Unusual Coulomb excitations in ABC-stacked trilayer graphene

TL;DR

This paper develops a layer-based RPA method to explore unique electronic excitations in ABC-stacked trilayer graphene, revealing complex plasmon modes and their damping influenced by energy bands and doping.

Contribution

It introduces a comprehensive layer-dependent RPA approach to analyze Coulomb excitations in ABC-stacked trilayer graphene, highlighting novel plasmon behaviors and damping effects.

Findings

Identification of five distinct plasmon modes.

Significant Landau damping affecting excitation spectra.

Dramatic change in acoustic plasmon dispersion with doping.

Abstract

The layer-based random-phase approximation is further developed to investigate electronic excitations in tri-layer ABC-stacked graphene. All the layer-dependent atomic interactions and Coulomb interactions are included in the dynamic charge screening. There exist rich and unique (momentum, frequency)-excitation phase diagrams, in which the complex single-particle excitations and five kinds of plasmon modes, are dominated by the unusual energy bands and doping carrier densities. The latter frequently experience the significant Landau damping due to the former, leading to the coexistence/destruction in the energy loss spectra. Specifically, the dispersion of the only acoustic plasmon in pristine case is dramatically changed from linear into quadratic even at very low doping.