Oxygen on-site Coulomb energy in Pr1.3−xLa0.7CexCuO4 and Bi2Sr2CaCu2O8+δ and its relation with Heisenberg exchange

We study the electronic structure of electron-doped Pr1.3−x La0.7 Cex CuO4 (PLCCO; Tc = 27 K, x = 0.1) and hole-doped Bi2Sr2CaCu2O8+δ (Bi2212; Tc = 90K) cuprate superconductors using x-ray absorption spec- troscopy and resonant photoemission spectroscopy (Res-PES). From Res-PES across the O K-edge and Cu L-edge, we identify the O 2p and Cu 3d partial density of states (PDOS) and their correlation satellites, which originate in two-hole Auger final states. Using the Cini-Sawatzky method, analysis of the experimental O 2p PDOS shows an oxygen on-site Coulomb energy for PLCCO to be Up = 3.3 ± 0.5 eV, and for Bi2212, Up = 5.6 ± 0.5 eV, while the copper on-site Coulomb correlation energy is Ud = 6.5 ± 0.5 eV for Bi2212. The expression for the Heisenberg exchange interaction J in terms of the electronic parameters Ud, Up, charge-transfer energy 􏰀, and Cu-O hopping tpd obtained from a simple Cu2O cluster model is used to carry out an optimization analysis consistent with J known from scattering experiments. The analysis also provides the effective one-band on-site Coulomb correlation energy U ̃ and the effective hopping t ̃. PLCCO and Bi2212 are shown to exhibit very similar values of U ̃ /t ̃ ∼ 9–10, confirming the strongly correlated nature of the singlet ground state in the effective one-band model for both materials.