Harnessing Graphene Plasmons by Accessing the Retardation Regime

Plasmons in graphene are highly tunable, mainly by leveraging the carrier density and Drude scattering. Here, we introduce another scheme, i.e., accessing the retardation regime (originated from the finite speed of light), to engineer the lifetime and dispersion of plasmons in graphene in the terahertz regime. We find that the retardation regime can be approached by reducing plasmon momentum in artificially stacked multilayer graphene systems with large Drude weight, and this can significantly increase the plasmon lifetime. In addition, an explicit theoretical model along with finite-element simulation was given, consistent with the experimental findings. Our work opens another avenue to manipulate terahertz plasmons in graphene.