Spatial coherence of room-temperature monolayer WSe<sub>2</sub> exciton-polaritons in a trap.

Shan, Hangyong; Lackner, Lukas; Han, Bo; Sedov, Evgeny; Rupprecht, Christoph; Knopf, Heiko; Eilenberger, Falk; Beierlein, Johannes et al. · Nat Commun · 2021

basic_science · Level V

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Abstract

The emergence of spatial and temporal coherence of light emitted from solid-state systems is a fundamental phenomenon intrinsically aligned with the control of light-matter coupling. It is canonical for laser oscillation, emerges in the superradiance of collective emitters, and has been investigated in bosonic condensates of thermalized light, as well as exciton-polaritons. Our room temperature experiments show the strong light-matter coupling between microcavity photons and excitons in atomically thin WSe<sub>2</sub>. We evidence the density-dependent expansion of spatial and temporal coherence of the emitted light from the spatially confined system ground-state, which is accompanied by a threshold-like response of the emitted light intensity. Additionally, valley-physics is manifested in the presence of an external magnetic field, which allows us to manipulate K and K' polaritons via the valley-Zeeman-effect. Our findings validate the potential of atomically thin crystals as versatile components of coherent light-sources, and in valleytronic applications at room temperature.