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

TL;DR

This study uses first-principles calculations to analyze plasmon excitations in graphene, silicene, and germanene, revealing their dispersion behaviors, lifetimes, and unique features related to their electronic structures.

Contribution

It provides a comparative analysis of plasmon properties in three 2D materials using RPA, highlighting differences due to band structure complexities.

Findings

Extrinsic plasmons have infinite lifetime in SPE-free regions.

Silicene and germanene show a two-peak structure in intrinsic plasmon dispersion.

Plasmon dispersion follows  behavior in SPE regions.

Abstract

Plasmon excitations in graphene, silicene and germanene are studied using linear-response time dependent density functional theory within the random phase approximation (RPA). Here, 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 single-particle excitation 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.