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Possible spin-triplet $f$-wave pairing due to disconnected Fermi surfaces in Na$_x$CoO$_2\cdot y$H$_2$O

Kazuhiko Kuroki·Yukio Tanaka·Ryotaro Arita
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Abstract

We propose that spin-triplet pairing mechanism due to disconnected Fermi surfaces proposed in our previous study [Phys. Rev. B {\bf 63} 174507 (2001)] may be at work in a recently discovered superconductor Na$_x$CoO$_2$ $\cdot y$ H$_2$O. We introduce a single band effective model that takes into account the pocket-like Fermi surfaces along with the van Hove singularity near the K point found in the band calculation results. Applying fluctuation exchange method and solving the linearized {É}liashberg equation, the most dominant pairing is found to have spin-triplet $f$-wave symmetry, where the nodes of the gap function do not intersect the pocket Fermi surfaces. Presence of finite $T_c$ is suggested in sharp contrast with cases when the gap nodes intersect the Fermi surface.

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Kazuhiko Kuroki, Yukio Tanaka, Ryotaro Arita. 2004-06-23. Possible spin-triplet $f$-wave pairing due to disconnected Fermi surfaces in Na$_x$CoO$_2\cdot y$H$_2$O. https://doi.org/10.1103/physrevlett.93.077001

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