Surface-plasmon polaritons in a lattice of metal cylinders

TL;DR

This paper rigorously investigates plasmon modes in a 2D lattice of metal cylinders, revealing how collective and localized surface-plasmon polaritons evolve with filling fraction and interparticle separation.

Contribution

It introduces an embedding technique to solve Maxwell's equations for plasmon modes in a lattice of metal cylinders, highlighting new resonances at higher filling fractions.

Findings

Collective modes accumulate at surface-plasmon frequency at low filling fractions.

New resonances emerge as filling fraction increases, depending on interparticle separation.

Multipole resonances appear in the spectral range for touching wires.

Abstract

Plasmon modes of a two-dimensional lattice of long conducting circular wires are investigated by using an embedding technique to solve Maxwell's equations rigorously. The frequency-dependent density of states is calculated for various values of the wave vector and the filling fraction. At low filling fractions, collective modes are all found to accumulate at the surface-plasmon frequency $\omega_p/\sqrt{2}$, $\omega_p$ being the bulk plasmon frequency. As the filling fraction increases, the interference between the electromagnetic fields generated by localized surface-plasmon polaritons leads to the presence of {\it new} resonances, whose frequency strongly depends on the interparticle separation. For touching wires, a number of multipole resonances fill the spectral range between dipole resonances, as occurs in the case of a three-dimensional packing of metal spheres.