Observation of macroscopic valley-polarized monolayer exciton-polaritons at room temperature

TL;DR

This study demonstrates room-temperature valley-polarized exciton-polaritons in a monolayer WS2 microcavity, showing enhanced valley polarization and revealing dynamics through a microscopic model of relaxation and decay processes.

Contribution

It reports the first observation of macroscopic valley-polarized exciton-polaritons at room temperature in a monolayer WS2 microcavity, with detailed analysis of their dynamics.

Findings

Enhanced valley polarization in exciton-polaritons compared to bare WS2

Valley polarization observable under non-resonant excitation at ambient conditions

Microscopic model explains wave vector-dependent valley depolarization

Abstract

In this letter, we address the chiral properties of valley exciton-polaritons in a monolayer of WS2 in the regime of strong light-matter coupling with a Tamm-Plasmon resonance. We observe that the valley polarization, which manifests in the circular polarization of the emitted photoluminescence, is strongly enhanced in comparison to bare WS2 monolayers, and can even be observed under non-resonant excitation at ambient conditions. We study the relaxation and decay dynamics of exciton-polaritons in our device, and present a microscopic model to explain the wave vector-dependent valley depolarization as an interplay of bright and dark states, electron-hole exchange interaction and the linear polarization splitting inherent to the microcavity.