Excitons in Defective Monolayer WSe₂.

To understand the role of localized excitons in defective 2D WSe₂, for example as single-photon emission sources, we aim in this work to confirm theoretically the type of defects that will result in defect-induced states that were experimentally characterized, and to predict excitations for larger engineered defects. First, by applying many-body G₀W₀ and G₀W₀-BSE methods, including spin-orbit coupling, calculations of dark and bright excitons of pristine 2D WSe₂ will be described. Next, we note that single and double Se vacancies incorporated in the monolayer resulted in red-shifted localized excitons consistent with measurements, while interestingly, results for experimentally observed three-fold rotational defects demonstrated significantly larger red-shifts from the X_A exciton. Finally, calculations of Raman band intensities of defective monolayer WSe₂ will be discussed, indicating that such Raman signatures could be used for characterization of defects in these 2D structures.