Defect-Induced Modification of Low-Lying Excitons and Valley Selectivity in Monolayer Transition Metal Dichalcogenides

Sivan Refaely-Abramson; Diana Y Qiu; Steven G Louie; Jeffrey B Neaton

doi:10.1103/PhysRevLett.121.167402

Defect-Induced Modification of Low-Lying Excitons and Valley Selectivity in Monolayer Transition Metal Dichalcogenides

Phys Rev Lett. 2018 Oct 19;121(16):167402. doi: 10.1103/PhysRevLett.121.167402.

Authors

Sivan Refaely-Abramson^{1

2}, Diana Y Qiu^{1

3}, Steven G Louie^{1

3}, Jeffrey B Neaton^{1

2

4}

Affiliations

¹ Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
² Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
³ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
⁴ Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, USA.

PMID: 30387666
DOI: 10.1103/PhysRevLett.121.167402

Abstract

We study the effect of point-defect chalcogen vacancies on the optical properties of monolayer transition metal dichalcogenides using ab initio GW and Bethe-Salpeter equation calculations. We find that chalcogen vacancies introduce unoccupied in-gap states and occupied resonant defect states within the quasiparticle continuum of the valence band. These defect states give rise to a number of strongly bound defect excitons and hybridize with excitons of the pristine system, reducing the valley-selective circular dichroism. Our results suggest a pathway to tune spin-valley polarization and other optical properties through defect engineering.