Ultrafast Mid-Infrared and Terahertz Phenomena in Graphene

Graphene, the first atomically thin 2D material that was intensely investigated since its discovery in 2014, is a gapless semiconductor or semimetal with linear dispersion. Consequently, graphene absorbs light at all energies, in particular also at low photon energies in the THz frequency range. Here we show that pump-probe experiments at low photon energies can provide deep insights into the carrier dynamics. In particular, electron-phonon scattering can be disentangled from Coulomb scattering processes [1, 2]. Coulomb scattering in graphene is responsible for a number of unusual effects like strong Auger scattering under Landau quantization [3].
With respect to applications we present a graphene based detector with ultrafast response time of 40 ps. It operates in the very broad frequency range from visible to THz radiation [4].
[1] 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 und M. Helm, Phys. Rev. Lett. 107, 237401 (2011).
[2] 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 und S. Winnerl, Phys. Rev. Lett. 117, 087401 (2016).
[3] M. Mittendorff, F. Wendler, E. Malic, A. Knorr, M. Orlita, M. Potemski, C. Berger, W. A. de Heer, H. Schneider, M. Helm und S. Winnerl, Nature Phys. 11, 75 (2015).
[4] M. Mittendorff, J. Kamann, J. Eroms, D. Weiss, C. Drexler, S. D. Ganichev, J. Kerbusch, A. Erbe, R. J. Suess, T. E. Murphy, S. Chatterjee, K. Kolata, J. Ohser, J. C. König-Otto, H. Schneider, M. Helm, S. Winnerl, Optics Express 23, 28728 (2015).