Phenomenological theory in reentrant uranium-based superconductors

We develop a phenomenological theory for a family of uranium-based heavy fermion superconductors (URhGe, UCoGe, and UTe2). The theory unifies the understanding of both superconductivity (SC) with a weak magnetic field and reentrant superconductivity (RSC) that appears near the first-order transition line with a high magnetic field. It is shown that the magnetizations along the easy and hard axes have opposite effects on SC. The RSC is induced by the fluctuation parallel to the direction of the magnetic field. The theory makes specific predictions about the variation of triplet SC order parameters →d with applied external magnetic fields and the existence of a metastable state for the appearance of the RSC.