Strong coupling between excitons and quasibound states in the continuum in bulk transition metal dichalcogenides

We investigate the strong coupling between excitons and quasibound states in the continuum (BICs) resonance in a bulk WS2 metasurface. Here, we employ bulk WS2 to construct an ultrathin nanodisk metasurface, support-ing the symmetry-protected magnetic dipole quasi-BIC resonance, which can self-hybridize with the excitons and lead to a strong light-matter interaction enhancement within the structure without the necessity for an external cavity. This strong coupling can be characterized by the considerable Rabi splitting of 159 meV and the clearly anticrossing behavior appearing in the absorption spectrum. Furthermore, we analyze such light-matter coupling by constructing a Hamiltonian model including the surplus excitons and tune the interaction from weak-to strong-coupling regimes via the tunability radiation loss of the quasi-BIC resonance. Our results have great potential for manipulating the exciton-polaritons at room temperature and provide a promising prospect for photonic devices that exploit strong coupling in applications.