ABSTRACT
The spectra and damping of surface plasmon-polaritons (SPPs) in double graphene layer structures are studied. It is proved that SPPs in those structures exhibit an outstanding voltage tunability of velocity and damping, inherent to gated graphene, and a pronounced low-frequency coupling with photons inherent to non-gated structures. The models disregarding the spatial dispersion were widely used before; though, they can overestimate the damping of SPPs by an order of magnitude. The bias voltage applied between graphene layers shifts their Fermi energies and, hence, changes the rate of interband plasmon absorption. At low bias voltages, the SPPs are strongly damped, while at high voltages their propagation length is large since it is limited only by Drude absorption. The propagation length of SPPs turns out to be by an order of magnitude higher than that obtained from previous models neglecting the spatial dispersion.
