Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.74: Poster

Tuesday, March 12, 2013, 18:15–21:45, Poster B1

Coulomb- and phonon-induced inter-Landau-level carrier dynamics of graphene in a magnetic field — •Florian Wendler, Andreas Knorr, and Ermin Malić — Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Germany

Motivated by a recent experiment [1], we investigate the relaxation dynamics of Dirac electrons in graphene in the presence of a magnetic field. In the experiment, a pump-probe setup is used to measure the relaxation times of electrons in the energetically lowest Landau levels. Exploiting the optical selection rules emerging in a magnetic field as well as the graphene-specific non-equidistant Landau-level splitting, single Landau-level transitions can be selectively measured using circularly polarized light. Here, we apply a theoretical approach within the framework of the density matrix formalism [2], which allows us to microscopically track the equilibration of excited electrons in reciprocal space. We investigate the impact of Coulomb- and phonon-induced relaxation channels between the lowest Landau levels. We find a phonon-dominated picosecond decay time confirming the experimentally observed trend. Furthermore, we discuss the importance of disorder-assisted carrier-phonon scattering processes, which are known to be important for the relaxation dynamics close to the Dirac point [3].

[1] M. Mittendorf, S. Winnerl, and M. Helm (unpublished)

[2] E. Malić et al., Phys. Rev. B 84, 205406 (2011)

[3] J.C.W. Song et al., Phys. Rev. Lett. 109, 106602 (2012)