Excitonic structure of the optical conductivity in MoS$_2$ monolayers

TL;DR

This study models the excitonic spectrum and optical conductivity of MoS$_2$ monolayers, incorporating anomalous screening effects and substrate influence, and validates results against experimental data.

Contribution

It introduces a combined approach using a Keldysh potential and tight-binding model to accurately compute excitonic properties in MoS$_2$ monolayers.

Findings

Optical conductivity matches experimental data up to UV energies.

C excitons originate from extended Brillouin zone regions.

Effective models are advantageous for exploring exciton properties.

Abstract

We investigate the excitonic spectrum of MoS$_2$ monolayers and calculate its optical absorption properties over a wide range of energies. Our approach takes into account the anomalous screening in two dimensions and the presence of a substrate, both cast by a suitable effective Keldysh potential. We solve the Bethe-Salpeter equation using as a basis a Slater-Koster tight-binding model parameterized to fit ab initio MoS$_2$ band structure calculations. The resulting optical conductivity is in good quantitative agreement with existing measurements up to ultraviolet energies. We establish that the electronic contributions to the C excitons arise not from states in the vicinity of the $\Gamma$ point, but from a set of $k$-points over extended portions of the Brillouin zone. Our results reinforce the advantages of approaches based on effective models to expeditiously explore the properties and tunability of excitons in TMD systems.