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

Abstract

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.

Andreev reflection and bound state formation in a ballistic two-dimensional electron gas probed by a quantum point contact

“…It is worth mentioning the difference between the SN junctions studied here and SNS Josephson junctions studied previously [33][34][35][36], in which multiple ARs can take place. In Ref.…”

Quantized conductance doubling and hard gap in a two-dimensional semiconductor–superconductor heterostructure

“…In nanowires, the soft-gap problem was recently resolved by growing Al epitaxially on InAs nanowires, yielding greatly reduced subgap conductance 6 7 . Studies of Sm–S systems based on top-down processed gateable two-dimensional electron gases (2DEGs) coupled to superconductors have not explicitly addressed the soft-gap issue yet 8 9 . However experiments on such systems have demonstrated other theoretical predictions, such as quantization of critical current 9 10 11 , the retro-reflection property of Andreev scattering 12 , and spectroscopy of a gate-defined quantum dot with superconducting leads 13 14 , which do not require a hard proximity-induced gap in the semiconductor.…”

On-chip Hybrid Superconducting-Semiconducting Quantum Circuit

“…From these peaks at B= 0 T and T= 300 mK, we estimate the induced gap ind =0.65 meV using the relation = eVSD. The ind obtained here is about half of the value of high quality bulk Nb [10]. The separation of the peaks of induced superconducting gap, suppresses by increasing the magnetic field B, the position of the peaks shifts toward zero bias with further increasing the applied magnetic field B and the peaks disappear near B≈ 50 mT.…”