Dirac-like plasmons in honeycomb lattices of metallic nanoparticles

TL;DR

This paper demonstrates that honeycomb lattices of metallic nanoparticles support Dirac-like plasmons, exhibiting graphene-like electronic properties, and explores how to manipulate these properties for tunable plasmonic applications.

Contribution

It introduces a theoretical framework for Dirac-like plasmons in nanoparticle lattices and shows how polarization controls the Dirac points and bandgap, enabling tunable plasmonic devices.

Findings

Dirac cones appear in the plasmon spectrum for certain polarizations

Effective Dirac Hamiltonian describes massless bosonic excitations

Manipulating polarization opens a tunable bandgap in plasmon dispersion

Abstract

We consider a two-dimensional honeycomb lattice of metallic nanoparticles, each supporting a localized surface plasmon, and study the quantum properties of the collective plasmons resulting from the near field dipolar interaction between the nanoparticles. We analytically investigate the dispersion, the effective Hamiltonian and the eigenstates of the collective plasmons for an arbitrary orientation of the individual dipole moments. When the polarization points close to the normal to the plane the spectrum presents Dirac cones, similar to those present in the electronic band structure of graphene. We derive the effective Dirac Hamiltonian for the collective plasmons and show that the corresponding spinor eigenstates represent Dirac-like massless bosonic excitations that present similar effects to electrons in graphene, such as a non-trivial Berry phase and the absence of backscattering off smooth inhomogeneities. We further discuss how one can manipulate the Dirac points in the Brillouin zone and open a gap in the collective plasmon dispersion by modifying the polarization of the localized surface plasmons, paving the way for a fully tunable plasmonic analogue of graphene.