Excitonic theory of doping-dependent optical response in atomically thin semiconductors

TL;DR

This paper develops a microscopic theory to understand how residual doping affects excitonic optical responses in atomically thin semiconductors, revealing tunable many-body effects including trion formation and scattering states.

Contribution

It introduces a diagonalization approach for the exciton-Fermi sea interaction and models the coupled dynamics of excitons, trions, and scattering states in doped 2D semiconductors.

Findings

Doping influences exciton resonances significantly.

Identification of ground and excited state trions.

Theoretical framework matches experimental optical spectra.

Abstract

The interaction of optically excited excitons in atomically thin semiconductors with residual doping densities leads to many-body effects which are continuously tunable by external gate voltages. Here, we develop a fully microscopic theory to describe the doping-dependent manipulation of the excitonic properties in atomically thin transition metal dichalcogenides. In particular, we establish a diagonalization approach for the Schr\"odinger equation which characterizes the interaction of a virtual exciton with the Fermi sea of dopants. Solving this many-body Schr\"odinger equation provides access to trions as well as a continuum of scattering states. The dynamics of coupled excitons, trions, and scattering continua is subsequently described by Heisenberg equations of motion including mean-field contributions and correlation effects due to the interaction of excitons with trions and scattering continuum states. Our calculations for optical excitation close to the band edge reveal the influence of doping on the exciton resonances in combination with the simultaneous identification of not only ground-, but also excited-, state trion resonances.