When a system is driven across a continuous phase transition, the density of topological defects demonstrates a power-law scaling behavior versus the quenching rate, as predicted by the Kibble-Zurek mechanism. In this study, we generalize this idea and address the scaling of quantum state transport in a one-dimensional topological system subject to a linear drive through its topological quantum phase transition point. We illustrate the power-law dependences of the quantum state's transport distance, width, and peak magnitude on the driving velocity. Crucially, the power-law exponents are distinct for the edge state and bulk state. Our results offer a different perspective on quantum state transfer and enrich the field of Kibble-Zurek behaviors and nonadiabatic quantum dynamics.

This paper uses advanced first-principles calculation methods, combined with self-consistent phonon (SCP) theory, compressive sensing (CS) lattice dynamics, and Boltzmann transport equation (BTE), to calculate and study the lattice dynamics and phonon transport of 16 antifluorite structures. The lattice thermal conductivity (${\kappa }_L$) of these materials was studied in detail by analyzing the quartic anharmonic renormalization of phonon frequencies and four-phonon (4ph) scattering, revealing the significant influence of quartic anharmonicity on their thermal transport properties. Our study shows that strong quartic anharmonic renormalization is observed for eight materials, leading to enhanced ${\kappa }_L$. In contrast, for the five materials, the weak quartic anharmonic effect leads to negligible changes in thermal conductivity. Three materials exhibit reduced ${\kappa }_L$ due to phonon anharmonic renormalization. Furthermore, 4ph scattering rates (SRs) are important for many of the materials studied and can offset changes in frequency, leading to a reduction in thermal conductivity. At the same time, our calculations give an approximately linear relationship between ${\kappa }_L$ and 4ph scattering, which suggests that structures with low ${\kappa }_L$ have stronger 4ph scattering. Simultaneously, we chose ${\mathrm{Li}}_2\mathrm{O}$, characterized by high ${\kappa }_L$, and ${\mathrm{Rb}}_2\mathrm{Te}$, known for its low ${\kappa }_L$, to thoroughly examine their microscopic thermal transport mechanisms. This involved detailed analysis of the thermal conductivity spectrum ${\kappa }_L$ ($\omega$), scattering phase space, group velocity, and scattering processes. Finally, this study provides insights into the underlying physical mechanisms of thermal transport in 16 antifluorite materials and highlights the need to consider 4ph scattering for thermal transport in materials.

Magnetic-field-induced electric polarization has been observed in trigonal noncentrosymmetric paramagnetic ${\mathrm{Pr}}_3{\mathrm{Ga}}_5{\mathrm{SiO}}_{14}$ langasite. We detected quadratic electric polarization along the $a$ axis in the basal $ab$ plane for various magnetic field orientations. Electric polarization along the $c$ axis is only evident starting from the fourth power of magnetic field, in accordance with the trigonal symmetry. The magnetic properties of ${\mathrm{Pr}}_3{\mathrm{Ga}}_5{\mathrm{SiO}}_{14}$ primarily stem from the local anisotropic magnetic moment of the two lowest $\mathrm{P}{\mathrm{r}}^{3+}$ singlets (quasidoublet) in the crystal electric field. The random distribution of Ga/Si in the $2d$ positions leads to a local distortion of the $C_2$ symmetry and to a distribution of the quasidoublet splitting. By considering the interactions of local moments among different $\mathrm{P}{\mathrm{r}}^{3+}$ positions within a phenomenological approach for the allowed magnetoelectric coupling, we derive the electric polarization in terms of symmetry-allowed combinations of local magnetic susceptibilities and field components. The magnetic field dependence of electric polarization in the basal plane, $P_{a,b*}$, is mainly determined by the accumulation of effective local susceptibilities, exhibiting similar behavior in low fields, while polarization along the $c$ axis, $P_c$, arises from the nonequivalence of local effective magnetic susceptibilities in different $\mathrm{P}{\mathrm{r}}^{3+}$ positions. Our findings suggest that the temperature dependencies of magnetic and magnetoelectric susceptibilities are highly sensitive to the distribution of the quasidoublet splitting, which reflects the local symmetry breaking.

Effective field theory of low-energy excitations (magnons) that describe antiferromagnets is mapped into electrodynamics of a charged scalar field interacting with an external magnetic background. In this theory magnons and antimagnons are described by a corresponding scalar field. If the external background is a constant inhomogeneous magnetic field in the quantum version of the model, then there exists vacuum instability which can be analyzed by an analogy with the scalar QED with electric potential steps. Here magnons and antimagnons are treated as charged particles, whereas the magnetic moment plays the role of the electric charge such that magnons and antimagnons differ from each other in the sign of this moment. The vacuum instability is related to the magnon-antimagnon production from the corresponding vacuum by magnetic field inhomogeneities. Characteristics of the vacuum instability can be calculated nonperturbatively using special exact solutions of the Klein-Gordon equation. In particular, we consider examples of the magnetic field that correspond to some regularizations of the Klein step. In the case of smooth-gradient steps, we have derived a universal behavior of the flux density of created magnon-antimagnon pairs. It is noted that there exists an opportunity, for the first time, to observe the Schwinger effect in the case of Bose particle creation. Moreover, it turns out that in the case of the Bose statistics appears a new mechanism for amplifying the effect of pair creation, which we call statistically assisted Schwinger effect.

Antiferromagnetic (AFM) spintronics offer several benefits compared to their ferromagnetic (FM) counterparts, such as high storage capacity and faster processing speed, however, difficulties in manipulating and detecting the AFM moments impede their implementation. Spin-flop coupling, the interfacial perpendicular coupling between FM and AFM moments, can be utilized to control the orientation of AFM moments with the application of moderate magnetic fields on the scale of tenths of a Tesla. In this work, epitaxial bilayers of AFM $\mathrm{L}{\mathrm{a}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Fe}{\mathrm{O}}_3$ (LSFO)/FM $\mathrm{L}{\mathrm{a}}_{0.7}\mathrm{S}{\mathrm{r}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$ (LSMO) with fixed LSMO thickness ($\sim 85$ u.c.) and LSFO thicknesses varying from 10 to 50 u.c. were investigated to determine the effect of Sr doping and $\mathrm{L}{\mathrm{a}}_{1-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Fe}{\mathrm{O}}_3$ magnetocrystalline anisotropy on the strength of spin-flop coupling. X-ray magnetic linear dichroism demonstrated that the spin-flop coupling strength decreased with increasing LSFO layer thickness, persisting at a thickness of 50 u.c. ($\sim 20$ nm). Furthermore, photoemission electron microscopy revealed a domain-by-domain correlation between the FM and AFM domains consistent with the perpendicular orientation dictated by spin-flop coupling. These results demonstrate that LSFO/LSMO bilayers have the potential to serve as a model materials system for AFM spin transport measurements.

The quasi-two-dimensional Shastry-Sutherland model has remained topical in the field of condensed matter physics for the last two decades, following the experimental realization of the model in the material ${\mathrm{SrCu}}_2{\left({\mathrm{BO}}_3\right)}_2$. Since then, research into the Shastry-Sutherland system has revealed more nuanced physics than initially predicted; recent theoretical works have even predicted a quantum spin liquid phase may exist. Herein, we report on a new Shastry-Sutherland lattice material, ${\mathrm{Yb}}_2{\mathrm{Be}}_2{\mathrm{GeO}}_7$, of the rare-earth melilite family ${\mathrm{RE}}_2{\mathrm{Be}}_2{\mathrm{GeO}}_7$. We find, through SQUID magnetometry, powder neutron diffraction, specific heat capacity, and muon spin relaxation, that ${\mathrm{Yb}}_2{\mathrm{Be}}_2{\mathrm{GeO}}_7$ lacks magnetic order and exhibits persistent spin dynamics to at least 17 mK. We propose the Shastry-Sutherland lattice material ${\mathrm{Yb}}_2{\mathrm{Be}}_2{\mathrm{GeO}}_7$ as a candidate to host a quantum spin liquid ground state.

We theoretically study Andreev reflection (AR) -induced conductance at antiferromagnet/antiferromagnet/ superconductor (AF/AF/S) junctions. The AF can become spin-polarized when the parity-time symmetry is broken. Equal-spin AR occurs due to spin-flip scattering when the Néel vectors of the AFs are noncollinear. We investigate how the staggered sublattice potential and the electrostatic potential affect the AR-induced conductance, and we demonstrate that a pure equal-spin AR is achievable. The signature of the equal-spin AR can be confirmed by studying the conductance spectra. When the left AF is fully spin-polarized, the pairing correlations involving spin-down quasiparticles decrease rapidly, but the equal-spin triplet pairing correlation $(\uparrow \uparrow )$ becomes long-range. This results in a conversion from spin-singlet to spin-triplet pairings, providing further evidence for the existence of equal-spin AR. Specifically, the study focuses on the AR-induced magnetoanisotropic conductance. The conductance exhibits relatively weak magnetoanisotropy due to the competing contributions of conventional and equal-spin ARs. In contrast, when only equal-spin AR is present, significant anisotropic magnetoresistance is observed, which can serve as a distinctive signature of equal-spin AR. The findings suggest that AF/S junctions are ideal platforms for future superconducting spintronics applications.

In diamond, the pivotal factor for quantum applications involving color centers hinges on extending the spin coherence time through a larger ground-state zero-field splitting (ZFS). Experimental observations indicate a correlation between the atomic number and the increasing of the ground-state ZFS of group-IV centers. Yet, the physical origin underlying the impurity-modulated ground-state ZFS remains insufficiently elucidated. In this study, utilizing density-functional theory and group analysis, we illustrate that the origin of the correlation between the ground-state ZFS in group-IV centers and the atomic number of impurity atoms, arises from the synergistic interplay of large atomic numbers and the extent of $p\text{−}d$ orbital hybridization. Simultaneously, our investigation identifies that the ground-state of group-IVB centers originates from a robust $p\text{−}p$ hybridization between impurity atom and divacancy. This interaction results in ground-state ZFS of 7728 GHz for $\mathrm{Hf}{V}^{-}$ centers, nearly doubling the experimentally observed value found in the largest $\mathrm{Pb}{V}^{-}$ centers. Our study, therefore, provides profound insights into the origins of the impurity-modulated ground-state ZFS, offering a promising pathway towards achieving larger ground-state ZFS of color centers.

Granular metals offer tailorable electronic properties and play crucial roles in device and sensor applications. We have fabricated a series of nonmagnetic granular ${\mathrm{CoSi}}_2$ thin films and studied the Hall effect and transport properties. We observed a two-order magnitude enhancement in the Hall coefficient in films that fall slightly above the metal-insulator transition. This giant Hall effect (GHE) is ascribed to the local quantum-interference effect-induced reduction of the charge carriers. Transmission electron microscopy images and transport properties indicate that our films form quasi-two-dimensional granular arrays. The GHE may provide useful and sensitive applications.

We investigate the magnetic order in single crystalline ${\mathrm{EuCd}}_2{\mathrm{Sb}}_2$ thin films using a combined theoretical and experimental approach. Resonant elastic x-ray scattering experiments reveal a sharp magnetic peak at $\mathbf{q}=(0,0,\frac{1}{2})$ below $T_{\mathrm{N}}=7.2$ K, indicative of interlayer antiferromagnetic ordering. Additionally, we observe a weak diffuse magnetic signal centered at $\mathbf{q}=(0,0,1)$ that persists above $T_{\mathrm{N}}$, up to $T_{\mathrm{C}}\sim 11$ K. Our Monte Carlo simulations of a classical spin model approximation of the Eu magnetic sublattice demonstrate that the diffuse signal can arise from ferromagnetic coupling in the top few layers due to surface oxidation. On the other hand, the bulk of the sample exhibits antiferromagnetic coupling between layers. Finally, our fit of the model parameters to the magnetic ordering temperatures shed light on the exchange couplings that are key in stabilizing the observed composite magnetic order.

The frustrated antiferromagnet ${\text{CuFeO}}_2$ exhibits pressure-induced complex magnetic phase transitions from the commensurate collinear (CM1) phase to several incommensurate noncollinear phases. To study the effect of high pressure on magnetic interactions, we performed neutron diffraction and inelastic neutron scattering experiments under high-pressure conditions. With increasing pressure, the CM1 ground state becomes less stable against application of a magnetic field even below the critical pressure ($P\le 3$ GPa), as proved by the significant reduction in the critical magnetic field from $H_{c1}=7.5$ T to 4.5 T at 2.1 GPa. Additionally, the energy gap in the spin-wave dispersion relation is reduced from 1.0 to 0.88 meV by the application of a pressure of $P=2.1$ GPa. Comparing the experimental results with spin-wave calculations revealed that the change in the spin-wave excitation can be explained by the reduction in either the uniaxial anisotropy term or the degree of separation in the nearest-neighbor exchange interactions.

In search of spin-orbit coupling driven nonmagnetic $J=0$ ground state and excitonic magnetism, various pentavalent iridates have been studied in recent years. However, a finite moment was observed in most of the cases due to solid state effects. In this work, we investigate the electronic and magnetic structure of $6H$ hexagonal compound ${\mathrm{Ba}}_3{\mathrm{NiRuIrO}}_9$, where ${\mathrm{Ir}}^{5+}$ is present along with magnetic ${\mathrm{Ni}}^{2+}$ and ${\mathrm{Ru}}^{5+}$ ions. Magnetic susceptibility measurements and neutron powder diffraction (NPD) experiments demonstrate the appearance of short-range magnetic ordering below 170 K and a long-range antiferromagnetic ordering below 80 K. The refinement of the NPD pattern further shows that the Ru and Ir moments interact antiferromagnetically within the dimer and interact ferromagnetically with the Ni sublattice. These experimental findings have been complemented by first-principles density functional theory calculations incorporating spin-orbit coupling effects and electronic correlations for the transitional metal $d$ states. The computed magnetocrystalline anisotropy is also found to be significant and the crystallographic $c$ axis comes out to be the easy axis of magnetization, consistent with the spin alignment direction found from NPD. This study shows that the mixed ruthenate iridate triple perovskite series is a promising family to study the interplay among spin-orbit coupling, electron correlation, and electron filling as a variety of ${\mathrm{Ba}}_{3}M{\mathrm{RuIrO}}_9$ with $M$ as a transition metal ion, rare-earth ion, and alkali metal ions can be synthesized.

The elegant spin physics of Dirac electrons in topological insulators (TIs) have considerably endowed fertile tunability of magnetic/TI heterojunction performance with modified spin-orbit effect engineering. Signatures of proximate hybridization between magnetic states and topological surface states have been reported. However, the nature of the spin relaxation process in these systems remains elusive. Here, we unambiguously demonstrate anisotropic spin relaxation in a spin-orbit-hybridized $\mathrm{Fe}\text{/}{\mathrm{Bi}}_2{\mathrm{Se}}_3$ system. We find a sixfold anisotropy of the Gilbert damping parameter with modulation of up to 33% in $\mathrm{Fe}\text{/}{\mathrm{Bi}}_2{\mathrm{Se}}_3$ in the presence of a topological surface state, together with a sixfold magnetic anisotropy. We anticipate the presence of a spin interplay between the topological spin-orbit texture and magnetic orbital states would manifest an anisotropic Gilbert damping, which corroborates with the density functional theory calculations. It is further demonstrated by the spin Hanle effect indicative of anisotropic spin relaxation time ${\tau }_s$ in the adjacent topological layer, inversely scaling with the Gilbert damping factor ${\alpha }_G$. Our findings present an alternative scenario of the anisotropic spin transport process and offer insights into spin manipulation in spin-logic/memory devices utilizing proximity-hybridized Dirac electrons.

We investigate the quantum spin-1/2 zigzag chain with frustrated $J_1-J_2$ Heisenberg interactions, incorporating additional off-diagonal exchange interactions known as the $\mathrm{\Gamma }$ term, both with and without an applied magnetic field. Based on the density-matrix renormalization group calculation, we map out the ground-state phase diagram that shows a variety of magnetic and nonmagnetic phases including multicritical points and several exactly solvable points. Upon introducing a finite $\mathrm{\Gamma }$ term, we observe the persistent dimer-singlet state of the $J_1-J_2$ Heisenberg model, sustaining a nonzero spin gap, while also hosting a gapless nonmagnetic excitation that manifests in the substantial zero-energy peak in the nematic dynamical structure factor. This gapless peak-mode, remaining almost as a fluctuation to the ground state, induces a dilute but robust concentration of nematicity on top of singlets on dimers, which we call the nematic singlet-dimer phase. When the whole nematic excited mode condenses and replaces the singlet, the nematic-dimer phase transforms into the Ising-type ferromagnetic or antiferromagnetic long-range orders. The $\mathrm{\Gamma }$ term spontaneously selects magnetic easy axes, and their orientations dictate the type of magnetic order under geometric frustration effects as predicted by Landau's mean-field theory. These theoretical findings provide insights into the exotic low-temperature phase observed in ${\mathrm{YbCuS}}_2$, characterized by gapless excitations and seemingly nonmagnetic behavior.

We present a methodology based on the calculation of the inelastic scattering from magnons via the spin-scattering function in confined geometries such as thin films using a second quantization formalism, for both ferromagnetic and antiferromagnetic materials. The case studies are chosen with an aim to demonstrate the effects of film thickness and crystal orientation on magnon modes, using bcc Fe(100) and NiO with (100) and (111) crystallographic orientations as prototypical systems. Due to the quantization of the quasimomentum, we observe a granularity in the inelastic spectra in the reciprocal space path reflecting the orientation of the thin film. This approach also allows for the capture of softer modes that appear due to the partial interaction of magnetic moments close to the surface in a thin film geometry, in addition to bulk modes. The softer modes are also affected by crystallographic orientation, as illustrated by the different surface-related peaks of the NiO magnon density of states at approximately $\sim 65\mathrm{meV}$ for (100) and $\sim 42\mathrm{meV}$ for a (111)-oriented film. Additionally, we explore the role of anisotropy, revealing that anisotropy increases the overall hardness of the magnon modes. The introduction of a surface anisotropy produces a shift of the surface-related magnon DOS peak to higher energies with increased surface anisotropy, and in some cases leads to a surface-confined mode.

We study the electronic band structures and topological properties of nonmagnetic kagome metal $\mathrm{N}{\mathrm{i}}_3\mathrm{Sn}$ when applying in-plane biaxial strains through first-principles calculations. From these calculations, we confirm that the flat band of $\mathrm{N}{\mathrm{i}}_3\mathrm{Sn}$ is located at 250 meV below the Fermi level for pristine $\mathrm{N}{\mathrm{i}}_3\mathrm{Sn}$, and its position can be raised to the Fermi level by applying a finite in-plane biaxial strain. In this deformation process, we also find that there are two distinct topological phase transitions between trivial and nontrivial topological states at 1.5% and 2.9% strains. Finally, through the calculations of electron-phonon coupling, we examine the possibility of superconductivity mediated by electron-phonon coupling for pristine and strained $\mathrm{N}{\mathrm{i}}_3\mathrm{Sn}$ structures and confirm theoretically that the 5% biaxial strained $\mathrm{N}{\mathrm{i}}_3\mathrm{Sn}$ shows superconductivity. Therefore, biaxial strain in kagome metal $\mathrm{N}{\mathrm{i}}_3\mathrm{Sn}$ triggers the flat band to move toward the Fermi level, thereby inducing nontrivial topology and superconductivity simultaneously.

Recent advances in all-dielectric topological photonics offer unprecedented opportunities for achieving robust waveguides. However, most topological waveguides are localized at small areas around the interfaces and usually operate in a single frequency window, leading to the low-throughput energy transmission over a narrow bandwidth. Here we report on the implementation of a dual-band topological large-area waveguide in heterostructures based on valley photonic crystals, in which the bandwidths are effectively widen by exploiting the dual-band topology. Inherited from the valley topology, the topological large-area waveguides exhibit the valley-locking effect at two separate frequency windows and are robust against sharp corners and defects. We also observe intriguing topological refractions of the topological large-area waveguides into the ambient space at zigzag and armchair terminations. Our work highlights both the tunable width and the large bandwidth of topological waveguides, paving the way for topological photonic integrated circuits with high performance and multifunctionality.