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We present energy-momentum mapping of the photocurrent in the Dirac cone of the topological insulator Sb$_2$Te$_3$ 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 Sb$_2$Te$_3$ by a direct optical excitation [1]. Here, we show that magnitude and direction of this current both depend on the azimuthal orientation of the sample and reflect the threefold symmetry of the surface. For orientations in which 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).
