Plasmons in anisotropic Dirac systems

TL;DR

This paper analyzes plasmon excitations in anisotropic two-dimensional Dirac systems, revealing anisotropic dispersion relations and showing that their properties depend on only two key material parameters, opening new avenues in Dirac plasmonics.

Contribution

It generalizes the density response function to anisotropic Dirac systems and derives the anisotropic plasmon dispersion, highlighting their dependence on two dimensionless parameters.

Findings

Plasmon dispersion is anisotropic at low frequencies.

Two dimensionless parameters characterize all plasmon properties.

Strong anisotropy enables directional control of plasmon modes.

Abstract

We consider the plasmon excitations in anisotropic two-dimensional Dirac systems, be it either anisotropic graphene or surfaces of topological insulators. Generalizing the exact density-density response function one finds a plasmon dispersion that is anisotropic already at the lowest frequencies. Asymptotic expressions are obtained for the dispersion in this regime. We show that the plasmon properties of the complete material class of anisotropic Dirac systems are characterized by just two dimensionless material parameters. The strong anisotropy can be used to guide the plasmon modes, introducing new functionalities to the field of Dirac plasmonics.