Electron-exciton interactions in the exciton-polaron problem

TL;DR

This paper provides a microscopic derivation of electron-exciton interactions in doped 2D semiconductors, revealing classical charge-dipole behavior and explaining absorption features with a simple contact potential model.

Contribution

It introduces a microscopic approach to electron-exciton interactions, improving understanding of exciton-polaron formation in doped semiconductors.

Findings

Interactions exhibit classical charge-dipole behavior at long range.

Weak modification of interactions at moderate doping levels.

Absorption dependence on doping is captured by a contact potential model.

Abstract

Recently, it has been demonstrated that the absorption of moderately doped two-dimensional semiconductors can be described in terms of exciton-polarons. In this scenario, attractive and repulsive polaron branches are formed due to interactions between a photo-excited exciton and a Fermi sea of excess charge carriers. These interactions have previously been treated in a phenomenological manner. Here, we present a microscopic derivation of the electron-exciton interactions which utilizes a mixture of variational and perturbative approaches. We find that the interactions feature classical charge-dipole behaviour in the long-range limit and that they are only weakly modified for moderate doping. We apply our theory to the absorption properties and show that the dependence on doping is well captured by a model with a phenomenological contact potential.