Ultrafast terahertz studies of dirac fermion dynamics in graphene

We report the broadband optical conductivity and ultrafast carrier dynamics of few-layer graphene. Equilibrium spectra exhibit significant THz and near-IR absorption, consistent with a model of intra- and interband transitions in a dense Dirac electron plasma. Ultrafast THz transmission changes after photoexcitation are dominated by excess holes, with a 1.2-ps exponential decay that reflects minority-carrier recombination.