Magnetic and bond-charge interactions can arise from the same microscopic interaction. Motivated by this observation, we compute magnetic and bond-charge excitation spectra on an equal footing by introducing a simple effective model on a square lattice, which describes antiferromagnetic and $d$-wave superconducting phases around half-filling on the electron-doped side. The magnetic excitation spectrum $\mathrm{Im}\chi (\mathbf{q},\omega )$ has strong weight around $\mathbf{q}=(\pi ,\pi )$ in low energy, and its intensity map exhibits a pencil-tip-like shape in $\mathbf{q}\text{−}\omega$ space. Around $\mathbf{q}=(0,0)$ magnetic excitations show a steep dispersion toward the $(\pi ,\pi )$ and $(\pi ,0)$ directions, which is very similar to a spin-wave dispersion although the system is nonmagnetic. Bond-charge excitations are characterized by four different symmetries and studied for all possible couplings. Bond-charge fluctuations with three different symmetries have large spectral weight around $\mathbf{q}=(\pi ,\pi )$ in a relatively low-energy region and extend widely more than the magnetic excitation spectrum. The $d$-wave symmetry of bond-charge excitations also has sizable spectral weight along the direction $(\pi /2,\pi /2)\text{−}(0,0)\text{−}(\pi /2,0)$ in a low-energy region and exhibits softening around $\mathbf{q}\approx (0.5\pi ,0)$, whereas no such softening is present in the other symmetries. These results capture the essential features observed in electron-doped cuprates and may motivate an experimental test of bond-charge excitations around $\mathbf{q}=(\pi ,\pi )$ on top of the strong magnetic excitations there as well as additional softening in the $d$-wave channel in the $(\pi ,\pi )\text{−}(\pi /2,\pi /2)$ region at low temperatures near the magnetic phase. We extend the present analysis to the hole-doped side and highlight a contrast to the electron-doped side, which includes incommensurate correlations, electronic nematic correlations, and spin and bond-charge resonance modes in the superconducting state.

The moiré system provides a tunable platform for exploring exotic phases of materials. This article shows the possible realization of a non-Abelian state characterized by the Moore-Read wavefunction in a half-filled moiré Chern band, exemplified by twisted ${\mathrm{MoTe}}_2$. This is achieved by introducing short-range repulsive three-body interaction. Exact diagonalization is employed to examine the spectrum in finite size. The incompressibility of the system, the degeneracy of the ground states, and the number of low-energy states provide compelling evidence to identify the ground state as the Moore-Read state. We further interpolate between the three-body interaction and Coulomb interaction to show a phase transition between the composite Fermi-liquid and the Moore-Read state. Finally, we explore the conditions under which the three-body pseudopotential from band mixing effects mimic short-range repulsive three-body interaction. We provide insights toward realizing non-Abelian phases of matter in the moiré system.

Crossed Andreev reflection (CAR) is a scattering phenomenon occurring in a superconductor (SC) connected to two metallic leads, where an incident electron on one side of the SC emerges on the opposite side as a hole. Despite its significance, CAR detection is often impeded by the prevalent electron tunneling (ET), wherein the incident electron exits on the opposing side as an electron. One approach to augment CAR over ET involves employing two antiparallel ferromagnets across the SC. However, this method is constrained by the low polarization in ferromagnets and necessitates the application of a magnetic field. Altermagnets (AMs) present a promising avenue for detecting and enhancing CAR due to their distinct Fermi surfaces for the two spins. Here, we propose a configuration utilizing two AMs rotated by ${90}^{\circ }$ with respect to each other on either side of an SC to enhance CAR. We calculate local and nonlocal conductivities across the AM-SC-AM junction using the Landauer-Büttiker scattering approach. Our findings reveal that in the strong phase of AMs, CAR overwhelmingly dominates nonlocal transport. In the weak phase, CAR can exhibit significant enhancement for larger values of the altermagnetic parameter compared to the scenario where AMs are in the normal metallic phase. As a function of the length of the SC, the conductivities exhibit oscillations reminiscent of Fabry-Pérot interference.

We have investigated the electron pair emission from a Ag(100) surface upon photon absorption which leads to the emission of a $4p$ photoelectron. The subsequent Auger decay proceeds in a single-step process as shown previously. Key finding was the emergence of a diagonal intensity feature in a two-dimensional kinetic energy distribution of the electron pair whose width reveals a characteristic time of 30 as for the dynamics of the core-hole decay process. We utilize this observation as a tool to identify an unexpected pathway of electron pair emission. Once the photon energy is at the threshold of a double $4p$ core hole creation we notice a sizeable broadening of the energy sharing distribution. We associate this process to the excitation of two $4p$ electrons between the Fermi and vacuum level followed by radiation less double electron excitation. This feature is characterized by an energy sum of the pair which disperses linearly with the photon energy. Therefore, we regard it as a double resonant Raman decay.

The characterization of quantum spin liquid phases in Kitaev materials has been a subject of intensive studies over the recent years, both theoretically and experimentally. Most theoretical studies have focused on an isotropically interacting model with its coupling strength being equivalent on each bond in an attempt to simplify the problem. In this Letter, we study an extended spin-1/2 Kitaev-$\mathrm{\Gamma }$ model on a honeycomb lattice with an additional tuning parameter that controls the coupling strength on one of the bonds: We connect the limit of isolated Kitaev-$\mathrm{\Gamma }$ chains, which is known to exhibit an emergent $SU{\left(2\right)}_1$ Tomonaga-Luttinger liquid phase [Yang et al., Phys. Rev. Lett. 124, 147205 (2020)], to the two-dimensional model. We report on an instance, in which properties of the Tomonaga-Luttinger liquid persist for finite interchain coupling forming a phase we call the proximate Tomonaga-Luttinger liquid (pTLL). This pTLL is strongly anisotropic in character analogous to sliding Luttinger liquids, and features spinon-like excitations similar to those of the antiferromagnetic Heisenberg chain. We use numerical exact diagonalization and density matrix renormalization group on various cluster geometries in a complementary way to overcome finite-size limitations.

We develop a simulation procedure for angle-resolved photoemission spectroscopy (ARPES), where a photoelectron wave function is set to be an outgoing plane wave in a vacuum associated with the emitted photoelectron wave packet. ARPES measurements on the transition metal dichalcogenide $1T\text{−}\mathrm{Ti}{\mathrm{S}}_2$ are performed, and our simulations exhibit good agreement with experiments. Analysis of our calculated final state wave functions quantitatively visualizes that they include various waves due to the boundary condition and the uneven crystal potential. These results show that a more detailed investigation of the photoelectron final states is necessary to fully explain the photon-energy- and light-polarization-dependent ARPES spectra.

Photonic platforms invariant under parity ($\mathcal{P}$), time-reversal ($\mathcal{T}$), and duality ($\mathcal{D}$) can support topological phases analogous to those found in time-reversal invariant ${\mathbb{Z}}_2$ electronic systems with conserved spin. Here, we demonstrate the resilience of the underlying spin Chern phases against non-Hermitian effects, notably material dissipation. We identify that non-Hermitian, $\mathcal{P}\mathcal{D}$-symmetric, and reciprocal photonic insulators fall into two topologically distinct classes. Our analysis focuses on the topology of a $\mathcal{P}\mathcal{D}$-symmetric and reciprocal parallel-plate waveguide (PPW). We discover a critical loss level in the plates that marks a topological phase transition. The Hamiltonian of the $\mathcal{P}\mathcal{T}\mathcal{D}$-symmetric system is found to consist of an infinite direct sum of Kane-Mele-type Hamiltonians with a common band gap. This structure leads to the topological charge of the waveguide being an ill-defined sum of integers due to the particle-hole symmetry. Each component of this series corresponds to a spin-polarized edge state. Our findings present a unique instance of a topological photonic system that can host an infinite number of edge states in its band gap.

The ability for real-time control of topological defects can open up prospects for dynamical manipulation of macroscopic properties of solids. A subcategory of these defects, formed by particle dislocations, can be effectively described using the Frenkel-Kontorova chain, which characterizes the dynamics of these particles in a periodic lattice potential. This model is known to host solitons, which are the topological defects of the system and are linked to structural transitions in the chain. This work addresses three key questions. Firstly, we investigate how imperfections present in concrete implementations of the model affect the properties of topological defects. Secondly, we explore how solitons can be injected after the rapid change in lattice potential or nucleated due to quantum fluctuations. Finally, we analyze the propagation and scattering of solitons, examining the role of quantum fluctuations and imperfections in influencing these processes. Furthermore, we address the experimental implementation of the Frenkel-Kontorova model. Focusing on the trapped ion quantum simulator, we set the stage for controllable dynamics of topological excitations and their observation in this platform.

${\mathrm{TlBiSe}}_2$ is considered a potential thermoelectric material due to its ultralow lattice thermal conductivity ${\kappa }_{\mathrm{L}}$ and excellent electrical properties. However, previous studies on the thermal properties of ${\mathrm{TlBiSe}}_2$ only considered the effects of three-phonon scattering, which resulted in significant differences between theoretical and experimental values. In this material, four-phonon scattering processes mainly reduce the thermal transport of acoustic phonons, resulting in an approximate 28% reduction in particlelike thermal conductivity ${\kappa }_{\mathrm{p}}$ at 300 K. The high-frequency optical branches are dense and the phonon lifetime is short, making it easy to generate wavelike phonon tunneling. After considering wavelike thermal conductivity ${\kappa }_{\mathrm{c}}$, ${\kappa }_{\mathrm{L}}$ along the in-plane direction is in good agreement with the experimental values. A nonstandard ${\kappa }_{\mathrm{L}}\propto {\mathrm{T}}^{-0.36}$ dependence is revealed in the cross-plane direction. At high temperatures, ${\kappa }_{\mathrm{c}}$ in the cross-plane direction is greater than ${\kappa }_{\mathrm{p}}$ and ${\kappa }_{\mathrm{c}}$ dominates the thermal transport with 61% of ${\kappa }_L$ at 700 K. In addition to the frequency difference of the phonon pairs, the interbranch phonon group velocity also has an important effect on ${\kappa }_{\mathrm{c}}$. Our work improves the calculational accuracy of thermal conductivity for ${\mathrm{TlBiSe}}_2$ and broadens the field for application of ternary-layered thallium-based semiconductors.

Mutually coupled spin-Hall nano-oscillators (SHNO) can exhibit a binarized phase state, offering pathways to realize Ising machines and efficient neuromorphic hardware. Conventionally, phase binarization is achieved in coupled identical SHNOs via injecting an external microwave at twice the oscillator frequency in the presence of a strong biasing magnetic field. However, this technology poses potential challenges of higher energy consumption and complex circuit design. Moreover, differences in the individual characteristic frequencies of SHNOs resulting from fabrication-induced mismatch in SHNO dimensions may hinder their mutual synchronization. Addressing these challenges, we demonstrate purely dc current-driven mutual synchronization and phase binarization of two nonidentical nanoconstriction SHNOs without biasing magnetic field and microwave injection. We thoroughly investigate these phenomena and underlying mechanisms using micromagnetic simulation. We show how the localized fundamental mode of the spin wave emerging from the magnetization auto-oscillation reinforces the mutual synchronization, while the second-harmonic spin wave induces the phase binarization in the coupled SHNO pair. We further demonstrate the bias field free synchronized SHNO pair efficiently performing a reservoir computing benchmark learning task: sin- and square-wave classification, with 100% accuracy, utilizing the current-tunable phase binarization phenomenon. Our results showcase promising magnetization dynamics of coupled bias field free SHNOs for future computing applications.

We present comprehensive investigations into the structural, superconducting, and topological properties of ${\mathrm{Bi}}_2\mathrm{PdPt}$. Magnetization and heat-capacity measurements performed on polycrystalline ${\mathrm{Bi}}_2\mathrm{PdPt}$ demonstrate a superconducting transition at $\simeq$ 0.8 K. Moreover, muon spin relaxation/rotation ($\mu \mathrm{SR}$) measurements present evidence for a time-reversal symmetry preserving, isotropically gapped superconducting state in ${\mathrm{Bi}}_2\mathrm{PdPt}$. We have also performed density-functional theory (DFT) calculations on ${\mathrm{Bi}}_2\mathrm{PdPt}$ alongside the more general isostructural systems ${\mathrm{BiPd}}_x{\mathrm{Pt}}_{1-x}$, of which ${\mathrm{Bi}}_2\mathrm{PdPt}$ and $\gamma$-BiPd are special cases for $x=0.5$ and $x=1$, respectively. We have calculated the $Z_2$ topological index from our DFT calculations for a range of substitution fractions $x$, between $x=0$ and $x=1$, characterizing the topology of the band structure. We find a nontrivial topological state when $x>0.75$ and a trivial topological state when $x<0.75$. Therefore our results indicate that ${\mathrm{BiPd}}_x{\mathrm{Pt}}_{1-x}$ could be a topological superconductor for $x>0.75$.

We investigate the photocurrent and spectral features in a simplified model of a Mott photovoltaic system consisting of a multilayered insulating heterostructure. The central correlated region is coupled to two metallic leads kept at different chemical potentials. A periodic drive applied to the correlated region produces excited doublons and holons across the Mott gap, which are then separated by a potential gradient, which mimics the polarization-induced electric field present in oxide heterostructures. The nonequilibrium Floquet steady-state is addressed by means of dynamical mean-field theory and its Floquet extension, while the so-called auxiliary master equation approach is employed as impurity solver. We find that impact ionization, identified by a kink in the photocurrent as function of the driving frequency, becomes significant and is generally favored by weak, narrowband hybridizations to the leads beyond a certain strength of the driving field. On the other hand, in the case of a direct coupling to metallic leads with a flat band, we observe a drastic reduction of impact ionization and of the photocurrent itself.

We extend our theory of slow magnons in a two-component Bose-Einstein condensate to the case of two spatial dimensions (2D). We provide a detailed discussion of polaronic corrections to the magnon branch of the elementary excitation spectrum in weakly and strongly interacting regimes. In a dilute system, the latter may be achieved by adjusting interspecies attraction so as to obtain a resonance in the $p$-wave scattering channel. Resonantly enhanced $p$-wave attraction results in the self-localization of magnons and the formation of a magnetoroton. The nature of a ground state beyond the magnetoroton instability remains to be explored. We suggest a dilute $p$-wave crystal of alternating polarization as a possible candidate. In contrast to 3D, the required strength of the attractive potential in the $s$-wave channel here corresponds to tight binding, and we suggest a potential realization of our model with excitons in 2D semiconductors.

Quantum magneto-oscillations have long been a vital subject in condensed matter physics, with ubiquitous quantum phenomena and diverse underlying physical mechanisms. Here, we demonstrate the intrinsic and reproducible DC-current-driven quantum electro-oscillations with a periodicity in the inverse of the current ($1/I$), in quasi-one-dimensional charge-density-wave (CDW) insulator ${\left(\mathrm{Ta}{\mathrm{Se}}_4\right)}_2\mathrm{I}$ and $\mathrm{Ta}{\mathrm{S}}_3$ nanowires. Such oscillations manifest in the nearly infinite Fröhlich conductivity region where the undamped CDW flow forms in a finite electric current, and finally disappear after the oscillation index $n$ reaches 1. A systematic investigation on the effect of temperature and magnetic field establishes that the observed electro-oscillations are a coherent quantum phenomenon. We discuss the possibilities of the physical mechanisms, including the formation of sliding-driven inherent Floquet sidebands. Our results introduce a member in the family of quantum oscillations and shed light on plausible avenues to explore the physics and potential applications of coherent density-wave condensates.

The van der Waals material ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ and the related Sb-substituted compounds $\mathrm{Mn}{\left({\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x\right)}_2{\mathrm{Te}}_4$ are prominent members of the family of magnetic topological insulators, in which rare quantum mechanical states can be realized. In this work, we study the evolution of the charge dynamics in ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ and the Sb-substituted compound $\mathrm{Mn}{\left({\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x\right)}_2{\mathrm{Te}}_4$ with $x=0.26$ under hydrostatic pressure. For ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$, the pressure dependence of the screened plasma frequency, the dc conductivity, and the reflectance at selected frequencies show weak anomalies at $\sim 2$ and $\sim 4$ GPa, which might be related to an electronic phase transition driven by the enhanced interlayer interaction. We observe a pressure-induced decrease in the optical gap, consistent with the decrease in and closing of the energy gap reported in the literature. Both studied materials show an unusual decrease in the low-energy optical conductivity under pressure, which we attribute to the decreasing spectral weight of the Drude terms describing the free charge carrier excitations. Our results suggest a localization of conduction electrons under pressure, possibly due to hybridization effects.

Recently, we have demonstrated helicity-dependent photocurrent (HDPC) in strain-free Dirac semimetal ${\mathrm{Cd}}_3{\mathrm{As}}_2$ nanobelts at room temperature. Here, we investigate their photocurrent response and the photon-helicity modulation at various temperatures and gate voltages. Field effect transistors composed of ${\mathrm{Cd}}_3{\mathrm{As}}_2$ nanobelts exhibit electron mobility as high as 1.8 ${\mathrm{m}}^2$/Vs at 13 K with Ohmic contacts achieved by ${\mathrm{Ar}}^{+}$ plasma etching. Light exposure to a device at low temperatures substantially reduces its conductivity, likely due to light induced charge trapping. The HDPC is tuned by a factor of 3 as the device is cooled from 200 to 13 K. The solid-state back gating modulates the HDPC by about 25% at 13 K, limited by the persistent negative photoconductance. In contrast, the HDPC magnitude can be enhanced two times by the ionic-liquid gating at room temperature. The symmetry analysis excludes the possibility of the circular photon drag effect and supports the circular photogalvanic effect as the origin of the observed HDPC. We also discuss the temperature and gate dependence based on several interplaying factors including channel resistance, carrier recombination and diffusion, spin relaxation and diffusion, as well as band bending at the junctions.

Adiabatic protocols are often employed in state preparation schemes but require the system to be driven by a slowly varying Hamiltonian so that transitions between instantaneous eigenstates are exponentially suppressed. Counterdiabatic driving is a technique to speed up adiabatic protocols by including additional terms calculated from the instantaneous eigenstates that counter diabatic excitations. However, this approach requires knowledge of the full eigenspectrum meaning that the exact analytical form of counterdiabatic driving is only known for a subset of problems, e.g., the harmonic oscillator and transverse field Ising model. We extend this subset of problems to include the general family of one-dimensional noninteracting lattice models with open boundary conditions and arbitrary onsite potential, tunneling terms, and lattice size. We will derive a general analytical form for the counterdiabatic term for all states of lattice models, including bound and in-gap states which appear, e.g., in topological insulators. We also derive the general analytical form of targeted counterdiabatic driving terms which are tailored to enforce the dynamical state to remain in a specific state. As an example of the use of the derived analytical forms, we consider state transfer using the topological edge states of the Su-Schrieffer-Heeger model. The derived analytical counterdiabatic driving Hamiltonian can be utilized to inform control protocols in many-body lattice models or to probe the nonequilibrium properties of lattice models.

A new nonlinear magnetothermal effect, namely nonlinear planar Nernst effect (NPNE), has been recently predicted in nonmagnetic topological insulators and Weyl semimetals. Both of the asymmetric energy dispersion and the in-plane magnetic field play significant roles in the reported materials. Here, we prove that the NPNE can also be generated in magnetic/nomagnetic topological heterostructures in the presence of an in-plane magnetization and in the absence of asymmetric energy dispersion. It is found that the NPNE has a quantum origin from the asymmetric magnon scattering and exhibits a cosine dependence on the orientation of the magnetization with respect to the direction of the temperature gradient ($x$ direction).

The control of any type of quantum hardware invariably necessitates time-dependent driving. If the basis depends on the control parameter, the presence of a time-dependent control field yields an extra term in the Schrödinger equation that is often neglected. Here, we examine the effect of this term in a flux-controlled Majorana junction. We show that a time-varying flux gives rise to an electromotive force, which is highly nonlinear when truncating to the junction's low-energy degrees of freedom. As a result, it compromises the robustness of the ground-state degeneracy present in the absence of the drive. The resulting flattening of the energy spectrum can be measured by a strong suppression of the dc supercurrent.

The Anderson localization transition in quantum graphs has garnered significant recent attention due to its relevance to many-body localization studies. Typically, graphs are constructed using top-down methods. Here, we explore a bottom-up approach, employing a simple local rewriting rule to construct the graph. Through the use of ratio statistics for the energy spectrum and Kullback-Leibler divergence correlations and multifractal analysis for the eigenstates, numerical analysis demonstrates that slight adjustments to the rewriting rule can induce a transition from a localized to an extended quantum phase. This extended state exhibits nonergodic behavior, akin to the nonergodic extended phase observed in the Porter-Rosenzweig model and suggested for many-body localization. Thus, by adapting straightforward local rewriting rules, it becomes feasible to assemble complex graphs from which desired global quantum phases emerge. This approach holds promise for numerical investigations and could be implemented in building optical realizations of complex networks using optical fibers and beam splitters.