Doping dependent exciton dynamics in a monolayer WSe2

Since the first observation of photoluminescence from a monolayer of MoS₂, studies of monolayer-thick semiconducting transition metal dichalcogenides (TMDCs) have brought a number of interesting discoveries.  The unique optical properties are determined by strong excitonic effects, the inversion-lacking hexagonal crystal symmetry and very strong spin-orbit interactions. As a result, monolayers of TMDCs are able to host different neutral and charged excitonic complexes. WSe₂ exhibits a very large range of such complexes because of its excitonic band inversion. Research into exciton properties has focused on studies of undoped or electron-doped WSe₂ because of the small spin splitting of the conduction band. In this talk, I will show that the large spin splitting of the valence band provides insight into interactions between different excitonic complexes and the role of localization in their dynamics. I will show that the binding of excitons into larger complexes occurs via phonon or free carrier scattering and discuss the role of disorder in the process.  These experiments shed light on the potential of using WSe_{2 ­}for non-classical light emitters.