Normal-state Fermi surface of pristine and Pb-doped Bi2Sr2CaCu2O8+δ from angle-resolved photoemission measurements and its photon energy independence

Abstract

We address the question as to whether the topology of the normal-state Fermi surface of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$---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 ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ 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 $\ensuremath{\Gamma}\overline{M}Z$ direction in reciprocal space, even for a photon energy of 32 eV, thus ruling out the existence of a \ensuremath{\Gamma}-centered, electronlike Fermi surface in this archetypal high-${T}_{C}$ 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.