Role of spin-orbit coupling on the spin triplet pairing in Na xCoO2·yH2O: I. d-vector under zero magnetic field

Youichi Yanase, Masahito Mochizuki, Masao Ogata

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17 Citations (Scopus)


The d-vector in possibile spin triplet superconductor Na xCoO2·yH2O is microscopically investigated on the basis of the multi-orbital Hubbard model including the atomic spin-orbit coupling. As a result of the perturbation theory, we obtain the stable spin triplet superconductivity where the p-wave and f-wave states can be stabilized. If we neglect the spin-orbit coupling, superconducting state has 6-fold (3-fold) degeneracy in the p-wave (f-wave) state. This degeneracy is lifted by the spin-orbit coupling. We determine the d-vector within the linearlized Dyson-Gorkov equation. It is shown that the d-vector is always along the plane when the pairing symmetry is p-wave, while it depends on the parameters in case of the f-wave state. The lifting of degeneracy is significant in the p-wave state while it is very small in the f-wave state. This is because the first order term with respect to the spin-orbit coupling is effective in the former case, while it is ineffective in the latter case. The consistency of these results with NMR and μSR measurements are discussed.

Original languageEnglish
Pages (from-to)2568-2578
Number of pages11
Journaljournal of the physical society of japan
Issue number9
Publication statusPublished - 2005 Sep
Externally publishedYes


  • Multi-orbital model
  • NaCoO·yHO
  • Spin triplet superconductivity
  • d-vector

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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