Atomistic investigation of hybrid plasmonic systems

By using time-dependent density functional theory, we investigate in a fully quantum mechanical framework the interactions, in an ultra-near-field regime, between a localized surface plasmon excitable in a silver tetrahedral cluster and a molecular exciton with excitation energy in the same range. We show that, for metal–molecule distances below 5 Å, the optical response of the system results characterized by the appearance of a double peak structure. We analyze the transition densities for the resonant energies and propose a plasmon–exciton electromagnetic interaction model to explain the emerging of a lower energy resonance in the spectra of such kind of hybrid systems of interest for molecular plasmonics.