Coherent Coupling of WS<sub>2</sub> Monolayers with Metallic Photonic Nanostructures at Room Temperature

Room temperature strong coupling of WS<sub>2</sub> monolayer exciton transitions to metallic Fabry–Pérot and plasmonic optical cavities is demonstrated. A Rabi splitting of 101 meV is observed for the Fabry–Pérot cavity. The enhanced magnitude and visibility of WS<sub>2</sub> monolayer strong coupling is attributed to the larger absorption coefficient, the narrower line width of the <i>A</i> exciton transition, and greater spin–orbit coupling. For WS<sub>2</sub> coupled to plasmonic arrays, the Rabi splitting still reaches 60 meV despite the less favorable coupling conditions, and displays interesting photoluminescence features. The unambiguous signature of WS<sub>2</sub> monolayer strong coupling in easily fabricated metallic resonators at room temperature suggests many possibilities for combining light–matter hybridization with spin and valleytronics.