On the phase diagrams of the ferromagnetic superconductors ZrZn2 and UGe2

TL;DR

This paper develops a phenomenological theory to describe the temperature-pressure phase diagrams of ferromagnetic superconductors ZrZn2 and UGe2, focusing on spin-triplet pairing and quantum phase transitions.

Contribution

It provides a detailed theoretical framework for understanding phase behavior and criteria distinguishing different types of unconventional ferromagnetic superconductors.

Findings

Detailed phase diagrams for ZrZn2 and UGe2 are explained.

Quantitative criteria for type I and type II ferromagnetic superconductors are derived.

Insights into quantum phase transitions in these materials are provided.

Abstract

A general phenomenological theory is presented for the phase behavior of ferromagnetic superconductors with spin-triplet electron Cooper pairing. The theory accounts in detail for the temperature-pressure phase diagram of ZrZn$_2$, while the main features of the diagram for UGe$_2$ are also described. Quantitative criteria are deduced for the U-type (type I) and Zr-type (type II) unconventional ferromagnetic superconductors with spin-triplet Cooper electron pairing. Some basic properties of quantum phase transitions are also elucidated.