Quantum spin Hall edge states in twisted bilayer 1T’-WTe<sub>2</sub>

ORAL

Abstract

The quantum spin Hall (QSH) effect, characterized by counter-propagating spin-polarized edge states, was recently demonstrated in monolayers of the transition metal dichalcogenide 1T'-WTe2. The presence of the QSH edge state is expected to be protected by time-reversal symmetry, however, the robustness of this topological protection and any potential scattering mechanisms remain largely unexplored in van der Waals heterostructures containing one or more layers of a QSH insulator. In this work, we use scanning tunneling microscopy and spectroscopy (STM/STS), to study the QSH edge state in WTe2 bilayers for three different twist angles. We observe the characteristic spectroscopic signature of the QSH edge state in the twisted bilayers, including along a coinciding edge. In addition, we report the presence of the QSH edge state at a junction of a monolayer and an as-grown bilayer. By comparing our experimental observations to first principles calculations, we conclude that the constituent layers of the twisted bilayers are weakly coupled, in contrast to the topologically trivial as-grown bilayer, due to their larger interlayer spacing.

*This work supported by the Department of Energy, Oak Ridge National Laboratory, National Science Foundation, and Alexander von Humboldt Foundation.

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Presenters

  • Dacen Waters

    • Physics, University of Washington

Authors

  • Dacen Waters

    • Physics, University of Washington

  • Felix Lüpke

    • Center for Nanophase Materials Sciences, Oak Ridge National Lab

  • Anh Pham

    • Center for Nanophase Materials Sciences, Oak Ridge National Lab
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Jiaqiang Yan

    • Materials Science and Technology Division, Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • University of Tennessee
    • Oak Ridge National Lab
    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Materials Science and Technology, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory, Materials Science and Technology Division

  • David George Mandrus

    • Materials Science and Technology Division, Oak Ridge National Labratory
    • Materials Science and Engineering, University of Tennessee
    • Department of Materials Science and Engineering, University of Tennessee
    • University of Tennessee
    • Department of Materials Science and Engineering, University of Tennessee Knoxville
    • Department of Materials Science & Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
    • Oakridge National Laboratory
    • Materials Science and Engineering, University of Tennessee, Knoxville
    • Oak Ridge National Laboratory
    • University of Tennessee - Knoxville
    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Department of Physics, University of Tennessee Knoxville
    • Materials Science and Technology, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory, Materials Science and Technology Division
    • Department of Materials Science, The University of Tennessee
    • University of Tennessee, Knoxville

  • Panchapakesan Ganesh

    • Center for Nanophase Materials Sciences, Oak Ridge National Lab
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Benjamin Matthew Hunt

    • Physics, Carnegie Mellon University
    • Physics, Carnegie Mellon Univ