Emergent scale invariance of non-classical plasmons in graphene nanoribbons

TL;DR

This paper reveals a scale-invariant quantum behavior of plasmons in graphene nanoribbons, deviating from classical predictions, with edge states influencing plasmon shifts, and clarifies the conditions for Dirac theory applicability.

Contribution

It uncovers emergent scale invariance in quantum plasmons of graphene nanoribbons and links deviations from classical models to band structure features.

Findings

Scale invariance relates narrow high-doping to wide low-doping ribbons.

Edge states cause a blueshift in plasmon resonance.

Quantum effects deviate from classical models based on band structure.

Abstract

Using a nearest-neighbor tight-binding model we investigate quantum effects of plasmons on few-nanometer wide graphene nanoribbons, both for zigzag and armchair edge terminations. With insight from the Dirac description we find an emerging scale-invariant behavior that deviates from the classical model both for zigzag and armchair structures. The onset of the deviation can be related to the position of the lowest parabolic band in the band structure. Dirac theory is only valid in the parameter subspace where the scale invariance holds that relates narrow ribbons with high doping to wide ribbons with low doping. We also find that the edge states present in zigzag ribbons give rise to a blueshift of the plasmon, in contrast to earlier findings for graphene nanodisks and nanotriangles.