THz spectroscopy of electric field modulated Dirac surface states of topological insulator thin films

ORAL

Abstract

Topological insulators (TIs) exhibit symmetry protected conducting surface states with Dirac like dispersion and novel spin textures. TIs can also be described as bulk magnetoelectric materials with quantized magneto-optical response functions. However, observing such phenomena in real materials can be challenging because of the finite bulk contributions which tend to screen the surface state effects. Here, we present a novel ionic gel gating technique that can be used to tune the chemical potential while simultaneously measuring the optical spectra. We demonstrate that the Fermi level for naturally n-doped Bi2Se3 films can be lowered down to ~10 meV above the Dirac point, resulting in a reduction in the carrier concentration by an order of magnitude. At high magnetic fields, quantization of Faraday angle is observed which provides evidence for the topological magnetoelectric effects. Furthermore, we also demonstrate that the filling factor in the surface states can be altered by changing the applied bias voltage.

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Presenters

  • Dipanjan Chaudhuri

    Johns Hopkins Univ, Johns Hopkins University

Authors

  • Mintu Mondal

    Johns Hopkins University

  • Dipanjan Chaudhuri

    Johns Hopkins Univ, Johns Hopkins University

  • Maryam Salehi

    Department of Physics and Astronomy, Rutgers University, Material Science and Engineering, Rutgers University, Physics and Astronomy, Rutgers Univ, Rutgers, the State University of New Jersey, Rutgers University

  • Cheng Wan

    Johns Hopkins University

  • Nicholas Laurita

    Department of Physics and Astronomy, Johns Hopkins Unversity, Johns Hopkins Univ, Johns Hopkins University, Institute For Quantum Information and Matter, California Institute of Technology

  • Bing Cheng

    Johns Hopkins Univ, Johns Hopkins University

  • Michael Quintero

    Johns Hopkins University

  • Deepti Jain

    Physics and Astronomy, Rutgers University, Rutgers University

  • Jisoo Moon

    Physics and Astronomy, Rutgers University, Physics and Astronomy, Rutgers Univ, Rutgers University

  • Pavel Shibayev

    Physics and Astronomy, Rutgers University, Rutgers University

  • Tyrel McQueen

    Johns Hopkins University, Institute for Quantum Matter, Johns Hopkins University, Department of Chemistry , Johns Hopkins University, The Johns Hopkins University

  • Seongshik Oh

    Department of Physics and Astronomy, Rutgers University, Physics and Astronomy, Rutgers University, Physics and Astronomy, Rutgers Univ, Rutgers, the State University of New Jersey, Rutgers University

  • Peter Armitage

    Department of Physics and Astronomy, The Johns Hopkins University, Department of Physics and Astronomy, Johns Hopkins Unversity, Johns Hopkins University, Johns Hopkins Univ, Institute for Quantum Matter, Johns Hopkins University, The Johns Hopkins University