Exploring electronic and valley properties of single-layer SMSiN2 (M = Mo, W): a first-principles study on two-dimensional Janus materials

Abstract

In this study, we employ first-principles calculations to explore the electronic and valleytronic properties of single-layer (SL) SMSiN₂ (M = Mo, W), which are two-dimensional Janus materials with strong spin–orbit coupling. Our findings indicate that SL SMoSiN₂/SWSiN₂ possess a direct/indirect band gap, where the valence band maximum is situated at the K/K′ point, giving rise to the formation of degenerate valleys. When considering spin–orbit coupling, SMoSiN₂ and SWSiN₂ demonstrate intriguing valley spin splitting in their valleys, with a maximum splitting of up to 0.14/0.39 eV in the valence bands. By implementing magnetic doping with V and Cr, we provide a demonstration that valley polarization could be realized in SL SMSiN₂. Moreover, the findings reveal high carrier mobility in SL SMSiN₂, notably in SWSiN₂, where hole carriers can achieve a remarkable mobility of up to 7.98 × 10³ cm² V⁻¹ s⁻¹ along the zigzag direction. Furthermore, our observations suggest that strain can be effectively utilized to manipulate the character and magnitude of the band gap, as well as the valley spin splitting in these materials.