1209.3367 (Hiroshi Shimahara)
Hiroshi Shimahara
Noncentrosymmetric superconductors with various types of pairing interactions are systematically examined with particular focus on phenomena that originate from the differences of the Fermi surfaces split by strong spin-orbit coupling. In particular, when the spin-orbit coupling increases and one of the split Fermi surfaces disappears, the phase diagram and the structure of the gap function change drastically. For example, we examine the conditions for transition from full-gap states to line-node states, which may explain differences in experimental results between noncentrosymmetric superconductors Li_2Pd_3B and Li_2Pt_3B discovered recently. Comparing the theoretical phase diagrams, it is found that such a transition occurs in a wider and realistic parameter region for the charge-charge interactions, i.e., where short-range Coulomb repulsion is strong and p-wave and d-wave interactions are attractive, while it occurs in narrower and rather unrealistic parameter regions for the interactions of magnetic origin. It is suggested that the superconductivity in Li_2Pd_3B is an s-wave spin-triplet state, while that in Li_2Pt_3B is a d-wave state that has both spin-singlet and triplet components of comparable weights. It is also found that d-wave spin-triplet pairing may occur, when the pairing interactions are of magnetic origin and anisotropic in the spin space.
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http://arxiv.org/abs/1209.3367
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