Jiaqi Zhou's scientific contributions

Spin Hall effect plays a critical role in spintronics since it can convert charge current to spin current. Using state-of-the-art ab initio calculations including quadrupole and spin-orbit coupling, the charge and spin transports have been investigated in pristine and doped two-dimensional III-V semiconductors. Valence bands induce a strong scattering which limits charge conductivity in the hole-doped system, where spin Hall conductivity is enhanced by the spin-orbit splitting, yielding an ultrahigh spin Hall ratio $\xi\approx0.9$ in GaAs monolayer at room temperature.

The control of spin current is pivotal for spintronic applications, especially for spin-orbit torque devices. The spin Hall effect is a prevalent method to generate spin current. However, it is difficult to manipulate its spin polarization in a nonmagnet. Recently, the discovery of spin current in ferromagnets offers an opportunity to realize the manipulation. In the present Letter, the spin current in the van der Waals ferromagnet Fe3GeTe2 (FGT) with varying magnetization is theoretically investigated. It has been observed that the spin current in FGT presents a nonlinear behavior with respect to magnetization. In-plane and out-of-plane spin polarizations emerge simultaneously, and the bilayer FGT can even exhibit arbitrary polarization owing to the reduced symmetry. More intriguingly, the correlation between the anomalous Hall effect and spin anomalous Hall effect has been interpreted from the aspect of Berry curvature and spin. This work illustrates that the interplay of magnetism and symmetry can effectively control the magnitude and polarization of the spin current, providing a practical method to realize exotic spin-orbit torques.

The control of spin current is pivotal for spintronic applications, especially for spin-orbit torque devices. Spin Hall effect (SHE) is a prevalent method to generate spin current. However, it is difficult to manipulate its spin polarization in nonmagnet. Recently, the discovery of spin current in ferromagnet offers opportunity to realize the manipulation. In the present work, the spin current in van der Waals ferromagnet Fe3 GeTe2 (FGT) with varying magnetization is theoretically investigated. It has been observed that the spin current in FGT presents the nonlinear behavior with respect to magnetization. The in-plane and out-of-plane spin polarization emerges simultaneously, and the bilayer FGT can even exhibit arbitrary spin polarization thanks to the reduced symmetry. More intriguingly, the correlation between anomalous Hall effect (AHE) and spin anomalous Hall effect (SAHE) has been interpreted from the aspect of Berry curvature. This work illustrates that the interplay of symmetry and magnetism can effectively control the magnitude and spin polarization of the spin current, providing a practical method to realize exotic spin-orbit torques.