Effect of anisotropic band curvature on carrier multiplication in graphene

We study relaxation of an excited electron in the conduction band of intrinsic graphene at zero temperature due to production of interband electron-hole pairs by Coulomb interaction. The electronic band curvature, being anisotropic because of trigonal warping, is shown to suppress relaxation for a range of directions of the initial electron momentum. For other directions, relaxation is allowed only if the curvature exceeds a finite critical value; otherwise, a nondecaying quasiparticle state is found to exist. DOI: 10.1103/PhysRevB.87.165437