Tunable Resonance Coupling in Single Si Nanoparticle-Monolayer WS₂ Structures

Two-dimensional semiconducting transition metal dichalcogenides (TMDCs) are extremely attractive materials for optoelectronic applications in the visible and near-infrared range. Coupling these materials to optical nanocavities enables advanced quantum optics and nanophotonic devices. Here, we address the issue of resonance coupling in hybrid exciton-polariton structures based on single Si nanoparticles (NPs) coupled to monolayer (1L)-WS₂. We predict a strong coupling regime with a Rabi splitting energy exceeding 110 meV for a Si NP covered by 1L-WS₂ at the magnetic optical Mie resonance because of the symmetry of the mode. Further, we achieve a large enhancement in the Rabi splitting energy up to 208 meV by changing the surrounding dielectric material from air to water. The prediction is based on the experimental estimation of TMDC dipole moment variation obtained from the measured photoluminescence spectra of 1L-WS₂ in different solvents. An ability of such a system to tune the resonance coupling is realized experimentally for optically resonant spherical Si NPs placed on 1L-WS₂. The Rabi splitting energy obtained for this scenario increases from 49.6 to 86.6 meV after replacing air by water. Our findings pave the way to develop high-efficiency optoelectronic, nanophotonic, and quantum optical devices.