Josephson coupling through one-dimensional ballistic channel in semiconductor-superconductor hybrid quantum point contacts

TL;DR

This paper demonstrates a semiconductor-superconductor hybrid Josephson junction with a single ballistic channel, showing quantized Josephson critical current variations due to transverse momentum quantization in a narrow InGaAs channel.

Contribution

It provides the first clear evidence of Josephson coupling through a single ballistic channel in a semiconductor-superconductor hybrid system.

Findings

Josephson critical current shows discretized variation with gate tuning.

Quantization persists down to the single-channel regime.

Unambiguous demonstration of a single ballistic channel Josephson junction.

Abstract

We study a superconducting quantum point contact made of a narrow In$_{0.75}% $Ga$_{0.25}$As 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.