Graphene plasmons and retardation: strong light-matter coupling

TL;DR

This paper explores the strong light-matter coupling in doped graphene plasmons within the retardation regime, revealing enhanced plasmonic effects and perfect light transmission in double-layer configurations, with potential applications in simple graphene devices.

Contribution

It demonstrates the impact of retardation on graphene plasmons, showing enhanced coupling and novel transmission phenomena not previously detailed in the literature.

Findings

Strong coupling between light and graphene plasmons in the retardation regime.

Perfect light transmission in double-layer graphene configurations.

Transformation of Fabry-Pérot resonances into sharp quasi-discrete modes.

Abstract

We study the retardation regime of doped graphene plasmons, given by the nominal crossing of the unretarded plasmon and light-cone. In addition to modifications in the plasmon dispersion relation, retardation implies strong coupling between propagating light and matter, even for homogeneous graphene, which opens up the possibility of efficient plasmonics in simple graphene devices. We exemplify this enhancement in a double-layer configuration that exhibits {\em perfect} (if lossless) light transmissions across a classically forbidden region, providing a simpler analog of the corresponding phenomenon in perforated metal sheets. We also show that (broad) Fabry-P\'erot resonances present without graphene turn into sharply peaked, quasi-discrete modes in the presence of graphene where graphene's response function is given by the typical Fano lineshape.