Unusual Coulomb effects in graphene

In many semiconductors Coulomb scattering plays an essential role in the thermalization process of a non-equilibrium carrier distribution. Here we discuss three surprising and fascinating manifestations of Coulomb scattering in graphene. All phenomena are explored both experimentally and by manybody theory. The experimental techniques for time-resolved studies at rather low photon energy (mi-infrared and terahertz range) are introduced and we explain why epitaxial graphene samples are particularly well suited for our experiments.
The first observation concerns a double-bended saturation behavior of bleaching induced by near-infrared radiation. The second phenomenon is the optically induced anisotropy in k-space for excitation with linearly polarized radiation and its relaxation to a Fermi-Dirac distribution. The third set of experiments tackles the dynamics of graphene in a magnetic field perpendicular to the graphene layer. Here evidence for strong Auger scattering is found. We discuss the possibility to apply Landau quantized graphene as a gain medium in a tunable laser and as a tunable nonlinear optical material.