Spin-Polarization-Induced Chiral Polariton Lasing at Room Temperature

Abstract

Exciton-polaritons are hybrid bosons that define the peculiar interaction between the semiconductor and the optical cavity. The ultra-low effective mass of polariton inherited from its photon fraction benefits the efficient Bose–Einstein condensation process. Due to the unique superfluidity of polariton condensate, the persistent angular momentum of the system will facilitate plenty of chiral phenomena, such as the spin precession, the spin–orbit coupling, and the emergence of quantum vortices. Here, we report a chiral polariton laser via robust spin-polarization of polariton condensation at room temperature. The self-formed chirality of the microcavity breaks the spatial inversion symmetry and lifts the energy degeneracy of polariton spin doublets by a considerable value of 11 meV, which can be demonstrated by the angle-resolved spectra recorded after a Wollaston prism. The bosonic condensation only occurs in the low-energy spin-up polaritons, resulting in polariton lasing with stable right-circular (σ+) polarization. The second-order coherence of a polariton chiral laser is determined by performing the Hanbury Brown–Twiss measurement, which indicates the quantum phase transition during the condensation process. Moreover, the robustness of the chirality of polariton lasing is demonstrated, and the basic physical mechanisms of the system are illustrated by the generalized Gross–Pitaevskii (G–P) equation. The results set solid building blocks for the development of chiral quantum photonics and spin polaritonics.