Polarization analysis of x-ray absorption at the O 1s absorption edge in PrBa₂Cu₃O₇: Unusual electronic structure in CuO₂ plane

The polization dependence of x-ray absorption at the oxygen 1s absorption edge in untwinned LuBa₂Cu₃O₇ and PrBa₂Cu₃O₇ single crystal specimens was measured. The hole states of oxygen in the CuO₂ plane in PrBa₂Cu₃O₇ locate at higher energy position than those of the oxygen in the CuO₂ in superconducting LuBa₂Cu₃O₇, although the hole states of chain sites remain at the same energy position in both Pr123 and Lu123 samples. Although they are mainly of pσ character rather than of pπ and were attributed as an upper Hubbard band, a possibility was pointed out that a trace of pπ character hole states in the CuO₂ plane exists in Pr 123. The formation of Zhang-Rice singlet is suppressed by pπ holes in the CuO₂ plane on account of the strong Coulomb interaction on an oxygen site.