Collective plasmon-molecule excitations in nanojunctions: Quantum consideration

We present a pseudoparticle nonequilibrium Green function formalism as a tool to study the coupling between plasmons and excitons in nonequilibrium molecular junctions. The formalism treats plasmon-exciton couplings and intramolecular interactions exactly and is shown to be especially convenient for exploration of plasmonic absorption spectrum of plexitonic systems, where combined electron and energy transfers play an important role. We demonstrate the sensitivity of the molecule-plasmon Fano resonance to junction bias and intramolecular interactions (Coulomb repulsion and intramolecular exciton coupling) and compare our predictions for nonlinear optical effects to previous studies. Our study opens a way to deal with strongly interacting plasmon-exciton systems in nonequilibrium molecular devices.