We explore the strong variations of the electronic properties of copper-oxygen compounds across the doping phase diagram in a quantitative way. To this end we calculate the electronic Raman response on the basis of results from angle-resolved photoem
ission spectroscopy (ARPES). In the limits of our approximations we find agreement on the overdoped side and pronounced discrepancies at lower doping. In contrast to the successful approach for the transport properties at low energies, the Raman and the ARPES data cannot be reconciled by adding angle-dependent momentum scattering. We discuss possible routes towards an explanation of the suppression of spectral weight close to the $(pi,0)$ points which sets in abruptly close to 21% doping.
We performed Raman experiments on superconducting ${rm Bi_2 Sr_2 (Ca_{1-x} Y_x) Cu_2 O_{8+delta}}$ (Bi-2212) and ${rm YBa_{2} Cu_{3}O_{6+x}}$ (Y-123) single crystals. These results in combination with earlier ones enable us to analyze systematically
the spectral features in the doping range $0.07 le p le 0.23$. In $B_{2g}$ ($xy$) symmetry we find universal spectra and the maximal gap energy $Delta_0$ to follow the superconducting transition temperature $T_c$. The $B_{1g}$ ($x^2-y^2$) spectra in Bi-2212 show an anomalous increase of the intensity towards overdoping, indicating that the corresponding energy scale is neither related to the pairing energy nor to the pseudogap, but possibly stems from a symmetry breaking transition at the onset point of superconductivity at $p_{rm sc2} simeq 0.27$.
