Theoretical two-particle momentum density in YBa₂Cu₃O_7-δ

We present calculations of the electron-positron momentum density for YBa₂Cu₃O_7-δ for δ = 0 and 1 respectively and for an ordered YBa₂Cu₃O₇/YBa₂Cu₃O₆ (100) superlattice, based on first-prindples 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 δ = 0 the chain related breaks are large, they are predicted to be smaller by a factor of two for δ = 0.5, and to be hardly visible in experiments.