Valleytronics with interlayer excitons in MoSe$_{\mathrm{2}}$-WSe$_{\mathrm{2}}$ heterostructures

Monolayer transition metal dichalcogenides (MoSe$_{\mathrm{2}}$, WSe$_{\mathrm{2}})$ are direct bandgap semiconductors. The optical properties of these two-dimensional (2D) semiconductors are dominated by excitons that occur at two nonequivalent (K and --K) valleys on the edge of the Brillouin zone. In this presentation, I will discuss the electronic and optical physics of 2D heterostructures that are fabricated by vertically stacking single monolayers of WSe$_{\mathrm{2\thinspace }}$and MoSe$_{\mathrm{2}}$ together. The resulting 2D heterostructure realizes a type-II junction, allowing for the formation of interlayer excitons with the electron in the MoSe$_{\mathrm{2}}$ layer and the hole in the WSe$_{\mathrm{2}}$ layer. I will show that the valley physics of the monolayers is inherited by the interlayer excitons, evidenced by helicity dependent photoluminescence measurements, and report on the dynamics of interlayer exciton relaxation. I will discuss applications of interlayer excitons to valleytronics, which in analogy to spin in spintronic, seeks to utilize valley polarizations for low power information processing.