Spatial coherence of room-temperature monolayer WSe2 exciton-polaritons in a trap

Hangyong Shan,Evgeny Sedov,Lukas Lackner,Christoph Rupprecht,Carlos Antón-Solanas,Sven Höfling,Falk Eilenberger,Johannes Beierlein,Alexey V Kavokin,Kenji Watanabe,Sebastian Klembt,Martin Esmann,Sefaattin Tongay,Heiko Knopf,Bo Han,Kentaro Yumigeta,Takashi Taniguchi,Nils Kunte,Christian Schneider

doi:10.1038/s41467-021-26715-9

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 WSe2. 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.

Highlights

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
A dashed white arrow indicates the slice resolved in the energy versus real space measures, the pump spot is placed in the centre of the monolayer. c Room temperature polariton dispersion relation encoded in a logarithmic false colour-scale
The resulting upper (UP) and lower polariton (LP) dispersion relations are shown as guides to the eye in light and dark blue colours, respectively

Summary

Introduction

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. Thin transition metal dichalcogenide crystals (TMDCs) have emerged as a highly interesting material class in opto-electronic[1,2] and nanophotonic[3] applications because of their giant light-matter coupling strength. While at thermal equilibrium, such a phenomenon is commonly described in the framework of a Bose-Einstein condensate[10,11], the kinetic nature of polariton quantum liquids, arising from rapid particle tunnelling out of the microcavity puts the bare formation of coherent states in the polariton laser class[12] Such devices, far, were realised in GaAs and II/ VI microcavities at cryogenic temperatures[12,13] and under electrical injection[14], and realized in GaN15, and later in organic[16] and perovskite[17] microcavities at ambient conditions. The possibility to expand towards multiple, even rotationally aligned monolayers facilitates to harness twistronics approaches[25] to engineer quantum states of light

Methods

Results

Conclusion