Seminar: Localized inter-valley defect excitons as single-photon emitters in WSe₂

June 3^rd 2019, 1G09 room at 11am

Single-photon emitters play a key role in present and emerging quantum technologies. Several recent measurements have established monolayer WSe₂ as a promising candidate for a reliable single photon source. The origin and underlying microscopic processes have remained, however, largely elusive. We present a multi-scale tight-binding simulation for the optical spectra of WSe₂ under non-uniform strain and in the presence of point defects employing the Bethe-Salpeter equation. Strain locally shifts excitonic energy levels into the band gap where they overlap with localized intra-gap defect states. The resulting hybridization allows for efficient filing and subsequent radiative decay of the defect states. We identify inter-valley defect excitonic states as the likely candidate for anti-bunched single-photon emission. This proposed scenario is shown to account for a large variety of experimental observations including brightness, radiative transition rates, the variation of the excitonic energy with applied magnetic and electric fields as well as the variation of the polarization of the emitted photon with the magnetic field.

Info: Associate Professor, Institute for Theoretical Physics, Vienna University of Technology