Valley polarization of exciton-polaritons in monolayer WSe2 in a tunable microcavity

TL;DR

This paper demonstrates tunable valley polarization of exciton-polaritons in monolayer WSe2 within a voltage-controlled microcavity, revealing control over valley dynamics via resonance with different trion states.

Contribution

It introduces a voltage-tunable microcavity system enabling control over exciton-polariton resonance and valley polarization in monolayer WSe2, a novel approach for manipulating light-matter interactions.

Findings

Valley polarization occurs when lower polaritons resonate with bright trions.

Valley depolarization occurs when resonating with dark trions.

System allows tuning of exciton-polariton states over a wide energy range.

Abstract

Monolayer transition metal dichalcogenides, known for exhibiting strong excitonic resonances, constitute a very interesting and versatile platform for investigation of light-matter interactions. In this work we report on a strong coupling regime between excitons in monolayer WSe2 and photons confined in an open, voltage-tunable dielectric microcavity. The tunability of our system allows us to extend the exciton-polariton state over a wide energy range and, in particular, to bring the excitonic component of the lower polariton mode into resonance with other excitonic transitions in monolayer WSe2. With selective excitation of spin-polarized exciton-polaritons we demonstrate the valley polarization when the polaritons from the lower branch come into resonance with a bright trion state in monolayer WSe2 and valley depolarization when they are in resonance with a dark trion state.