Electron momentum-space densities of Li metal: A high-resolution Compton-scattering study

Abstract

Directional Compton profiles~CP’s ! of Li metal were measured for 11 directions of the momentum transfer q with 0.14 a.u. ~a.u.5atomic units: \5e5m51! momentum-space resolution using synchrotron radiation from the DORIS ~Doppel-Ring-Speicheranlage! storage ring monochromatized to 31 keV. Both the total valence-electron CP’s and the directional differences of the CP’s exhibit considerable deviations from the most recent density-functional calculations, performed by Sakurai et al. @Phys. Rev. Lett. 74, 2252 ~1995!# within the limits of the local density approximation. These discrepancies are attributed to self-energy effects connected with the excitation of so-called plasmaron modes. The three-dimensional ~3D! valence-electron momentum density, r~p!, as well as the 3D occupation number density N~k!, were reconstructed using the Fourier-Bessel method. The reconstructed r~p! exhibits clear evidence of higher momentum components due to 110 umklapp processes. The reconstructed N~k! enables a direct experimental access to the Fermi-surface anisotropy of Li, which was found to be 3.661.1%. The reconstructed N~k! for ki @001# was fitted to a model with the renormalization factor z as the only free parameter, which was found to be z50.160.1. @S0163-1829~96!07843-5#