Prediction of a new two-dimensional valleytronic semiconductor MoGeP with large valley spin splitting.

Recently, MoSiN with large valley spin splitting was experimentally synthesized. However, materials with large valley spin splitting are still rare. We predict a new two-dimensional (2D) MoGeP material. It has large valley spin splitting and excellent optical absorption properties. The results show that 2D MoGeP is a direct semiconductor with a bandgap of 887 meV. Its valley spin splitting (Δ) at the top of the valence band is 153 meV because of the inversion symmetry breaking and spin-orbit coupling (SOC). 2D MoGeP transforms from a semiconductor to a metal under a biaxial strain of 6%. Δ increases monotonically from 137 meV to 157 meV under biaxial strain. In addition, the lowest exciton state of 2D MoGeP is near 770 nm, and the optical absorption coefficient in the ultraviolet range is higher than that of MoS. Our results suggest that 2D MoGeP has excellent potential for applications in valley electronics and optoelectronic devices.