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.

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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