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arXiv · 1511.00460

Generation of Transient Photocurrents in the Topological Surface State of Sb$_{2}$Te$_{3}$ by Direct Optical Excitation with Mid-Infrared Pulses

K. Kuroda·J. Reimann·J. Güdde·U. Höfer
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Abstract

We combine tunable mid-infrared (MIR) 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 MIR pulses permit a direct excitation of the unoccupied TSS owing to an optical coupling across the Dirac point. The novel optical coupling provokes asymmetric transient populations of the TSS at ${\pm}k_{||}$, which mirrors a macroscopic photoexcited electric surface current. By observing the decay of the asymmetric population, we directly demonstrate the dynamics of the long-lived photocurrent and its protection against backscattering. Our discovery promises important advantages of photoexcitation by MIR pulses for spintronic applications.

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K. Kuroda, J. Reimann, J. Güdde, U. Höfer. 2016-01-26. Generation of Transient Photocurrents in the Topological Surface State of Sb$_{2}$Te$_{3}$ by Direct Optical Excitation with Mid-Infrared Pulses. https://doi.org/10.1103/physrevlett.116.076801

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