Exploring Electronic and Valley Properties of Single-layer SMSiN (M = Mo, W): a First-principles Study on Two-dimensional Janus Materials

In this study, we employ first-principles calculations to explore the electronic and valleytronic properties of single-layer (SL) SMSiN (M = Mo, W), which are two-dimensional Janus materials with strong spin-orbit coupling. Our findings indicate that SL SMoSiN/SWSiN possess a direct/indirect band gap, where the valence band maximum is situated at the /' point, giving rise to the formation of degenerate valleys. When considering spin-orbit coupling, SMoSiN and SWSiN 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 SMSiN. Moreover, the findings reveal high carrier mobility in SL SMSiN, notably in SWSiN, where hole carriers can achieve a remarkable mobility of up to 7.98 × 10 cm V s 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.