Role of the Cu-O charge-transfer energy in the superconductivity of cuprates: Evidence from Cu 2pcore-level spectroscopy and theory

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.