Angle-resolved photoemission on untwinnedYBa2Cu3O6.95.II. Determination of Fermi surfaces

We present complete Fermi-surface mappings of an untwinned single crystal of ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ in two distinct photon polarization geometries. Various methods for Fermi-surface determination with angle-resolved photoelectron spectroscopy are discussed and a technique based on the momentum space density of states is developed and applied. The data reveal the presence of two ${\mathrm{CuO}}_2$ plane-derived Fermi-surface pockets, along with weak evidence for a single chain sheet, in agreement with earlier work on twinned crystals and ab initio predictions, but show no sign of the expected “stick” pocket centered at $(\pi ,\pi )$. In contrast with earlier work on ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta },$ we see no evidence for “shadow bands” in optimally doped ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta },$ supporting the contention that these features arise from structural rather than magnetic correlations.