Theory of Ferromagnetic Superconductors —Analogue of Superfluid ³He A Phase—

Abstract

Ferromagnetic superconductors, UGe 2 , URhGe, and UCoGe are theoretically investigated by a unified point of view. In terms of a non-unitary triplet pairing state, analogous to the superfluid 3 He A phase under magnetic fields, we analyze various superconducting properties, in particular the upper critical field H c2 , which consists of three phases, A 1 , A 2 and A phases in general. A reentrant H c2 in URhGe, an S-shaped ones in UCoGe and UGe 2 , and L-shaped H c2 in UTe 2 are reproduced within the GL framework. UTe 2 is also treated by assuming that ferromagnetic fluctuations are slow enough to be regarded as "static" for the superconducting subsystem.