First-principles calculations of plasmon excitations in graphene, silicene, and germanene

Abstract

Plasmon excitations in graphene, silicene, and germanene are studied using linear-response time-dependent density functional theory within the random phase approximation (RPA). In this work, we examine both the plasmon dispersion behavior and lifetime of extrinsic and intrinsic plasmons for these three materials. For extrinsic plasmons, we found that their properties are closely related to Landau damping. In the region without single-particle excitation (SPE), the plasmon dispersion shows a $\sqrt{q}$ behavior and the lifetime is infinite at the RPA level, while in the SPE region, the plasmon dispersion shows a quasilinear behavior and the lifetime is finite. Moreover, for intrinsic plasmons, unlike graphene, the plasmon dispersion behavior of silicene and germanene exhibits a two-peak structure, which can be attributed to the complex and hybridized band structure of these two materials.