Interlayer Interaction Effects and Spin-Pseudospin Transfer in 2D MoSe$_{2}$-WSe$_{2}$ Heterostructures

Heterostructures composed of MoSe$_{2}$-WSe$_{2}$ monolayer semiconductors host spatially indirect interlayer excitons, which are bound states of an electron in the MoSe$_{2}$ layer and a hole in the WSe$_{2}$ layer. Interlayer excitons are observable in photoluminescence experiments as a low energy peak whose spectral position is consistent with the predicted type-II band alignment. The electron and hole which form the interlayer exciton are localized in momentum space valleys that occur at the (K and -K) corners of the Brillouin zone. To probe this interlayer valley physics, we perform two color pump-probe measurements to investigate the interactions between intralayer excitons in the heterostructure, resonantly pumping excitons in one layer and probing excitons in the other layer. We observe evidence of interlayer interaction effects in the nonlinear differential reflection spectra. Polarization dependent spectroscopy reveals evidence of interlayer spin-valley pseudospin transfer.