Effects of Fermi-surface anisotropy on cyclotron waves in metals

Abstract

We have shown that the spread in cyclotron frequencies of electrons on different orbits of a nonspherical closed Fermi surface leads to a collisionless damping of cyclotron waves for a range of wave numbers that depends on the geometry of the surface, and also to a shift, from the isotropic limit, in the onset of the waves. Explicit calculation of the dispersion relation, in the long-wavelength limit and in the absence of interactions, is performed for a metal whose Fermi surface has a small cubic distortion (as, for example, the heavy alkali metals, Cs and Rb). We find that Fermi-surface anisotropy produces effects similar in both magnitude and quality to those caused by Fermi-liquid interactions in a metal with an essentially spherical Fermi surface (as, for example, Na and K).