Plane-polarized Raman continuum in the insulating and superconducting layered cuprates.

Electronic properties of copper oxygen planes (and chains in Y-Ba-Cu-O) were studied with Raman spectroscopy of plane-polarized photons. The electronic continuum was found to be independent of doping in 2: 1:4 and 1:2:3 materials at energies above ∼1000 cm -1 . Temperature dependence at low energies differs significantly in undoped, lightly doped, and fully doped YBa 2 Cu 3 O 6+x . A feature consistent with the superconducting gap was observed below T c in YBa 2 Cu 3 O 6.9 in all scattering geometries. However, the gaplike redistribution was not complete, with 40-60% of states not shifted to higher energies at temperatures well below T c