Tunable plasmon modes in doped AA-stacked bilayer graphene

TL;DR

This paper analyzes plasmon modes in doped AA-stacked bilayer graphene, deriving analytical expressions for their dispersion relations and revealing their tunability and damping characteristics, with implications for plasmonic device applications.

Contribution

It provides the first analytical expressions for plasmon dispersion in doped AA-stacked bilayer graphene and explores their tunability and damping behavior.

Findings

Long-wavelength acoustic plasmon disperses as √(max(|μ|, t₁) q)

Optical plasmon exists only under specific conditions related to chemical potential

Optical plasmon disperses as Δ + C q², tunable via chemical potential

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 low-energy 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 $\omega_{+}\approx\sqrt{max(|\mu|,t_{1})q}$ 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 coherent optical plasmon only when the condition $(1+\frac{g_{\sigma}g_{v}e^{2}t_{1}d}{\kappa v_{F}^{2}}\frac{|\mu|}{t_{1}})^{1/2}<\frac{|\mu|}{t_{1}}$ is satisfied, specially indicating Landau damping of the optical plasmon in undoped AA-staked BLG even at long-wavelength limit. We also find that the optical plasmon mode disperses as $\omega_{-}\approx \Delta+Cq^{2}$ with constants that can be tuned by tuning the chemical potential.