Relation between the electronic structure and the superconductivity of cuprates as revealed by Cu 2p photoemission and theoretical investigations

Abstract

Cu 2p core-level photoemission studies of La_2-xSr_xCuO₄, BiPbSr₂Y_1−xCa_1−xCu₂O₈, and other cuprates show that the relative intensity of the satellite varies with the composition in a direction opposite to that of the hole concentration, n_h. The I_S/I_M−n_h relations in the different cuprate series can be understood in terms of the Δ/t_pd ratio, where Δ is the charge-transfer excitation energy and t_pd is the hybridization strength between the Cu 3d and O 2p orbitals. Interestingly, the I_S/I_M ratio increases with the Δ/t_pd ratio in the cuprates. At a given value of n_h, e.g., around the value corresponding to maximum T_c, I_S/I_M increases in the same direction as T_c among the different series of cuprates, suggesting thereby that T_c itself may be determined by Δ/t_pd.