Effective model for plasmonic coupling: A rigorous derivation

We rigorously derived an effective model to describe the plasmonic couplings between nanoparticles of general shape. In addition to usual electric/magnetic dipolar interactions, the model also contains a radiation-correction term and an electric/magnetic cross-interacting term. The effective model was justified by full-wave simulations in different coupled plasmonic systems, for which the interplays among these terms generate fascinating behaviors. As an application of our theory, we show that the coupling strength between certain plasmonic nanoparticles can be tuned through varying the orientations of nanoparticles, leading to interesting phenomena such as ultraslow-wave plasmon propagation.