Based on Cu 2p core-level spectroscopy and theoretical calculations, it has been demonstrated that the Cu-O charge-transfer excitation energy which determines the Cu 2p satellite intensity also plays a crucial role in the superconductivity of cuprates. The relative intensity of the satellite generally decreases with an increase in the ${\mathit{T}}_{\mathit{c}}$ or in the hole concentration in a given series of cuprate superconductors. In the case of ${\mathrm{Bi}}_2$${\mathrm{Ca}}_{1\mathrm{-}\mathit{x}}$${\mathit{R}}_{\mathit{x}}$${\mathrm{Sr}}_2$${\mathrm{Cu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$ (R=rare earth), the satellite intensity goes through a minimum around the same composition where the hole concentration as well as the ${\mathit{T}}_{\mathit{c}}$ show maxima.

• Received 3 April 1990

DOI:https://doi.org/10.1103/PhysRevB.42.1026