Electron polarization function and plasmons in metallic armchair graphene nanoribbons

TL;DR

This paper calculates the polarization function and plasmon modes in metallic armchair graphene nanoribbons, revealing temperature-independent behavior and mode splitting in coupled ribbons, with implications for nanoelectronic applications.

Contribution

It provides an analytical calculation of the polarization function at arbitrary temperature and doping, showing temperature independence and plasmon mode splitting in coupled nanoribbons.

Findings

Polarization function becomes temperature-independent due to phase space redistribution.

A single plasmon mode exists for a given nanoribbon width.

Coupled nanoribbons exhibit split plasmon modes with energy determined by inter-ribbon spacing.

Abstract

We calculate the polarization function of Dirac fermions in metallic armchair graphene nanoribbons for an arbitrary temperature and doping. We find that at finite temperatures due to the phase space redistribution among inter-band and intra-band electronic transitions in the conduction and valence bands, the full polarization function becomes independent of the temperature and the position of the chemical potential. As a result, for a given width of nanoribbons there exists a single plasmon mode, with the energy dispersion determined by the graphene's fine structure constant. In Coulomb-coupled nanoribbons, this plasmon splits into the basic in-phase and out-of-phase plasmon modes, with the splitting energy determined additionally by the inter-ribbon spacing.