ANGLE-RESOLVED PHOTOEMISSION ON UNTWINNED YBA2CU3O6.95 - II - DETERMINATION OF FERMI SURFACES

We present complete Fermi-surface mappings of an untwinned single crys tal of YBa2Cu3O7-delta in two distinct photon polarization geometries. Various methods for Fermi-surface determination with angle-resolved p hotoelectron spectroscopy are discussed and a technique based on the m omentum space density of states is developed and applied. The data rev eal the presence of two CuO2 plane-derived Fermi-surface pockets, alon g with weak evidence for a single chain sheet, in agreement with earli er work on twinned crystals and ab initio predictions, but show no sig n of the expected ''stick'' pocket centered at (pi,pi). In contrast wi th earlier work on Bi2Sr2CaCu2O8+delta we see no evidence for ''shadow bands'' in optimally doped YBa2Cu3O7-delta supporting the contention that these features arise from structural rather than magnetic correla tions.