Topological defects in triplet superconductors UPt$_{3}$, Sr$_{2}$RuO$_{4}$, etc

TL;DR

This paper reviews topological defects in triplet superconductors like UPt$_{3}$ and Sr$_{2}$RuO$_{4}$, highlighting experimental observations and theoretical textures such as vortices and domain walls.

Contribution

It introduces the concept of topological defects in triplet superconductors and discusses experimental evidence and theoretical textures, including solitons and half-quantum vortices.

Findings

Observation of flux pinning in some triplet superconductors.

Ubiquity of Abrikosov vortices across different superconductors.

Potential detection of domain walls and half-quantum vortices.

Abstract

After a brief introduction on nodal superconductors, we review the topological defects in triplet superconductors such as UPt$_{3}$, Sr$_{2}$RuO$_{4}$, etc. This is in part motivated by the surprising discovery of Ana Celia Mota and her colleagues that in some triplet superconductors the flux motion is completely impeded (the ideal pinning). Among topological defects the most prominent is Abrikosov's vortex with quantum flux $\phi_{0}= \frac{hc}{2e}$. Abrikosov's vortex is universal and ubiquitous and seen in both conventional and unconventional superconductors by the Bitter decoration technique, small angle neutron scattering (SANS), scanning tunneling microscopy (STM), micromagnetometer and more recently by Lorentz electron micrograph. In order to interpret the experiment by Mota et al a variety of textures are proposed. In particular, in analogy to superfluid $^{3}$He-A the $\hat{\ell}$-soliton and $\hat{d}$-soliton play the prominent role. We review these notions and point out possible detection of these domain walls and half-quantum vortices in some triplet superconductors.