Chiral exciton polaritons in a WS2 monolayer

Transition metal dichalcogenides (TMDs) monolayers exhibit a unique band structure that allows for valley-selective optical excitation at the K/K' points of the Brillouin zone. The formation of K and K' excitons, which possess high oscillator strength and strong photoluminescence, can be controlled by circularly polarized light, which opens exciting possibilities for spintronics and quantum information technologies [1]. In the experiment, however, the degree of circular polarization of K/K' excitons is usually quenched due to non-elastic scattering events, which can be suppressed by strong exciton-photon coupling [2]. Chiral photonic bound states in the continuum (BICs) emerge as a promising candidate for further enhancing the polarization properties in TMDs due to their polarization selectivity and strong confinement of photons [3].