Polariton hyperspectral imaging of two-dimensional semiconductor crystals

TL;DR

This study uses cavity-assisted hyperspectral imaging to map and analyze the spatial properties of polaritons in monolayer TMDs, revealing their homogeneity, intrinsic correlations, and non-thermal behaviors at room temperature.

Contribution

It introduces a novel hyperspectral imaging technique to spatially resolve polariton properties in 2D TMDs and uncovers the role of phonons in polariton dynamics.

Findings

High homogeneity of polariton splitting across the sample

Correlation between polariton splitting and exciton properties

Deviation from thermal equilibrium due to polariton-phonon coupling

Abstract

Atomically thin crystals of transition metal dichalcogenides (TMDs) host excitons with strong binding energies and sizable light-matter interactions. Coupled to optical cavities, monolayer TMDs routinely reach the regime of strong light-matter coupling, where excitons and photons admix coherently to form quasiparticles known as polaritons up to room temperature. Here, we explore the two-dimensional nature of TMD polaritons with cavity-assisted hyperspectral imaging. Using extended WS$_2$ monolayers, we establish the regime of strong coupling with a scanning microcavity to map out polariton properties and correlate their spatial features with intrinsic and extrinsic effects. We find a high level of homogeneity, and show that polariton splitting variations are correlated with intrinsic exciton properties such as oscillator strength and linewidth. Moreover, we observe a deviation from thermal equilibrium in the resonant polariton population, which we ascribe to non-perturbative polariton-phonon coupling. Our measurements reveal a promisingly consistent polariton landscape, and highlight the importance of phonons for future polaritonic devices.