Phonon signatures in spectra of exciton polaritons in transition metal dichalcogenides

TL;DR

This paper investigates how phonons influence the spectra of exciton polaritons in transition metal dichalcogenides embedded in optical cavities, revealing temperature and detuning effects on line shapes and linewidths.

Contribution

It introduces a time convolutionless master equation approach to analyze phonon effects on polariton spectra, highlighting unique dispersion and linewidth behaviors.

Findings

Lower polariton linewidth is largely unaffected by acoustic phonons.

Acoustic phonons create a low-energy shoulder in the upper polariton resonance.

Inhomogeneous broadening dominates the lower polariton linewidth at low temperatures.

Abstract

Embedding a monolayer of a transition metal dichalcogenide in a high-Q optical cavity results in the formation of distinct exciton polariton modes. The polaritons are affected by the strong exciton-phonon interaction in the monolayer. We use a time convolutionless master equation to calculate the phonon influence on the spectra of the polaritons. We discuss the non-trivial dependence of the line shapes of both branches on temperature and detuning. The peculiar polariton dispersion relation results in a linewidth of the lower polariton being largely independent of the coupling to acoustic phonons. For the upper polariton, acoustic phonons lead to a low-energy shoulder of the resonance in the linear response. Furthermore, we analyze the influence of inhomogeneous broadening being the dominant contribution to the lower polariton linewidth at low temperatures. Our results point towards interesting phonon features in polariton spectra in transition metal dichalcogenides.