Antiferromagnetism and Superconductivity in UPt_3

TL;DR

This paper investigates the nature of antiferromagnetism and superconductivity in UPt_3, demonstrating that existing 2D models are incompatible with observed short-range order and predicting a first-order transition inconsistent with experiments.

Contribution

It provides a variational analysis of the Ginzburg-Landau equations showing the limitations of 2D models in explaining UPt_3's magnetic and superconducting phases.

Findings

2D models predict a large latent heat at the lower transition

The lower transition is likely first order, contradicting experimental observations

A simple periodic model rules out crossover scenarios

Abstract

The short ranged antiferromagnetism recently seen in UPt_3 is proved incompatible with two dimensional (2D) order parameter models that take the antiferromagnetism as a symmetry breaking field. To adjust to the local moment direction, the order parameter twists over very long length scales as per the Imry-Ma argument. A variational solution to the Ginzburg-Landau equations is used to study the nature of the short ranged order. Although there are still two transitions, the lower one is of first order -- in contradiction to experiments. It is shown that the latent heat predicted by the 2D models at the lower transition is too large not to have been seen. A simple periodic model is numerically studied to show that the lower transition can not be a crossover either.