Pair-breaking in superconductors with strong spin-orbit coupling

TL;DR

This paper introduces a field-fitness function to analyze how symmetry-breaking perturbations, especially magnetic fields, affect superconductivity in multiorbital materials, revealing parity-dependent effects on pair-breaking.

Contribution

It develops a novel field-fitness function to quantify pair-breaking effects of magnetic fields in multiorbital superconductors, highlighting differences between even and odd parity states.

Findings

For even parity superconductors, the paramagnetic response is governed solely by an effective g-factor.

In odd parity superconductors, the interplay of g-factor and field-fitness function can produce unexpected behaviors.

Demonstrates these effects explicitly for p-wave pairing in j=3/2 electronic states.

Abstract

We study the influence of symmetry-breaking perturbations on superconductivity in multiorbital materials, with a particular focus on an external magnetic field. We introduce the field-fitness function which characterizes the pair-breaking effects of the perturbation on a given superconducting state. For even parity superconductors we find that this field-fitness function for an external magnetic field is one, implying that the paramagnetic response is controlled only by a generalized effective $g$-factor. For odd parity superconductors, the interplay of the effective $g$-factor and the field-fitness function can lead to counter-intuitive results. We demonstrate this for $p$-wave pairing in the effective $j=3/2$ electronic states of the Luttinger-Kohn model.