Josephson current carried by Andreev levels in superconducting quantum point contacts

TL;DR

This paper reviews how Andreev levels are fundamental to the dc Josephson effect in superconducting quantum point contacts, highlighting their role in supercurrent flow and quantization phenomena.

Contribution

It provides an intuitive understanding of the Josephson effect through Andreev levels and discusses the quantization of critical current in quantum point contacts.

Findings

Andreev levels carry the entire supercurrent in short symmetric junctions.

The paper offers an intuitive view based on multiple Andreev reflections.

Quantization of critical current is briefly discussed.

Abstract

The dc Josephson effect in a superconducting quantum point contact, where supercurrent flows through a small number of channels, is reviewd. The central role of Andreev levels is emphasized which carry the whole supercurrent in short symmetric Josephson junctions including tunnel junctions. A simple intuitive view of the dc Josephson effect in a quantum point contact is given in terms of multiple Andreev reflections. The quantization of the critical current in superconducting quantum point contacts is briefly discussed.