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Superconductivity in van der Waals materials, such as NbSe2 and TaS2, is fundamentally novel due to the effects of dimensionality, crystal symmetries, and strong spin-orbit coupling. In this work we perform tunnel spectroscopy on NbSe2 by utilizing MoS2 or hexagonal Boron Nitride (hBN) as a tunnel barrier. We observe subgap excitations and probe their origin by studying various heterostructure designs. We show that the edge of NbSe2 hosts many defect states, which strongly couple to the superconductor and form Andreev bound states. Furthermore, by isolating the NbSe2 edge we show that the subgap states are ubiquitous in MoS2 tunnel barriers, but absent in hBN tunnel barriers, suggesting defects in MoS2 as their origin. Their magnetic nature reveals a singlet or a doublet type ground state and based on nearly vanishing g-factors or avoided-crossing of subgap excitations we highlight the role of strong spin-orbit coupling.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Superconductivity, van der Waals materials, tunnel spectroscopy

Date published: 2023-04-12

Publisher: American Chemical Society (ACS)

Journal:

• Nano Letters (ISSN: 15306984) vol. 23 issue. 7 p. 2454-2459

Funding:

• Schweizerischer Nationalfonds zur F?rderung der Wissenschaftlichen Forschung
• Swiss Nanoscience Institute, University of Basel
• Core Research for Evolutional Science and Technology JPMJCR15F3
• Japan Society for the Promotion of Science 19H05790
• Japan Society for the Promotion of Science 20H00354
• H2020 European Research Council 787414

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1021/acs.nanolett.2c02777

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Updated at: 2025-02-14 16:31:09 +0900

Published on MDR: 2025-02-14 16:31:09 +0900