Terahertz radiation induced ballistic electron transport in graphene
  We investigated ultrafast carrier dynamics in graphene with near-infrared transient absorption measurement after intense half-cycle terahertz pulse excitation. The terahertz electric field efficiently drives the carriers, inducing large transparency in the near-infrared region. Theoretical calculations using the Boltzmann transport equation quantitatively reproduce the experimental findings. This good agreement suggests that the intense terahertz field should promote remarkable impact ioniza- tion process, which leads to suppression of optical phonon emission and results in efficient carrier transport in graphene. 
Shuntaro Tani, Fran\c{c}ois Blanchard and Koichiro Tanaka
cond-mat.mes-hall