Anisotropic Many-Body Effects in the Quasiparticle Velocity of Nb

Abstract

Fermi radii and velocities are determined by deconvoluting de Haas—van Alphen data. Comparison of these data with accurate augmented—plane-wave band-structure results establishes the reliability of the augmented—plane-wave calculations and allows a determination of the anisotropic many-body enhancement factor $\lambda \left(\overrightarrow{\mathrm{k}}\right)$. The Fermi-surface average $〈\lambda 〉$ of 1.33 suggests a large electron-electron contribution. Our anisotropic $\lambda \mathrm{}\left(k\right)\mathrm{}$ provide a detailed test and guide for model calculations of many-body enhancement.