Spin precession in spin-orbit coupled weak links: Coulomb repulsion and Pauli quenching

TL;DR

This paper models electron pair transmission through a spin-orbit coupled nanowire, revealing how Coulomb interactions and the Pauli principle affect spin precession and Josephson current behavior.

Contribution

It introduces a simple model accounting for Coulomb and Pauli effects on spin precession, showing how Pauli quenching modifies coherent spin transport in weak links.

Findings

Pauli exclusion quenches coherent spin precession when wave packets overlap.

Josephson current oscillates with spin-orbit interaction strength, potentially reversing sign.

Coherent propagation breaks into incoherent hops due to Pauli quenching.

Abstract

A simple model for the transmission of pairs of electrons through a weak electric link in the form of a nanowire made of a material with strong electron spin-orbit interaction (SOI) is presented, with emphasis on the effects of Coulomb interactions and the Pauli exclusion principle. The constraints due to the Pauli principle are shown to "quench" the coherent SOI-induced precession of the spins when the spatial wave packets of the two electrons overlap significantly. The quenching, which results from the projection of the pair's spin states onto spin-up and spin-down states on the link, breaks up the coherent propagation in the link into a sequence of coherent hops that add incoherently. Applying the model to the transmission of Cooper pairs between two superconductors, we find that in spite of Pauli quenching, the Josephson current oscillates with the strength of the SOI, and may even change its sign. Conditions for an experimental detection of these features are discussed.