Post-transient relaxation in graphene after an intense laser pulse
1 Department of Physics, College of William and Mary, Williamsburg, Virginia 23187, USA
2 Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
3 Institute for Theory of Condensed Matter and Center for Functional Nanostructures, Karlsruhe Institute of Technology, Karlsruhe 76128, Germany
Revised: 12 May 2013
Published online: 15 July 2013
High intensity laser pulses were recently shown to induce a population inverted transient state in graphene [T. Li, et al., Phys. Rev. Lett. 108, 167401 (2012)]. Using a combination of hydrodynamic arguments and a kinetic theory we determine the post-transient state relaxation of hot, dense, population inverted electrons towards equilibrium. The cooling rate and charge-imbalance relaxation rate are determined from the Boltzmann-equation including electron-phonon scattering. We show that the relaxation of the population inversion, driven by inter-band scattering processes, is much slower that the relaxation of the electron temperature, which is determined by intra-band scattering processes. This insight may be of relevance for the application of graphene as an optical gain medium.
© EDP Sciences, Springer-Verlag, 2013