From single-particle-like to interaction-mediated plasmonic resonances in graphene nanoantennas

TL;DR

This paper applies the energy-based plasmonicity index (EPI) to graphene nanoantennas to classify their resonances, revealing that doping levels significantly influence whether resonances are plasmonic or single-particle-like.

Contribution

It demonstrates the first application of the EPI to graphene nanoantennas, providing insights into how doping affects resonance nature.

Findings

Undoped and moderately doped nanoantennas show single-particle-like resonances.

Heavy doping induces plasmonic resonances according to EPI analysis.

EPI effectively distinguishes resonance types in complex nanostructures.

Abstract

Plasmonic nanostructures attract tremendous attention as they confine electromagnetic fields well below the diffraction limit while simultaneously sustaining extreme local field enhancements. To fully exploit these properties, the identification and classification of resonances in such nanostructures is crucial. Recently, a novel figure of merit for resonance classification has been proposed 1 and its applicability was demonstrated mostly to toy model systems. This novel measure, the energy-based plasmonicity index (EPI), characterizes the nature of resonances in molecular nanostructures. The EPI distinguishes between either a single-particle-like or a plasmonic nature of resonances based on the energy space coherence dynamics of the excitation. To advance the further development of this newly established measure, we present here its exemplary application to characterize the resonances of graphene nanoantennas. In particular, we focus on resonances in a doped nanoantenna. The structure is of interest, as a consideration of the electron dynamics in real space might suggest a plasmonic nature of selected resonances in the low doping limit but our analysis reveals the opposite. We find that in the undoped and moderately doped nanoantenna, the EPI classifies all emerging resonances as predominantly single-particle-like and only after doping the structure heavily, the EPI observes plasmonic response.