Spin-Polarization-Induced Chiral Polariton Lasing at Room Temperature

Exciton-polaritons are hybrid bosons that define thepeculiar interactionbetween the semiconductor and the optical cavity. The ultra-low effectivemass of polariton inherited from its photon fraction benefits theefficient Bose-Einstein condensation process. Due to the uniquesuperfluidity of polariton condensate, the persistent angular momentumof the system will facilitate plenty of chiral phenomena, such asthe spin precession, the spin-orbit coupling, and the emergenceof quantum vortices. Here, we report a chiral polariton laser viarobust spin-polarization of polariton condensation at room temperature.The self-formed chirality of the microcavity breaks the spatial inversionsymmetry and lifts the energy degeneracy of polariton spin doubletsby a considerable value of 11 meV, which can be demonstrated by theangle-resolved spectra recorded after a Wollaston prism. The bosoniccondensation only occurs in the low-energy spin-up polaritons, resultingin polariton lasing with stable right-circular (sigma(+)) polarization. The second-order coherence of a polariton chirallaser is determined by performing the Hanbury Brown-Twiss measurement,which indicates the quantum phase transition during the condensationprocess. Moreover, the robustness of the chirality of polariton lasingis demonstrated, and the basic physical mechanisms of the system areillustrated by the generalized Gross-Pitaevskii (G-P)equation. The results set solid building blocks for the developmentof chiral quantum photonics and spin polaritonics.