ISSN - 01631829, Physical Review B - Condensed Matter and Materials Physics, 2017, vol. 95, 8, p. -
Ultrafast energy- and momentum-resolved surface Dirac photocurrents in the topological insulator Sb2Te3
© 2017 American Physical Society. We present energy-momentum mapping of the surface Dirac photocurrent in the topological insulator Sb2Te3 by means of time- and angle-resolved two-photon photoemission spectroscopy combined with polarization-variable midinfrared pulsed laser excitation. It is demonstrated that a direct optical transition from the occupied to the unoccupied part of the surface Dirac cone permits the linear and circular photogalvanic effect, which thereby enables us to coherently control the electric surface photocurrent by laser polarization. Moreover, the photocurrent mapping directly visualizes ultrafast current dynamics in the Dirac cone as a function of time. We unravel the ultrafast intraband relaxation dynamics of the inelastic scattering and momentum scattering separately. Our observations pave the way for coherent optical control over surface Dirac electrons in topological insulators.