Abstract

Although signatures of superconductivity in Dirac semimetals have been reported, for instance by applying pressure or using point contacts, our understanding of the topological aspects of Dirac semimetal superconductivity is still developing. Here, we utilize nanoscale phase-sensitive junction technology to induce superconductivity in the Dirac semimetal Bi1−xSbx. Our radiofrequency irradiation experiments then reveal a significant contribution of 4π-periodic Andreev bound states to the supercurrent in Nb–Bi0.97Sb0.03–Nb Josephson junctions. The conditions for a substantial 4π contribution to the supercurrent are favourable because of the Dirac cone’s very broad transmission resonances and a measurement frequency faster than the quasiparticle poisoning rate. In addition, we show that a magnetic field applied in the plane of the junction allows tuning of the Josephson junctions from 0 to π regimes. Our results open the technologically appealing avenue of employing the topological bulk properties of Dirac semimetals for topological superconductivity research and topological quantum computer development.

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Acknowledgements

The authors thank the Diamond Light Source for access to beamline I05 (proposal no. 12969), which contributed to the results presented here, and A. Schiphorst, T. Kim and M. Hoesch for assistance with ARPES experiments. The authors thank R. Lier for numerical calculations. This work was financially supported by the Foundation for Fundamental Research on Matter (FOM), associated with the Netherlands Organization for Scientific Research (NWO), and the European Research Council (ERC) through a Consolidator Grant.

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Affiliations

  1. MESA+ Institute for Nanotechnology, University of Twente, Enschede, the Netherlands

    • Chuan Li
    • , Jorrit C. de Boer
    • , Bob de Ronde
    • , Alexander A. Golubov
    •  & Alexander Brinkman
  2. Van der Waals–Zeeman Institute, IoP, University of Amsterdam, Amsterdam, the Netherlands

    • Shyama V. Ramankutty
    • , Erik van Heumen
    • , Yingkai Huang
    • , Anne de Visser
    •  & Mark S. Golden
  3. Moscow Institute of Physics and Technology, Dolgoprudny, Moscow, Russia

    • Alexander A. Golubov

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Contributions

Y.H. made single crystals. C.L. and B.d.R. fabricated devices. C.L, J.C.d.B., B.d.R. and A.d.V. performed transport measurements. C.L., J.C.d.B., B.d.R., A.A.G. and A.B. analysed and modelled transport data. S.V.R., E.v.H. and M.S.G. performed and analysed ARPES measurements. All authors contributed to writing the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Alexander Brinkman.

Supplementary information

  1. Supplementary Information

    Supplementary Figures 1–16, Supplementary Tables 1–2, Supplementary References 1–26

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DOI

https://doi.org/10.1038/s41563-018-0158-6

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