomer and dimer moieties. The dependence of the SHG signals was also investigated as a function of the separation between the monomer and dimer moieties. The SHG conversion efficiency shows a considerable increase as the separation narrows down to $\sim 20$% of the AuNR size. Our present research demonstrates that second-order nonlinear plasmonic behavior can be engineered by appropriately arranging the constituent simply shaped metal nanoparticles.

The interface itself becomes the device with increasing miniaturization in semiconductor spintronic devices. To obtain the interface and transport behaviors of novel low-dimensional spintronic devices, a fundamental physical understanding of the van der Waals magnetic system is highly desired. The interface and transport properties of the $\mathrm{InN}/{\mathrm{VSi}}_2{\mathrm{P}}_4$ van der Waals magnetic heterostructure are studied systematically by combining first-principles calculations and Schrödinger-Poisson simulations. The ${\mathrm{VSi}}_2{\mathrm{P}}_4$ layer in the $\mathrm{InN}/{\mathrm{VSi}}_2{\mathrm{P}}_4$ van der Waals heterostructure possesses unique electronic and magnetic properties such as a ferromagnetic ground state, stable easy magnetization axis, high Curie temperature, and high mobility. The semiconductor to half metal transition and significantly enhanced conductivities can be realized in the $\mathrm{InN}/{\mathrm{VSi}}_2{\mathrm{P}}_4$ van der Waals heterostructure via electrostatic doping. The sheet carrier density can effectively modulate the conduction band distribution, the average charge position, and the interfacial electric fields of the $\mathrm{InN}/{\mathrm{VSi}}_2{\mathrm{P}}_4$ van der Waals heterostructure. The capacitance of the $\mathrm{InN}/{\mathrm{VSi}}_2{\mathrm{P}}_4$ van der Waals heterostructure increases with the sheet carrier density under a suitable voltage range. Our results indicate that the $\mathrm{InN}/{\mathrm{VSi}}_2{\mathrm{P}}_4$ van der Waals heterostructure is a promising material for the low-dimensional spintronic devices.

A critical element towards the realization of scalable quantum processors is nonlocal coupling between nodes. Scaling connectivity beyond nearest-neighbor interactions requires the implementation of a mediating interaction often termed a quantum bus. Cavity photons have long been used as a bus by the superconducting qubit community, but it has only recently been demonstrated that spin-based qubits in double quantum dot architectures can reach the strong coupling regime and exhibit spin-spin interactions via the exchange of real or virtual photons. Two-qubit gate operations are predicted in the dispersive regime where cavity loss plays a less prominent role. In this work we combine a cross-resonance entangling drive with simultaneous local rotations to propose a framework for a resonant direct-cnot operation, between two nonlocal single-spin qubits dispersively coupled to a common mode of a superconducting resonator. We expect gate times near 100 ns and fidelities above 90% with existing technology.

Chiral van der Waals bilayers with interlayer quantum coupling provide an exceptional platform for manipulating the intrinsic chirality within atomically thin films. In this paper, we delve into the intrinsic chirality of two-dimensional (2D) bilayers possessing time-reversal symmetry (TRS), based on the constitutive equations and circular dichroism (CD), using the methodologies pioneered in recent works by Stauber et al. [Phys. Rev. Lett. 120, 046801 (2018); Phys. Rev. B 98, 195414 (2018)]. We introduce chiral conductivity ${\sigma }_{\mathrm{chir}}$ and demonstrate that ${\sigma }_{\mathrm{chir}}\ne 0$ leads to a nonzero CD, unveiling the distinctive chiral response inherent in a 2D bilayer. According to the criterion, to achieve a chiral response in 2D bilayers while preserving TRS, it is essential to eliminate both mirror and spatial inversion symmetries. Through the derivation of Poynting vectors, it becomes evident that ${\sigma }_{\mathrm{chir}}\ne 0$ assumes a crucial role in realizing chiral plasmons within isotropy 2D bilayers characterized by TRS in the local response limit. We also simulate the chiral response of untwisted bilayer graphene under a bias voltage by means of numerical calculations.

We introduce a compact cluster expansion method constructed over Jacobi and Legendre polynomials to generate highly accurate and flexible machine-learning force fields. The constituent many-body contributions are separated, interpretable, and adaptable to replicate the physical knowledge of the system. In fact, the flexibility introduced by the use of the Jacobi polynomials allows us to impose, in a natural way, constraints and symmetries to the cluster expansion. This has the effect of reducing the number of parameters needed for the fit and of enforcing desired behaviors of the potential. For instance, we show that our Jacobi-Legendre cluster expansion can be designed to generate potentials with a repulsive tail at short interatomic distances, without the need of imposing any external function. Our method is here continuously compared with available machine-learning potential schemes, such as the atomic cluster expansion and potentials built over the bispectrum. As an example, we construct a Jacobi-Legendre potential for carbon by training a slim and accurate model capable of describing crystalline graphite and diamond, as well as liquid and amorphous elemental carbon.

We present a dual-band topological transport of edge states and corner states in a composite acoustic higher-order topological metamaterial (AHOTM) composed of meta-atoms of hollow tubes (HTs) and meta-molecules of opened-hole hollow tubes (OHTs) arrayed as a regular triangle in a hexagonal lattice with $C_{3v}$ symmetry. The AHOTM has two degenerate Dirac points (DPs) in the high-symmetry point $K$ that are separately tuned by the geometry sizes of HTs and OHTs because of their local resonances and weak interactions. The rotation of HTs and OHTs in a unit cell with an angle of $-{30}^{\circ }$ [unit cell A (UCA)] or ${30}^{\circ }$ [unit cell B (UCB)] lifts the degeneracies of the two DPs and produces two entire opened band gaps, in which there are two pairs of topological edge bands. We numerically and experimentally demonstrate topological valley transports of edge states for the AHOTM in two bands. The AHOTM presents frequency-selective topological transport of edge states by rotating one structure and can sustain the topologically robust edge states against some defects. In the two frequency regions, higher-order corner states are also observed in the vertices of the triangular UCB array surrounded by the UCA array, which can also realize frequency-selective higher-order corner states by rotating one structure. This study may pave a feasible way to design multiband and broadband acoustic topological insulators for their flexible manipulation of sound waves.

Information scrambling is nowadays one of the most important topics in various fields of research. Measurement-only circuits (MoCs) exhibit specific information scrambling dynamics, depending on the types of projective measurements and their mutual anticommutativity. The spatial range of the projective measurements in MoCs gives significant influences on circuit dynamics. In this work, we introduce and study long-range MoCs, which exhibit an interesting behavior in their dynamics. In particular, the long-range measurements can induce volume-law phases in MoCs without unitary time evolution, which come from anticommutative frustration of measurements specific to the long-range MoCs. This phenomenon occurs even in MoCs composed of solely two-body measurements, and it accompanies an entanglement phase transition. Crucially, our numerics find evidences that MoCs can be a fast scrambler. Interplay of high anticommutativity among measurements and their long-range properties generates fast entanglement growth in the whole system beyond linear-light-cone spreading.

Topology and many-body localization (MBL) have opened new avenues for preserving quantum information at finite energy density. Resonant delocalization plays a crucial role in destabilizing these phenomena. In this paper, we study the statistical properties of many-body resonances in a disordered interacting Ising model—which can host symmetry-protected topological order—using a Clifford circuit encoding of the real-space renormalization group which allows the resonant properties of the wave functions to be efficiently characterized. Our findings show that both the trivial and topologically ordered MBL phases remain stable in the presence of the resonances but, in the vicinity of the transition between them, localization is destabilized by resonance proliferation. Diverging susceptibility towards the development of an avalanche instability suggests an intervening ergodic phase. We are also able to access the local integrals of motion in the MBL phases and identify the topological edge-mode operators in the ordered phase. Our results have important implications for the stability of MBL and phase transitions between distinct MBL phases with and without symmetries.

The intriguing discovery of bidimensional structures in solid-state physics has motivated the seeking of their analogs in many fields. In this paper, we propose a general scheme to achieve Dirac cones in the microwave domain. It is based on a bidimensional locally resonant metamaterial ruled by a tight-binding Hamiltonian with asymmetric coupling. By specifically controlling the hopping links between meta-atoms, the Dirac cones can be moved in the first Brillouin zone. A proof of this assertion is performed theoretically, numerically, and experimentally using a brick-wall lattice of resonant metallic wires. The results directly evidence that the crystalline description of a subwavelength-scaled microwave system provides a really convenient tabletop platform for investigating the tempting challenges offered in solid-state physics.

We study the prethermal Floquet phases of a two-dimensional Rydberg atom array on a rectangular lattice in the presence of a periodic drive with large drive amplitude. We derive an analytic, albeit perturbative, Floquet Hamiltonian using Floquet perturbation theory (FPT) which charts out these phases and shows that the transition between them can be accessed by tuning the drive frequency. Using both numerical exact diagonalization on finite-size arrays and an analytical first-order Floquet Hamiltonian derived using FPT, we show that these prethermal Floquet phases and the transitions between them can be detected by studying the dynamics of equal-time density-density correlation functions of the Rydberg atoms. Our analysis thus provides a simple way of detecting these phases and associated transitions in this system; such a detection can be achieved in standard experiments, which we discuss.