Multi-orbital analysis on the superconductivity in NaxCoO 2·yH2O

Youichi Yanase*, Masahito Mochizuki, Masao Ogata

*この研究の対応する著者

研究成果: Article査読

62 被引用数 (Scopus)

抄録

We preform a multi-orbital analysis on the novel superconductivity in NaxCoO2·yH2O. We construct a three-orbital model which reproduces the band structure expected from the LDA calculation. The effective interaction leading to the pairing is estimated by means of the perturbation theory. It is shown that the spin triplet superconductivity is stabilized in the wide parameter region. This is basically owing to the ferromagnetic character of spin fluctuation. The p-wave and f-wave superconductivity are nearly degenerate. The former is realized when the Hund's rule coupling is large, and vice versa. In a small part of the parameter space, the d-wave superconductivity is also stabilized. We point out that the orbital degeneracy plays an essential role for these results. In particular, the momentum dependence of wave function of quasi-particles is quite important. The nearly degeneracy of p-wave and f-wave superconductivity is explained by analysing the microscopic character of each Fermi surface. We discuss the validity of some reduced models. While the single-orbital Hubbard model reproducing the Fermi surface is qualitatively inappropriate, we find an effective two-orbital model appropriate for studying the superconductivity. We investigate the vertex corrections higher than the third order on the basis of the two-orbital model. It is shown that the vertex correction induces the screening effect but does not affect qualitative results.

本文言語English
ページ(範囲)430-444
ページ数15
ジャーナルjournal of the physical society of japan
74
1
DOI
出版ステータスPublished - 2005 1月
外部発表はい

ASJC Scopus subject areas

  • 物理学および天文学(全般)

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