Unconventional double-bended saturation of optical transmission in   graphene due to many-particle interactions
  We present a joint theory-experiment study on the transmission/absorption saturation after ultrafast pulse excitation in graphene. We reveal an unconventional double-bended saturation behavior: Both bendings separately follow the standard saturation model exhibiting two saturation fluences, however, the corresponding fluences differ by three orders of magnitude and have different physical origin. Our results reveal that this new and unexpected behavior can be ascribed to an interplay between fluence- and time-dependent many-particle scattering processes and phase-space filling effects. 
Torben Winzer, Martin Mittendorff, Stephan Winnerl, Manfred Helm,   Ermin Malic, Andreas Knorr
cond-mat.mes-hall