Tunable PL in W-based TMDs probed by optical vortex beam*

Selection rules for optical transitions in monolayer transition metal dichalcogenides are governed by the spin and valley degree of freedom of excitons. The intravalley scattering dynamics is responsible for photoluminescence (PL) quenching in WS₂ and WSe₂ at low temperature. The PL intensity of bright exciton at steady state is determined by intravalley scattering rate between bright and dark exciton states. In this work we propose a technique to probe the PL spectrum of monolayer W-based TMDs via photo excitation utilizing optical vortex beam and investigate the effect of intravalley scattering.