Theory of exciton polarons in 2D Wigner crystals

TL;DR

This paper develops a microscopic theoretical model to understand exciton polarons in 2D Wigner crystals within monolayer TMDs, explaining experimental spectral features and revealing signatures of strong electronic correlations.

Contribution

The paper introduces a novel microscopic model that incorporates vibrational motion and electronic interactions to explain exciton-polaron spectra in 2D Wigner crystals.

Findings

Reproduces exciton-Umklapp feature in spectra

Explains higher-band attractive-polaron resonances

Identifies strong correlations via equal-strength polarons

Abstract

Monolayer transition-metal dichalcogenides (TMDs) provide a platform for realizing Wigner crystals and enable their detection via exciton spectroscopy. We develop a microscopic theoretical model for excitons interacting with the localized electrons of the Wigner crystal, including their vibrational motion. In addition to the previously observed exciton-Umklapp feature, the theory reproduces and explains the higher-band attractive-polaron resonances recently reported experimentally. Our model further uncovers that the appearance of two equal-strength and parallel attractive polarons, as commonly observed in WSe$_2$ and WS$_2$, is a signature of strong correlations in the electronic system. Altogether, our results demonstrate that accounting for electronic interactions is essential to reproduce and interpret the exciton-polaron spectra of TMDs.