Multiple Andreev Reflections in Weak Links of Superfluid 3He-B

TL;DR

This paper models the current-pressure behavior of weak links in superfluid 3He-B, emphasizing multiple Andreev reflections and their relaxation effects, with numerical and analytical comparisons to experiments.

Contribution

It introduces a self-consistent numerical approach to account for surface suppression of the order parameter in superfluid 3He-B weak links, extending previous analytical models.

Findings

Numerical results match experimental data.

Surface suppression significantly affects dissipation.

Multiple Andreev reflections dominate current flow.

Abstract

We calculate the current-pressure characteristics of a ballistic pinhole aperture between two volumes of B-phase superfluid 3He. The most important mechanism contributing to dissipative currents in weak links of this type is the process of multiple Andreev reflections. At low biases this process is significantly affected by relaxation due to inelastic quasiparticle-quasiparticle collisions. In the numerical calculations, suppression of the superfluid order parameter at surfaces is taken into account self-consistently. When this effect is neglected, the theory may be developed analytically like in the case of s-wave superconductors. A comparison with experimental results is presented.