Quantum percolation theory explains anomalies in Raman-scattering and tunneling data which indicate intrinsic states below the energy gap of Y-Ba-Cu-O. Separation of these states into localized and extended components shows that the tunneling and Raman-scattering data are compatible with the observed linear temperature dependence of the planar resistivity.

• Received 28 June 1989

DOI:https://doi.org/10.1103/PhysRevB.41.8968