Collinear scattering of photoexcited carriers in graphene

We propose an explicitly solvable model for collinear scattering of photoexcited carriers in intrinsic graphene irradiated by monochromatic light. We find that the collinear scattering rate is directly proportional to the photocarrier energy and derive an analytic expression for the corresponding relaxation time. The result agrees with the recent numerical prediction [Mihnev et al. Nat. Commun. vol. 7, 11617 (2016)] and is able to describe the photocarrier evolution at low energies, where scattering on optical phonons is strongly suppressed.