We use junctions of critical spin-1 chains as the basic elements to construct a honeycomb network that harbors a gapless chiral spin liquid phase. The low-energy modes are described by spin-1 Majorana fermions that form a two-dimensional Fermi surface when the interactions at the junctions are tuned to the vicinity of chiral fixed points with staggered chirality. We discuss the physical properties and the stability of this chiral spin liquid phase against perturbations from the point of view of the effective field theory for the network. We find clear connections with the excitation spectrum obtained in parton constructions on the kagome lattice.

We propose an electrostatically coupled phononic metamaterial for angular velocity sensing, whose sensitivity is immune to external damping and local material defects; furthermore, the coupling strength and frequency range of bands are tunable by the voltages applied to the lattices. The induced Coriolis force could open up the topologically nontrivial band gaps, and the edge band bandwidths increase gradually with respect to the angular velocity. Hence, according to the dispersion relation of edge modes and the difference between edge states and bulk states, an angular velocity sensing method based on the band structure variation of the tunable phononic metamaterial is proposed by using the phase difference and amplitude ratio of edge states. In contrast to traditional amplitude-dependent microelectromechanical system gyroscopes, such a frequency-dependent angular velocity sensing method makes the sensitivity independent of the external damping coefficient. In addition, the topological properties ensure the robustness of the proposed angular velocity sensing method against local defects. The tunable metamaterial-based angular velocity sensing mechanism provides a bridge between physics and engineering applications.

Second-order nonlinear optical effects in monolayer transition-metal dichalcogenides (ML TMDCs) have attracted significant attention; these are almost exclusively associated with their in-plane second-order nonlinear susceptibility arising from the intrinsically broken in-plane inversion symmetry. However, a key challenge is the induction and manipulation of out-of-plane symmetry breaking that governs out-of-plane polarized second-order nonlinear processes such as second-harmonic generation in ML TMDCs. Using first-principle density functional theory, we show that applying an electrostatic field perpendicular to the monolayer plane can induce out-of-plane second-order nonlinear susceptibility (${\chi }_{zxx}={\chi }_{zyy}$) in the visible wavelength range in the four most representative TMDCs (${\mathrm{MoS}}_2, {\mathrm{MoSe}}_2, {\mathrm{WS}}_2, {\mathrm{WSe}}_2$), with magnitude comparable to their intrinsic in-plane components (${\chi }_{yyy}$). The susceptibility peak values (${\chi }_{zxx}^{*}, {\chi }_{yyy}^{*}$), with incident energy around half of the C exciton energy in each material, exhibit a linear dependence on the applied field strength $E$. This behavior originates from the joint effects of field-induced asymmetric out-of-plane charge density distribution and structural deformation. Although the asymmetric charge distribution predominantly governs this effect, the structural deformation also contributes to the overall response in all four ML TMDCs. To accurately describe and predict the induced out-of-plane nonlinear susceptibility in ML TMDCs under varied $E$, we introduce a structural deformation descriptor $\tau$ which exhibits a linear correlation with ${\chi }_{zxx}^{*}$ to measure the magnitude of the electric-field-induced out-of-plane dipole moment. Our study provides an easy-to-implement approach for generating and tuning the out-of-plane second-order optical nonlinearity in ML TMDCs and hence opens a different avenue for investigating active control of their second-order nonlinear optical processes.

A Coulomb impurity of charge $Ze$ is known to destabilize the ground state of undoped graphene with respect to creation of screening space charge when $Z$ exceeds the critical value $Z_c=1/2\alpha$ set by the material's fine structure constant $\alpha$. Recent experimental advances have made it possible to explore this transition in a controlled manner by tuning $Z$ across the critical point. Combined with relatively large value of $\alpha$ this makes it possible to study graphene's screening response to a supercritical impurity $Z\alpha \gg 1$ when the screening charge is large using a Thomas-Fermi analysis. The character of screening in this regime is controlled by the dimensionless screening parameter $Z{\alpha }^2$. Specifically, for a circular impurity cluster in the weak-screening regime $Z{\alpha }^2\ll 1$ most of the screening charge is found to reside outside the cluster. The strong-screening regime $Z{\alpha }^2\gg 1$ provides a realization of the Thomson atom: Most of the screening charge is inside the cluster, nearly perfectly neutralizing the source charge with the exception of a transition layer near the cluster's edge where the rest of the space charge is localized.

Armed with the extended semiclassical theory, we propose a Hall effect at $EB$ order, particularly in Weyl semimetals (WSMs). We dub this effect the in-plane magnetononlinear Hall effect (IMHE) since the Hall current and the driving electric and magnetic fields are confined in the same plane. Similar to the intrinsic anomalous Hall effect, the IMHE features an intrinsic nature because it arises from the field-induced anomalous velocity $\mathit{E}\times {\mathbf{\Omega }}^B$, where ${\mathbf{\Omega }}^B$ is the Berry curvature induced by the magnetic field through both minimal and Zeeman couplings. Employing the low-energy effective Hamiltonian of WSMs, we reveal that the tilt of the Weyl cone is the key to triggering this effect. Notably, we find that the IMHE can survive even when the chiral anomaly disappears because ${\mathbf{\Omega }}^B$ (as the correction of the conventional Berry curvature) does not contribute to the monopole charge. Furthermore, we elucidate the interplay between minimal and Zeeman couplings for this effect. Finally, the experimental strategy to detect the IMHE is discussed.

We study the nondegenerate one-dimensional two-orbital Hubbard model with an interorbital Coulomb interaction. By means of the density-matrix renormalization group technique, we calculate the local single-particle density of states and the optical conductivity at zero temperature. We find that a finite interorbital Coulomb repulsion $V$ generates a different class of states within the Mott-Hubbard band which has a large weight of holon-doublon pairs, which we hence call the holon-doublon band (HDB). When $V$ is sufficiently large, the HDB specifies the gapless low-energy excitations, and the system becomes an unconventional correlated metal. Optical conductivity results resolve different metallic behaviors for zero and finite interaction $V$. Compared to the case without an interorbital interaction, the conductivity is strongly reduced in the correlated holon-doublon metal for finite $V$. In addition, the absorption spectrum is dominated by the HDB, which is clearly distinguishable from the Mott-Hubbard band.

In this paper we characterize the macroscopic electromagnetic response of a nested wire metamaterial with a high degree of bulk structural asymmetry. The unit cell of the considered metamaterial contains two sets of metallic wires: one set consisting of an array of straight wires and another formed by a racemic array of helical-shaped wires. We study the scattering of electromagnetic waves in a metamaterial slab and show that the electromagnetic coupling between both arrays of wires can originate Fano resonances with narrow line shape. The origin of the resonances is rooted in the formation of a subradiant mode in the metamaterial wherein the net polarization vector vanishes. We envision that the proposed configuration, with sharp resonances whose quality factor can be greatly enhanced by tuning the structural parameters of the wires, may have promising applications in sensing and switching in a broad frequency range from the microwave regime up to terahertz frequencies.

The implementation of optimal strictly localized atomic orbitals basis for plutonium (Pu) using norm-conserving pseudopotential density-functional theory (DFT) is presented. The basis set was applied to the α, β, γ, δ, ${\delta }^{\prime }$, and ε phases of Pu, δ-Pu surface, and δ-PuGa alloys. The computed properties of the Pu phases and δ-Pu surface were in good agreement with both available experimental data and prior DFT calculations based on plane-wave methodologies. Results for the δ-PuGa alloys were also in good agreement with experimental data. The reliability of the basis set was further demonstrated by using ab initio molecular dynamics to model the diffusion coefficient and activation barrier for atomic diffusion in a δ-PuGa alloy.

Unlike momentum-dependent Rashba spin splitting, materials exhibiting intrinsic momentum-independent unidirectional spin polarization, also known as persistent spin texture (PST), in the full Brillouin zone are scarce. In this work, a list of characteristic electronic properties for identifying an ideal PST material is provided based on earlier analytical models, and a semiconductor, the MgTe(110) facet, is proposed which satisfies all these conditions and exhibits PST in the full Brillouin zone. The atomic arrangement in this particular facet exhibits three basic symmetries found in nature: rotation, reflection, and translation. Using the method of invariance, an effective Hamiltonian is constructed which reproduces the results obtained using the density functional theory. Further, mono/few layers of MgTe (110) facets of the zinc-blende structure are proposed for a ferromagnet-free nonballistic spin-field-effect transistor (s-FET) that combines both the spin-Hall effect and the inverse spin-Hall effect, thus harmonizing spintronics with conventional electronics. Although only quantum well structures have been experimentally studied for nonballistic s-FET under the stringent condition of equal Rashba and Dresselhaus strength, PST originating intrinsically in the proposed two-dimensional structures makes them an ideal alternate.

We study the influence of quantizing perpendicular magnetic fields on the ground state of a bilayer with electron and hole fluids separated by an opaque tunnel barrier. In the absence of a field, the ground state at low carrier densities is a condensate of $s$-wave excitons that has spontaneous interlayer phase coherence. We find that a series of phase transitions emerge at strong perpendicular fields between condensed states and incompressible incoherent states with full electron and hole Landau levels. When the electron and hole densities are unequal, condensation can occur in higher angular momentum electron-hole pair states and, at weak fields, break rotational symmetry. We explain how this physics is expressed in dual-gate phase diagrams, and predict transport and capacitively probed thermodynamic signatures that distinguish different states.

We demonstrate a microwave power-to-electrical energy conversion in a resonator-coupled double quantum dot. The system, operated as a photodiode, converts individual microwave photons to electrons tunneling through the double dot, resulting in an electrical current flowing against the applied voltage bias at input powers down to 1 fW. The device attains a maximum power harvesting efficiency of 2%, with the photon-to-electron conversion efficiency reaching 12% in the single-photon absorption regime. We find that the power conversion depends on thermal effects showing that thermodynamics plays a crucial role in the single-photon energy conversion.

When applying two-dimensional materials in advanced electronics, catalysts, and quantum computing, point defects play crucial roles. However, experimentally determining the local structures and charge states of these defects is challenging, and the use of first-principles calculations is beneficial. Yet the number of studies in this area remains limited compared to those on three-dimensional materials, which is primarily due to difficulties in corrections related to finite model sizes. In this study, we introduce a method to automate these corrections and to reduce computational costs. Furthermore, we explore the impact of ill-defined dielectric profiles on the corrections and demonstrate that the selection of the profiles potentially affects the corrections for defects far from the surfaces significantly. We also illustrate how to correct the eigenvalues of host-derived orbitals in calculations of charged defects.

Substrate induces mechanical strain on perovskite devices, which can result in alterations to its lattice dynamics and thermal transport. Herein, we have performed a theoretical investigation on the anharmonic lattice dynamics and thermal property of perovskite ${\mathrm{Rb}}_2{\mathrm{SnBr}}_6$ and ${\mathrm{Cs}}_2{\mathrm{SnBr}}_6$ under strains using perturbation theory up to the fourth-order terms and the unified thermal transport theory. We demonstrate a pronounced hardening of low-frequency optical phonons as temperature increases, indicating strong lattice anharmonicity and the necessity of adopting temperature-dependent interatomic force constants in the lattice thermal conductivity (${\kappa }_{\mathrm{L}}$) calculations. It is found that the low-lying optical phonon modes of ${\mathrm{Rb}}_2{\mathrm{SnBr}}_6$ are extremely soft and their phonon energies are almost strain independent, which ultimately lead to a lower ${\kappa }_{\mathrm{L}}$ and a weaker strain dependence than ${\mathrm{Cs}}_2{\mathrm{SnBr}}_6$. We further reveal that the strain dependence of these phonon modes in the ${\mathrm{A}}_{2}X{B}_6$ -type perovskites weakens as their vibrational frequency decreases. This study deepens the understanding of lattice thermal transport in perovskites ${\mathrm{A}}_2{X\mathrm{B}}_6$ and provides a perspective on the selection of materials that meet the expected thermal behaviors in practical applications.

The interplay between entropy transport and charge carriers–paramagnon interaction in the Onsager linear system has been a subject of debate due to the limited theoretical and experimental understanding of paramagnon heat capacity. In this study, we investigate this interplay in an anisotropic layered magnetic system using cluster mean-field theory with spin quantum correlations. By examining spin correlation functions between different spins with various types of clustering, we derive the spin correlation function as a function of distance and temperature for the interlayer clusters both below and above the magnetic order phase transition. Our analysis reveals that paramagnons characterized by pronounced spin correlations among interlayer nearest-neighbor spins exhibit a nonzero heat capacity, providing valuable insights into the dynamics of entropy transport. The findings align with experimental observations, lending strong support to the validity of the paramagnon-drag thermopower concept. This study sheds light on the intricate dynamics and thermodynamic properties of paramagnons, advancing our understanding of entropy transport in complex systems.

Pr-containing perovskite cobaltites exhibit unusual valence transitions, coupled to coincident structural, spin-state, and metal-insulator transitions. Heteroepitaxial strain was recently used to control these phenomena in the model ${\left({\mathrm{Pr}}_{1-y}{\mathrm{Y}}_y\right)}_{1-x}{\mathrm{Ca}}_x\mathrm{Co}{\mathrm{O}}_{3-\delta }$ system, stabilizing a nonmagnetic insulating phase under compression (with a room-temperature valence/spin-state/metal-insulator transition) and a ferromagnetic (FM) metallic phase under tension, thus exposing a potential spin-state quantum-critical point. The latter has been proposed in cobaltites and can be probed in this system as a function of a disorder-free variable (strain). We study this here via thickness-dependent strain relaxation in compressive $\mathrm{SrLaAl}{\mathrm{O}}_4$(001)/${\left({\mathrm{Pr}}_{0.85}{\mathrm{Y}}_{0.15}\right)}_{0.70}{\mathrm{Ca}}_{0.30}\mathrm{Co}{\mathrm{O}}_{3-\delta }$ epitaxial thin films to quasicontinuously probe structural, electronic, and magnetic behaviors across the nonmagnetic-insulator/FM-metal boundary. High-resolution x-ray diffraction, electronic transport, magnetometry, polarized neutron reflectometry, and temperature-dependent magnetic force microscopy provide a detailed picture, including abundant evidence of temperature- and strain-dependent phase coexistence. This indicates a first-order phase transition as opposed to spin-state quantum-critical behavior, which we discuss theoretically via a phenomenological Landau model for coupled spin-state and magnetic phase transitions.

We investigate the superconducting properties of two-dimensional topological materials, in particular the quantum spin Hall system with on-site pairing. Accordingly, three types of edge states are found, which are topologically protected fermionic states at zero field, topologically protected Majorana states at finite Zeeman fields, and unpaired fermionic states without topological protection. Applications to transition metal dichalcogenides are also discussed.

We describe a scheme to exchange fermion parity between two pairs of Majorana bound states mediated by coupling with a centralized quantum dot. We formulate such a scheme for Majorana bound states nucleated in the Josephson vortices formed in a fourfold crossroads junction of planar topological superconductors in the presence of a perpendicular magnetic field. This platform yields several advantages to the execution of our scheme as compared to similar ideas proposed in wire geometries, including control over the positions of the Majorana bound states (MBS) and hence a tunable coupling with the quantum dot. We show that moving the MBS along the junctions through voltage pulses can facilitate parity exchange via a two-step process, with intermediate projective measurements of the quantum dot charge. Thus we formulate a way to achieve single qubit operations for MBS in extended Josephson junctions through projective measurements of quantum dot charge. We also discuss the physical viability of our scheme with a particular focus on changes in quantum dot energy levels as a measurable indicator of the success of the scheme.

Conducting metal oxides offer many advantages for novel electronics applications, including sensors, fuel cells, piezoelectric devices, and microelectronic circuits, due to their conductivity, hardness, and chemically inert surfaces. In particular, their high electrical conductivity and mechanical properties make these materials suitable for microelectromechanical and nanoelectromechanical system (MEMS/NEMS) devices. NEMS switches have great potential for next-generation electronic computing associated with scalability to small dimensions, low power consumption, and (relatively) high speed. Oxygen-deficient Ti oxides with ordered planes of vacancies (${\mathrm{Ti}}_n{\mathrm{O}}_{2n-1}$, Magnéli phases) are good candidates for NEMS applications because of their metallic conductivity, environmental resistance, and low cost, as compared with other conductive oxides like ${\mathrm{RuO}}_2$. Although Ti suboxides have been produced in crystalline form, various synthesis methods may also produce amorphous material. In this paper, we focus on the structural and electrical transport properties of several Ti suboxides. In particular, we examine the effects of temperature, transition-metal dopants, and amorphization on these structural and electronic properties and the potential applicability of Magnéli phase Ti suboxides for NEMS switch applications.

The front dynamics in the Harper (or Aubry-André) model (which has a localization transition) is investigated using two different settings: the particle number front, where the system is at zero temperature and, initially, the particle numbers differ on the two sides, and the temperature front, where the two sides have different temperatures initially. The two differently prepared half systems are connected suddenly, and the following dynamics is investigated. In the extended phase, the dynamics is ballistic, similar to the dynamics of a pure system. At the critical point, one finds a power-law time dependence of the particle number and the entanglement entropy of the zero-temperature setting. In the localized phases, the observables oscillate around an average value, which is independent of the system size. The particle number front shapes have been investigated at the zero-temperature setting: In the extended phase they scale together exactly as in the homogeneous XX chain; however, at the critical point the scaling relation contains a power ($t^{0.55}$) of time. The mutual information between neighboring intervals at the front has been calculated, and it is proportional to the logarithm of the interval length and also to the logarithm of time in the extended phase and at the critical point. The prefactors of the time and size dependence are equal for the zero-temperature process but differ for the finite-temperature front.