Coupled plasmonic graphene wires: theoretical study including complex frequencies and field distributions of bright and dark surface plasmons

Abstract

Theoretical research on localized surface plasmons (LSPs) supported by a structure formed by two parallel dielectric wires with a circular cross section wrapped with a graphene sheet has an impact in the practical realm. Here, LSPs are represented in the form of an infinite series of cylindrical multipole partial waves linked to each of the graphene wires. To obtain the kinematics (complex eigenfrequencies) and dynamic characteristics (field distributions) of the LSPs, we consider the analytic extension to the complex plane of the solution to the boundary value problem. The lower frequency LSP group is formed by four branches, two of them corresponding to bright modes and the others to dark modes. By tuning the chemical potential of the graphene covers so that the dimer symmetry breaks, these dark modes are transformed into resonant observables that can be excited by plane wave incidence.