Strong spin-orbit coupling effect induced large valley splitting in Janus MSeXH (M = Cr, Mo W; X = N, P)

Abstract

The exploration of valley physics in two-dimensional materials with strong spin-orbit coupling is of great significance to fundamental physics. In this work, we demonstrated the family of two-dimensional MSeXH (M = Cr, Mo, W; X = N, P) is the promising 2D valley materials based on the first-principles calculations. We found that monolayer MSeXH exhibit large valley splitting, in which, monolayer WSePH has the largest value as high as 495 meV. This is mainly due to the strong spin-orbital coupling effect and the built-in vertical E-field in the Janus structure. The valley splitting remain existence under biaxial strain from -4% to 4% and 1L MoSeNH exhibits a relatively high carrier mobility as the example. The study assessed the Berry curvature at the valence band maximum and analysed its relationship with the valley Hall effect. The computational results confirm that the material has good mechanical and dynamic stability. This work provides a promising family of 2D valleytronic materials for the practical application of valley electronics.