  Despite decades of progress, an understanding of unconventional
superconductivity still remains elusive. An important open question is about
the material dependence of the superconducting properties. Using the
quasiparticle self-consistent GW method, we re-examine the electronic structure
of copper oxide high-Tc materials. We show that QSGW captures several important
features, distinctive from the conventional LDA results. The energy level
splitting between dx2-y2 and d3z2-r2 is significantly enlarged and the van Hove
singularity point is lowered. The calculated results compare better than LDA
with recent experimental results from resonant inelastic xray scattering and
angle resolved photoemission experiments. This agreement with the experiments
supports the previously suggested two-band theory for the material dependence
of the superconducting transition temperature, Tc.
