X-RAY-ABSORPTION SPECTROSCOPY OF PRXY1-XBA2CU3O7-Y SINGLE-CRYSTALS

Substituting Y in orthorhombic (Y,RE)Ba2Cu3O7 by arty rare-earth eleme nt RE has generally little effect on the superconducting properties, F or RE = Pr, however, superconductivity is completely suppressed. To el ucidate this effect we have studied the unoccupied electronic structur e of PrxY1-xBa2Cu3O7-y (x = 0.0, 0.4, 0.8) by polarization-dependent O ls x-ray absorption spectroscopy on detwinned single crystals. Along w ith the comparison of undoped (y approximate to 0.9) to the doped mate rials (y approximate to 0.1), this allows a test of the current theore tical explanations for the suppression of super-conductivity, While we can rule out models involving hole filling or charge transfer from pl anes to chains our data is consistent with approaches based on Pr4f-O2 p(pi) hybridization.