Environmentally-Sensitive Theory of Electronic and Optical Transitions in Atomically-Thin Semiconductors

TL;DR

This paper develops an electrostatic theory for atomically-thin semiconductors that accurately predicts how their electronic and optical properties depend on the surrounding dielectric environment, aligning well with ab initio calculations.

Contribution

It introduces a new electrostatic model that captures environment-sensitive band gap renormalization and optical transitions in atomically-thin semiconductors, improving upon previous approaches.

Findings

The theory agrees with GW and Bethe-Salpeter calculations for MoS₂.

Electronic band gap changes are offset by exciton binding energy shifts.

Optical transition energies are nearly environment-independent.

Abstract

We present an electrostatic theory of band gap renormalization in atomically-thin semiconductors that captures the strong sensitivity to the surrounding dielectric environment. In particular, our theory aims to correct known band gaps, such as that of the three-dimensional bulk crystal. Combining our quasiparticle band gaps with an effective mass theory of excitons yields environmentally-sensitive optical gaps as would be observed in absorption or photoluminescence. For an isolated monolayer of MoS$_2$, the presented theory is in good agreement with ab initio results based on the GW approximation and the Bethe-Salpeter equation. We find that changes in the electronic band gap are almost exactly offset by changes in the exciton binding energy, such that the energy of the first optical transition is nearly independent of the electrostatic environment, rationalizing experimental observations.