Manipulating spin-polarized photocurrents in 2D transition metal dichalcogenides

Manipulating spin polarization of electrons in nonmagnetic semiconductors by means of electric fields or optical fields is an essential theme of the conceptual nonmagnetic semiconductor-based spin-tronics. Here we experimentally demonstrate an electric method of detecting spin polarization in monolayer transition metal dichalcogenides (TMDs) generated by circularly polarized optical pumping. The spin-polarized photocurrent is achieved through the valley-dependent optical selection rules and the spin-valley locking in monolayer WS2, and electrically detected by a lateral spin-valve structure with ferromagnetic contacts. The demonstrated long spin-valley lifetime, the unique valley-contrasted physics, and the spin-valley locking make monolayer WS2 an unprecedented candidate for semiconductor-based spintronics.