Spin-Peierls fluctuation and dimerization: a possible mechanism of superconductivity

A characteristic and unique feature of electron-phonon coupling in strongly correlated metals is examined. Significant properties due to spin-Peierls fluctuation near the Mott transition recently clarified are reviewed, especially in terms of the pairing mechanism and spin gap formation in the metallic phase. A superconducting state appears when the singlet ground state of a Mott insulator with a spin gap is doped with metallic carriers. The spin-Peierls t-J model is shown to be a relevant model. Exotic features of the spin-Peierls pairing mechanism are discussed. Experimental consequences and possible relevance in high T_c oxides and fullerenes are also discussed.