Effects of Point Defects on the Optical Spectra of Monolayer Transition Metal Dichalcogenides*

Point defects are known to play an important role in the optical properties of quasi-two-dimensional materials. For instance, the photoluminescence spectra of transition metal dichalcogenides (TMDs) show broad, low energy features that are attributed to defects, and researchers have proposed exploiting defects in TMDs as catalytic centers and single-photon emitters. We use the GW and GW-BSE approach to study the quasiparticle energy levels and optical spectra associated with point defects in monolayer TMDs. We find that defect-state excitons hybridize very strongly with normal excitons in the pristine monolayer, allowing a defect to act as an exciton trap or as a pathway for exciton dephasing.