THEORETICAL 2-PARTICLE MOMENTUM DENSITY IN YBA2CU3O7-DELTA

We present calculations of the electron-positron momentum density for YBa2Cu3O7-delta for delta = 0 and 1 respectively and for an ordered YBa2Cu3O7/YBa2Cu3O6 (100) superlattice, based on first-principles electronic structure calculations performed within the local density approximation (LDA) using the full potential linearized augmented plane wave (FLAPW) method. Our present results account for the trends observed in the experimental two-dimensional angular correlation of annihilation radiation (2D-ACAR) of the metallic and insulating compounds, as measured in Geneva. The Lock, Crisp, and West folding is applied in order to emphasize Fermi surface structures. While for delta = 0 the chain related breaks are large, they are predicted to be smaller by a factor of two for delta = 0.5, and to be hardly visible in experiments.