Multi-Q magnets consist of superposed spin-density waves with distinct magnetic modulation vectors, enabling a wide range of magnetic orders depending on their combination. Among them, topologically nontrivial spin textures, such as a magnetic skyrmion, have been extensively studied owing to the emergence of topological Hall effects induced by real-space scalar spin chirality. Contrary to this expectation, we theoretically investigate another route to enhancing the Hall response under a topologically trivial double-Q spin textures with neither net scalar spin chirality nor a nonzero skyrmion number. Despite the cancellation of the scalar spin chirality, the double-Q magnetism exhibits a Hall response significantly larger than that of the ferromagnetic phase with a nonmonotonic dependence on the uniform magnetization, which is in stark contrast with a ferromagnetic state and a single-Q spiral state. Analyzing the multiorbital Kondo lattice model, we show that orbital hybridization induced by the double-Q superstructure result in a proliferation of Berry curvature hot spots in $\mathbf{k}$ space, thereby giving rise to a large anomalous Hall effect (AHE). This mechanism accounts for the observed giant AHE in ${\mathrm{GdRu}}_2{\mathrm{Si}}_2$ and ${\mathrm{GdRu}}_2{\mathrm{Ge}}_2$, thereby highlighting topologically trivial double-Q spin textures as promising spintronic materials.

Mesoscopic transport measurements are underexplored as probes of quasiparticles and their properties in correlated metals. The mixed valence compound ${\mathrm{YbAl}}_3$ exhibits a single-ion Kondo temperature of 670 K, while thermodynamic and transport properties (probed with specific heat, magnetic susceptibility, Hall effect, and resistivity) imply the onset of coherence of heavy fermion quasiparticles at $T^{*}\approx 37$ K. To characterize these quasiparticles, we utilize mesoscopic techniques familiar from weakly correlated conductors. In lithographically defined nanowires etched from epitaxial films, we observe weak antilocalization magnetoresistance and universal conductance fluctuations, consistent with electronic coherence lengths of tens of nanometers. Additionally, analysis of Johnson-Nyquist noise measurements as a function of bias current reveal, within the context of a range of accepted models, a significant electron-phonon energy loss that increases with decreasing temperature, a finding that we contextualize within the broader properties of ${\mathrm{YbAl}}_3$.

Flat bands, in which kinetic energy is quenched and quantum states become macroscopically degenerate, host a rich variety of correlated and topological phases, from unconventional superconductors to fractional Chern insulators. In Hermitian lattices, their formation mechanisms are now well understood, but whether such states persist, and acquire new features in non-Hermitian (NH) crystals, relevant to open and driven systems, has remained an open question. Here we show that the Hermitian principle for flat-band formation in bipartite lattices, based on a sublattice degeneracy mismatch, extends directly to the NH regime: whenever one sublattice hosts a momentum-independent eigenvalue with degeneracy exceeding that of its partner on the other sublattice, flat bands arise regardless of gain, loss, or complex couplings. Strikingly, at exceptional points, dispersive bands coalesce to form exceptional flat bands (EFBs) that persist beyond these singularities, exhibiting biorthogonal eigenmodes spanning both sublattices, with energies and lifetimes tunable via sublattice asymmetry and nonreciprocal couplings. This general framework unifies Hermitian and NH flat-band constructions, and reveals dispersionless states with no closed-system analog, as is the case of a bipartite lattice with imbalanced but constant sublattice chemical potentials. The proposed construction is applicable to synthetic platforms, from classical metamaterials, where flat bands can be directly emulated, to quantum-engineered systems such as photonic crystals and ultracold atom arrays, which should host correlated and topological phases emerging from such EFBs.

Identification of isolated Majorana zero modes (MZMs) is a key step toward the realization of fault-tolerant topological quantum computation. Here we show how the $T_1$-based noise magnetometry of a nitrogen-vacancy (NV) center qubit can reveal unique signatures of Majorana fermions bound to vacancies in a non-Abelian Kitaev quantum spin liquid (KQSL). The $1/T_1$ of the NV center is found to increase significantly when the working frequency of the NV center matches the energy difference between a MZM and a low-energy hybridized mode involving dangling Majorana fermions adjacent to vacancies. In experiments, this energy difference can be tuned by an external Zeeman field. Owing to the large excitation gap for flipping a local $Z_2$ gauge field, compared to the working frequency of NV centers, the $1/T_1$ spectrum is robust against other fluctuations in KQSLs at low temperatures. Our study presents a promising probe for identifying the non-Abelian phase in Kitaev materials.

The square-kagome lattice (SKL) antiferromagnet, composed of two-dimensional corner-sharing triangles, provides a prominent platform for studying frustrated magnetism. However, material realizations of the SKL remain scarce. Here, we report the single-crystal growth, structural characterization, magnetic and electric properties of ${\mathrm{KCu}}_7{\mathrm{TeO}}_4{\left({\mathrm{SO}}_4\right)}_5\mathrm{Cl}$, a nabokoite compound featuring a distorted and decorated SKL. Weak anomalies at temperature near 4 K are observed in both the magnetization and the specific heat data, indicating the onset of a magnetic transition. The observation of the ${}^{35}\mathrm{Cl}$ nuclear magnetic resonance line splits below 4.5 K further confirms the formation of the long-range-order antiferromagnetism. Magnetic susceptibility data reveal nearly isotropic Curie-Weiss temperatures ($\sim -145\mathrm{K}$) and $g$ factors ($\sim 2.4$) for both in-plane and out-of-plane magnetic fields. Moreover, we observe two successive ferroelectric transitions at $T_{\mathrm{FE}}1\sim 30\mathrm{K}$ and $T_{\mathrm{FE}}2\sim 27\mathrm{K}$, driven by inversion symmetry breaking, most likely associated with distortions in the ${\mathrm{Cu}2\mathrm{O}}_4{\mathrm{Cl}}_1$ pyramids and the adjacent ${\mathrm{SO}}_4$ tetrahedra. These results suggest that a three-dimensional model incorporating interlayer couplings via decorating Cu2 sites is essential for capturing the magnetic and electric behaviors in ${\mathrm{KCu}}_7{\mathrm{TeO}}_4{\left({\mathrm{SO}}_4\right)}_5\mathrm{Cl}$.

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.