Superconductivity in NaxCoO2•yH2O due to charge fluctuation

A new mechanism of superconductivity due to charge fluctuation in the newly discovered Co-based oxide is proposed. A single-band extended Hubbard model on a triangular lattice is studied within the random phase approximation. f-wave triplet superconductivity is stabilized in the vicinity of charge-density-wave instability, which is in sharp contrast to the square-lattice case. The physical origin of the realization of the f-wave triplet state as well as its relevance to experiments are discussed.