Superconductivity in Heavy Electron Systems: Axial or Polar State?
Recently, there has been some difference of opinion as to the nature of the gap anisotropy in heavy electron superconducting materials. Some workers1 have suggested that the similarity of the specific heat measurements on UBe13 with those on the A phase of 3He was indicative of an axial-like state, in which the superconducting gap exhibits isolated nodal points. Other workers2 suggested that the specific heat measurements on UPt3 were more indicative of a polar-like state, in which the superconducting gap exhibits a line or lines of nodes. There have been interpretations of many other experiments as well that have been controversial. It is the purpose of this paper to address the question of the nodal structure of the gap in those materials. To do so, we would like to examine the cases of the upper critical field Hc2, the ultrasonic attenuation a, and especially the microwave conductivity tensor Qij.
KeywordsMicrowave Anisotropy Attenuation Hexagonal Coherence
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