THEORY OF HIGH-TEMPERATURE SUPERCONDUCTIVITY IN CUPRATES - IV - CALCULATION OF ELECTRON-PHONON COUPLING AND SPECTRAL-FUNCTION FOR LA2-XSRXCUO4, AND THE APPEARANCE OF THE D-WAVE PAIRING

We have calculated the k, k'-dependence of the spectral function alpha (2)F(Omega, k, k') using the renormalized one-electron-type band struc ture obtained in the previous paper III of this series in which the st ates of carriers and localized spins are separated by the mean field a pproximation for the localized spins and the latter form a local antif erromagnetic order. It is shown that the electron-phonon interaction w hich scatter the pairs of electrons from a pair-state (k up arrow, -k down arrow) to a different pair-state (k'up arrow, -k'down arrow) is r epulsive for some combinations of (k, k') and attractive for other com binations, because of the characteristic feature of the wavefunctions in LSCO in the presence of the local antiferromagnetic order. As a res ult the spectral function has mainly a d-wave component, and the effec tive electron-phonon coupling constant for the d-wave pairing, lambda( d), is estimated as 1.96 for x = 0.15.