title: Generation of Transient Photocurrents in the Topological Surface State of Sb_{2}Te_{3} by Direct Optical Excitation with Midinfrared Pulses.
abstract: We combine tunable midinfrared (mid-IR) pump pulses with time- and angle-resolved two-photon photoemission to study ultrafast photoexcitation of the topological surface state (TSS) of Sb_{2}Te_{3}. It is revealed that mid-IR pulses permit a direct excitation from the occupied to the unoccupied part of the TSS across the Dirac point. The novel optical coupling induces asymmetric transient populations of the TSS at ±k_{∥}, which reflects a macroscopic photoexcited electric surface current. By observing the decay of the asymmetric population, we directly investigate the dynamics of the long-lived photocurrent in the time domain. Our discovery promises important advantages of photoexcitation by mid-IR pulses for spintronic applications.
authors.affiliation: Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Kuroda
authors.affiliation: Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Reimann
authors.affiliation: Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Güdde
authors.affiliation: Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Höfer