三重态双极化子的超导A相与B相

本文应用对称破缺的自洽Hartree近似讨论了三重态双极化子的超导A相和B相。在弱耦合的情况下,通过自由能的计算得到B相总比A相稳定;在强耦合的情况下,加入涨落反馈项可使得A相的自由能比B相的自由能低,或者发生A相到B相的转变,这和³He超流的情形类似。本文还精确计算了超导稳定相的热力学临界场H_c随温度的变化,并与重费密子超导体UBe₁₃,UPt₃和URi₂Si₂的上临界场作了比较,发现H_c能定性解释所有这些超导体的上临界场的反常温度特性。 关键词：

SUPERCONDUCTING A AND B PHASES IN TRIPLET BIPOLARON SYSTEMS

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 H_c 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 H_c can qualitatively account for the abnormal temperature dependences of the upper critical fields of these superconductors.