Molecular nanopolaritonics: cross manipulation of near-field plasmons and molecules. I. Theory and application to junction control

Near-field interactions between plasmons and molecules are treated in a simple unified approach. The density matrix of a molecule is treated with linear-response random phase approximation and the plasmons are treated classically. The equations of motion for the combined system are linear, governed by a simple Liouvillian operator for the polariton (plasmon+molecule excitation) dynamics. The dynamics can be followed in time or directly in frequency space where a trace formula for the transmission is presented. A model system is studied, metal dots in a forklike arrangement, coupled to a two level system with a large transition-dipole moment. A Fano-type resonance Phys. Rev. 103, 1202 (1956)] develops when the molecular response is narrower than the width of the absorption spectrum for the plasmons. We show that the direction of the dipole of the molecule determines the direction the polariton chooses. Further, the precise position of the molecule has a significant effect on the transfer.