Demonstration of TiO2-monolayer TMDC interface

We demonstrate the integration of TiO2 nanophotonics and monolayer transition metal dichalcogenides (TMDCs) by fabricating a TiO2 waveguide on top of hBN-encapsulated monolayer tungsten diselenide (WSe2). The evanescent field of the propagating modes in the waveguide carries transverse optical spins, which can selectively couple to the WSe2 excitonic states in the two opposite valleys. The coupling allows us to generate a flux of spatially separated valley-polarized excitonic states when we pump from the waveguide. This study sheds light on future valleytronic applications of nanophotonic-TMDC interfaces.