Multi-orbital analysis on the Superconductivity in Na_{x}CoO_{2} \cdot y H_{2}O

Abstract

We preform a multi-orbital analysis on the novel superconductivity in Na_{x}CoO_{2} \cdot yH_{2}O. 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 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 through the wave function of quasi-particles. The nearly degeneracy of p-wave and f-wave superconductivity is explained by analysing the orbital character of each Fermi surface. We discuss the validity of some reduced models. While the single band 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 on the qualitative results.

To appear in J. Phys. Soc. Jpn. 74 (2005) No.1

References in corpus (17)

• Charge-ordering, commensurability and metallicity in the phase diagram of layered Na(x)CoO(2)
• Theory of Superconductivity in Strongly Correlated Electron Systems
• Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
• ARPES on Na${}_{0.6}$CoO${}_2$: Fermi surface, extended flat dispersion, and unusual band splitting
• Charge Disproportionation and Spin Ordering Tendencies in Na(x)CoO2
• Giant electron-electron scattering in the Fermi-liquid state of Na_0.7CoO_2
• Possible effects of charge frustration in Na${}_x$CoO${}_2$: bandwidth suppression, charge orders and resurrected RVB superconductivity
• Possible spin-triplet $f$-wave pairing due to disconnected Fermi surfaces in Na${}_x$CoO${}_2\cdot y$H${}_2$O
• Nesting, spin-fluctuations, and odd-gap superconductivity in NaxCoO2 yH2O
• Superconductivity in Na_xCoO_2yH_2O by charge fluctuation
• Possible unconventional superconductivity in Na${}_x$CoO${}_2$yH${}_2$O probed by $\mu$SR
• Muon Spin Relaxation Measurements in Na_xCoO_2*yH_2O
• Impurity Effects on the Superconducting Transition Temperature of NazCoO2.yH2O
• Mass-Enhanced Fermi Liquid Ground State in Na${}_{1.5}$Co${}_2$O${}_4$
• Superconducting Properties under Magnetic Field in Na${}_{0.35}$CoO${}_2\cdot 1.3$H${}_2$O Single Crystal
• Possible Pairing Symmetry of Superconductor Na_xCoO_2yH_2O
• A Mechanism of Spin-Triplet Superconductivity in Hubbard Model on Triangular La ttice: Application to UNi_2Al_3

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