Carrier dynamics in graphene
|Pump probe signals for different photon energies, corresponding microscopic calculations and energy diagram. As the photon energy is reduced to values below the optical phonon energy of about 200 meV, the relaxation is significantly slowed down.|
Graphene, i.e. a single layer of hexagonally arranged carbon atoms, features a gapless band structure with linear dispersion. Essentially electrons in graphene behave like massless Dirac fermions. The band structure and the fairly large optical phonon energy (~200 meV) result in carrier relaxation dynamics that strongly differs from other materials. We study the carrier relaxation dynamics in a wide range of photon energies from the near-infrared spectral range to the THz range. In close collaboration with theorists from the Technische Universität Berlin the role of carrier-carrier and carrier phonon processes is revealed. We also study the carrier relaxation in Landau quantized graphene, where we find evidence for extremely efficient Auger scattering. Furthermore we explore the potential of graphene for fast electro-optic device applications such as saturable absorbers and broadband detectors.
This research is supported by the German Research Foundation (DFG) in the framework of the Priority Programme "Graphene" (SPP 1459).
J. C. König-Otto, M. Mittendorff, T. Winzer, F. Kadi, E. Malic, A. Knorr, C. Berger, W. A. de Heer, A. Pashkin, H. Schneider, M. Helm, and S. Winnerl, Slow noncollinear Coulomb scattering in the vicinity of the Dirac point in graphene, Phys. Rev. Lett. 117, 087401 (2016)
M. Mittendorff, F. Wendler, E. Malic, A. Knorr, M. Orlita, M. Potemski, C. Berger, W. A. de Heer, H. Schneider, M. Helm, and S. Winnerl, Carrier dynamics in Landau-quantized graphene featuring strong Auger scattering, Nature Physics 11, 75 (2015)
M. Mittendorff, M. Orlita, M. Potemski, C. Berger, W. A. de Heer, H. Schneider, M. Helm, and S. Winnerl, Intraband carrier dynamics in Landau-quantized multilayer epitaxial graphene, New J. Phys. 16, 123021 (2014)
M. Mittendorff, T. Winzer, E. Malic, A. Knorr, C. Berger, W.A. de Heer, H. Schneider, M. Helm, and S. Winnerl, Anisotropy of excitation and relaxation of photogenerated Dirac electrons in graphene, Nano Lett. 8, 1504 (2014)
M. Mittendorff, S. Winnerl, J. Kamann, J. Eroms, D. Weiss, H. Schneider, and M. Helm, Ultrafast graphene-based broadband THz detector, Appl. Phys. Lett. 103, 021113 (2013)
S. Winnerl, F. Göttfert, M. Mittendorff, H. Schneider, M. Helm, T. Winzer, E. Malic, A. Knorr, M. Orlita, M. Potemski, M. Sprinkle, C. Berger, and W.A. de Heer, Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation dynamics and saturation behavior, J. Phys.: Condens. Matter 25, 054202 (2013)
S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W.A. de Heer, H. Schneider, and M. Helm, Carrier relaxation in epitaxial graphene photoexcited near the Dirac point, Phys. Rev. Lett. 107, 237401 (2011)