Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier   Relaxation and Recombination Dynamics in Epitaxial Graphene
  The ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene are studied using optical-pump Terahertz-probe spectroscopy. The conductivity in graphene at Terahertz frequencies depends on the carrier concentration as well as the carrier distribution in energy. Time-resolved studies of the conductivity can therefore be used to probe the dynamics associated with carrier intraband relaxation and interband recombination. We report the electron-hole recombination times in epitaxial graphene for the first time. Our results show that carrier cooling occurs on sub-picosecond time scales and that interband recombination times are carrier density dependent. 
Paul A. George, Jared Strait, Jahan Dawlaty, Shriram Shivaraman, Mvs   Chandrashekhar, Farhan Rana, Michael G. Spencer