Plasmonics of coupled graphene micro-structures

TL;DR

This paper investigates how coupling between graphene micro-structures affects their plasmonic resonances, revealing strong vertical coupling, hybridization effects, and interactions with substrate phonons, advancing understanding of graphene plasmonics.

Contribution

It provides new insights into the coupling effects in graphene micro-structures, including vertical stacking and hybridization, and explores plasmon-phonon interactions.

Findings

Strong coupling between vertically stacked graphene disks.

Hybridization of plasmons in complex structures like micro-rings.

Observation of a hybrid resonance involving surface phonons and plasmons.

Abstract

The optical response of graphene micro-structures, such as micro-ribbons and disks, is dominated by the localized plasmon resonance in the far infrared (IR) spectral range. An ensemble of such structures is usually involved and the effect of the coupling between the individual structures is expected to play an important role. In this paper, the plasmonic coupling of graphene microstructures in different configurations is investigated. While a relatively weak coupling between graphene disks on the same plane is observed, the coupling between vertically stacked graphene disks is strong and a drastic increase of the resonance frequency is demonstrated. The plasmons in a more complex structure can be treated as the hybridization of plasmons from more elementary structures. As an example, the plasmon resonances of graphene micro-rings are presented, in conjunction with their response in a magnetic field. Finally, the coupling of the plasmon and the surface polar phonons of SiO2 substrate is demonstrated by the observation of a new hybrid resonance peak around 500cm-1.