Theoretical study of population inversion in graphene under pulse excitation

We study theoretically the population inversion in intrinsic graphene under optical pulse excitation at room temperature. We develop the theoretical model of carrier relaxation dynamics based on the rate equations derived from the quasi-classical Boltzmann equation. We take into account the energy relaxation and recombination by the intra and interband optical phonon (OP) scattering, and we assume that the carrier-carrier (CC) scattering is dominant so that the carrier distribution is always the quasi-Fermi distribution. Using the model developed, we demonstrate that the population inversion can be achieved under the pulse excitation even in the limiting case of the dominant CC scattering.