Quasiparticle operators for high-temperature cuprate superconductors

A complete set of quasiparticle operators diagonalizing operators of the Coulomb and exchange interactions of copper and oxygen holes in cuprate high-temperature superconductors (HTSCs) is obtained. A scheme of energy bands in the regime of strong electron correlations is constructed. The effective operator for the singleband approximation is obtained with this scheme. It is found that the role of three-site correlations in hole HTSCs is negligibly small. This circumstance explains both the sharp increase in critical temperatures of hole HTSCs in comparison with electron-doped ones and the asymmetry between the spectra of collective spin excitations in these compounds.