Critical Current of the Spin-Triplet Superconducting Phase in Sr$_2$RuO$_4$

TL;DR

This paper compares two models of the spin-triplet superconducting order parameter in Sr$_2$RuO$_4$ by analyzing their critical current behavior in thin films, proposing an experiment to distinguish between them.

Contribution

It introduces a method to differentiate between the $f$-wave and multigap models of Sr$_2$RuO$_4$ using critical current measurements in thin films.

Findings

Supercurrent behavior differs significantly between models.

Critical current measurement can identify the correct order parameter.

Provides a practical experimental test for the superconducting state.

Abstract

There have been two different proposals for the spin-triplet order parameter of the superconducting phase in Sr$_2$RuO$_4$; an $f$-wave order parameter and the multigap model where some of the bands have the line node. In an effort to propose an experiment that can distinguish two cases, we study the behavior of the supercurrent and compute the critical current for these order parameters when the sample is a thin film with the thickness $d \ll \xi$ where $\xi$ is the coherence length. It is found that the supercurrent behaves very differently in two models. This will serve as a sharp test for the identification of the correct order parameter.