We study a superconducting quantum point contact made of a narrow In0.75Ga0.25As channel with Nb proximity electrodes. The narrow channel is formed in a gate-fitted constriction of InGaAs/InAlAs/InP heterostructure hosting a two-dimensional electron gas. When the channel opening is varied with the gate, the Josephson critical current exhibits a discretized variation that arises from the quantization of the transverse momentum in the channel. The quantization of Josephson critical current persists down to the single-channel regime, providing an unambiguous demonstration of a semiconductor--superconductor hybrid Josephson junction involving only a single ballistic channel.
@article{arxiv.1404.5390,
title = {Josephson coupling through one-dimensional ballistic channel in semiconductor-superconductor hybrid quantum point contacts},
author = {Hiroshi Irie and Yuichi Harada and Hiroki Sugiyama and Tatsushi Akazaki},
journal= {arXiv preprint arXiv:1404.5390},
year = {2014}
}