Hole depletion and localization due to disorder in insulating PrBa2Cu3O3O7-delta: A Compton scattering study

The (mostly) insulating behavior of PrBa2Cu3O7-delta a is still unexplained and even more interesting due to the occasional appearance of superconduct ivity in this material. Since YBa2Cu3O7-delta is nominally isostructural an d always superconducting, we have measured the electron momentum density in these materials. We find that they differ in a striking way, the wave func tion coherence length in PrBa2Cu3O7-delta being strongly suppressed. We con clude that Pr on Ba-site substitution disorder is responsible for the metal -insulator transition. Preliminary efforts at growth with a method to preve nt disorder yield 90 K superconducting PrBa2Cu3O7-delta crystallites. [S016 3-1829(99)02517-5].