Josephson tunnel junction arrays and Andreev weak links: linked by a single energy-phase relation

TL;DR

This paper reviews how Josephson tunnel junctions and Andreev weak links can be described by a unified energy-phase relation, linking their theoretical and experimental understanding in superconducting technology.

Contribution

It demonstrates a unified framework for SIS and SNS Josephson junctions through a single energy-phase relation, clarifying their connections and differences.

Findings

Unified energy-phase relation describes both SIS and SNS junctions.

Connections between theoretical models and experimental results are established.

Differences between the two junction types are identified and discussed.

Abstract

Josephson elements are cornerstones of cryogenic classical and quantum superconducting technology, owing to their nonlinearity. Two important types of Josephson elements are often considered distinct: the tunnel junction (superconductor-insulator-superconductor, SIS) and the Andreev weak link (superconductor-normal-superconductor, SNS) referring to any non-superconducting and non-insulating central region. SNS junctions and SIS junctions have appeared in related technological and fundamental science contexts over the last decade, such as in the design of protected qubit concepts. In this perspective article, we review correspondences between SISIS junctions and SNS junctions in limiting regimes, in which a single energy-phase relationship describes both systems. We show how this insight helps to connect recent bodies of theoretical and experimental work in both systems, and conclude by describing a few important differences.