Plexcitons in metal Nanotriangle-WS2 Composite System Studied by Electron Energy Loss Spectroscopy

Abstract

Strong coupling between plasmons and excitons in transition metal dichalcogenides enables roomtemperature plexciton formation, providing a crucial platform for investigating Bose-Einstein condensation, low-threshold nanolasers, and ultrafast optical switches. Plexcitons can be produced by far-field optical excitation and near-field electron beam excitation, while electron beam excitation enables the detection of dark plasmon modes and their spatial imaging. Using the boundary element method with a coupled harmonic oscillator model, electron energy loss spectroscopy of silver nanotriangle, WS₂ , and their composite system is simulated. Our numerical results are consistent with the corresponding experiments. From the charge distributions of silver nanotriangle in electron beam excitation, the dipole configurations corresponding to bright and dark plasmon modes are identified. Additionally, spatial imaging maps of electron loss from plexcitons are simulated, and the proportions of plasmon and exciton in plexciton produced by different detunings are analyzed theoretically. This study provides guidance for further experimental and theoretical research on strong coupling in analogous composite systems.