Inelastic X-ray scattering (Compton) study of La1.85Sr0.15CuO4 -: anisotropic electron momentum distribution

High resolution Compton profiles along two principal symmetry directions (with scattering vector q parallel to [100] and [001]) have been measured from a single crystal of La1.85Sr0.15CuO4 using 58 keV X-rays at a momentum resolution of 0.17 a.u. The measurements are interpreted in terms of highly accurate all-electron computations of the profiles in the parent compound La2CuO4 within the local density approximation (LDA) based conventional band-theory framework, assuming that the resulting metallic state is representative of the Sr-doped compound. Although the experimental anisotropy of the profiles, DeltaJ = J([001]) - J([100]), and the first and second derivatives of the profiles are in reasonable overall accord with the computations, there are striking discrepancies as well. We suggest that these discrepancies may indicate a substantially larger O 2p character of the doped holes in La2CuO4 than implicit in the standard band-theory picture. (C) 2001 Elsevier Science Ltd, All rights reserved.