Anomalous Quasiparticle Lifetime in Graphite: Band Structure Effects

We report ab initio calculations of quasiparticle lifetimes in graphite, as determined from the imaginary part of the self-energy operator within the $\mathrm{GW}$ approximation. The inverse lifetime in the energy range from 0.5 to 3.5 eV above the Fermi level presents significant deviations from the quadratic behavior naively expected from Fermi liquid theory. The deviations are explained in terms of the unique features of the band structure of this material. We also discuss the experimental results from different groups and make some predictions for future experiments.