Coulomb scattering rates of excited states in germanene

TL;DR

This paper investigates the Coulomb decay rates of excited states in monolayer germanene, revealing diverse decay mechanisms involving plasmons and SPEs, with anisotropic and energy-dependent behaviors.

Contribution

It provides a detailed analysis of Coulomb decay channels and rates for various excited states in germanene using Matsubara's screened exchange energy method.

Findings

Valence holes decay rapidly via undamped acoustic plasmons.

Low-energy conduction electrons and holes behave like 2D electron gas.

Decay rates depend on energy, wave vector, and quasiparticle type.

Abstract

The excited conduction electrons, conduction holes and valence holes in monolayer germanene exhibit the feature-rich Coulomb decay rates. The dexcitation processes are studied using the Matsubara's screened exchange energy. They might utilize the intraband single-particle excitations (SPEs), the interband SPEs, and three kinds of plasmon modes, depending on the quasiparticle states and the Fermi energies. The low-lying valence holes can decay by the undamped acoustic plasmon, so that they present very fast Coulomb deexcitations, the non-monotonous energy dependence and the anisotropic behavior. However, the low-energy conduction holes and electrons behave as 2D electron gas. The high-energy conduction states and the deep-energy valence ones are similar in the available deexcitation channels and the dependence of decay rate on wave vector k.