Quasiparticle Scattering Rates in The Extrinsic Germanene

The excited conduction electrons, conduction holes and valence holes in monolayer
germanene exhibit the feature-rich Coulomb decay rates. The deexcitation 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.