2010 年 20 巻 2 号 p. 149-157
In this article, mechanism of superconductivity in strongly correlated electron systems is briefly reviewed paying attention to roles of spin and charge fluctuations. Valence-skip mechanism is also discussed as a potential one for superconductivity with relatively high transition temperature. Recent new developments in the critical-valence-fluctuation mechanism of Ce-based heavy fermions under high pressure are discussed.