Chiral nanophotonic interfaces for near-field optical control of two-dimensional semiconductors

The evanescent fields of waveguided optical modes in nanophotonic structures exhibit transverse spin angular momentum. These circularly polarized fields, which depend on position and propagation direction, enable reconfigurable interactions with circularly dichroic materials. Monolayer transition metal dichalcogenides (TMDCs) host valley-selective, circularly polarized optical transitions. Moreover, due to spin-valley locking in monolayer TMDCs, the spin degree of freedom of charge carriers can be manipulated. Here, we fabricate titanium dioxide (TiO2) nanophotonic structures on gated, encapsulated tungsten diselenide (WSe2) monolayers. We demonstrate near-field optical control of the spin polarization of resident electrons, illustrating the potential use of such interfaces for integrated photonics and opto-spintronics.