Theory of the strongly nonlinear electrodynamic response of graphene: A hot electron model

An electrodynamic response of graphene to a strong electromagnetic radiation is considered. A hot electron model (HEM) is introduced and a corresponding system of nonlinear equations is formulated. Solutions of this system are found and discussed in detail for intrinsic and doped graphene: the hot electron temperature, nonequilibrium electron and hole densities, absorption coefficient, and other physical quantities are calculated as functions of the incident wave frequency omega and intensity I, of the equilibrium chemical potential mu(0), and temperature T-0, scattering parameters, as well as of the ratio tau(epsilon)/tau(rec) of the intraband energy relaxation time tau(epsilon), to the recombination time tau(rec). The influence of the radiation intensity on the absorption coefficient A at low ((h) over bar omega less than or similar to 2 vertical bar mu(0)vertical bar, dA/dI > 0) and high ((h) over bar omega greater than or similar to vertical bar mu(0)vertical bar, dA/dI < 0) frequencies is studied. The results are shown to be in good agreement with recent experimental data.