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A unified origin for the 3D magnetism and superconductivity in NaxCoO2

Kazuhiko Kuroki, Shuhei Ohkubo, Takumi Nojima, Ryotaro Arita, Seiichiro Onari, Yukio Tanaka

cond-mat.str-elarXiv:cond-mat/0610494

Abstract

We analyze the origin of the three dimensional (3D) magnetism observed in nonhydrated Na-rich NaxCoO2 within an itinerant spin picture using a 3D Hubbard model. The origin is identified as the 3D nesting between the inner and outer portions of the Fermi surface, which arise due to the local minimum structure of the a1g band at the Γ-A line. The calculated spin wave dispersion strikingly resembles the neutron scattering result. We argue that this 3D magnetism and the spin fluctuations responsible for superconductivity in the hydrated systems share essentially the same origin.

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