Density-functional approximation for the quasiparticle dynamics of Rb

The quasiparticle mass variation over the Fermi surface of Rb has been evaluated using approximations for the mass operator based on the density-functional formalism. A nonlocal approximation for the mass operator is found to yield a Fermi surface more nearly in accord with experiment than the usual local band theory approximation. However, both local and nonlocal mass operator approximations predict a much more anisotropic quasiparticle mass than has been inferred from the recent experiments of Paul and Springford (see ibid., vol.8, p.1713 (1978)).