Control of Strong Light-Matter Interaction in Monolayer WS₂ through Electric Field Gating

Strong light-matter coupling results in the formation of half-light half-matter quasiparticles that take on the desirable properties of both systems such as small mass and large interactions. Controlling this coupling strength in real-time is highly desirable due to the large change in optical properties such as reflectivity that can be induced in strongly coupled systems. Here we demonstrate modulation of strong exciton-photon coupling in a monolayer WS₂ through electric field induced gating at room temperature. The device consists of a WS₂ field effect transistor embedded inside a microcavity structure which transitions from strong to weak coupling when the monolayer WS₂ becomes more n-type under gating. This transition occurs due to the reduction in oscillator strength of the excitons arising from decreased Coulomb interaction in the presence of electrostatically induced free carriers. The possibility to electrically modulate a solid state system at room temperature from strong to weak coupling is highly desirable for realizing low energy optoelectronic switches and modulators operating both in quantum and classical regimes.