Terahertz Pump-Terahertz Probe Spectroscopy Of Multilayer Graphene

We report the result of the terahertz pump terahertz probe spectroscopy of multilayer graphene. The amplitude of the probe pulses deceases after the arrival of the pump pulses with the peak electric field of similar to 100 kV/cm. This indicates that the impact ionization and the resulting carrier multiplication process are induced by the pump pulse irradiation in the multilayer graphene.