SUPERCONDUCTING A AND B PHASES IN TRIPLET BIPOLARON SYSTEMS
三重态双极化子的超导A相与B相

Superconducting A and B phases in triplet bipolaron system have been treated by useing the selfconsistent broken-symmetry Hartree approximation. The B phase is always more stable than the A phase in the weak coupling case. But in the strong coupling case, owing to the fluctuation feedback effect, the free energy of the A phase can be lower than that of the B phase, or the A-B transition may occur, which is analogous to the superfluid of 3He. The thermody-namic critical field Hc of the stable phase of the system has also been calculated and compared with the upper critical fields of heavy-fermion superconductors, UBe13, UPt3 and URi2Si2. It has been found that Hc can qualitatively account for the abnormal temperature dependences of the upper critical fields of these superconductors.