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HL: Fachverband Halbleiterphysik
HL 59: THz and MIR physics in semiconductors
HL 59.5: Vortrag
Donnerstag, 19. März 2020, 10:30–10:45, POT 151
Anisotropic nonlinear THz response of bilayer graphene — •Angelika Seidl1,2, Peter Richter3, Thomas Seyller3, Harald Schneider1, Manfred Helm1,2, and Stephan Winnerl1 — 1Helmholtz-Zentrum Dresden-Rossendorf — 2Technische Universität Dresden, Dresden — 3Technische Universität Chemnitz, Chemnitz
The intraband absorption of doped graphene is utilized in novel devices for the THz frequency range, in particular for detectors and modulators. In many cases the nonlinear THz response can be understood as a hot carrier effect, i.e. by modelling the response of an isotropic hot Fermi-Dirac distribution of carriers [1]. We have performed degenerate pump-probe experiments at 2 THz on quasi-freestanding bilayer graphene (QFBLG) on SiC utilizing the free-electron laser FELBE.We find a pump-induced transmission, corresponding to a reduced Drude absorption of hot carriers. The induced transmission is about two times lager for the case of co-polarized pump and probe beam as compared to the cross-polarized case, which clearly indicates an anisotropic distribution of carriers after intraband excitation. The fluence dependence of this phenomenon is discussed for fluences up to 10 µ J/cm2.
[1] H. A. Hafez, S. Kovalev, J.-C. Deinert, Z. Mics, B. Green, N. Awari, M. Chen, S. Germanskiy, U. Lehnert, J. Teichert, Z. Wang, K.-J. Tielrooij, Z. Liu, Z. Chen, A. Narita, K. Müllen, M. Bonn, M. Gensch and D. Turchinovich, Nature textbf561, 507 (2018).