Manipulation of the Rashba spin-orbit coupling of a distorted <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mtext>-phase</mml:mtext></mml:mrow></mml:math> Janus WSSe monolayer: Dominant role of charge transfer and orbital components
Wenzhe Zhou, Jianyong Chen, Bei Zhang, Haiming Duan, Fangping Ouyang
Abstract
Janus monolayer materials, as the thinnest materials that may possess strong Rashba spin-orbit coupling, are helpful for the miniaturization of the charge-spin conversion devices. Using first-principles calculations, we investigated the structural stability and Rashba spin-orbit coupling of distorted $1T\text{-phase}$ Janus monolayer WSSe. Although the W atoms rotating around the Se atom are dynamically unstable in the stress-free state, the imaginary frequency disappears by applying a small compressive strain. From the perspectives of macroscopic charge transfer and microscopic atomic orbital compositions, the mechanism of the Rashba spin-orbit coupling strength of the distorted $1T\text{-phase}$ Janus monolayer WSSe was analyzed. The coupling strength can be greatly manipulated when \ensuremath{-}5 to 5% biaxial strain is applied. The charge transfer caused by the larger lattice constant and the rotation of the W atoms reduce the gradient of the potential so that the greater the electric polarization, the weaker the spin-orbit coupling. The coupling strength of different electronic states is determined by the proportion of the out-of-plane atomic orbitals, where ${d}_{\mathrm{x}z}$ and ${d}_{yz}$ orbits play the dominant role. These results contribute to the design of materials with greater Rashba spin-orbit coupling and the understanding of its mechanism.