Anisotropic quasiparticle properties in aluminum

We have studied the electron-phonon interaction in aluminum using Fermi-surface-fitted 4-orthogonalized-plane-wave electron states, a realistic phonon spectrum, and integration mesh density varying with local Fermi-surface curvature. The resulting electron-mass enhancement λ and thermal scattering rate τ^-1 are evaluated as functions of position on the Fermi surface, with the following results: (i) The agreement between observed and calculated cyclotron masses is improved slightly by the use of our anisotropic λ rather than the average one. (ii) The anisotropy of λ is determined predominantly by mixing coefficient variations, rather than by phonon anisotropy. (iii) The scattering rate τ^-1 exhibits order-of-magnitude variations over the Fermi surface at low temperatures. Its values at 5 K are within 50% of the experimentally observed ones everywhere, with considerably better agreement in free-electron regions. (iv) Deviations from the naively expected T³ behavior are predicted: In free-electron regions, umklapp processes cause a more rapid increase than T³ for temperatures above 15-25 K. On ridges, where the initial "T³ coefficient" is very large, we find a slower increase. There results a washing out of anisotropy with increasing temperature. The results on λ are in good agreement with those of a recent similar calculation; the τ^-1 results agree qualitatively but not quantitatively.