Letter

Current–phase relations of few-mode InAs nanowire Josephson junctions

  • Nature Physics volume 13, pages 11771181 (2017)
  • doi:10.1038/nphys4224
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Abstract

Gate-tunable semiconductor nanowires with superconducting leads have great potential for quantum computation1,2,3 and as model systems for mesoscopic Josephson junctions4,5. The supercurrent, I, versus the phase, ϕ, across the junction is called the current–phase relation (CPR). It can reveal not only the amplitude of the critical current, but also the number of modes and their transmission. We measured the CPR of many individual InAs nanowire Josephson junctions, one junction at a time. Both the amplitude and shape of the CPR varied between junctions, with small critical currents and skewed CPRs indicating few-mode junctions with high transmissions. In a gate-tunable junction, we found that the CPR varied with gate voltage: near the onset of supercurrent, we observed behaviour consistent with resonant tunnelling through a single, highly transmitting mode. The gate dependence is consistent with modelled subband structure that includes an effective tunnelling barrier due to an abrupt change in the Fermi level at the boundary of the gate-tuned region. These measurements of skewed, tunable, few-mode CPRs are promising both for applications that require anharmonic junctions6,7 and for Majorana readout proposals8.

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Acknowledgements

We thank S. Hart, J. Kirtley and C. Beenakker for useful discussions and C. Watson, Z. Cui and I. Sochnikov for useful discussions and experimental assistance. The scanning SQUID measurements were supported by the Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515. Nanowire growth and device fabrication was supported by Microsoft Project Q, the Danish National Research Foundation, the Lundbeck Foundation, the Carlsberg Foundation, and the European Commission. C.M.M. acknowledges support from the Villum Foundation.

Author information

Affiliations

  1. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

    • Eric M. Spanton
    •  & Kathryn A. Moler
  2. Department of Physics, Stanford University, Stanford, California 94305, USA

    • Eric M. Spanton
    •  & Kathryn A. Moler
  3. Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen DK-2100, Denmark

    • Mingtang Deng
    • , Saulius Vaitiekėnas
    • , Peter Krogstrup
    • , Jesper Nygård
    •  & Charles M. Marcus
  4. State Key Laboratory of High Performance Computing, NUDT, Changsha 410073, China

    • Mingtang Deng
  5. Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

    • Saulius Vaitiekėnas
  6. Department of Applied Physics, Stanford University, Stanford, California 94305, USA

    • Kathryn A. Moler

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Contributions

P.K. and J.N. developed the nanowire materials, M.D. and S.V. fabricated the devices and E.M.S. performed the scanning SQUID measurements, analysed the data, and performed simulations. E.M.S. and K.A.M. wrote the manuscript with input from all coauthors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Kathryn A. Moler.

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