Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Graphene: Dynamics (O with HL/TT)
HL 46.3: Talk
Wednesday, March 18, 2015, 11:00–11:15, MA 041
Microscopic description of intraband absorption in graphene — •Faris Kadi1, Ermin Malic1, Torben Winzer1, Manfred Helm2, Fabian Göttfert2, Martin Mittendorff2, Stephan Winnerl2, and Andreas Knorr1 — 1Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Germany — 2Helmholtz- Zentrum Dresden-Rossendorf, Dresden, Germany
We present a microscopic explanation for the occurrence of the controversially discussed transient negative differential transmission observed in optical pump-probe measurements in graphene [1]. Within the density matrix formalism we investigate the transient transmission with respect to optical interband as well as phonon-assisted intraband transitions. While interband processes yield a positive contribution due to absorption bleaching, we find intraband transitions to decrease differential transmission. Interestingly, in the low excitation regime, the phonon-assisted absorption prevails over the absorption bleaching resulting in the experimentally observed negative differential transmission [2]. The zero-crossing occurs within the first hundreds of femtoseconds and is followed by a recovery of the transmission spectrum on a picosecond timescale in a good agreement with experimental observations. [1] S.Winnerl, F. Göttfert, M. Mittendorff, et al., Journal of Physics: Condensed Matter 25, 054202 (2013) [2] F. Kadi, T. Winzer, E. Malić, et al., Phys. Rev. Lett. 113, 035502, (2014)