Plasmons of hot-carrier graphene

Graphene, as a 2D semi-metal, is able to support surface plasmon modes. These plasmons interact, scattering the electrons in graphene, by way of emission and absorption. For electrons in thermal equilibrium, the energy scale of the optical response can be tuned by setting the Fermi level via external gate voltage. However, for non-equilibrium cases, such as photo-excitation, plasmons can become amplified through stimulated emission. We present how the non-local sheet conductivity can be calculated for graphene in non-equilibrium cases, how this affects the plasmon dispersion, as well as absorption and emission rates, and how the plasmon channel contributes to carrier relaxtion.