Strongly interacting plasmon nanoparticles: from dipole interaction to conductively coupled regime

We have investigated the electromagnetic interaction of periodic arrays of metallic (gold) nanoparticles, composed of a pair of particles on each lattice site. By varying the interparticle separation from dielectric proximity to conductive contact on nm scale, we observe very large renormalization and splitting of the surface plasmon energy associated with an abrupt transition from the dipolar to a conductively coupled regime