Excitonic Stark effect in MoS$_2$ monolayers

TL;DR

This paper theoretically studies the excitonic Stark effect in MoS₂ monolayers under in-plane electric fields, revealing quadratic energy shifts, exciton ionization, and potential applications in energy harvesting and photodetection.

Contribution

It introduces a theoretical framework predicting the excitonic Stark effect and scaling relations in MoS₂ monolayers, enabling electro-optical response engineering.

Findings

Quadratic Stark shift of a few meV at 10 V/μm

Decrease in exciton spectral weight with increasing electric field

Subpicosecond exciton decay lifetimes at tens of V/μm

Abstract

We theoretically investigate excitons in MoS$_2$ monolayers in an applied in-plane electric field. Tight-binding and Bethe-Salpeter equation calculations predict a quadratic Stark shift, of the order of a few meV for fields of 10 V/$\mu$m, in the linear absorption spectra. The spectral weight of the main exciton peaks decreases by a few percent with an increasing electric field due to the exciton field ionization into free carriers as reflected in the exciton wave functions. Subpicosecond exciton decay lifetimes at fields of a few tens of V/$\mu$m could be utilized in solar energy harvesting and photodetection. We find simple scaling relations of the exciton binding, radius, and oscillator strength with the dielectric environment and an electric field, which provides a path to engineering the MoS$_2$ electro-optical response.