Greatly Enhanced Plasmon-Exciton Coupling in Si/WS<sub>2</sub>/Au Nanocavities.

Deng, Fu; Huang, Hongxin; Chen, Jing-Dong; Liu, Shimei; Pang, Huajian; He, Xiaobing; Lan, Sheng · Nano Lett · 2022

basic_science · Level V

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Abstract

A strong light-matter interaction is highly desirable from the viewpoint of both fundamental research and practical application. Here, we propose a dielectric-metal hybrid nanocavity composed of a silicon (Si) nanoparticle and a thin gold (Au) film and investigate numerically and experimentally the coupling between the plasmons supported by the nanocavity and the excitons in an embedded tungsten disulfide (WS<sub>2</sub>) monolayer. When a Si/WS<sub>2</sub>/Au nanocavity is excited by the surface plasmon polariton generated on the surface of the Au film, greatly enhanced plasmon-exciton coupling originating from the hybridization of the surface plasmon polariton, the mirror-image-induced magnetic dipole, and the exciton modes is clearly revealed in the angle- or size-resolved scattering spectra. A Rabi splitting as large as ∼240 meV is extracted by fitting the experimental data with a coupled harmonic oscillator model containing three oscillators. Our findings open new horizons for constructing nanoscale photonic devices by exploiting dielectric-metal hybrid nanocavities.