Role of the Cu-O charge-transfer energy in the superconductivity of cuprates: Evidence from Cu 2<i>p</i>core-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}$${\mathrm{Ca}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathit{R}}_{\mathit{x}}$${\mathrm{Sr}}_{2}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\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.