Ultrafast Relaxation Processes of Hot Carriers in Graphite
Because of the simple quasi-two-dimensional structure  and small overlap of the valence- and conduction band states in highly oriented pyrolytic graphite (HOPG) the relaxation dynamics of nonequilibrium electronic carriers should differ distinctly from that already observed in semiconductors. Due to its short absorption depth (30 nm) hot carrier populations with a density above 1021cm−3 can be easily generated with amplified fs-pulses at λ = 625 nm. We report for the first time femtosecond details of the relaxation process of extremely dense carrier gases in HOPG at room temperature over a wide range of optical excitation densities.
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