Photoemission of Bi$_2$Se$_3$ with Circularly Polarized Light: Probe of Spin Polarization or Means for Spin Manipulation?

ORAL

Abstract

Topological insulators are characterized by Dirac cone surface states with spins aligned in the surface plane and perpendicular to their momenta. Recent theoretical and experimental work implied that this specific spin texture should enable control of photoelectron spins by circularly polarized light. However, these reports questioned the so far accepted interpretation of spin-resolved photoelectron spectroscopy. We solve this puzzle and show that vacuum ultraviolet photons (50-70 eV) with linear or circular polarization probe indeed the initial state spin texture of Bi$_2$Se$_3$ while circularly polarized 6 eV low energy photons flip the electron spins out of plane and reverse their spin polarization. Our photoemission calculations, considering the interplay between the varying probing depth, dipole selection rules and spin-dependent scattering effects involving initial and final states explain these findings, and reveal proper conditions for light-induced spin manipulation for future applications in opto-spintronic devices.

*Supported by SPP 1666 of Deutsche Forschungsgemeinschaft.

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Authors

  • Oliver Rader

    • Helmholtz-Zentrum Berlin
    • The Helmholtz Centre Berlin for Materials and Energy Research

  • J. S\'anchez-Barriga

    • Helmholtz-Zentrum Berlin

  • A. Varykhalov

    • Helmholtz-Zentrum Berlin

  • J. Braun

    • Ludwig-Maximilians-Universit\"at M\"unchen

  • Su-Yang Xu

    • Princeton University
    • Dept. of Physics, Princeton University, USA
    • Joseph Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
    • Dept. of Physics, Princeton University, NJ, USA

  • Nasser Alidoust

    • Princeton University
    • Dept. of Physics, Princeton University, USA
    • Dept. of Physics, Princeton University, NJ, USA

  • O. Kornilov

    • Max-Born-Institut Berlin

  • J. Min\'ar

    • Ludwig-Maximilians-Universit\"at M\"unchen

  • K. Hummer

    • University of Vienna

  • G. Springholz

    • Johannes Kepler Universit\"at Linz

  • G. Bauer

    • Johannes Kepler Universit\"at Linz

  • R. Schumann

    • Max-Born-Institut Berlin

  • L.V. Yashina

    • Moscow State University

  • H. Ebert

    • Ludwig-Maximilians-Universit\"at M\"unchen

  • M. Zahid Hasan

    • Princeton Univ
    • Princeton University
    • Dept. of Physics, Princeton University, USA
    • Dept. of Physics, Princeton University, NJ, USA

  • G. Bauer

    • Johannes Kepler Universit\"at Linz