C-AXIS PROJECTED ELECTRON POSITRON MOMENTUM DENSITY IN YBA2CU3O7

We present the theoretical c-axis projected electron-positron momentum density N2-gamma-(P(x), P(y)) in YBa2Cu3O7 based on the local density approximation (LDA) framework along various lines in momentum space. The calculations use the Korringa-Kohn-Rostoker (KKR) band structure formalism. The anisotropic distribution defined by taking cuts through the calculated spectra along different lines in the (p(x), p(y)) plane possesses complex structures which arise from both Fermi surface effects and the anisotropy of the smoothly varying underlying background from filled bands; the maximum size of the anisotropy is about 10% of N2-gamma-(0, 0). The theoretically predicted N2-gamma-(p(x), p(y)) distribution is compared with the measured 2D-ACAR spectrum. Our considerations suggest that in interpreting the 2D-ACAR data on YBa2Cu3O7 in terms of a band theory LDA picture, a substantial, largely isotropic, background should be subtracted from both the 2D-ACAR's and the associated LCW-folded spectra.