Jia-Wei Mei

We systematically investigate the prominent third-order longitudinal nonlinear transport in centrosymmetric van der Waals antiferromagnet Fe5AsTe2. It is shown that the third-order longitudinal response can be decomposed into a magnetism-driven term and a field-induced term. Below the Néel temperature, the magnetism contribution dominates over the field contribution by an order of magnitude and evolves markedly with the magnetic phase transitions. It manifests as a plateau in the zero-field antiferromagnetic state and saturates in the high-field ferromagnetic phase. Scaling law analysis further reveals that the third-order longitudinal conductivity follows a characteristic polynomial in the linear conductivity expected for the third-order skew scattering. Our work demonstrates that the third-order longitudinal nonlinear response serves as an effective electrical probe of magnetic order evolution in centrosymmetric antiferromagnets, laying a foundation for future nonlinear antiferromagnetic spintronic devices.

Quantum interference phenomena in superconductors, such as Josephson interference and Little-Parks oscillations, serve as powerful probes of phase coherence, symmetry breaking, and vortex dynamics. However, they are typically observed in well-defined mesoscopic structures, and their behavior in the two-dimensional limit remains largely unexplored. Here, we report periodic magnetoresistance oscillations, superconducting interference patterns, and interfering diode effect in unpatterned few-layer NbSe_{2}. These phenomena emerge exclusively within the superconducting fluctuation regime of thin samples, consistent with the enhanced anomalous metallic behavior of atomically thin NbSe_{2}. The nonmonotonic temperature dependence of both the oscillation amplitude and the diode efficiency can be captured by a model in which thermally activated vortices traverse intrinsic supercurrent loops. Our results reveal that the observed interference phenomena originate from the lost of global phase coherence, providing a new route to accessing interference effects in unpatterned superconductors.

The quantum geometric tensor unifies the Berry curvature (its imaginary part) and the quantum metric (its real part), yet Raman studies of chiral phonons have so far accessed only the former. We perform circularly polarized Raman spectroscopy on the quantum magnet K_{2}Co(SeO_{3})_{2}, where the field-odd chiral splitting Δω and the field-even center shift δω_{c} collapse onto a single curve across temperature and magnetic field, revealing a common microscopic origin for both observables. Since Δω reflects the Berry curvature, the concomitant even component δω_{c}, arising from the same microscopic origin, captures the field-induced change of the quantum metric-the diagonal Born-Oppenheimer correction. Across two resolvable E_{g} modes, the unified data are well captured by a simple empirical relation, δω_{c}=γ(Δω)^{2}. These results establish Raman spectroscopy as a direct probe of the quantum metric and an operational decomposition of quantum geometry within a single measurement.

Van der Waals antiferromagnetic semiconductors are promising platforms for energy-efficient two-dimensional spintronics. However, their intrinsic spin degeneracy and the difficulty of achieving electrical spin control pose major challenges for practical device implementation. Here, we present a distinct spintronic platform based on an antiferromagnetic semiconductor CrSBr, in which carrier doping induced by gate-controlled intercalation drives a reversible, zero-field antiferromagnetic to ferromagnetic phase transition, enabling direct and full electrical control of both magnetic order and spin polarization. Exploiting this transition, we engineer CrSBr/graphene heterostructures that leverage interfacial charge transfer to spatially pattern magnetic phases, resulting in lateral spin valves with gate-controlled spin polarization reversal, all without ferromagnetic contacts. Crucially, this mechanism also enables electrical switching of magnetic order via spin-transfer torque at ultralow current densities (3 A/cm²), demonstrating its efficiency and device compatibility. These findings open a new paradigm for reconfigurable, all-electrical spintronic systems based on van der Waals antiferromagnetic semiconductors.

The quantum geometric tensor (QGT) unifies the Berry curvature (its imaginary part) and the quantum metric (its real part), yet Raman studies of chiral phonons have so far accessed only the former. We perform circularly polarized Raman spectroscopy on the quantum magnet K2Co(SeO3)2, where the field-odd chiral splitting and the field-even center-frequency shift collapse onto a single curve across temperature and magnetic field, revealing a common microscopic origin for both observables. Since the chiral splitting reflects the Berry curvature, the concomitant even component, arising from the same microscopic origin, captures the field-induced change of the quantum metric, corresponding to the diagonal Born-Oppenheimer correction. Across two resolvable Eg modes, the unified data are well captured by a simple empirical quadratic relation. These results establish Raman spectroscopy as a direct probe of the quantum metric and an operational decomposition of quantum geometry within a single measurement.