Strong coupling of monolayer and bilayer MoS2 in plasmonic nanocavities via scattering spectroscopy

The phenomenon of strong coupling (SC) between plasmonic nanocavities and excitons in two-dimensional transition metal dichalcogenides (2D TMDs) is acquiring significant attention due to its potential in enhancing light–matter interactions, which is vital for the development of advanced quantum devices and next-generation photonic technologies. While much of the existing research has focused on the plasmonic properties of various nanocavities, the SC between gold nanorods (GNRs) and 2D bilayer materials remains relatively underexplored. In this work, we examine the SC between GNRs and both monolayer (ML) and bilayer (BL) molybdenum disulfide (MoS2), employing dark-field scattering spectroscopy and finite-difference time-domain simulations. Our findings reveal a distinct difference in the plasmon-exciton coupling strength, with ML-MoS2 showing a larger Rabi splitting (105 meV) than BL-MoS2 (92.5 meV), which is attributed to the larger dipole moment of ML-MoS2. Furthermore, theoretical simulations using a coupled oscillator model provide strong agreement with the experimental scattering results, accurately capturing the energy separation and intensity ratios of the polaritonic peaks. The substantial emission energy splitting observed in single plasmonic cavity systems at room temperature opens up exciting possibilities for exploring their nonlinear, electrical, and quantum correlation properties essential for the realization of practical quantum optoelectronic devices.