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  • Letter
  • Open Access

Transparent Josephson junctions in higher-order topological insulator WTe2 via Pd diffusion

Martin Endres1,*, Artem Kononov1, Michael Stiefel2, Marcus Wyss3, Hasitha Suriya Arachchige4, Jiaqiang Yan4,5, David Mandrus4,5,6, Kenji Watanabe7, Takashi Taniguchi7 et al.

Christian Schönenberger1,3,†

  • 1Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
  • 2Laboratory for Nanoscale Material Science, Swiss Federal Laboratories for Material Science and Technology, EMPA, Überlandstrasse 129, 8600 Dübendorf, Switzerland
  • 3Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
  • 4Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
  • 5Material Science and Technology Division, Oak Ridge Laboratory, Oak Ridge, Tennessee 37831, USA
  • 6Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
  • 7National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

  • *martin.endres@unibas.ch
  • †christian.schoenenberger@unibas.ch
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Phys. Rev. Materials 6, L081201 – Published 29 August, 2022

DOI: https://doi.org/10.1103/PhysRevMaterials.6.L081201

Abstract

Highly transparent superconducting contacts to a topological insulator (TI) remain a persistent challenge on the route to engineer topological superconductivity. Recently, the higher-order TI WTe2 was shown to turn superconducting when placed on palladium (Pd) bottom contacts, demonstrating a promising material system in pursuing this goal. Here, we report the diffusion of Pd into WTe2 and the formation of superconducting PdTex as the origin of observed superconductivity. We find an atomically sharp interface in the direction vertical to the van der Waals layers between the diffusion crystal and its host crystal, forming state-of-the-art superconducting contacts to a TI. The diffusion is discovered to be nonuniform along the width of the WTe2 crystal, with a greater extent along the edges compared to the bulk. The potential of this contacting method is highlighted in transport measurements on Josephson junctions by employing external superconducting leads.

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Phys. Rev. Materials 6, L081201– Published 29 August, 2022
  • Received 30 May 2022
  • Revised 25 July 2022
  • Accepted 8 August 2022
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