In this paper a review is given on the mechanism of high temperature superconductivity recently developed by Kamimura, Matsuno, and Saito. In this mechanism spin-polarons associated with itinerant holes in the e v band (Cu dz 2- Op π band) are created in CuO 2 layers by strong intra-atomic exchange interaction (Hund's coupling) with localized dx 2− y 2 holes. Then the interplay of Hund's coupling and superexchange between Cu 2+( dx 2− y 2) spins gives rise to an attractive exchange interaction between spin-polarons, which leads to the formation of spin-singlet spin-polarons pairs. This contributes to high temperature superconductivity. Further the s-wave pairing reproduces the observed x dependence of T c as well as the right magnitudes of T c in ( La 1−x Sr x )2 CuO 4 satisfactorily.
The spin polaron theory as a mechanism for high temperature superconductivity
