Switching the Symmetry of Graphene Plasmons with Nanoemitters for Ultimate Infrared-Light Confinement

Vertical plasmonic coupling in double-layer graphene leads to two hybridized plasmonic modes: the optical and the acoustic plasmon with symmetric and antisymmetric charge distributions across the interlayer gap, respectively. However, in most experiments based on far-field excitation, only the optical plasmon are dominantly excited in the double-layer graphene systems. Here, we propose strategies to selectively and efficiently excite the acoustic plasmon with single or multiple nanoemitters. The analytical model developed here elucidates the role of the position and arrangement of the emitters on the symmetry of the resulting graphene plasmons. In addition, we present an optimal device structure to enable an experimental observation of the acoustic plasmon in double-layer graphene toward the ultimate level of plasmonic confinement defined by a monoatomic spacer, which is inaccessible with a graphene-on-a-mirror architecture.