Exciton-polarons in doped semiconductors in a strong magnetic field

TL;DR

This paper investigates how strong magnetic fields affect exciton-polarons in doped two-dimensional semiconductors, revealing magnetic oscillations and cyclotron resonance effects on the repulsive branch.

Contribution

It introduces a theoretical framework accounting for magnetic translation symmetry to analyze exciton-polaron behavior under magnetic fields in doped semiconductors.

Findings

Repulsive exciton-polaron branch shows magnetic oscillations.

Discrete peaks in the repulsive branch reflect exciton-cyclotron resonance.

Attractive branch remains weakly affected by magnetic fields.

Abstract

In previous work we have argued that the optical properties of moderately doped two-dimensional semiconductors can be described in terms of excitons dressed by their interactions with a degenerate Fermi sea of additional charge carriers. These interactions split the bare exciton into attractive and repulsive exciton-polaron branches. The collective excitations of the coupled system are many-body generalizations of the bound trion and unbound states of a single electron interacting with an exciton. In this article we consider exciton-polarons in the presence of an external magnetic field that quantizes the kinetic energy of the electrons in the Fermi sea. Our theoretical approach is based on a transformation to new basis that respects the underlying symmetry of magnetic translations. We find that the attractive exciton-polaron branch is only weakly influenced by the magnetic field, whereas the repulsive branch exhibits magnetic oscillations and splits into discrete peaks that reflect combined exciton-cyclotron resonance.