Effective electrical control and detection of Néel vectors are crucial for antiferromagnetic (AFM) spintronics-based applications. However, the robustness of AFM materials to external magnetic fields and the absence of spin polarization limits their application in magnetic tunnel junctions. Herein, we propose a strategy to achieve both AFM phase transition (Zigzag phase to Néel phase) and electronic phase transition (metal to insulator transition) in $\mathrm{FePS}{\mathrm{e}}_3$ through the electrical control using even weak polarization ferroelectric (FE) materials. FE polarization induces charge accumulation in the $\mathrm{FePS}{\mathrm{e}}_3$ layer, modulating near-neighbor magnetic exchange interactions to trigger the AFM phase transition. Concurrently, this shifts the energy levels of the primarily occupied orbitals away from the Fermi level, consequently opening a band gap. Utilizing this electric field–controllable phase transition, we design three fully electrically controlled $\mathrm{FePS}{\mathrm{e}}_3/\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$-based multiferroic tunneling junctions, exhibiting up to ${10}^{15}\%$ in-plane tunneling magnetoresistance (TMR), 319.27% tunneling electroresistance (TER) and 2178.36% out-of-plane TMR. These giant TMRs and large TERs originate from the changes in the tunneling barrier due to this Néel vector flipping and metal to insulator transition, achieving a performance comparable to the ferromagnetism-based multiferroic tunneling junctions. This flipping effect is robust, as even the weak-polarization, sliding ferroelectric $h$-BN-based multiferroic tunneling junctions can achieve similar performance to $\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$. These findings are expected to provide theoretical guidance for developing high-performance, easy-to-write, and easy-to-read AFM magnetic tunnel junctions.

We studied the structural and magnetic properties of the double perovskite oxides containing mercury, $A_2{\mathrm{MnTeO}}_6$ ($A$ = Hg, ${\mathrm{Hg}}_{0.8}{\mathrm{Ca}}_{0.2}$, and Ca). ${\mathrm{Hg}}_2{\mathrm{MnTeO}}_6$ and (${\mathrm{Hg}}_{0.8}{\mathrm{Ca}}_{0.2}{)}_2{\mathrm{MnTeO}}_6$ crystallize in a rhombohedral phase with $R\overline{3}$ space group, while ${\mathrm{Ca}}_2{\mathrm{MnTeO}}_6$ crystallizes in a monoclinic phase with $P{2}_1/n$ space group. The magnetic susceptibility, specific heat, and neutron diffraction measurements show that, upon cooling, the commensurate antiferromagnetic (AFM) order occurs at 10 K, 8 K, and 11 K for $A$ = Hg, ${\mathrm{Hg}}_{0.8}{\mathrm{Ca}}_{0.2}$, and Ca systems, respectively. The first-principles calculations agree well with the experimental results, showing that the type-I AFM spin arrangement, i.e., magnetic moments aligned ferromagnetically within the planes and antiferromagnetically between adjacent planes, has the lowest total energy compared to other types of long-range order. For all three systems, the magnetic entropy associated with the AFM order amounts to less than 80% of the theoretical value for the high-spin state of ${\mathrm{Mn}}^{2+}$, indicating magnetic frustration across the series. Additionally, an incommensurate order at 5 K was identified by neutron diffraction for ${\mathrm{Hg}}_2{\mathrm{MnTeO}}_6$, which can be described by helicoidal spin order. This observation makes ${\mathrm{Hg}}_2{\mathrm{MnTeO}}_6$ one of the most complex magnetic systems among double perovskite oxides.

We study the stability of vortices in a binary system of Bose-Einstein condensat es, with their wave functions modeled by a set of coupled, time-dependent Gross-Pitaevskii equations. Beginning with an effective two-dimensional system, we identify miscible and immiscible regimes characterized by the inter- and intra-atomic interactions and the initial configuration of the system. We then consider a binary system of Bose-Einstein condensates placed in a rotating harmonic trap and study the single united vortex state in this system. We derive an approximate form for the energy of a single united vortex in the binary system and the critical angular velocity for the global stability of a vortex at the center of the trap. We also compute the metastability onset angular velocity for the local stability of a vortex at the center of the trap. Numerical solutions to the Gross-Pitaevskii equations support these expressions. These rotational results inform us of a novel bimodal formation within the miscible regime of the binary condensate system. We thus demonstrate the nontrivial aspects of vortex stability in interacting binary Bose-Einstein condensates as a result of their nonlinear interactions.

Using the density matrix renormalization group method, we systematically investigate the evolution of the Luttinger integral in the one-dimensional generalized $t\text{−}V$ model as a function of filling and interaction strength, and identify three representative phases. In the weak-coupling regime, the zero-frequency Green's function exhibits a branch-cut structure at the Fermi momentum, and the Luttinger integral accurately reflects the particle density, indicating that the Luttinger theorem holds. As the interaction increases, the spectral weight near the Fermi momentum is gradually suppressed. Interestingly, in the strong-coupling regime near half filling, this singularity is progressively destroyed, accompanied by the emergence of momentum-space zeros in the real part of the Green's function, leading to a novel non-Fermi liquid metallic phase beyond the classic Luttinger liquid paradigm, where the Luttinger surface is no longer defined by a single singularity. While finite spectral weight remains at the original Fermi momentum, the singularity gradually diminishes. Meanwhile, zeros with negligible spectral weight appear away from this momentum, significantly affecting the integral. At exact half filling, a single-particle gap opens, and the Green's function becomes nearly vanishing across the entire momentum space, indicating the complete suppression of low-energy electronic states consistent with the nature of an insulating charge-density-wave phase. These results suggest that the breakdown of the Luttinger theorem is not triggered by a single mechanism, but rather results from the interplay between interaction-driven evolution of excitation modes and the breaking of particle-hole symmetry, ultimately leading to a continuous reconstruction of the generalized Fermi surface from topologically protected to correlation driven.

The reported remarkably high electron mobility of two-dimensional (2D) ${\mathrm{Ga}}_2{\mathrm{O}}_3$ brings this ultrawide band-gap semiconductor to the forefront of high-speed power electronics applications. Using the generalized gradient approximation+U approach, we systematically investigate the electric-field-dependent structural evolution, electronic structures and transport characteristics of 2D ${\mathrm{Ga}}_2{\mathrm{O}}_3$ and its alloys, 2D ${\mathrm{TM}}_{0.5}{\mathrm{Ga}}_{1.5}{\mathrm{O}}_3$ ($\mathrm{TM}=\mathrm{Al}$, In). Our analysis reveals marked anisotropic responses in metal-oxygen bond lengths: field-parallel bonds demonstrate progressive contraction while transverse bonds systematically elongate with the increase in field strength. The nearly free electron gas states emerge in the conduction band of these materials under applied electric fields, progressively shifting toward the conduction-band minimum—a direct consequence of the Stark effect that drives continuous band-gap reduction until complete closure. The band-gap reduction of 2D ${\mathrm{Ga}}_2{\mathrm{O}}_3$ transitions from parabolic dependence in low fields $\left(|E_{fd}|\le 1.02\mathrm{V}/\AA \right)$ to linear regimes at moderate field and high field $\left(|E_{fd}|\ge 1.46\mathrm{V}/\AA \right)$. Notably, 2D ${\mathrm{Ga}}_2{\mathrm{O}}_3$ undergoes a semiconductor-to-metal transition at the critical fields of ±1.48 V/Å, while Al- and In-doped 2D ${\mathrm{Ga}}_2{\mathrm{O}}_3$ alloys exhibit asymmetric closure thresholds due to structural asymmetry. Electron mobility displays a distinctive nonmonotonic field dependence, reaching minima in moderate fields before sharply increasing to maxima at band-gap collapse. The 2D ${\mathrm{In}}_{0.5}{\mathrm{Ga}}_{1.5}{\mathrm{O}}_3$ alloy achieves exceptional field-tunable performance, attaining a peak mobility of $28254.92\mathrm{c}{\mathrm{m}}^2/\mathrm{V}\mathrm{s}$ at −1.87 V/Å, an improvement of more than 200 times over bulk β-${\mathrm{Ga}}_2{\mathrm{O}}_3$. These results not only demonstrate the potential of 2D InGaO alloy as an electron transport material and gate-tunable platform for ultrafast electronics but also establish field-engineering strategies through alloy content for tailoring ultrawide band-gap semiconductor performance.

We theoretically study the spin-orbit interaction in the outer regions of core-shell nanowires that can act as tubular, prismatic conductors. The polygonal cross section of these wires induces nonuniform electron localization along the wire perimeter. In particular, low-energy electrons accumulate in the corner regions, and in the case of narrow shells, conductive channels form along the sharp edges. In contrast, higher-energy electrons are shifted toward the facets. These two groups of states may be separated by large energy gaps, which can exceed the room-temperature energy in the case of triangular geometries. We compare the impact of spin-orbit interaction on the corner and side states of hexagonal and triangular shells grown on hexagonal cores as well as on triangular shells grown on triangular cores. We find that the spin-orbit splitting, and thus the degeneracy of energy states at finite wave vectors, strongly depend on the tube's geometry. We demonstrate that the weak spin-orbit coupling observed in clean wires can be significantly enhanced if the intermixing of core and shell materials takes place. Moreover, we show that the energy spectrum in the presence of spin-orbit interaction allows for estimating the interaction between states and shows that triangular shells can act as three independent wires in the low-energy regime, while they behave as interacting systems at higher-energy ranges.

Recent experimental and computational studies suggest that biexcitons (BX) confined in large ${\mathrm{CsPbBr}}_3$ nanocrystals experience reduced dielectric screening as compared to excitons (X) and trions $\left({\mathrm{X}}^{*}\right)$. Here we provide a physical rationale to explain such a behavior. A characteristic frequency is introduced, which describes the internal dynamics of an exciton within the excitonic complex. By means of effective mass–variational Quantum Monte Carlo simulations, we show that in large nanocrystals, the frequency is similar for X and ${\mathrm{X}}^{*}$, but smaller for BX. Because the frequencies exceed that of the bulk longitudinal optical phonon, this leads to a reduced dielectric constant for BX, which is in contrast to the behavior of strongly confined nanocrystals.

This work investigates the intrinsic second-order nonlinear valley Hall response in $\mathcal{PT}$-symmetric antiferromagnets, highlighting the pivotal role of the quantum metric in driving this phenomenon. We demonstrate that the valley-dependent nonlinear response can be effectively distinguished through the electric-field-induced orbital magnetization, which exhibits opposite signs across inequivalent valleys, analogous to the behavior of orbital angular momentum in the linear valley Hall response. Employing a minimal two-band model on an antiferromagnetic honeycomb lattice, we systematically examine the influence of intrinsic material parameters on the nonlinear valley Hall response. The analysis is further extended to realistic $\mathcal{PT}$-symmetric antiferromagnetic systems and anisotropic semiconductors. Our findings advance the fundamental understanding of valley-based transport in centrosymmetric magnetic systems and open new avenues for theoretical and experimental developments in the field of valleytronics.

The optical absorption spectra and excitonic properties of poly($p$-phenylene vinylene) (PPV) polymers are investigated using first-principles $\mathit{GW}$ and $\mathit{GW}$ plus Bethe-Salpeter equation ($\mathit{GW}$-BSE) method. The calculated optical absorption spectra show much improved agreement with experiment than previous theoretical $\mathit{GW}$-BSE studies. However, we observe a discrepancy in the relative intensity of the two most dominant peaks in the absorption spectra between experimental measurements and calculations, which is caused by the suppression of coherent formation of certain exciton states by the finite chain length of the crystalline PPV samples. The absorption spectra calculated by $\mathit{GW}$-BSE are also shown to be weakly dependent on the mean-field density functional theory (DFT) starting points.

Density matrix embedding theory (DMET) provides a framework to describe ground-state expectation values in strongly correlated systems, but its extension to dynamical quantities is still an open problem. We show one route to obtaining excitations and dynamical spectral functions by using the techniques of DMET to approximate the matrix elements that arise in a single-mode inspired excitation ansatz. We demonstrate this approach in the one-dimensional Hubbard model, comparing the neutral excitations, single-particle density of states, charge, and spin dynamical structure factors to benchmarks from the Bethe ansatz and density matrix renormalization group. Our work highlights the potential of these ideas in building computationally efficient approaches for dynamical quantities.

Crystal engineering is a method for discovering new quantum materials and phases, which may be achieved using external pressure or strain. Chemical pressure is unique in that it generates internal pressure perpetually to the lattice. As an example, GdAlSi from the rare-earth ($R$) $R\mathrm{Al}X$ ($X=\mathrm{Si}$ or Ge) family of Weyl semimetals is considered. Replacing Si with the larger isovalent element Ge creates sufficiently large chemical pressure to induce a structural transition from the tetragonal structure of GdAlSi, compatible with a Weyl semimetallic state, to an orthorhombic phase in GdAlGe, resulting in an inversion-symmetry-protected nodal-line metal. We find that GdAlGe hosts an antiferromagnetic ground state with two successive orderings, at $T_{\mathrm{N}}1=35\mathrm{K}$ and $T_{\mathrm{N}}2=30\mathrm{K}$. In-plane isothermal magnetization shows a magnetic field induced metamagnetic transition at 6.2 T for 2 K. Furthermore, electron-hole compensation gives rise to a large magnetoresistance of $\sim 100\%$ at 2 K and 14 T. Angle-resolved photoemission spectroscopy measurements and density functional theory calculations reveal a Dirac-like linear band dispersion over an exceptionally large energy range of $\sim 1.5\mathrm{eV}$ with a high Fermi velocity of $\sim {10}^6$ m/s, a rare feature not observed in any magnetic topological materials.

Efforts to engineer nearly topological flat bands (TFBs) have opened a promising avenue for realizing the lattice version of fractional quantum Hall states without an external magnetic field. Most of the TFB models are proposed based on Chern insulator (CI) models with isotropic hopping parameters. To our knowledge, rare TFBs are found in the CI models with anisotropy. In this work, we explore the TFBs in the biphenylene network by adding the hopping terms up to the next-nearest neighbor. This model hosts anisotropy which comes from the lattice structure itself and the various nearest-neighbor hoppings. By tuning the hopping parameters, the best TFB with a flatness ratio 21 appears. According to the large flatness ratio, the flat distribution of Berry curvature and band geometry, fractional Chern insulator (FCI) states possibly emerge. Very convincingly, numerical evidence suggests the existence of a $\nu =1/2$ FCI state when hard-core bosons are loaded into this anisotropic TFB model. Our findings not only demonstrate that the TFBs can be proposed in the anisotropic lattices, but also provide a promising platform to explore the geometrical description of FCIs.

Superexchange most often leads to antiferromagnetism in transition-metal perovskite oxides, yet ferromagnetism or ferrimagnetism would be preferred for many applications, for example in data storage. While alloying, epitaxial strain, and defects were shown to lead to ferromagnetism, engineering this magnetic order remains a challenge. We propose, based on density functional theory calculations, a novel route to defect-engineer ferrimagnetism, which is based on preferential displacements of oxygen vacancies due to finite temperature vibrations. This mechanism has an unusual temperature dependence, as it is absent at 0 K, strengthens with increasing temperature, before vanishing with increasing thermal disorder, giving it a unique experimentally detectable signature.

The $\beta$ ensemble is a prototypical model of a single-particle system on a one-dimensional disordered lattice with inhomogeneous nearest-neighbor hopping. The corresponding nonergodic phase has an anomalous critical energy scale, $E_c$: Correlations are present above and absent below $E_c$, as reflected in the number variance. We study the dynamical properties of the $\beta$ ensemble where the critical energy controls the characteristic timescales. In particular, the spectral form factor equilibrates at a relaxation time $t_{\mathrm{R}}\equiv E_c^{-1}$, which is parametrically smaller than the Heisenberg time, $t_{\mathrm{H}}$, given by the inverse of the mean level spacing. Incidentally, the dimensionless relaxation time, ${\tau }_{\mathrm{R}}\equiv t_{\mathrm{R}}/t_{\mathrm{H}}\ll 1$ is equal to the Dyson index, $\beta$. We show that the energy correlations are absent within a temporal window $t_{\mathrm{R}}<t<t_{\mathrm{H}}$, which we term as the correlation void. This is in contrast to the mechanism of equilibration in a typical many-body system. We analytically explain the qualitative behavior of the number variance and the spectral form factor of the $\beta$ ensemble by a spatially local mapping to the Anderson model.

We investigate the nonequilibrium dynamics of the transverse field Ising chain (TFIC) using time-resolved resonant inelastic x-ray scattering (tr-RIXS) in a pump-probe setup within a condensed matter setting. The tr-RIXS spectra reveal distinctive features, including two-kink continua at high energies and oscillatory spectral weight at low energies, both strongly influenced by the pump dynamics. By systematically analyzing the nonequilibrium tr-RIXS cross section under various pump configurations, we demonstrate how the spectra encode detailed information about the system's transient states, capturing instantaneous Hamiltonian parameters and the traversal of equilibrium quantum critical points during dynamic evolution. Notably, we uncover a one-to-one correspondence between oscillatory features in the low-energy spectra and dynamical quantum phase transitions, offering an experimentally accessible approach for their detection. These findings highlight the versatility of tr-RIXS as a powerful tool for studying quantum systems far from equilibrium and their critical phenomena.

We propose a mechanism for Néel switching via suppressed heating in a hybrid magnon-phonon cavity. A terahertz-driven cavity mode couples to a spin-phonon chain, and all particles dissipate energy through baths. Mean-field analysis shows that cavity photons enable switching by imbalancing the spin-density on sublattices—a symmetry-breaking effect absent without the cavity. Switching occurs at low fields $(1-5\mathrm{V}/\mu \mathrm{m})$ and selectively targets low magnon energies and perpendicular magnon modes. Laser fluence, damping, and photon loss tune the switching, advancing cavity-assisted optospintronics.

We report a comprehensive theoretical analysis of the Ruddlesden-Popper layered nickelates ${\mathrm{La}}_{m+1}{\mathrm{Ni}}_m{\mathrm{O}}_{3m+1}$ ($m=1$ to 6) under pressure. These materials have recently received significant attention due to the discovery of superconductivity in some nickelates under pressure. Our results suggest that, while these Ruddlesden-Popper layered nickelates display many similarities, they also show noticeable differences. One of the common features of ${\mathrm{La}}_{m+1}{\mathrm{Ni}}_m{\mathrm{O}}_{3m+1}$ is that the electronic states near the Fermi level are mainly contributed by Ni $3d$ orbitals, slightly hybridized with O $2p$ orbitals. The Ni $d_{3z^2-r^2}$ orbitals display bonding-antibonding, or bonding-antibonding-nonbonding, characteristic splittings, depending on the even or odd number of stacking layers $m$. In addition, the ratio of the in-plane interorbital hopping between $d_{3z^2-r^2}$ and $d_{x^2-y^2}$ orbitals and in-plane intraorbital hopping between $d_{x^2-y^2}$ orbitals was found to be large in ${\mathrm{La}}_{m+1}{\mathrm{Ni}}_m{\mathrm{O}}_{3m+1}$ ($m=1$ to 6), and this ratio increases from $m=1$ to $m=6$, suggesting that the in-plane hybridization will increase as the layer number $m$ increases. In contrast to the dominant $s^{\pm }$-wave state driven by spin fluctuations in the bilayer ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ and trilayer ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$, two nearly degenerate $d_{x^2-y^2}$-wave and $s^{\pm }$-wave leading states were obtained in the four-layer stacking ${\mathrm{La}}_5{\mathrm{Ni}}_4{\mathrm{O}}_{13}$ and five-layer stacking ${\mathrm{La}}_6{\mathrm{Ni}}_5{\mathrm{O}}_{16}$. The leading $s^{\pm }$-wave state was recovered in the six-layer material ${\mathrm{La}}_7{\mathrm{Ni}}_6{\mathrm{O}}_{19}$ with slightly higher calculated pairing strength $\lambda$ than that of the $d_{x^2-y^2}$-wave state. All this evidence suggests that both $s^{\pm }$-wave and $d_{x^2-y^2}$-wave channels are strongly competing in the high-order niceklates based on our random-phase approximation calculations. In general, at the level of the random-phase approximation treatment, the superconducting transition temperature $T_c$ decreases in stoichiometric bulk systems from the bilayer ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ to the six-layer ${\mathrm{La}}_7{\mathrm{Ni}}_6{\mathrm{O}}_{19}$, despite the $m$-dependent dominant pairing. Both in-plane and out-of-plane magnetic correlations are found to be quite complex. Within the in-plane direction, we obtained the peak of the magnetic susceptibility at $\mathbf{q}=(0.6\pi ,0.6\pi )$ for ${\mathrm{La}}_5{\mathrm{Ni}}_4{\mathrm{O}}_{13}$ ($m=4$) and ${\mathrm{La}}_7{\mathrm{Ni}}_6{\mathrm{O}}_{19}$ ($m=6$) and at $\mathbf{q}=(0.7\pi ,0.7\pi )$ for ${\mathrm{La}}_6{\mathrm{Ni}}_5{\mathrm{O}}_{16}$ ($m=5$). Along the out-of-plane direction, four layers are coupled as $\downarrow -\uparrow -\uparrow -\downarrow$ in ${\mathrm{La}}_5{\mathrm{Ni}}_4{\mathrm{O}}_{13}$, five layers are coupled as $\uparrow -\uparrow -\downarrow -\uparrow -\uparrow$ in ${\mathrm{La}}_6{\mathrm{Ni}}_5{\mathrm{O}}_{16}$, and six layers are coupled as $\uparrow -\downarrow -\downarrow -\uparrow -\uparrow -\downarrow$ in ${\mathrm{La}}_7{\mathrm{Ni}}_6{\mathrm{O}}_{19}$.

Modern superconducting radio frequency (SRF) applications demand precise control over material properties across multiple length scales—from microscopic composition, to mesoscopic defect structures, to macroscopic cavity geometry. We present a time-dependent Ginzburg-Landau (TDGL) framework that incorporates spatially varying parameters derived from experimental measurements and ab initio calculations, enabling realistic, sample-specific simulations. As a demonstration, we model Sn-deficient islands in ${\mathrm{Nb}}_3\mathrm{Sn}$ and calculate the field at which vortex nucleation first occurs for various defect configurations. These thresholds serve as a predictive tool for identifying defects likely to degrade SRF cavity performance. We then simulate the resulting dissipation and show how aggregate contributions from multiple small defects can reproduce trends consistent with high-field $Q$-slope behavior observed experimentally. Our results offer a pathway for connecting microscopic defect properties to macroscopic SRF performance using a computationally efficient mesoscopic model.