Gate-Control Spin-Orbit Torques in Centrosymmetric Two-Dimensional Materials

Chuang-Han Hsu^1,2*, Zhifeng Zhu³, Vitor M. Pereira⁴, Gengchiau Liang^1,4

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, email:hanshsu@gate.sinica.edu.tw

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