Radially polarized light beams from spin-forbidden dark excitons and trions in monolayer WSe2

The rich optical properties of transition metal dichalcogenide monolayers (TMD-MLs) render these materials promising candidates for the design of new optoelectronic devices. Despite the large number of excitonic complexes in TMD-MLs, the main focus has been placed on optically bright neutral excitons. Spin-forbidden dark excitonic complexes have been addressed for basic science purposes, but not for applications. We report on spin-forbidden dark excitonic complexes in ML WSe2 as an ideal system for the facile generation of radially polarized light beams. Furthermore, the spatially resolved polarization of photoluminescence beams can be exploited for basic research on excitons in two-dimensional materials.