title: Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite.
abstract: Ultrafast charge carrier dynamics in graphite has been investigated by time-resolved terahertz spectroscopy. Analysis of the transient dielectric function and model calculations show that more than 90% of the initially deposited excitation energy is transferred to a few strongly coupled lattice vibrations within 500 fs. These hot optical phonons also substantially contribute to the striking increase of the Drude relaxation rate observed during the first picosecond after photoexcitation. The subsequent cooling of the hot phonons yields a lifetime estimate of 7 ps for these modes.
authors.affiliation: Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Kampfrath
authors.forename: Luca
authors.initials: L
authors.lastname: Perfetti
authors.forename: Florian
authors.initials: F
authors.lastname: Schapper
authors.forename: Christian
authors.initials: C
authors.lastname: Frischkorn
authors.forename: Martin
authors.initials: M
authors.lastname: Wolf