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

Eric M. Spanton: Mingtang Deng, Saulius Vaitiekėnas, Peter Krogstrup, Jesper Nygård, Charles M. Marcus & Kathryn A. Moler; Nature Physics, 08/14/17.

Additional Authors: Mingtang Deng, Saulius Vaitiekėnas, Peter Krogstrup, Jesper Nygård, Charles M. Marcus & Kathryn A. Moler

Abstract:

Gate-tunable semiconductor nanowires with superconducting leads have great potential for quantum computation123 and as model systems for mesoscopic Josephson junctions45. 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 junctions67 and for Majorana readout proposals8.