Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 77: Topological Insulators: Structure and Electronic Structure (jointly with HL, DS, MA, O)

TT 77.3: Vortrag

Mittwoch, 18. März 2015, 15:30–15:45, ER 270

Observation of the photon drag effect in epitaxially grown (Bi_1−xSb_x)₂Te₃ based topological insulators — •H. Plank¹, L. E. Golub², P. Olbrich¹, T. Herrmann¹, S. Bauer¹, V. V. Bel’kov², G. Mussler³, J. Kampmeier³, D. Grützmacher³, and S. D. Ganichev¹ — ¹University of Regensburg, Regensburg, Germany — ²Ioffe Institute, St. Petersburg, Russia — ³Jülich Aachen Research Alliance (JARA-FIT), Jülich, Germany

We report on the observation of a terahertz (THz) radiation induced photon drag effect in epitaxially grown (Bi_1−xSb_x)₂Te₃ three-dimensional topological insulators. We demonstrate that the excitation with polarized radiation results in a dc electric photocurrent. While at normal incidence a current arises due to the photogalvanic effect in the surface states, caused by asymmetrical scattering of Dirac fermions [1], at oblique incidence it is overweighted by the trigonal photon drag effect. The currents are generated in n- and p-type (Bi_1−xSb_x)₂Te₃ samples with various composition applying linearly and circularly polarized THz radiation. Results are analysed in terms of phenomenological theory and microscopic model based on transfer of photon momentum to free carriers resulting in an asymmetric distribution of electrons (holes) in k-space. Our analysis describes well all experimental findings including e.g. variation of the angle of incidence, radiation polarization and frequency. The observed trigonal photon drag and photogalvanic effect provide an opto-electronic method to study high frequency transport of Dirac fermions even at room temperature.

[1] P. Olbrich et al., Phys. Rev. Lett. 113, 096601(2014)