Superconductivity in Na_<i>x</i>CoO₂·<i>y</i>H₂O due to Charge Fluctuation

Abstract

A new mechanism for superconductivity in the newly discovered Co-based oxide\nis proposed by using charge fluctuation. A single-band extended Hubbard model\non the triangular lattice is studied within random phase approximation.\n$f$-wave triplet superconductivity is stabilized in the vicinity of\ncharge-density-wave instability, which is in sharp contrast with the\nsquare-lattice case. The physical origin of the realization of the $f$-wave\ntriplet state as well as the relevance to experiments are discussed.\n