Exciton-Trion-Polaritons in Two-Dimensional Materials

TL;DR

This paper develops a many-body theoretical framework to describe exciton-trion-polaritons in doped two-dimensional materials, revealing their energy dispersions, compositions, and doping-dependent spectral features.

Contribution

It introduces a comprehensive model capturing exciton-trion-photon interactions and calculates polariton properties across doping levels, advancing understanding of hybrid excitations in 2D materials.

Findings

Polariton energy bands exhibit three distinct dispersions.

Spectral weights depend on Coulomb coupling strength and doping density.

Inclusion of unbound trion states is essential for accurate spectral transfer analysis.

Abstract

We present a many-body theory for exciton-trion-polaritons in doped two-dimensional materials. Exciton-trion-polaritons are robust coherent hybrid excitations involving excitons, trions, and photons. Signatures of these polaritons have been recently seen in experiments. In these polaritons, the 2-body exciton states are coupled to the material ground state via exciton-photon interaction and the 4-body trion states are coupled to the exciton states via Coulomb interaction. The trion states are not directly optically coupled to the material ground state. The energy-momentum dispersion of these polaritons exhibit three bands. We calculate the energy band dispersions and the compositions of polaritons at different doping densities using Green's functions. The energy splittings between the polariton bands, as well as the spectral weights of the polariton bands, depend on the strength of the Coulomb coupling between the excitons and the trions and which in turn depends on the doping density. The excitons are Coulomb coupled to both bound and unbound trion states. The latter are exciton-electron scattering states and their inclusion is necessary to capture the spectral weight transfer among the polariton bands as a function of the doping density.