Manipulation of the large Rashba spin splitting in polar two-dimensional transition metal dichalcogenides

TL;DR

This study demonstrates that the Rashba spin splitting in polar transition metal dichalcogenide monolayers can be significantly tuned using biaxial strain, offering potential for advanced spintronic and valleytronic applications.

Contribution

The paper reveals how biaxial strain effectively modulates Rashba SOC in MXY monolayers, highlighting the role of orbital overlap and electric fields in this process.

Findings

Large Rashba spin splitting induced by mirror symmetry breaking.

Biaxial strain can tune Rashba SOC by approximately ±50%.

External electric field has a lesser effect than strain on Rashba SOC.

Abstract

Transition metal dichalcogenide (TMD) monolayers MXY (M=Mo, W, X(not equal to)Y=S, Se, Te) are two-dimensional polar semiconductors. Setting WSeTe monolayer as an example and using density functional theory calculations, we investigate the manipulation of Rashba spin orbit coupling (SOC) in the MXY monolayer. It is found that the intrinsic out-of-plane electric field due to the mirror symmetry breaking induces the large Rashba spin splitting around the Gamma point, which, however, can be easily tuned by applying the in-plane biaxial strain. Through a relatively small strain (from -2% to 2%), a large tunability (from around -50% to 50%) of Rashba SOC can be obtained due to the modified orbital overlap, which can in turn modulate the intrinsic electric field. The orbital selective external potential method further confirms the significance of the orbital overlap between W-dz2 and Se-pz in Rashba SOC. In addition, we also explore the influence of the external electric field on Rashba SOC in the WSeTe monolayer, which is less effective than strain. The large Rashba spin splitting, together with the valley spin splitting in MXY monolayers may make a special contribution to semiconductor spintronics and valleytronics.