Tunable plasmon modes in doped AA-stacked bilayer graphene

Abstract

We study plasmon modes in doped AA-stacked bilayer graphene (BLG) within the nearest-neighbor tight-binding and the random phase approximation. We obtain closed analytical expressions for the polarizability function which are used to obtain the lowenergy dispersion relations of and the numerical results for both acoustic and optical plasmon modes. Our result reveal the potential of AA-stacked BLG to be used as a tunable plasmonic device. In particular we find that the long-wavelength acoustic plasmon disperse as ω + ≈ max(|µ|, t 1 )q with a phase space which shrinks and vanishes as the chemical potential approaches the interlayer hopping energy, preventing the existence of long-lived acoustic plasmon. Furthermore, we show that AA-stacked BLG support undamped optical plasmon only when the condition (1specially indicating the optical plasmon in undoped AA-staked BLG is Landau damped even at long-wavelength limit. We also find that the optical plasmon mode disperses as ω − ≈ ∆ + Cq 2 with constants that can be tuned by tuning the chemical potential.