We study the superconducting proximity effect in an InAs nanowire contacted by Ta-based superconducting electrodes. Using local bottom gates, we control the potential landscape along the nanowire, tuning its conductance to a quasi-ballistic regime. At high magnetic field (B), we observe approximately quantized conductance plateaus associated with the first two spin-polarized one-dimensional modes. For B<1 T, the onset of superconductivity occurs in concomitance with the development of sizeable charge localization leading to a 0.7-type conductance anomaly. In this regime, the proximity supercurrent exhibits an unusual, non-monotonic B dependence. We interpret this finding in terms of a competition between the Kondo effect, dominating near B=0, and the Zeeman effect, enforcing spin polarization and the emergence of a π phase shift in the Josephson relation at higher B.
@article{arxiv.1801.01855,
title = {Supercurrent through a spin-split quasi-ballistic point contact in an InAs nanowire},
author = {J. C. Estrada Saldaña and R. Žitko and J. P. Cleuziou and E. J. H. Lee and V. Zannier and D. Ercolani and L. Sorba and R. Aguado and S. De Franceschi},
journal= {arXiv preprint arXiv:1801.01855},
year = {2019}
}