Strong coupling in the far-infrared between graphene plasmons and the surface optical phonons of silicon dioxide

TL;DR

This paper demonstrates strong coupling between graphene plasmons and silicon dioxide surface optical phonons in the far-infrared, revealing surface-plasmon-phonon-polariton modes through experimental spectra and theoretical calculations.

Contribution

It provides the first detailed analysis of plasmon-phonon coupling in graphene on silicon dioxide using both measurements and dielectric function modeling.

Findings

Multiple absorption peaks observed in spectra

Resonant frequencies depend on nanoribbon width

Coupling leads to surface-plasmon-phonon-polariton modes

Abstract

We study plasmonic resonances in electrostatically gated graphene nanoribbons on silicon dioxide substrates. Absorption spectra are measured in the mid-far infrared and reveal multiple peaks, with width-dependent resonant frequencies. We calculate the dielectric function within the random phase approximation and show that the observed spectra can be explained by surface-plasmon-phonon-polariton modes, which arise from coupling of the graphene plasmon to three surface optical phonon modes in the silicon dioxide.