Ferromagnetic fluctuation and possible triplet superconductivity in Na xCoO2·yH2O: Fluctuation-exchange study of the multiorbital hubbard model

Masahito Mochizuki; Youichi Yanase; Masao Ogata

doi:10.1103/PhysRevLett.94.147005

Ferromagnetic fluctuation and possible triplet superconductivity in Na _xCoO₂·yH₂O: Fluctuation-exchange study of the multiorbital hubbard model

Masahito Mochizuki, Youichi Yanase, Masao Ogata

Research output: Contribution to journal › Article › peer-review

81 Citations (Scopus)

Abstract

Spin and charge fluctuations and superconductivity in Na _xCoO₂·yH₂O are studied based on a multiorbital Hubbard model. Tight-binding parameters are determined to reproduce the results of band calculations. By applying the fluctuation-exchange approximation, we show that the Hund's-rule coupling between the Co t _2g orbitals causes ferromagnetic (FM) spin fluctuation. Triplet f_y(y2-3x2)-wave and p-wave pairings are favored by this FM fluctuation on the hole-pocket band. We propose that, in Na_xCoO ₂·yH₂O, the Co t_2g orbitals and interorbital Hund's-rule coupling play important roles on the triplet pairing, and this compound can be a first example of the triplet superconductor in which the orbital degrees of freedom play substantial roles.

Original language	English
Article number	147005
Journal	Physical Review Letters
Volume	94
Issue number	14
DOIs	https://doi.org/10.1103/PhysRevLett.94.147005
Publication status	Published - 2005 Apr 15
Externally published	Yes

ASJC Scopus subject areas

Physics and Astronomy(all)

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abstract = "Spin and charge fluctuations and superconductivity in Na xCoO2·yH2O are studied based on a multiorbital Hubbard model. Tight-binding parameters are determined to reproduce the results of band calculations. By applying the fluctuation-exchange approximation, we show that the Hund's-rule coupling between the Co t 2g orbitals causes ferromagnetic (FM) spin fluctuation. Triplet fy(y2-3x2)-wave and p-wave pairings are favored by this FM fluctuation on the hole-pocket band. We propose that, in NaxCoO 2·yH2O, the Co t2g orbitals and interorbital Hund's-rule coupling play important roles on the triplet pairing, and this compound can be a first example of the triplet superconductor in which the orbital degrees of freedom play substantial roles.",

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