pi states in Josephson Junction between He-3-B

TL;DR

This paper explores how the internal spin structure of superfluid He-3 B affects the current-phase relationship in Josephson junctions, revealing conditions for $\pi$-states influenced by magnetic field orientation.

Contribution

It demonstrates the emergence of $\pi$-states in He-3 B Josephson junctions due to internal spin effects and proposes a method to verify this mechanism via magnetic field dependence.

Findings

$\pi$-states can occur at low temperatures due to spin structure.

Supercurrent dependence on magnetic field orientation can confirm the mechanism.

Energy minima at phase difference $\pi$ under specific conditions.

Abstract

We investigate the dependence of the current-phase relationship on the orientation of the order parameter for a pinhole between two $^3$He-B reservoirs. We show that, due to the internal spin structure of the superfluid, the energy of the junction may have a relative minimum at phase difference equals $\pi$ at low temperatures. The dependence of the supercurrent on the direction of an applied magnetic field can be used to verify the present mechanism for the ``$\pi$-states''.