Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 91: Poster IIIb (Joint session of DS and HL, organized by HL)

HL 91.8: Poster

Donnerstag, 10. März 2016, 16:00–19:00, Poster A

THz Photoconductivity of Epitaxial Graphene and the Possible Opening of a Bandgap — •Markus Göthlich¹, Cay-Christian Kalmbach², Mattias Kruskopf², Klaus Pierz², Franz-Josef Ahlers², and Andreas Hangleiter¹ — ¹Institut für Angewandte Physik, Technische Universität Braunschweig, Mendelssohnstraße 2, D-38106 Braunschweig — ²Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig

Due to it’s Dirac like nature the Landau quantization in graphene is given by E_n = sgn(n)√Δ² + 2 ℏ v_F² e |B n| with Landau level (LL) index n. This gives a nontrivial Shubnikov-de Haas-effect (SdH) depending on the magnetic field B and – different to conventional material systems – on the chemical potential. It also allows the observation of resonant inter-Landau-level transitions at different magnetic fields for a given transition energy as shown by Gusynin et al. (Phys. Rev. Lett. 98, 157402 (2007)). Motivated by a simulation that shows that SdH measurements alone might not be able to distiguish between the effect of a bandgap and the effect of the chemical potential, we want to investigate here the influence of a possible opening of a band gap in epitaxial graphene on the cyclotron resonance. Therefore we use the change of the photoconductivity in the cyclotron resonance case in the SdH regime and in the THz spectral range (ℏ ω_photon ≈ 10 meV) for epitaxial graphene on SiC. Our results can also be relevant for the detection of THz radiation by spectrally selective detectors based on cyclotron resonance in graphene.