Osterwalder, J.J.OsterwalderAebi, P.P.AebiSchwaller, PatrickPatrickSchwallerSchlapbach, L.L.SchlapbachShimoda, M.M.ShimodaMochiku, T.T.MochikuKadowaki, K.K.Kadowaki2024-11-192024-11-191995-030947-839610.24451/arbor.9292https://doi.org/10.24451/arbor.929210.1007/BF01538399https://arbor.bfh.ch/handle/arbor/30083Core-level X-ray photoelectron-diffraction patterns have been measured from cleaved Bi2Sr2CaCu2O8+δ (001) surfaces for all elements present in this compound. The incommensurate modulation alongb ([010]) leads to a strong inequivalence ofa- andb-directions for Bi, Sr and Cu photoelectrons, while Ca and O emission show less effect. Ultraviolet-photoemission experiments recording the emission intensity at the Fermi energy over a large solid angle are also presented, providing a direct mapping of the Fermi surface. Ac(2×2) superstructure is observed on the Fermi surface suggesting antiferromagnetic correlations within the Cu−O planes. The effects of the lattice modulation are clearly observable at the Fermi energy, and they are enhanced for binding energies higher than a few tens of meV.enarticle