Plasmon dispersion in semimetallic armchair graphene nanoribbons

TL;DR

This paper calculates plasmon dispersion relations in semimetallic armchair graphene nanoribbons using a tight-binding approach, revealing new plasmon modes and the influence of wavefunction localization on their behavior.

Contribution

It introduces a detailed tight-binding model for plasmons in acGNR, predicting new modes for odd widths and analyzing the effects of wavefunction localization and overlap integrals.

Findings

New plasmon modes for odd atomic widths N=5,11,17,...

Plasmon dispersion depends strongly on wavefunction localization

Overlap integrals behave more complexly than in Dirac models

Abstract

The dispersion relations for plasmons in intrinsic and extrinsic semimetallic armchair graphene nanoribbons (acGNR) are calculated in the random phase approximation using the orthogonal p_z-orbital tight binding method. Our model predicts new plasmons for acGNR of odd atomic widths N=5,11,17,... Our model further predicts plasmons in acGNR of even atomic width N=2,8,14,... related to those found using a Dirac continuum model, but with different quantitative dispersion characteristics. We find that the dispersion of all plasmons in semimetallic acGNR depends strongly on the localization of the p_z electronic wavefunctions. We also find that overlap integrals for acGNR behave in a more complex way than predicted by the Dirac continuum model, suggesting that these plasmons will experience a small damping for all q not equal to 0. Plasmons in extrinsic semimetallic acGNR with the chemical potential in the lowest (highest) conduction (valence) band are found to have dispersion characteristics nearly identical to their intrinsic counterparts, with negligible differencs in dispersion arising from the slight differences in overlap integrals for the interband and intraband transitions.