C.H. Choi and J. A. Sauls
Comments: 4 pages with 1 figure
Journal Ref. Phys. Rev. Lett. 66, 484 (1991)
We present a theoretical explanation of the unusual temperature-dependent anisotropy of Hc2 reported by Shivaram, et al. for single crystals of UPt3, which we argue provides strong support for unconventional odd-parity pairing. We show that the observed low-temperature crossover in the anisotropy ratio, Hc2⊥/Hc2||, can be explained by paramagnetic limiting for H parallel to the sixfold axis within BCS pairing theory if the order parameter has odd-parity and there is strong spin-orbit coupling of the pair spin to the crystal axes.
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