The layered structure of LiPdH was theoretically suggested to be a superconductor as a result of its larger electron-phonon coupling constant compared to that of PdH. However, the experimental results reported contrary findings, with no trace of superconductivity. We study the electronic, vibrational, and superconducting properties of the ambient pressure tetragonal phase of LiPdH ($P4/mmm$) within first principles density functional theory methods, both in the harmonic and anharmonic approximations for the lattice dynamics, and conclude that it does not show any superconducting behavior. High-pressure crystal structure prediction calculations indicate that no structural transition is expected to occur under pressure up to 100 GPa in LiPdH. Our theoretical calculations demonstrate that increasing pressure reduces the density of states at the Fermi surface and consequently weakens electron-phonon interactions, leading to a further suppression of the superconducting critical temperature.

We study the out-of-equilibrium Kibble-Zurek (KZ) dynamics in quantum Ising chains in a transverse field, driven by a time-dependent longitudinal field $h\left(t\right)=t/t_s$ ($t_s$ is the timescale of the protocol), across their first-order quantum transitions (FOQTs) at $h=0$. The KZ protocol starts at time $t_i<0$ from the negatively magnetized ground state for $h_i=t_i/t_s<0$. Then, the system evolves unitarily up to a time $t_f>0$, such that the magnetization of the state at time $t_f$ is positive. In finite-size systems, the KZ dynamics develops out-of-equilibrium finite-size scaling (OFSS) behaviors. Their scaling variables depend either exponentially or with a power law on the size, depending on the boundary conditions (BC). The OFSS functions can be computed in effective models restricted to appropriate low-energy (magnetized and/or kink) states. The KZ scaling behavior drastically changes in the thermodynamic limit (TL), defined as the infinite-size limit keeping $t$ and $t_s$ fixed, which appears substantially unrelated with the OFSS regime, because it involves higher-energy multikink states, which are irrelevant in the OFSS limit. The numerical analyses of the KZ dynamics in the TL show the emergence of a quantum spinodal-like scaling behavior at the FOQTs for all considered BC, which is independent of the BC. The longitudinal magnetization changes sign at $h\left(t\right)=h_{★}>0$, where $h_{★}$ decreases with increasing $t_s$, as $h_{★}\sim 1/ln{t}_s$. Moreover, in the large-$t_s$ limit, the time dependence of the magnetization is described by a universal function of $\mathrm{\Omega }=t/{\tau }_s$, with ${\tau }_s=t_s/ln{t}_s$.

We report high-resolution inelastic neutron scattering measurements of the excitation spectrum in large single crystals of the spin-1/2 triangular-lattice Ising-like antiferromagnet ${\mathrm{Na}}_2\mathrm{BaCo}{\left({\mathrm{PO}}_4\right)}_2$ in magnetic fields applied transverse to the Ising axis. In the high-field polarized phase above a critical field $B_{\mathrm{C}}$, we observe sharp magnons, as expected in the case of no exchange disorder. Through simultaneous fits to the dispersions including data in a polarizing field along the Ising axis, we obtain an excellent match to an Ising-like XXZ Hamiltonian and rule out previously proposed Kitaev exchanges. In the intermediate-field phase below $B_{\mathrm{C}}$, we observe three dispersive modes, out of which only the lowest energy one is sharp and the others are broad and overlap with continuum scattering. We propose that the broadening effects are due to magnon decays into two-magnon excitations and confirm that such processes are kinematically allowed. The continuum scattering becomes progressively stronger upon lowering the field and, at 0.25 T and zero field, it dominates the entire spectrum with no clear evidence for even broadened magnon modes. We discuss the relevance of the continuous manifold of mean-field degenerate ground states of the refined Hamiltonian for capturing the observed spectrum in zero field, and compare the data with the one- and two-magnon spectrum averaged over this manifold. We also propose a model of the interlayer couplings to explain the observed finite interlayer magnetic propagation vector of the zero-field magnetic order; this requires the breaking of the mirror symmetry in the nominal $P\overline{3}m1$ space group and through refinement of x-ray diffraction data on an untwinned single crystal, we indeed confirm a rotation of the ${\mathrm{CoO}}_6$ octahedra around the $c$ axis, which lowers the symmetry to $P\overline{3}$.

Due to the antiferromgnetism in the room temperature multiferroic $\mathrm{BiFe}{\mathrm{O}}_3$, the electric field manipulation of exchange bias has been considered to be an efficient way to control the pinned magnetization of ferromagnetic layer. However, the irreversibility strongly impedes the practical application and the underlying mechanism needs clarification. Bilayers of Co with $\mathrm{BiFe}{\mathrm{O}}_3$ of various orientations, including (001), (110), and (111) in pseudo-cubic index, are fabricated. Exchange bias is observed in all the samples, originating from the interfacial spins of perfect crystal and surface defects in $\mathrm{BiFe}{\mathrm{O}}_3$ layer, respectively. The first reversal of out-of-plane component of polarization leads to the irreversible suppression of exchange bias, while the influence of in-plane component is little. Only the exchange bias from perfect crystalline $\mathrm{BiFe}{\mathrm{O}}_3$ is switchable, while that from surface defects remains unaffected. This can be understood by the in-plane component of cycloidal spins in $\mathrm{BiFe}{\mathrm{O}}_3$, anchored by the out-of-plane component of polarization, whose reversal leads to the rotation of cycloidal spins and break of unidirectional exchange coupling. This work provides a clue to the understanding of multiferroic exchange bias and the design of novel energy-efficient magnetoelectric devices.

In $f$-electron materials like Pr or U compounds with non-Kramers states of the $f$ shell the ground state may be a nonmagnetic singlet due to the action of the crystalline electric field. Nevertheless, these compounds can order magnetically. They develop a ground state moment and long-range order due to the spontaneous admixture of the excited state into the ground state caused by intersite exchange. This mechanism can establish magnetic order if a control parameter exceeds a critical value defining the quantum critical point between disordered and magnetic phases. Here we investigate the magnetocaloric properties of such quantum magnets where the entropy release at low temperature is due to a competition between thermal depopulation and spontaneous order effects. We determine field and temperature dependence of specific heat for ferromagnetic and antiferromagnetic order and also calculate the adiabatic magnetocaloric and barocaloric cooling rates. As a model application we discuss the magnetic specific heat of the new induced ferromagnet ${\mathrm{PrIr}}_3$. Furthermore, we analyze the excitation spectrum of the singlet induced moment magnets in an external field with particular emphasis on field and temperature dependence of the critical soft mode. We find that the latter is fragile and exists only at specific points in the phase diagram.

The one-dimensional Hatano-Nelson model with nonreciprocal hoppings is a prominent example of a relatively simple non-Hermitian quantum-mechanical system, which allows to study various phenomena in open quantum systems without adding extra gain and loss terms. Here we propose to use it as a building block to construct a correlated non-Hermitian Hamiltonian in two dimensions. It has the characteristic form of a flux model with clock-anticlockwise nonreciprocal hopping on each plaquette. Adding the on-site Hubbard type interaction, we analyze the formation of the longe-range antiferromagnetic order and its spin excitations. Such a model is non-Hermitian, but $\mathcal{PT}$-symmetric, which leads to the existence of two regions: a region of unbroken $\mathcal{PT}$ symmetry (real-valued spectrum) and a region of broken $\mathcal{PT}$ symmetry with exceptional lines and complex-valued energy spectrum. The transition from one region to another is controlled by the value of the on-site interaction parameter and coincides with the metal-insulator transition. We also analyze the spin wave spectrum, which is characterized by two diffusive $d$-wave type of modes corresponding to gain and loss.

The properties of magnons hosted in strained Heisenberg-Kitaev magnets are investigated using numerical and analytical calculations. Considering that deformation fields modulate the coupling parameters, we find a general expression for the weakly strained magnon Hamiltonian that depends on the (symmetric) strain tensor. We numerically tested our results in finite nanoribbon structures. We found that uniaxial deformations make the bulk bands more dispersive while topologically protected in-gap edge modes become nonreciprocal at the boundary of the Brillouin zone. On the other hand, when applying a twist deformation, the simultaneous modulation of both Heisenberg and Kitaev parameters enables the apparition of flat bands, promoting the presence of nonpropagative topologically protected magnonic edge states, whose properties strongly depend on the strain strength. In addition, the characteristic localization of magnon edge modes is preserved, which allows for testing the robustness of the bulk-boundary correspondence under lattice deformations. Our results contribute to a major understanding of Heisenberg-Kitaev magnets and how applying different strains allows for precise control over magnon properties.

We investigate topological phases in three-dimensional topological insulator (3DTI) thin films interfaced with altermagnetic (AM) orders. Starting from a modified Dirac equation, we elucidate the interplay between the Wilson mass, arising from lattice regularization, and the altermagnetic mass, and show how this interplay fundamentally alters the band topology and boundary modes. In particular, we demonstrate that coupling a 3DTI thin film to AM order induces a topological phase transition: although the total Chern number remains zero across the transition, topological helical edge states emerge after the transition. These helical edge states arise from opposite Chern numbers at different high-symmetry points, and are distinct from both the chiral edge states of the quantum anomalous Hall phase and the helical edge states of the conventional quantum spin Hall states. The quantum transport simulations reveal robust, quantized nonlocal resistance plateaus associated with these helical edge states, which persist even under strong potential and magnetic disorder. Our results establish 3DTI/AM heterostructures as a feasible material platform for engineering and detecting helical topological edge transport without time-reversal symmetry, thus expanding the landscape of topological matter and providing new opportunities for quantum devices.

As an emerging category of magnets, altermagnets are distinguished by their alternating spin-splitting band structures and a zero net magnetization. In this study, we explore the collective excitation modes within two-dimensional (2D) altermagnets, revealing unique modes of coupled charge density and spin density fluctuations, known as spin plasmons. We find that fluctuations in charge density can induce corresponding fluctuations in spin density, and vice versa. The momentum-dependent spin splitting inherent in altermagnets leads to significant anisotropy in spin plasmons. Through first-principles calculations, we demonstrate the existence of the anisotropic spin plasmons in altermagnetic ${\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$ monolayer. These spin plasmons establish a connection between spintronics and plasmonics, offering exciting possibilities for advancement in spin transport within spintronic devices.

The bosonic statistics, which allow for macroscopic multioccupancy of single-particle states, pose significant challenges for analyzing quantum phase transitions in interacting bosonic systems, both analytically and numerically. In this work, we systematically investigate the non-Hermitian Bloch core matrix of a Hermitian staggered bosonic Kitaev chain, formulated within the Nambu framework. We derive explicit analytic conditions for the emergence of exceptional points (EPs) in the $4\times 4$ Bloch core matrix, with each EP marking the onset of complex-conjugate eigenvalue pairs. By mapping the full many-body Hamiltonian onto an effective tight-binding network in Fock space and introducing the layer-resolved inverse participation ratio, we demonstrate that these EPs coincide precisely with sharp localization-delocalization transitions of collective eigenstates. Comprehensive numerical analyses across hopping amplitudes, pairing strengths, and on-site potentials confirm that the EP of the effective Hamiltonian universally capture the global many-body phase boundaries. Our results establish an analytically tractable, EP-based criterion for detecting critical behavior in interacting bosonic lattices, with direct relevance to photonic and cold-atom experimental platforms.

The degrees of the localization and hybridization of the valence $f$ states/covalency of the chemical bonding in actinide and lanthanide dioxides were investigated using the atomic, crystal-field multiplet and Anderson impurity model (AIM) approaches to calculate actinide $5d$ and lanthanide $3d$ x-ray photoemission spectra (XPS). The actinide $5d$ XPS can be largely described within atomic, crystal-field multiplet theory due to an extended multiplet structure as a result of the strong interaction of $5f$ electrons with a $5d$ core hole. The multiplet structure was found to be quite sensitive to the oxidation state of actinides. In turn, the lanthanide $3d$ XPS description requires the AIM type of calculations due to significant $4f$–O $2p$ hybridization effects. As a result derived from the analysis of the XPS spectra, an increase in the $f$-shell occupancy in the ground state due to the $f$–O $2p$ hybridization and covalency of the chemical bonding appears to be higher in lanthanide dioxides as compared to actinide dioxides.

Motivated by the study of stacking faults in weak topological insulators and the observation of magnetic domain walls in ${\mathrm{MnBi}}_{2n}{\mathrm{Te}}_{3n+1}$, we explore the topological properties of magnetic domain walls in antiferromagnetic topological insulators. We develop two tight-binding models for two different types of antiferromagnetic topological insulators: the first type obtained by adding antiferromagnetic order to a strong topological insulator and another built from stacked Chern insulating layers with alternating Chern numbers. Both systems are dual topological insulators, i.e., they are at the same time antiferromagnetic and crystalline topological insulators, but differ by the type of mirror symmetry protecting the crystalline phase: spinful versus spinless. We show that in the spinful case the mirror Chern number is invariant under time reversal and that it changes sign in the spinless case. This influences the properties of the two systems in the presence of a magnetic domain wall, which we model as an interface between two regions of opposite magnetization. In the first type, the bulk of the magnetic domain wall is gapped but the defect will host chiral edge states when it ends on an external ferromagnetic surface. In the second, due to the change in the sign of the mirror Chern number, the magnetic domain wall is a two-dimensional (2D) embedded semimetal with 2D gapless states protected by mirror symmetry. Our results show that magnetic domain walls can be a source of nontrivial topology, allowing one to generate and manipulate gapless states within the bulk and the ferromagnetic surfaces of antiferromagnetic topological insulators.

A $p$-wave magnet has zero-net magnetization and induces a momentum-dependent spin-splitted band structure just as in the case of an altermagnet. It will be useful for high-density and ultrafast memory, where the direction of the spin-splitting vector may be used as a bit. However, it is a nontrivial problem to detect the spin-splitting vector in a $p$-wave magnet because time-reversal symmetry is preserved, while this is not a problem in an altermagnet because the anomalous Hall conductivity is present due to the breaking of time-reversal symmetry. Here, we show that it is possible to detect the in-plane component of the spin-splitting vector in the $p$-wave magnet by measuring the linear transverse and longitudinal Drude conductivity. Remarkably, this measurement is possible without using magnetization. Furthermore, we study the nonlinear Drude conductivity, the quantum-metric and the Berry curvature dipole induced nonlinear conductivity in the presence of tiny magnetization along the $z$ axis. It is possible to detect the $z$-component of the spin-splitting vector by measuring the above nonlinear conductivities. We obtain analytic formulas for them in the first-order perturbation theory, which agree quite well with numerical results without perturbation.

The face-centered-cubic lattice is composed of edge-sharing tetrahedra, making it a leading candidate host for strongly frustrated magnetism, but relatively few face-centered frustrated materials have been investigated. In the hydroxide double perovskite $\mathrm{CuSn}{\left(\mathrm{OH}\right)}_6$, magnetic frustration of the ${\mathrm{Cu}}^{2+}$ quantum spins is partially relieved by strong Jahn-Teller distortions. Nevertheless, the system shows no signs of long-range magnetic order down to 45 mK and instead exhibits broad thermodynamic anomalies in specific heat and magnetization, indicating short-range dynamical spin correlations—a behavior typical of quantum spin liquids. We propose that such an unusual robustness of the spin-liquid-like state is a combined effect of quantum fluctuations of the $S=\frac{1}{2}$ quantum spins, residual frustration on the highly distorted face-centered ${\mathrm{Cu}}^{2+}$ sublattice, and correlated proton disorder. Similar to the disorder-induced spin-liquid mimicry in ${\mathrm{YbMgGaO}}_4$ and herbertsmithite, proton disorder destabilizes the long-range magnetic order by introducing randomness into the magnetic exchange interaction network. However, unlike the quenched substitutional disorder on the magnetic sublattice, which is difficult to control, proton disorder can, in principle, be tuned through pressure-driven proton ordering transitions. This opens up the prospect of tuning the degree of disorder in a magnetic system to better understand its influence on the magnetic ground state.

We consider Lindbladian operator dynamics in many-body quantum systems with one or more integrals of motion (IOMs), subject to weak local dissipation. We demonstrate that IOMs with small support become slow modes of these dynamics, in the sense that their Frobenius norms decay more slowly compared to generic operators. As a result, the eigenoperators of such Lindbladians with slowest decay rates have a large overlap with the IOMs of the underlying Hamiltonian. We demonstrate this correspondence between slow modes and IOMs numerically for a number of many-body models and further corroborate it with perturbative arguments. These results open up another method for the identification of IOMs and provide insights into the dissipative many-body dynamics.

The ferroelectric properties of type II multiferroic monolayers are intrinsically linked to their magnetic characteristics, wherein the noncollinear spin chirality generates a polarization perpendicular to the spin spiral plane. However, research into the control mechanisms and potential applications of their magnetic structures remains insufficient. In this context, we employ a combination of first-principles calculations and atomistic scale Landau-Lifshitz-Gilbert simulation to predict the simultaneous reversal of polarization and magnetization through a sliding mechanism. Significant alterations in the spin Hamiltonian and second harmonic generation are observed when the ferroelectricity transitions between distinct stable sliding configurations. Furthermore, we propose a strategy for deterministic control of the tunneling magnetoresistance of bilayer $\mathrm{VC}{\mathrm{l}}_2$ employing laser pulses affecting the ultrafast sliding polarization, and achieve continuous switching between magnetic storage states through repeated use of sliding devices. This investigation into the deterministic control of sliding polarization in conjunction with dynamic magnetic fields broadens the prospective applications of two-dimensional noncollinear antiferromagnetic materials in magnetic storage devices and spintronic applications.

Magnetic skyrmions are chiral spin textures whose nontrivial topology protects them from annihilation and are a prime candidate for logical bits in future spintronics devices and next-generation magnetic memories. While their topology and structure are typically described in two dimensions, recent works have focused on further understanding their three-dimensional (3D) structure. Specifically, in multilayer thin films, skyrmions stabilized by dipolar fields are expected to exhibit domain walls that are Bloch-type in the center of the film and twist to Néel-type towards the surfaces due to stray-field interactions, resulting in a hybrid structure. The thickness-dependent helicity underpins their exceptional stability and is predicted to strongly affect the skyrmions’ response to external forces and underlying topology. In this paper, we combine Lorentz transmission electron microscopy and scanning electron microscopy with polarization analysis to image in real space the 3D structure of hybrid skyrmions. We compare our measurements against micromagnetic simulations, which reveal the full hybrid structure, including the depth dependence of core diameter, domain wall width, and skyrmion helicity.

We systematically investigate the scaling behaviors of the disorder operator and the entanglement entropy (EE) of the easy-plane JQ (EPJQ) model at its transitions between the antiferromagnetic XY ordered phase (AFXY) and the valence bond solid (VBS) phase. We find there exists a tiny yet finite value of the order parameters at the AFXY-VBS phase transition points of the EPJQ model, and the finite order parameter is strengthened as anisotropy $\mathrm{\Delta }$ varies from the Heisenberg limit ($\mathrm{\Delta }=1$) to the easy-plane limit ($\mathrm{\Delta }=0$). This observation provides evidence that the Néel-VBS transition in the JQ model setting evolves from weak to prominent first-order transition as the system becomes anisotropic. Furthermore, both EE and disorder operator with smooth boundary cut exhibit anomalous scaling behavior at the transition points, resembling the scaling inside the Goldstone mode (AFXY) phase, and the anomalous scaling becomes strengthened as the transition becomes more first order. In particular, for $\mathrm{\Delta }\le 0.3$, the obtained log-coefficients of EE converge to 0.5 which is the same as the contribution from one Goldstone mode in the Néel phase. For $\mathrm{\Delta }>0.3$, the log-coefficients are smaller and our findings might suffer from strong finite-size effects due to the fact that the remaining Néel order here is quite tiny.