ABSTRACT
Plasmon excitations are intrinsic charge or current oscillations coupled via Coulomb interaction. One of them called surface plasmon polariton (SPP) is a plasmon bound to an interface with a dielectric medium. Plasmons can be excited in many conventional metals such as Au, Ag, Cu, and Al, and these metals were regarded as the best plasmonic materials in the past for a long time. The dispersion relation of plasmons is very important for graphene plasmonics, and numerous achievements have been made in theory and experiment, such as semi-classical model and random-phase approximation (RPA). Surface plasmons are the collective oscillation of charges, which are silent in plasmonic materials unless drawn by a definite amount of energy and momentum, such as photons, electrons, and phonons. Recently a large deal of work has been devoted to finding materials with improved plasmonic performance and fast tunability including the use of super-conductors in the sub- THz regime and conductive oxides in the visible and near-infrared.
