Normal-State Fermi Surface Of Pristine And Pb-Doped Bi2sr2cacu2o8+Delta From Angle-Resolved Photoemission Measurements And Its Photon Energy Independence

We address the question as to whether the topology of the normal-state Fermi surface of Bi2Sr2CaCu2O8+delta-as seen in angle-resolved photoemission-depends on the photon energy used to measure it. High-resolution photoemission spectra and Fermi-surface maps from pristine and Pb-doped Bi2Sr2CaCu2O8+delta are presented, recorded using both polarized and unpolarized radiation of differing energies. The data show clearly that no main band crosses the Fermi surface along the Gamma MZ direction in reciprocal space, even for a photon energy of 32 eV, thus ruling out the existence of a Gamma-centered, electronlike Fermi surface in this archetypal high-ire superconductor. The true topology of the normal-state Fermi surface remains that of holelike barrels centered at the X, Y points of the Brillouin zone.