We theoretically investigate emergent impedance induced by domain wall (DW) dynamics in antiferromagnets (AFMs). Emergent impedance, arising from a combined action of spin-transfer torque and spinmotive force, was previously predicted and observed in spiral magnets. Here, we develop a formalism for the electrical response of an AFM DW under ac currents and obtain analytical expressions for the resulting emergent impedance. We find that two dynamical modes play separate roles in the emergent impedance: Translational motion of the DW center generates a contribution proportional to its velocity, analogous to that arising from the corresponding motion of a spiral magnet. Another contribution, unique to AFM DWs, originates from the time-dependent canting of the sublattice magnetizations localized within the moving DW, whose magnitude is inversely proportional to the AFM exchange coupling constant. The competition between these two distinct contributions determines the sign and magnitude of the imaginary part of the emergent impedance at subresonant frequencies. Our results provide fundamental insight into electron transport in AFMs and open avenues for AFM-based spintronics devices.

Lead-free ferroelectrics based on the $\left(\mathrm{K},\mathrm{Na}\right){\mathrm{NbO}}_3$ solid solution have emerged as strong candidates to replace lead-containing ceramics due to their excellent piezoelectric and thermal properties. However, their practical application is hindered by high leakage currents and low ceramic density. Doping provides a strategy for enhancing material performance, highlighting the need for a deeper understanding of defect chemistry. For this purpose, we investigated the equilibrium of intrinsic defects and the doping behavior of Ca and Fe in the boundary phase ${\mathrm{KNbO}}_3$. We have found all elements to be prone to vacancy formation. Moreover, Ca acts as a donor and leads to a large concentration of charge carriers and therefore larger electronic conductivity. On the other hand, Fe behaves as an acceptor and shows oxidation states ranging from $2^{+}$ to $5^{+}$, whose concentrations depend on the total Fe concentration. As a consequence, the number of charge carriers and the electronic conductivity are reduced.

Operator spreading under stroboscopic time evolution under a unitary is studied. An operator Krylov space is constructed and mapped to orthogonal polynomials on a unit circle (OPUC), as well as to the Krylov space of the edge operator of the Floquet transverse field Ising model with inhomogeneous couplings (ITFIM). The Verblunsky coefficients in the OPUC representation are related to the Krylov angles parametrizing the ITFIM. The relations between the OPUC and spectral functions are summarized and several applications are presented. These include derivation of analytic expressions for the OPUC under persistent $m$-periodic dynamics, and the numerical construction of the OPUC for autocorrelations of the homogeneous Floquet-Ising model as well as the $Z_3$ clock model. The numerically obtained Krylov angles of the $Z_3$ clock model with long-lived period tripled autocorrelations show a spatial periodicity of six, and this observation is used to develop an analytically solvable model for the ITFIM that mimics this behavior.

In magnetic systems, the response functions exhibit power-law behavior in the vicinity of transition temperature, $T_{\mathrm{C}}$, and the associated critical exponents, which depend on the range and nature of the underlying interactions, characterize the scaling behavior of the respective system. Here, we analyze the magnetic behavior of trivially treated Ni and nontrivial Gd using computational and experimental investigations, respectively. Our findings suggest that (i) the critical behavior remains the same on either side of $T_{\mathrm{C}}$, (ii) the critical behavior associated with local electron moments remains unaffected by the magnetic field, and (iii) in Gd, the role of competing interactions becomes evident.

Pseudobrookite ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$ single crystal with highly disordered $\mathrm{F}{\mathrm{e}}^{3+}/\mathrm{T}{\mathrm{i}}^{4+}$ occupation was successfully grown using the floating zone technique. The bifurcation of zero-field cooling and field cooling curves of the dc magnetic susceptibilities and the frequency-dependent shift of the ac magnetic susceptibilities exhibits distinct longitudinal spin freezing in ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$ at $T_L\sim 35$ K. The existence of the cluster spin glass state was observed in ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$ below $T_L$. Additionally, the frequency dispersion behavior of dielectric permittivity indicates the existence of the cluster dipolar glass state in ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$. The observed nonzero magnetodielectric effect and the magnetic field dependent dynamic magnetoelectric coefficient reveal a correlated behavior between these two glass states, showing that ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$ is a rare multiglass magnetoelectric coupling material. Notably, large and anisotropic remnant electric polarization was found, where $\mathrm{\Delta }{\mathit{P}}_{c-\mathrm{axis}}\sim -1.6\times {10}^4\mu \mathrm{C}{\mathrm{m}}^{-2}$ and $\mathrm{\Delta }{\mathit{P}}_{b-\mathrm{axis}}\sim 3.5\times {10}^4\mu \mathrm{C}{\mathrm{m}}^{-2}$ at $T=10$ K. But the sign of $\mathrm{\Delta }\mathit{P}$ was not reversed by the electric field, implying that ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$ is a pyroelectric material. Our research further demonstrates that the highly distorted FeO6 octahedron induces the anisotropic $\mathrm{\Delta }\mathit{P}$ and the multiglass state, suggesting that clusters of spin glass and dipolar glass coexist in the same region in ${\mathrm{Fe}}_2{\mathrm{TiO}}_5$.

Guided by symmetry principles, we construct an effective-field theory that captures the long-wavelength dynamics of two-dimensional vortex crystals observed in rotating Bose-Einstein condensates trapped in a harmonic potential. By embedding the system into Newton–Cartan space-time and analyzing its isometries, we identify the appropriate space-time symmetry group for trapped condensates at finite angular momentum. After introducing a coarse-grained description of the vortex lattice, we consider a homogeneous equilibrium configuration and discuss the associated symmetry-breaking pattern. We apply the coset construction method to identify covariant structures that enter the effective action and discuss the physical interpretation of the inverse Higgs constraints. We verify that Kohn’s theorem is satisfied within our construction and subsequently focus on the gapless sector of the theory. In this regime, the effective theory accommodates a single gapless excitation–the Tkachenko mode–for which we construct both the leading-order and next-to-leading-order actions, the latter including cubic interaction terms.

We present a first-principles and quantum transport study of proximity-induced spin-orbit torque (SOT) in graphene on a trigonal CrSBr monolayer. Density functional theory combined with nonequilibrium Green's function calculations shows that the CrSBr substrate induces spin polarization and a sizable exchange splitting in the graphene Dirac states. The resulting current-driven spin density in graphene generates a self-SOT on the Dirac electrons. The proximity-induced exchange field breaks time-reversal symmetry and gives rise to a purely odd SOT component, while the even contribution vanishes. The torque magnitude exhibits a strong angular dependence with phase shifts arising from the noncollinearity between the CrSBr magnetization and the induced magnetic moments in graphene. Monte Carlo simulations based on the calculated exchange parameters predict a Curie temperature of $T_{\mathrm{c}}\approx 304\mathrm{K}$, confirming the robustness of ferromagnetism in the trigonal CrSBr monolayer. These results identify graphene/CrSBr heterostructures as a promising platform for room-temperature two-dimensional spintronics.

Motivated by recent advances in transition metal dichalcogenide (TMD) moiré materials, we propose TMD moiré multilayers as a platform for realizing an approximately SU(4)-symmetric triangular Kondo lattice, generalizing the concept of the double quantum dot model. Our model extends the conventional Kondo lattice by incorporating a three-site exchange of SU(4) local moments, which drives spontaneous time-reversal and lattice symmetry breaking. Using a parton mean-field approach, we map out the phase diagram as a function of three-site exchange and hole doping. In the Kondo-unscreened regime, we identify Mott insulating phases, including bond-ordered states and a chiral spin liquid. With increasing doping, Kondo hybridization gives rise to a heavy Fermi liquid that exhibits distinct patterns of lattice symmetry breaking, with or without topological responses. We conclude with directions for future study.

Several anomalous symmetry-breaking states have been reported at temperatures well below the charge-density wave (CDW) transition in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. Whether these states are concomitant with an electronic structure change remains elusive. Here, we present a study of the optical properties of ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ in the CDW state. In addition to the CDW gap, which opens below $T_{\text{CDW}}$ = 91 K, a conspicuous suppression of the optical conductivity develops around 200 ${\text{cm}}^{-1}$ below $T^{*}\simeq 50\mathrm{K}$, indicating the opening of another low-energy gap well below the CDW transition. A detailed Drude-Lorentz analysis manifests that, similar to the CDW gap, this low-energy gap also opens in the saddle-point bands with $\mathrm{V}\text{−}3d$ character near the $M$ point. Our experimental results not only reveal a Fermi surface reconstruction coinciding with the emergence of the anomalous symmetry-breaking states, but also underline the importance of the $\mathrm{V}\text{−}3d$ orbitals in driving these anomalous states in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$.

We investigated quantum states of ultracold hydrogen atoms in a combined potential comprising the H-He film interaction in the presence of a substrate and the Earth's gravitational field. We show that the shift and width of the gravitational quantum states are determined by the complex scattering length for the H-He film/substrate potential. We demonstrate that for specific helium film thicknesses above a substrate, zero-energy resonances occur if the combined potential supports a bound state exactly at the threshold. This effect leads to a complete restructuring of the bound states spectrum. The dynamics of gravitational levels as a function of the van der Waals interaction depth—controlled by the helium film thickness—is analyzed. It reveals the critical thicknesses of $\sim 6.1$ and $\sim 1.8\mathrm{nm}$, at which resonances appear in the case of the conductive substrate. With imaginary integral operators, we incorporate nonperturbatively the inelastic effects originating from the ripplon coupling. The inelastic effects show dramatic changes in the sticking-coefficient behavior near the critical points. The enhanced sticking coefficients provide a probe for studying critical phenomena and measuring atom-surface interaction parameters with unprecedented sensitivity.

We study the decoherence of a collection of Majorana zero modes weakly coupled to a gapless reservoir of noninteracting fermions. Using the Born-Markov approximation, we derive a Lindblad master equation for the dissipative dynamics of the Majorana zero modes. Due to the long-range coupling between Majorana zero modes mediated by the gapless reservoir, the Lindblad jump operators are nonlocal linear combinations of the Majorana operators. We show that, as a consequence, the dissipative dynamics can exhibit long relaxation times, i.e., a slow decay of fermion parities. A spectral analysis of the Liouvillian shows that the slowdown is suppressed as a power law of the distance between Majorana zero modes. Finally, we validate the Lindblad equation by comparison with unbiased numerical simulations of the time evolution of the full density matrix. In particular, these illustrate that non-Markovian dynamics establishes nonlocal correlations at small times.

Conventional ionic ferroelectrics enable exciton control through switchable polarization but face challenges like high switching barriers and fatigue. Sliding ferroelectricity in van der Waals structures is capable of addressing these limitations with low energy consumption and excellent endurance, presenting a promising platform for excitonic applications. In this work, we construct a Janus bilayer MoSeTe and investigate its exciton-related optoelectronic properties using the $\mathit{GW}$–Bethe-Salpeter equation method. Along the AB-BA sliding path, the system exhibits low energy barriers (3.56 meV/atom) and high polarization (1.147 pC/m), accompanied by an exchange between layers in their contributions to the valence band maximum and conduction band minimum. This leads to a transition of the first bright excitonic state from the sliding layer to the fixed layer. Notably, because of band degeneracy and hybridization, the nonpolar state that emerge during the sliding process exhibits enhanced and localized excitonic absorption as well as interlayer exciton components, which are absent in both AB and BA stackings. This work highlights the considerable potential of sliding ferroelectricity in modulating exciton dynamics and provides a theoretical basis for the design of low-power, high-performance optoelectronic devices.

Room-temperature spin-optical active quantum emitters in hexagonal boron nitride (hBN) are promising candidates for advancing quantum photonic technologies; however, their inherently low photoluminescence (PL) quantum yield presents a significant challenge for optical readout. Here, we report a single-step coformation strategy that simultaneously creates plasmonic microcavities and quantum emitters in hBN via thermal annealing of $\mathrm{hBN}/\mathrm{Au}/{\text{SiO}}_2/\mathrm{Si}$ substrates. This process produces an ultraclean, spacer-free cavity-emitter system with large-area integration capability. The resulting cavity-coupled emitters exhibit a $247\%$ increase in the overall PL intensity and a Purcell factor of $4.27\pm 0.27$, attributed to strong cavity-emitter coupling. The cavity-coupled system exhibited a reduced radiative lifetime of $0.33\pm 0.01\mathrm{ns}$ (radiative rate of $\sim 3.03\mathrm{GHz}$) compared to a cavity-free emitter of $1.41\pm 0.08\mathrm{ns}$ (radiative rate of $\sim 0.70\mathrm{GHz}$). Single-photon emission purity of $56\%$ was confirmed for emitters at 1.97 eV, while systematic analysis of emission dynamics revealed multilevel quantum system behaviors, which can be explained by using a scattering-Lindbladian-Hamiltonian (SLH) framework. These results demonstrate the control over emission properties through cavity design and emitter-cavity coupling, establishing a robust route toward integrated, room-temperature quantum photonic circuitry.

We investigate changes in the optical conductivity of doped Mott insulators by tuning ultrashort pump pulses to target either the Drude or low-energy absorption regions. Using a hole-doped two-leg Hubbard ladder and a four-leg $t\text{−}J$ ladder, we calculate the optical conductivity after pumping by employing the time-dependent density matrix renormalization group. We find that a monocycle electric field pulse tuned to the Drude absorption reduces the Drude weight, accompanied by a slight enhancement in the mid-infrared (mid-IR) spectral weight. However, this enhancement diminishes as the pulse intensity increases. In contrast, a pump pulse tuned to the mid-IR absorption only affects the Drude weight. This behavior arises because the mid-IR absorption originates from magnetic excitations that do not couple directly to photons. These predictions can be tested experimentally by applying ultrashort low-energy pump pulses to cuprate materials.

High-harmonic generation in solids by intense laser pulses provides a fascinating platform for studying material properties and ultrafast electron dynamics, where its coherent character is a central aspect. Using the semiconductor Bloch equations, we uncover a mechanism suppressing the high-harmonic spectrum arising from the coherent superposition of intraband vs. interband contributions. We provide evidence for the generality of this phenomenon by extensive numerical simulations exploring the parameter space in gapped systems with both linear dispersion, such as for massive Dirac fermions, and with quadratic dispersion, as, e.g., for bilayer graphene. Moreover, we demonstrate that, upon increasing dephasing, destructive interference between intraband and interband contributions is lifted. This leads to reentrant behavior of suppressed high harmonics, i.e., a crossover from the characteristic spectral shoulder to a slowly decaying signal involving much higher harmonics. We supplement our numerical observations with analytical results for the one-dimensional case.