Theory of Josephson Phenomena in Superfluid 3He

TL;DR

This paper provides a detailed theoretical analysis of Josephson phenomena in superfluid 3He, focusing on weak links, bound states, and unusual current-phase relations, with comparisons to experimental results.

Contribution

It introduces a theoretical framework for understanding Josephson effects in superfluid 3He, highlighting the role of bound states and spin splitting in current-phase relations.

Findings

Unusual pi state current-phase relations are predicted.

Order parameter modifications occur due to Josephson coupling.

Theoretical results align with experimental observations.

Abstract

Quite detailed theoretical description of superfluid 3He is possible on length scales that are much larger than the atomic scale. We discuss weak links between two bulk states of 3He-B. The current through the weak link is determined by the bound states at the link. The bound state energies are spin split depending on the order parameters in the bulk. As a result, unusual current-phase relations with pi state appear. For not too weak links, the order parameter in the bulk is modified because of the Josephson coupling. This leads to a stronger pi state and to an additional current at constant pressure bias. The theoretical results are compared with experiments.