The joys and pitfalls of Fermi surface mapping in Bi2Sr2CaCu2O8+d using angle resolved photoemission Borisenko, S.V.; Golden, M.S.; Legner, S.; Pichler, T.; Dürr, C.; Knupfer, M.; Fink, J.; Yang, G.; Abell, S. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We have carried out experimental and theoretical studies of the unoccupied electronic structure of Sr 2 CuO 3 , which can be regarded as the best realization of a one-dimensional model system containing cuprate chains. In the polarization-dependent x-ray absorption spectra, the contributions to the upper Hubbard band from states originating from the two inequivalent oxygen sites are energetically well separated. Theoretical analysis of the measured hole distribution within cluster calculations reveals a markedly enhanced effective nearest-neighbor intersite Coulomb interaction, V pd ϳ2 to 3 eV, or sizable contributions from next-nearest-neighbor interactions, provided a finite on-site energy difference of the two inequivalent oxygen sites ⌬ pp is taken into account. Including next-nearest-neighbor interactions, reasonable agreement can be achieved with recent electron energy-loss spectroscopy data from the same compound. The 2p oxygen orbital analysis of the unoccupied electronic structure of the single-chain cuprate Sr 2 CuO 3 reveals strong similarities with that of the double chain compound SrCuO 2 .

We have investigated the lowest binding-energy electronic structure of the model cuprate Sr 2 CuO 2 Cl 2 using angle-resolved photoemission spectroscopy. Our data from about 80 cleavages of Sr 2 CuO 2 Cl 2 single crystals give a comprehensive, self-consistent picture of the nature of the first electron-removal state in this model undoped CuO 2-plane cuprate. First, we show a strong dependence on the polarization of the excitation light which is understandable in the context of the matrix element governing the photoemission process, which gives a state with the symmetry of a Zhang-Rice singlet. Secondly, the strong, oscillatory dependence of the intensity of the Zhang-Rice singlet on the exciting photon energy is shown to be consistent with interference effects connected with the periodicity of the crystal structure in the crystallographic c direction. Thirdly, we measured the dispersion of the first electron-removal states along ⌫→(,) and ⌫→(,0), the latter being controversial in the literature, and have shown that the data are best fitted using an extended tJ model, and extract the relevant model parameters. An analysis of the spectral weight of the first ionization states for different excitation energies within the approach used by Leung et al. ͓Phys. Rev. B 56, 6320 ͑1997͔͒ results in a strongly photon-energy dependent ratio between the coherent and incoherent spectral weight. The possible reasons for this observation and its physical implications are discussed.

The strong dependence of the momentum distribution of the photoelectrons on experimental conditions raises the question as to whether angle-resolved photoemission spectroscopy (ARPES) is able to provide an accurate reflection of the Fermi surface in Bi-based cuprate superconductors. In this paper we experimentally prove that the main contribution to the intensity variation comes from matrix elements effects and develop an approach to overcome this problem. We introduce a concept of 'self-normalization' which makes the spectra essentially independent of both the matrix elements and particular experimental parameters. On the basis of this concept we suggest a simple and precise method of Fermi surface determination in quasi-2D systems. 74.25.Jb, 74.72.Hs, 71.18.+y