Prediction of a new two-dimensional valleytronic semiconductor MoGe 2 P 4 with large valley spin splitting.

Recently, MoSi 2 N 4 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) MoGe 2 P 4 material. It has large valley spin splitting and excellent optical absorption properties. The results show that 2D MoGe 2 P 4 is a direct semiconductor with a bandgap of 887 meV. Its valley spin splitting (Δ V ) at the top of the valence band is 153 meV because of the inversion symmetry breaking and spin-orbit coupling (SOC). 2D MoGe 2 P 4 transforms from a semiconductor to a metal under a biaxial strain of 6%. Δ V increases monotonically from 137 meV to 157 meV under biaxial strain. In addition, the lowest exciton state of 2D MoGe 2 P 4 is near 770 nm, and the optical absorption coefficient in the ultraviolet range is higher than that of MoS 2 . Our results suggest that 2D MoGe 2 P 4 has excellent potential for applications in valley electronics and optoelectronic devices.