Dirac Spectra and Edge States in Honeycomb Plasmonic Lattices

TL;DR

This paper theoretically investigates plasmonic honeycomb lattices, revealing Dirac spectra and edge states with unique characteristics, and analytically deriving conditions for their existence, drawing parallels to graphene nanoribbons.

Contribution

It introduces the first theoretical analysis of Dirac spectra and edge states in honeycomb plasmonic lattices, including conditions for their existence and their relation to electronic graphene systems.

Findings

Dirac spectra found for dipole and quadrupole modes

Zigzag edge states exist in plasmonic honeycomb ribbons

Edge states for in-plane and quadrupole modes have unique vector-based features

Abstract

We study theoretically the dispersion of plasmonic honeycomb lattices and find Dirac spectra for both dipole and quadrupole modes. Zigzag edge states derived from Dirac points are found in ribbons of these honeycomb plasmonic lattices. The zigzag edge states for out-of-plane dipole modes are closely analogous to the electronic ones in graphene nanoribbons. The edge states for in-plane dipole modes and quadrupole modes, however, have rather unique characters due to the vector nature of the plasmonic excitations. The conditions for the existence of plasmonic edge states are derived analytically.