Meissner phases in spin-triplet ferromagnetic superconductors

TL;DR

This paper investigates the phase behavior of spin-triplet ferromagnetic superconductors, revealing how spontaneous magnetization influences the stability of mixed and other superconducting phases, with implications for materials like UGe2 and ZrZn2.

Contribution

It provides a detailed analysis of phase stability and transition orders in ferromagnetic superconductors, considering anisotropies and specific material applications.

Findings

Mixed phase of coexistence is stable due to spontaneous magnetization.

Phase transitions from normal to coexistence phase are first order.

Transition from ferromagnetic to coexistence phase varies between first and second order.

Abstract

We present new results for the properties of phases and phase transitions in spin-triplet ferromagnetic superconductors. The superconductivity of the mixed phase of coexistence of ferromagnetism and unconventional superconductivity is triggered by the presence of spontaneous magnetization. The mixed phase is stable but the other superconducting phases that usually exist in unconventional superconductors are either unstable or for particular values of the parameters of the theory some of them are metastable at relatively low temperatures in a quite narrow domain of the phase diagram. Phase transitions from the normal phase to the phase of coexistence is of first order while the phase transition from the ferromagnetic phase to the coexistence phase can be either of first or second order depending on the concrete substance. Cooper pair and crystal anisotropies determine a more precise outline of the phase diagram shape and reduce the degeneration of ground states of the system but they do not change drastically phase stability domains and thermodynamic properties of the respective phases. The results are discussed in view of application to metallic ferromagnets as UGe2, ZrZn2, URhGe.