Electronic Structure Effects in the Coupling of a Single Molecule with a Plasmonic Antenna

Miniaturization of plasmonic devices and the possibility to address single-molecule quantum emitters (QEs) in plasmonic cavities allow one to approach a regime where the characteristic sizes of the system are on the scale of molecular dimensions. In such a situation, the actual spatial profile of the transition electron density associated with a molecular exciton affects the coupling between molecular excitons and metal (nano)objects. Using a quantum approach, we address the energies and lifetimes of the excited states of the zinc phthalocyanine dye molecule placed in the nanometer vicinity of a plasmonic antenna. We demonstrate that the interaction between the molecular excitons and a metal nanoparticle reflects the gross features of the atomic structure in the molecule. The possibility to “look” inside the molecule does not require the presence of atomic scale probes on the surfaces of plasmonic nanoparticles, which would lead to the corresponding localization of the optical field. We show that the QE i...