In this paper we introduce a theoretical model of a metallic magnetic system with noncollinear antiferromagnetic order. We introduce a mechanism of indirect interaction of conducting fermions with localized spins based on the tunneling processes of conducting fermions through the localized spins. We demonstrate that the interaction of conducting fermions with noncollinear antiferromagnetic order results in odd in momentum spin-momentum locking. The interaction resembles Rashba spin-orbit coupling but breaks the time-reversal symmetry. As a result, we show that a ferromagnet with noncollinear antiferromagnetic order is an insulator with anomalous Hall effect occurring without any spin-orbit coupling.

Advances in circuit quantum electrodynamics have enabled the generation of arbitrary nonclassical microwave states, enabling progress in physics. Here, we present a theoretical study of the electrical current in a Josephson tunnel junction interacting with a nonclassical electromagnetic environment. This allows us to generalize classical transport phenomena like photon-assisted tunneling and Shapiro steps to the quantum regime. We predict that the analysis of the supercurrent in such a setup enables the complete reconstruction of quantum states of the electromagnetic environment, something that is not possible with normal tunnel junctions.

Surface superconductivity is of scientific interest and technological significance. However, materials exhibiting robust surface superconductivity while preserving structurally stable bulk phases remain scarce. Here, we report an eclipsed configuration on the (111) surface of cubic diamond (ECDS), which resembles a hexagonal diamond motif and is stabilized by a periodic arrangement of boron and carbon atoms on the surface. First-principles calculations reveal that this structure is significantly more stable than the conventional staggered cubic diamond surface (SCDS). The enhanced stability is associated with hyperconjugation effects, resulting from wave-function overlap between surface C–B antibonding orbitals and subsurface C–C bonding orbitals. ECDS exhibits metallic behavior characterized by a two-dimensional hole band derived from the $p_x$ and $p_y$ orbitals of surface C and B atoms. Remarkably, it supports strong surface superconductivity with a transition temperature of 40.4 K, driven by the coupling between in-plane electronic states and out-of-plane vibrational modes of C–B bonds at the surface. These findings highlight the potential of chemically engineered diamond surfaces as a platform for achieving surface superconductivity, with promising applications in advanced materials.

Lacunar spinels $\mathrm{A}{\mathrm{M}}_4{\mathrm{X}}_8$ ($\mathrm{A}=\mathrm{Ga}$, Ge, Al; $\mathrm{M}=\mathrm{V}$, Mo, Nb, Ta; $\mathrm{X}=\mathrm{S}$, Se) have garnered significant attention due to their remarkable properties, including multiferroicity, Mott-Hubbard gaps, and skyrmion phases. In this study, we present temperature-dependent Raman spectroscopy measurements of $\mathrm{GaM}{\mathrm{o}}_4{\mathrm{S}}_8$, spanning the Jahn-Teller (JT) distortion and spin ordering transitions. Using group theory analysis and first-principles calculations, we identified and assigned ten Raman-active modes, among which the two lowest-energy modes, $A_1^1\left(T_2^1\right)$ and $A_1^2\left(T_2^2\right)$, were confirmed as JT active modes. The $A_1^2\left(T_2^2\right)$ mode exhibits a redshift as the temperature approaches 50 K from both sides, indicative of a soft mode and suggesting a displacive nature for the ferroelectric transition. Additionally, anomalies observed in the $A_1$ and $E$ modes near 50 K and 25 K correlate with the JT transition and subsequent magnetic ordering, pointing to significant electron-phonon and spin-phonon coupling in $\mathrm{GaM}{\mathrm{o}}_4{\mathrm{S}}_8$. These findings deepen our understanding of the mechanisms of the phase transition and the orbital-spin-lattice interactions in $\mathrm{GaM}{\mathrm{o}}_4{\mathrm{S}}_8$, while highlighting the crucial role of phonon dynamics in the $\mathrm{A}{\mathrm{M}}_4{\mathrm{X}}_8$ family.

Cr-based compounds are among the first single-layer magnets ever found. In addition, transition-metal dichalcogenides are promising candidates to show long-range ferromagnetic order down to the two-dimensional limit. We use ab initio calculations to provide a description of the various ${\mathrm{Cr}}_x{\mathrm{Se}}_{x+1}$ stoichiometries that may occur by analyzing from the bulk materials to the monolayer limit. We study the different structural distortions, including charge density waves that each system can present by analyzing their phonon spectra and dynamic stability. We provide a description of their basic electronic structure and study their magnetic properties, including the magnetocrystalline anisotropy energy. The evolution of all these properties with the dimensionality of the systems is discussed. This intends to be a comprehensive view of the broad family of quasi-two-dimensional Cr selenides.

In the research of the topological band phases, the conventional wisdom is to start from the crystalline translational symmetry systems. Nevertheless, the translational symmetry is not always a necessary condition for the energy bands. Here, we propose a systematic method of constructing the topological band insulators without translational symmetry in the amorphous systems. By way of the isospectral reduction approach from spectral graph theory, we reduce the structural-disordered systems formed by different multi-atomic cells into the isospectral effective periodic systems with the energy-dependent hoppings and potentials. We identify the topological band insulating phases with extended bulk states and topological in-gap edge states by the topological invariants of the reduced systems, density of states, and the commutation of the transfer matrix. In addition, when the building blocks of the two multi-atomic cells have different number of the lattice sites, our numerical calculations demonstrate that the existences of the flat band and the macroscopic bound states in the continuum in the amorphous systems. Our findings uncover an arena for the exploration of the topological band states beyond translational symmetry systems paradigm.

Landau levels play a crucial role in exploring fundamental phenomena of condensed-matter physics. Recently, a new paradigm for generating Landau levels by means of non-Hermiticity has been proposed. Notably, the zeroth Landau level states here are unpolarized, unlike the sublattice-polarized states in Hermitian Dirac systems. However, due to the challenges of implementing spatially varying dissipation and large gain-loss terms, the experimental demonstration of such Landau level has remained elusive. Here, we present an experimental observation in honeycomb circuit networks. Specifically, we construct a circuit lattice consisting of two types of non-Hermitian configurations to realize a large pseudomagnetic field. Through measuring the admittance spectrum and voltage responses, we successfully observe the unpolarized zeroth Landau level and Hall-like edge states in the non-Hermitian Dirac circuit lattice. Extending the system to a synthetic 3D non-Hermitian Weyl circuit, we further observe the non-Hermiticity-induced chiral LLs and surface modes. Our work paves the way for studying non-Hermitian quantum Hall physics and may be useful for designing novel topological devices.

We investigate the microscopic origin and spectral features of x-ray magnetic circular dichroism (XMCD) in collinear antiferromagnets with trigonal crystal fields, using $\alpha$-MnTe as a prototypical example. Although such systems exhibit zero net magnetization, we demonstrate that XMCD can emerge from the anisotropic magnetic dipole operator $T_z$, arising from quadrupolar spin distributions. By constructing a complete multipole basis and analyzing the symmetry conditions under trigonal distortion, we identify specific spin and orbital configurations that enable a finite XMCD response. Further, we employ both one-electron and multielectron models, including spin-orbit coupling and Coulomb interactions, to calculate the XMCD spectra for various $d^n$ configurations. Our findings provide theoretical benchmarks for XMCD in altermagnets and highlight the key role of orbital symmetry and magnetic anisotropy in realizing observable dichroic effects.

The dynamics of domain walls (DWs) was systematically investigated in epitaxial Pd/Co/Pd(111) samples with different thicknesses of the Pd bottom layer and, as a consequence, different interface roughnesses in the creep and flow regimes. The DWs were displaced by the simultaneous action of driving out-of-plane (OOP) and symmetry-breaking in-plane (IP) magnetic fields. A pronounced asymmetry in the dependencies of the velocities of the DWs on the applied IP magnetic field, $v\left(H_x\right)$, was observed in the creep regime, which was related to the dependence of the mobility of the DWs on their chirality, presumably due to a chiral damping. The investigated samples revealed different depinning fields due to different interface roughnesses. Notably, the asymmetry in the $v\left(H_x\right)$ dependencies almost disappeared in the flow regime, regardless of the extent of asymmetry observed in the creep regime and the values of depinning fields in the samples. We explain this fact by the precessional dynamics of DWs in the flow regime, in which the chirality of DWs changes between left-handed to right-handed with a large frequency, thus making DWs achiral on average. This study would deepen the understanding of the chiral dynamics of DWs and advance the development of DW devices.

The suppression of the amplitude of spectral resonances related to exciton states with large wave vectors is observed in the reflectance spectra of heterostructures with wide quantum wells in a transverse magnetic field (Voigt geometry). This effect becomes stronger with increasing exciton wave vector. This phenomenon is caused by the weakening of the exciton-light coupling and the ionization of excitons by the effective electric field arising owing to the magneto-Stark effect. An accurate microscopic theory that describes the exciton-light coupling of states with large wave vectors in a transverse magnetic field is developed. The reflectance spectra calculated within this theory show good agreement with the experimental data.

We observed enhanced magnetic phase shift signals at step edges of exfoliated $\mathrm{Cr}{\mathrm{Te}}_2$ flake's boundary as compared with that at the interior of a flake at room temperature, using magnetic force microscopy under zero applied magnetic field. The high quality and stochiometric crystal was grown by K-intercalation method. Rectangular and triangular flakes exfoliated from the bulk crystal exhibit stray field distributions at step edges of flakes and the stray field distribution depends on the shape of flake and number of domains inside the flake. This stray field is confirmed through magnetostatic simulations. The simulations show the surface normal components of in-plane magnetization at flake's geometric boundaries create stray field. The estimation of magnetic field strength at the steps is from scanning nitrogen-vacancy magnetometry. We observed the decay of magnetic contrast for flakes when exposed to an ambient environment for several weeks. These findings demonstrate how structural features such as steps and shape dictate magnetic textures in $\mathrm{Cr}{\mathrm{Te}}_2$.

Understanding the transport dynamics of orbital angular momentum in solids is crucial for the development of next-generation spintronic devices. Here, we provide experimental evidence of a ballistic-to-diffusive transition of orbital current transport in the ferromagnetic metal Ni. By systematically varying the Ni thickness and probing the resulting terahertz emission, we observe abrupt changes in both the delay and amplitude of the extracted ultrafast charge current. These changes are indicative of a transition from ballistic to diffusive orbital transport within the Ni layer. A numerical model is constructed to explain the observed delay, yielding a critical length of ballistic-to-diffusive transition ($\sim 4.05\mathrm{m}$). Our findings advance the understanding of orbital current transport in ferromagnetic metals and pave the way to designing novel functional orbitronics devices.

The nonlinear Hall effect (NLHE) can induce optical anisotropy by modifying a material's dielectric tensor, presenting opportunities for novel characterization and device applications. While the magneto-optical Kerr effect (MOKE) probes the linear Hall effect (LHE) in magnetic materials, an analogous optical probe for NLHE in nonmagnetic, time-reversal symmetric systems remains highly desirable. Here, we theoretically propose and investigate an NLHE-induced electro-optic Kerr effect (EOKE) as such a probe. Focusing on monolayer (ML) ${\mathrm{WTe}}_2$, a prototypical NLHE material, our analysis considers contributions from Berry curvature dipole (BCD), Drude, injection, and shift mechanisms. We demonstrate that the EOKE signal in ${\mathrm{WTe}}_2$ is predominantly governed by the BCD. Furthermore, the Kerr angle exhibits temporal oscillations at different optical frequencies, suggesting EOKE as a promising route for the time-resolved detection of NLHE and the dynamic investigation of material topology.

${\mathrm{LaNiGa}}_2$ has attracted attention due to evidence of time-reversal symmetry breaking in the superconducting state, alongside symmetry-enforced Dirac band crossings and anomalous pressure-dependent superconducting properties. Here we investigate the normal-state transport properties through Hall effect and magnetoresistance measurements. Our analysis reveals multiband behavior dominated by electron and hole bands with similar charge densities and mobilities. Density functional theory calculations support this multiband picture and show reasonable agreement with the experimentally determined carrier densities that remain nearly constant across the measured temperature range, indicating no electronic phase transitions. At low temperatures and high fields, the magnetoresistance exhibits quadratic to linear field dependence, which deviates from conventional semiclassical transport behavior. Possible explanations including quantum transport effects resulting from small Fermi surface pockets and impeded circular motions are discussed.

Two-dimensional arrays of ballistic Josephson junctions are important as model systems for synthetic quantum materials. Here, we investigate arrays of multiterminal junctions which exhibit a phase difference ${\phi }_0$ at zero current. When applying an in-plane magnetic field, we observe nonreciprocal vortex depinning currents. We explain this effect in terms of a ratchetlike pinning potential, which is induced by spontaneous supercurrent loops. Supercurrent loops arise in multiterminal ${\phi }_0$ junction arrays as a consequence of next-nearest-neighbor Josephson coupling. Tuning the density of vortices to commensurate values of the frustration parameter results in an enhancement of the ratchet effect. In addition, we find a surprising sign reversal of the ratchet effect near frustration 1/3. Our work calls for the search for novel magnetic structures in artificial crystals in the absence of time-reversal symmetry.

We investigate the thermoelectric transport properties of an interacting parallel double quantum dot in the Coulomb-blockade regime. Building on an analytical solution based on an equation-of-motion technique, we extend the formalism for the asymmetrically coupled situation and provide compact closed-form expressions for steady-state currents together with the differential conductance, Seebeck coefficient, and thermal conductance. We determine the operating points that maximize efficiency and output power of the system, clarifying their relation to standard near-equilibrium $ZT$ expressions. We further study the thermal rectification in both the open- and closed-circuit configurations and derive an expression for the open-circuit case. Interaction-induced resonances are understood in terms of the poles of the resulting Green's function, generating gate- and bias-dependent regions of enhanced efficiency at finite power, negative differential thermal conductance, and finite thermal rectification.

A site-selective ${}^{27}\mathrm{Al}$ nuclear magnetic resonance (NMR) study is carried out on the Kondo lattice compound ${\mathrm{CePtAl}}_4{\mathrm{Ge}}_2$, which crystallizes in a rhombohedral lattice with quasi-two-dimensional Ce layers forming a triangular lattice network. Two inequivalent Al sites, Al(1) and Al(2), are unambiguously assigned by comparing measured nuclear quadrupole parameters with electric field gradients obtained from electronic structure calculations. Knight shift analysis yields distinct hyperfine coupling constants, revealing that they arise predominantly from Ruderman-Kittel-Kasuya-Yosida (RKKY)-type transferred hyperfine fields through conduction electrons. Spin-lattice relaxation measurements reveal pronounced anisotropic spin fluctuations, and a comparison of the relaxation rates between the two Al sites clarifies the momentum-space structure of these fluctuations. At low magnetic fields, ${\left(T_{1}T\right)}^{-1}$ is strongly enhanced on cooling toward the Néel temperature, indicating the growth of in-plane antiferromagnetic correlations in the paramagnetic state.