Gate-Control Spin-Orbit Torques in Centrosymmetric Two-Dimensional Materials
Chuang-Han Hsu1,2*, Zhifeng Zhu3, Vitor M. Pereira4, Gengchiau Liang1,4
1Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
2Institute of Physics, Academia Sinica, Taipei, Taiwan
3School of Information Science and Technology, ShanghaiTech University, Shanghai, China
4Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore
* Presenter:Chuang-Han Hsu,
Controllable spin-orbit torque (SOT) in centrosymmetric two-dimensional (2D) materials is proposed by incorporating the hidden spin polarization. We center on the SOT driven by the Rashba- Edelstein effect, and consider the induced spin accumulation that can give rise to both field-like and spin-transfer-like torques. In this new mechanism, the sign of SOT is determined by an external gate-field instead of the direction of its driven current. Through a comprehensive analysis in all Layer groups for 2D systems, we identify particular types of polar site symmetry allowing us to generate perpendicular spin via an in-plane current, which can be applied in all-electric deterministic switching for perpendicular magnetic layers. We further demonstrate these compelling features in monolayer 1T’-MoTe2 and Td-WTe2, and reveal that the calculated effective magnetic field and spin-to-charge conversion efficiency are sizable. Furthermore, we uncover that the gate-field dependence of SOT can be either linear or sigmoid-type, which is achieved by tuning the Fermi level. This study opens a promising route to realize the SOT device with perpendicular magnetic anisotropy (PMA). Meanwhile, we introduce a new feasible way for the advanced logic design by integrating monolayer-thin transition metal dichalcogenide materials.

Keywords: spin-orbit torque, hidden spin polarization, Rashba- Edelstein effect