Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 75: Ultrafast Electron and Spin Dynamics

O 75.4: Talk

Wednesday, March 22, 2017, 15:45–16:00, TRE Phy

Polarization control of ultrafast photocurrents in the Dirac cone of the topological insulator Sb₂Te₃ — Johannes Reimann¹, Kenta Kuroda^{1, 2}, •Jens Güdde¹, and Ulrich Höfer¹ — ¹Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg — ²Institute for Solid State Physics (ISSP), University of Tokyo, 277-8581 Chiba, Japan

We present energy-momentum mapping of the photocurrent in the Dirac cone of the topological insulator Sb₂Te₃ by means of time- and angle-resolved two-photon photoemission (2PPE) after optical excitation with ultrashort linear and circular polarized mid-infrared laser pulses. Recently, we have demonstrated that linear polarized mid-infrared pulses permit the generation of photocurrents with ps-lifetime in the initially unoccupied part of the Dirac cone of Sb₂Te₃ by a direct optical excitation [1]. Here, we show that the magnitude and direction of this current depend on the azimuthal orientation of the sample and reflect the threefold symmetry of the surface. For orientations where no photocurrent is generated by linear polarized light, we are instead able to generate a photocurrent by circular polarized light and fully control its direction and magnitude by varying the light helicity.
[1] K. Kuroda et al., Phys. Rev. Lett. 116, 076801 (2016).