Optical Properties of Charged Defects in Monolayer MoS$_2$

TL;DR

This paper presents a theoretical study of how charged defects affect the optical spectrum of monolayer MoS$_2$, revealing defect-induced peaks that match experimental observations.

Contribution

It introduces a novel atomistic tight-binding approach to model charged defects and their impact on the optical properties of monolayer MoS$_2$.

Findings

Charged defects create new optical peaks 100-200 meV below the exciton peak.

Defect-induced peaks originate from in-gap bound states.

Results agree well with experimental data.

Abstract

We present theoretical calculations of the optical spectrum of monolayer MoS$_2$ with a charged defect. In particular, we solve the Bethe-Salpeter equation based on an atomistic tight-binding model of the MoS$_2$ electronic structure which allows calculations for large supercells. The defect is modelled as a point charge whose potential is screened by the MoS$_2$ electrons. We find that the defect gives rise to new peaks in the optical spectrum approximately 100-200 meV below the first free exciton peak. These peaks arise from transitions involving in-gap bound states induced by the charged defect. Our findings are in good agreement with experimental measurements.