New Paradigm of Triplet Superconductivity

H.Y. Kee a, Y. Morita b and K. Maki c a Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada b Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan c Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA

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Since 1980, more than 10 or so triplet superconductors have been discovered. Now we can put them into two separate classes. Type A consists of e.g. (TMTSF)2PF6, (TMTSF)2ClO4, UPt3, Sr2RuO4, PrOs4Sb12. These triplet superconductors are characterized with the extreme smallness of the spin-orbit coupling energy Eso (« Δp, where Δp is the superconducting gap). Also like superfluid 3He-A, the order parameter of these superconductors are characterized by l (the chiral vector) and d (the spin vector). In these superconductors, an Abrikosov vortex splits into a pair of half quantum vortices at low temperatures. Type A1 comprises most of non-centrosymmetric triplet superconductors discovered recently, e.g. CePt3Si, CeIrSi3, CeRhSi3, and Li2Pt3B. They are characterized by l and d1+id2 like superfluid 3He-A1. The spin-orbit coupling energy Eso is extremely large Eso ≈ 103 K. Therefore, as noted by Frigeri et al., the Fermi surface splits for the up-spin one and the down-spin one. However, contrary to Frigeri et al., the superconductivity should occupy only the larger Fermi surface (say for spin-up). The other Fermi surface remains in the normal state. Also in type A1 superconductors, an Abrikosov vortex does not split into a pair of half quantum vortices. Further all thase triplet superconductors (both type A and type A1) harbor the zero mode or the Majorana fermion attached to each vortex, of which implication should be further explored.

DOI: 10.12693/APhysPolA.115.73 PACS numbers: 74.20.-z, 73.43.Cd