Tunable Fano Resonance and Plasmon-Exciton Coupling in Single Au Nanotriangles on Monolayer WS2 at Room Temperature

Tunable Fano resonances and plasmon-exciton coupling are demonstrated at room temperature in hybrid systems consisting of single plasmonic nanoparticles deposited on top of the transition metal dichalcogenide monolayers. By using single Au nanotriangles (AuNTs) on monolayer WS2 as model systems, Fano resonances are observed from the interference between a discrete exciton band of monolayer WS2 and a broadband plasmonic mode of single AuNTs. The Fano lineshape depends on the exciton binding energy and the localized surface plasmon resonance strength, which can be tuned by the dielectric constant of surrounding solvents and AuNT size, respectively. Moreover, a transition from weak to strong plasmon-exciton coupling with Rabi splitting energies of 100-340 meV is observed by rationally changing the surrounding solvents. With their tunable plasmon-exciton interactions, the proposed WS2-AuNT hybrids can open new pathways to develop active nanophotonic devices.