Tunneling Plasmonics in Bilayer Graphene

TL;DR

This study demonstrates that interlayer tunneling in bilayer graphene significantly influences its plasmonic properties, enabling enhanced confinement and electrical control of plasmons, with potential for novel plasmonic devices.

Contribution

It provides the first experimental evidence linking interlayer tunneling to plasmonic behavior in bilayer graphene, including the ability to switch plasmons on and off via gating.

Findings

Bilayer graphene supports highly confined plasmons due to interlayer tunneling.

Gating can effectively shut off plasmons in bilayer graphene.

Interlayer tunneling induces a gapped insulating state affecting plasmonic properties.

Abstract

We report experimental signatures of plasmonic effects due to electron tunneling between adjacent graphene layers. At sub-nanometer separation, such layers can form either a strongly coupled bilayer graphene with a Bernal stacking or a weakly coupled double-layer graphene with a random stacking order. Effects due to interlayer tunneling dominate in the former case but are negligible in the latter. We found through infrared nano-imaging that bilayer graphene supports plasmons with a higher degree of confinement compared to single- and double-layer graphene, a direct consequence of interlayer tunneling. Moreover, we were able to shut off plasmons in bilayer graphene through gating within a wide voltage range. Theoretical modeling indicates that such a plasmon-off region is directly linked to a gapped insulating state of bilayer graphene: yet another implication of interlayer tunneling. Our work uncovers essential plasmonic properties in bilayer graphene and suggests a possibility to achieve novel plasmonic functionalities in graphene few-layers.