Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3

TL;DR

This paper interprets NMR data on UPt$_3$ as evidence of non-unitary spin-triplet pairing, revealing weak spin-orbit coupling and complex d-vector behavior, thus establishing UPt$_3$ as a unique example of such pairing in a heavy Fermion superconductor.

Contribution

It provides a theoretical interpretation of experimental NMR results indicating non-unitary triplet pairing in UPt$_3$, highlighting weak spin-orbit coupling and d-vector rotation.

Findings

Evidence of non-unitary spin-triplet pairing in UPt$_3$

Weak spin-orbit coupling in the superconductor

Observation of d-vector rotation under weak magnetic fields

Abstract

A NMR experiment recently done by Tou et al. on a heavy Fermion superconductor UPt$_3$ is interpreted in terms of a non-unitary spin-triplet pairing state which we have been advocating. The proposed state successfully explains various aspects of the seemingly complicated Knight shift behaviors probed for major orientations, including a remarkable d-vector rotation under weak fields. This entitles UPt$_3$ as the first example that a charged many body system forms a spin-triplet odd-par ity pairing at low temperatures and demonstrates unambiguously that the putative spin-orbit coupling in UPt$_3$ is weak.