New theory of superconducting copper oxides - From electronic structure to the d-wave pairing mechanism

Firstly, a brief review is given on recent theoretical developments made by our group as to the many-body effect including electronic structure of hole-doped cuprates. Then the mechanism of superconductivity is discussed on the basis of the above-mentioned electronic structure of LSCO. In doing so we present the results of quantitative calculation of the electron-phonon coupling constants and the k, k' dependence of the spectral function alpha(2)F(Omega, k, k') made on the basis of the renormalized one-electron-type band. The following important results emerge from this calculation: (1) d-wave pairing occurs even for the phonon mechanism, provided the localized spins form a local antiferromagnetic order; (2) phonon modes in which oxygen ions move vertically for CuO2 plane contribute to the electron-phonon interaction in cuprates while those like breathing modes in which oxygen and copper ions vibrate within a CuO2 plane do not contribute significantly; (3) the electron-phonon interaction in CuO5 pyramid-type cuprates is stronger than CuO6 octahedral-type cuprates.