Collective Mie Exciton-Polaritons in an Atomically Thin Semiconductor

Optically induced Mie resonances in dielectric nanoantennas feature low dissipative losses and a large resonant enhancement of both the electric and magnetic fields. They offer an alternative platform to plasmonic resonances to study light-matter interactions from weak to strong coupling regimes. Here, we experimentally demonstrate the strong coupling of bright excitons in monolayer WS2 with Mie surface lattice resonances (Mie-SLRs). We resolve both the electric and magnetic Mie-SLRs of a Si nanoparticle array in angular dispersion measurements. At the zero detuning condition, the dispersion of electric Mie-SLRs (e-SLRs) exhibits a clear anti-crossing and a Rabi splitting of 32 meV between the upper and lower polariton bands. The magnetic Mie-SLRs (m-SLRs) nearly cross the energy band of the excitons. These results suggest that the field of m-SLRs is dominated by out-of-plane components that do not efficiently couple with the in-plane excitonic dipoles of the monolayer WS2. In contrast, e-SLRs in dielectric nanoparticle arrays with relatively high quality factors (Q similar to 120) facilitate the formation of collective Mie exciton-polaritons and may allow the development of novel polaritonic devices, which can tailor the optoelectronic properties of atomically thin two-dimensional semiconductors.