Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 86: Graphene VI

O 86.6: Talk

Friday, March 30, 2012, 11:45–12:00, MA 041

Angle resolved Coulomb- and phonon-induced carrier dynamics in graphene — •Torben Winzer, Andreas Knorr, and Ermin Malic — Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany

We investigate the relaxation dynamics of optically excited charge carriers in graphene within the density matrix formalism resolved in time, momentum, and angle. The focus lies on the interplay between carrier-carrier and carrier-phonon scattering channels immediately after an excitation, when the carrier system is highly anisotropic. We observe that Coulomb-scattering prefers processes of carriers with parallel momentum corresponding to a relaxation dynamics carried out directly toward the Dirac point. In contrast, the emission of phonons leads efficiently and quickly to an isotropic carrier distribution in the states one phonon energy beneath the exciting energy. Accordingly, for large scattering angles Coulomb- and phonon-induced relaxation dynamics complement each other, whereas in the case of narrow scattering angles there is a direct competition [1]. We demonstrate how the combination of all relaxation channels results in an ultrafast thermalization, followed by a slower energy dissipation.

[1] E. Malic, T. Winzer, E. Bobkin, and A. Knorr, Phys. Rev. B 84, 205406, (2011)