Proximity-induced superconducting gap in the quantum spin Hall edge state of monolayer WTe<sub>2</sub>

 · Invited

Abstract

The quantum spin Hall (QSH) state was recently demonstrated in monolayers of the transition metal dichalcogenide 1T'-WTe2 and is characterized by a band gap in the two-dimensional (2D) interior and helical one-dimensional (1D) edge states. Inducing superconductivity in the helical edge states would result in a 1D topological superconductor, a highly sought-after state of matter. In the present study, we use a novel dry-transfer flip technique to place atomically-thin layers of WTe2 on a van der Waals superconductor, NbSe2. Using scanning tunneling microscopy and spectroscopy (STM/STS), we demonstrate atomically clean surfaces and interfaces and the presence of a proximity-induced superconducting gap in the WTe2 for thicknesses from a monolayer up to 7 crystalline layers. At the edge of the WTe2 monolayer, we show that the superconducting gap coexists with the characteristic spectroscopic signature of the QSH edge state. Taken together, these observations provide conclusive evidence for proximity-induced superconductivity in the QSH edge state in WTe2, a crucial step towards realizing 1D topological superconductivity and Majorana bound states in this van der Waals material platform.

*BMH acknowledges primary support from the Department of Energy Early Career program under award number DE-SC0018115; support for some STM work from the National Science Foundation under award number NSF DMR-1809145; and the NSF-MRI program for acquisition of the instrument under NSF DMR-1626099. Crystal growth at Oak Ridge National Laboratory was supported by the Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering; and additional crystal growth at Pennsylvania State University Two-Dimensional Crystal Consortium - Materials Innovation Platform (2DCC-MIP) was supported by NSF DMR-1539916.

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Presenters

  • Benjamin Hunt

    • Carnegie Mellon Univ
    • Physics Department, Carnegie Mellon University
    • Carnegie Mellon University
    • Department of Physics, Carnegie Mellon University

Authors

  • Benjamin Hunt

    • Carnegie Mellon Univ
    • Physics Department, Carnegie Mellon University
    • Carnegie Mellon University
    • Department of Physics, Carnegie Mellon University

  • Felix Luepke

    • Carnegie Mellon University
    • Carnegie Mellon Univ
    • Oak Ridge National Lab

  • Dacen Waters

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

  • Sergio C De La Barrera

    • Carnegie Mellon Univ
    • Department of Physics, Carnegie Mellon University

  • Michael Widom

    • Carnegie Mellon Univ
    • Carnegie Mellon University
    • Physics, Carnegie-Mellon University, Pittsburgh, PA 15213, USA

  • Jiaqiang Yan

    • Materials Science and Engineering, The University of Tennessee
    • Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Materials Science and Technology Division, Oak Ridge National Lab
    • Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

  • David Mandrus

    • Physics, University of Tennessee
    • Materials Science and Engineering, The University of Tennessee
    • Department of Materials Science & Engineering, University of Tennessee, Knoxville
    • The University of Tennesse, Knoxville
    • University of Tennessee
    • Department of Physics and Astronomy, University of Tennessee
    • Oak Ridge National Laboratory
    • Department of Materials Science and Engineering, University of Tennessee Knoxville
    • Department of Materials Science and Engineering, University of Tennessee
    • University of Tennessee, Knoxville
    • Material Science and Technology Division, Oak Ridge National Laboratory
    • Material Science and Technology Division, Oak Ridge National Lab

  • Randall M Feenstra

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