Electronic excitations in Bi2Sr2 CaCu2O8: Fermi surface, dispersion, and absence of bilayer splitting

From a detailed study, including polarization dependence, of the normal state angle-resolved photoemission spectra for Bi2Sr2CaCu2O8, we find only one CuO2 band related feature. All other spectral features can be ascribed either to umklapps from the superlattice or to “shadow bands.” Even though the dispersion of the peaks looks like band theory, the line shape is anomalously broad and no evidence is found for bilayer splitting. We argue that the “dip feature” in the spectrum below Tc arises not from bilayer splitting, but rather from many-body effects.