Nearly isotropic d-wave pairing in UPt 3

Abstract

The available phase diagram of UPt 3 in H-T-P coordinates imposes strong restrictions on all theories which are going to explain it. We present a self-consistent solution of this problem. In our picture UPt 3 is a d-wave nearly isotropic superconductor with small splitting of critical temperature according to the irreducible representations of a D 6h group. Two of these representations A 1g and E 1g are responsible for the phase transitions in UPt 3. The order of high- and low-temperature representations reverses under pressure. This scenario explains all the peculiarities of the UPt 3 phase diagram such as the existence of a tetracritical point in the H-T plane, a kink in H c2( T) for different orientations of magnetic field, the behavior of superconducting phases under pressure and others.