We numerically and analytically study the transient dynamics of magnetic skyrmions in synthetic antiferromagnets under a magnetic field gradient. We consider skyrmions in a bilayer with antiferromagnetic coupling between the layers. The skyrmions in the two layers move almost perpendicular to the field gradient and the motion is eventually halted with the two skyrmions at a distance from each other. We find that the skyrmion displacement is proportional to the field gradient, while the time it takes to reach their final position is almost independent of it. Below a critical magnetic field gradient strength, the system displays an unusual remembering dynamics: when the magnetic field gradient is removed, the skyrmions return to their original positions to a high degree of accuracy. We explain this observation and other quantitative features using a moduli space dynamics approximation. We further provide an exact treatment of the dynamics that indicates that deviations from exact memory of the skyrmion position can arise.

The development of superconducting data storage devices is one of the coveted goals for next-generation low-power electronics, and interaction between superconducting and nontrivial topological states can potentially be useful to achieve this goal. Here we show that the superconducting diboride ${\mathrm{OsB}}_2$ hosts an anisotropic superconducting order parameter along with topological surface states which are spin polarized. Through the measurement of Andreev reflection on the surface of ${\mathrm{OsB}}_2$ we find that the superconducting order parameter senses the spin polarization of the topological surface states. As a consequence, the order parameter retains the memory of the exposure to a magnetic field, leading to a magnetic-field-dependent hysteresis effect. Thus we present nanoscale metallic junctions made on the surface of ${\mathrm{OsB}}_2$ as energy-efficient superconducting memory devices.

The propagation of waves in crystals is known to be strongly affected by the choice and the spatial distribution of inclusions in a matrix. We argue herewith that in-contact, impermeable inclusions lead to extremely wide band gaps for all 2D Bravais lattices. Contact points entail constrictions that efficiently slow wave propagation and lead to strongly flattened bands. A numerical demonstration is provided for a generic Helmholtz equation that is applicable to electromagnetic, acoustic, elastic, or water waves alike. Experiments conducted on square and hexagonal photonic crystals composed of touching copper tubes reveal that waves of certain radio frequencies quite remarkably traverse the minute gaps within the metallic framework, thereby confirming the theoretical predictions, including the presence of deeply subwavelength Bragg band gaps.

The thermoelectric effect, as a pivotal research domain bridging condensed matter physics and energy science, has garnered considerable research interest in recent decades owing to its critical applications in industrial waste heat recuperation and thermal regulation of micro/nanoelectronic devices. Conventional thermoelectric phenomena such as the Seebeck and Peltier effects have achieved widespread implementation in thermoelectric generators and solid-state refrigeration systems. The emergence of spincaloritronics has redirected scientific focus toward magnetic-originated thermoelectric effects, exemplified by the anomalous Nernst effect, the anomalous Ettingshausen effect, the spin Seebeck effect and the spin Peltier effect, all exhibiting an odd-symmetric dependence on magnetization, alongside a mutual orthogonal geometry among magnetization, temperature gradient, and charge current. However, the thermoelectric phenomenon of even-magnetization symmetry has rarely been studied. Here, we show the observation of the planar Ettingshausen effect proportional to the quadratic magnetization term in $3d$ ferromagnetic materials. This effect manifests as the generation of an in-plane thermal current induced by an in-plane electrical current under coplanar magnetization configurations, a feature that defies the orthogonal geometry in most magnetic thermoelectric effects. This observation not only establishes completeness in the symmetry landscape of magnetization-dependent thermoelectric responses but also provides possibilities for designing spintronic chips through thermoelectric synergy.

The interaction of light and matter under strong isotope disorder gives rise to unconventional physics that goes beyond the quantum perturbation theory. In boron arsenide, the large mass difference between the two stable boron isotopes presents a paradigmatic case where perturbation theory fails, yet a unified theoretical framework across the perturbative and nonperturbative regime has remained elusive. Here, we develop a nonperturbative approach to capture isotope-disorder effect in boron arsenide, which fundamentally alters light-matter interactions. We reveal that coherently mixed vibrations between two boron isotopes reshape the dielectric function in the nonperturbative regime. The nonperturbative isotope interactions dictate the properties of coupled surface phonon polaritons and near-field radiative heat transfer. Twofold tuning of radiative heat flux is achieved by modulating the surface phonon polariton resonance via isotope engineering. This work establishes a unified framework connecting the perturbative and nonperturbative limits, enabling quantitative predictions across the weak to strong disorder regime.

We perform a systematic study on the effects of electric fields in the Luttinger liquid phase of the one-dimensional spin-$1/2 K_1{J}_1{\mathrm{\Gamma }}_1{\mathrm{\Gamma }}_1^{\prime }{K}_2{J}_2$ model in the region of ferromagnetic nearest-neighboring Kitaev coupling. We find that while electric fields along (1,1,1) direction maintain the Luttinger liquid behavior, fields along other directions drive the system to a dimerized state. An estimation is made on how effective a (1,1,1) field is for tuning the Luttinger parameter in real materials. Our work is useful for understanding the effects of electric fields in one-dimensional generalized Kitaev spin models, and provides a starting point for exploring the electric-field-related physics in two dimensions based on a quasi-one-dimensional approach.

Among the superconducting hydrides under high pressure, a number of studies concentrate on the ternary compounds to explore unique superconductors, which are capable of reducing the stable pressure and maintain superconductivity. In this work, to verify our proposed strategy of ternary composition lines (TCLs) to explore ternary compounds, we combined the first-principles calculations and crystal structure predictions to study the ternary compounds Li-$X$-B ($X=\mathrm{Mo}$, W) under high pressure. After calculations along five and four TCLs in Li-W-B and Li-Mo-B, respectively, five Li-W-B compounds and four Li-Mo-B compounds were predicted. The compositions of ${\mathrm{LiWB}}_4, {\mathrm{Li}}_4{\mathrm{MoB}}_2$ and ${\mathrm{LiMo}}_2{\mathrm{B}}_2$ could be thermodynamically stable under high pressure, and ${\mathrm{Li}}_2{\mathrm{WB}}_6$ is around 0.02 eV/atom above the convex hull at 0 GPa, which has potential for synthesizing. Both of the predicted ${\mathrm{Li}}_2{\mathrm{WB}}_6 P6$/mmm and ${\mathrm{Li}}_2{\mathrm{WB}}_4 R\text{−}3m$ are superconducting and their $T_{\mathrm{c}}$ are around 11 K, which are similar to the $T_{\mathrm{c}}$ of ${\mathrm{WB}}_2 P6$/mmm around 100 GPa. An anomalous increase of $T_{\mathrm{c}}$ was found in ${\mathrm{Li}}_4{\mathrm{MoB}}_2 C2/m$ upon compression. We carried out full ternary search to evaluate the validity of the TCLs strategy in the Li-W-B system at 0 GPa. Our results are helpful for understanding the phase diagram of Li-$X$-B ($\mathit{X}=\mathrm{Mo}$, W) under high pressure and the introducing of Li atoms provide candidate structures to reduce the measured stable pressure from $\sim 100$ GPa in ${\mathrm{WB}}_2 P6$/mmm to 0 GPa. Meanwhile, we preliminarily validate the strategy of TCLs in structure predictions and we expect to improve this strategy in the future, shedding light on the studies of ternary compounds.

Motivated by the analogy between many-body localization (MBL) and single-particle Anderson localization on hierarchical graphs, we study localization on the Husimi tree, a generalization of the Bethe lattice with a finite density of local loops of arbitrary but finite length. The exact solution of the model provides a transparent and quantitative framework to systematically inspect the effect of loops on localization. Our analysis indicates that local loops enhance resonant processes, thereby reducing the critical disorder with increasing their number and size. At the same time, loops promote local hybridization, leading to an increase in the spatial extent of localized eigenstates. These effects reconcile key discrepancies between MBL phenomenology and its single-particle Anderson analog on hierarchical graphs. These results show that local loops are a crucial structural ingredient for realistic single-particle representations of many-body Hilbert spaces.

For a general non-Hermitian Floquet topological system, the interplay between periodic driving and non-Hermiticity not only complicates and diversifies the definition of the topological invariant but also makes it difficult to establish a direct correspondence between the topological invariant and dynamical observable quantities. In this work, we demonstrate that the winding number of a one-dimensional non-Hermitian Floquet system can be defined via the subspace of the effective Hamiltonian in both the frequency and time domains. More importantly, the topological winding number can be fully determined by measuring the dynamic winding number, which is defined in terms of the time-averaged stroboscopic spin texture, regardless of the initial state, driving frequency, and $\mathcal{P}\mathcal{T}$-symmetry. It is found that periodic driving can induce band inversion and create new band-gap closing points in the subspace of the effective Hamiltonian. These closing points constitute the origin of spontaneous $\mathcal{P}\mathcal{T}$-symmetry breaking. In particular, the $\mathcal{P}\mathcal{T}$-symmetry near the closing point induced by band inversion is more robust against perturbations of the gain or loss parameter than that associated with parameter renormalization. Our work not only clarifies the definition of the topological invariant for non-Hermitian Floquet systems in both the frequency and time domains, but it also provides a simpler dynamical approach for detecting non-Hermitian Floquet topological phases.

Deterministic, field-free switching of perpendicular magnetization is a key requirement for scalable and energy-efficient spintronic memory. Recent experiments have demonstrated threefold rotational ($3m$) symmetry-driven spin-orbit torque (SOT) switching in epitaxial (111)-oriented ${\mathrm{Tm}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ (TmIG)/Pt bilayers, where the deterministic switching is intrinsically governed by the magnetocrystalline anisotropy (MCA) of TmIG. In this study, we employ micromagnetic simulations to investigate the role of the interfacial Dzyaloshinskii-Moriya interaction (DMI) on the switching behavior, which is governed by the same $3m$ crystal symmetry. We find that the DMI substantially reduces the effective anisotropy energy barrier by stabilizing a canted magnetization state, while simultaneously amplifying the symmetry-guided effective magnetic field arising from the intrinsic $3m$ MCA. This synergy between the DMI and the underlying crystal symmetry significantly accelerates the deterministic SOT switching process, resulting in an approximately 40% reduction in the magnetization switching relaxation time, with a distinct maximum reduction observed at an optimal DMI strength. These findings reveal a unique synergistic acceleration mechanism between the DMI and the $3m$ crystal symmetry, extending beyond the conventional symmetry-breaking role typically attributed to a DMI.

An incommensurate charge-density wave is a periodic modulation of charge that breaks translational symmetry at a momentum that does not coincide with the primitive lattice vectors. Its Goldstone excitation, the phason, comprises collective gapless phase fluctuations. Aiming to unveil the mechanism behind the onset of incommensurate charge order in layered materials, we study a half-filled, four-band tight-binding model on a ladder with a relative shift $\delta =p/q$ between the legs, induced by the dimerization of one of them. The shift results in a moiré supercell comprising $q$ composite cells and a modulated interleg tunneling. The moiré potential compresses the leg bands into flat minibands near the Fermi level, resulting in additional low-energy peaks in the density of states. Including Coulomb interactions, we find an incommensurate charge-density-wave phase in which the charge modulation is out of phase between the legs. The collective excitations of this state are long-lived neutral, acoustic phasons whose speed is controlled by the moiré parameter $\delta$ and the interleg tunneling amplitude. This model sheds light on the role of interlayer incongruities in the formation of excitonic charge-ordered phases in van der Waals and heterostructured materials.

Recently developed artificial Kitaev chains, realized in quantum-dot arrays coupled via superconducting segments, offer a great degree of experimental control over parameters. Motivated by these advances, we study a dimerized Kitaev chain where onsite energies can be independently controlled. The dimerized Kitaev system can be interpreted as two effective Kitaev chains coupled via the onsite energies. We show that interference between Majorana edge modes from each effective chain can be controlled by these energies, resulting in either normal or Andreev transmission dominating the nonlocal conductance across the system. Such effect on the nonlocal conductance is connected to the fermion parity of the chain and, thus, to the system topological invariant. We explain the previous results using an analytical model describing the spatial decay and overlap of the Majorana edge modes from each effective chain.

Motivated by recent reports of ambient-pressure superconductivity in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ films grown on ${\mathrm{LaSrAlO}}_4$, we investigate the superconducting instability in a one-unit-cell (1UC) thin film using ab initio and random-phase approximation techniques. Compared to the high-pressure bulk system, the ratio of interlayer $d_{3z^2-r^2}$ hopping to intralayer $d_{x^2-y^2}$ hopping is suppressed in the 1UC thin film, and the crystal-field splitting of the $e_g$ orbitals is increased. Our calculation indicates that spin-fluctuation-driven pairing correlations are weak for the stoichiometric case at ambient pressure, but increase significantly under hole doping. The leading pairing symmetry is also found to change by hole doping. Specifically, we obtain a leading $d_{x^2-y^2}$ pairing state at moderate hole doping, followed by a $d_{xy}$ state at higher doping. These states are driven by intraband spin-fluctuation scattering within the $\gamma$ hole pocket centered around the $M$ point, and arise primarily from states in the Ni layer farther from the substrate. These results strongly suggest that the thin-film superconducting samples are hole-doped and that pairing in this system predominantly arises in the layer, as opposed to the interlayer pairing in the pressurized bulk system.

Dielectric screening plays a crucial role in shaping the electronic structure of two-dimensional (2D) materials. In 2D semiconductors, screened Coulomb interactions arising from the surrounding dielectric environment are known to induce band renormalization, which is typically understood as a rigid shift of the electronic bands. Here, we experimentally demonstrate that dielectric screening can also give rise to nonrigid, momentum-dependent band renormalization. Using temperature-dependent angle-resolved photoemission spectroscopy, we observe pronounced changes in the electronic band structure of monolayer ${\mathrm{MoS}}_2$ on a highly oriented pyrolytic graphite substrate. The results indicate that temperature-driven variations in the effective interlayer separation modulate the dielectric screening experienced by monolayer ${\mathrm{MoS}}_2$. At room temperature, the screening behavior is well described by a momentum-independent monopole approximation, whereas at liquid-helium temperatures the screening evolves into a multipolelike regime, leading to momentum-dependent band shifts.