Carrier dynamics in graphene studied by ultra-broadband optical-pump/terahertz probe spectroscpy

Carrier dynamics in single-layered graphene has been studied by reflection-type of THz time domain spectroscopic ellipsometry (THz-TDSE) and optical-pump/THz-probe spectroscopy (OPTP). We successfully determined the frequency-dependent complex sheet conductivity of photo-excited monolayer Graphene from 0.3 to 16 THz. By analyzing with Drude model, the time dependence of Drude weight and carrier scattering rate in Graphene were estimated. It is found that Drude weight decreases and carrier scattering rate increases after photo-excitation, which contribute to the negative photoconductivity in graphene.