De Haas-van Alphen effect in alkali metal dispersions and the Fermi surface of lithium

Abstract

Measurements of the de Haas-van Alphen effect in polycrystalline dispersions of metallic lithium are described. X-ray studies indicate that the low-temperature martensitic transformation is suppressed in samples of this form, and that the room temperature BCC structure is retained down to liquid helium temperatures. The de Haas-van Alphen amplitude shows a characteristic beat structure arising from the Fermi surface anisotropy. The radial distortion of the BCC Fermi surface is estimated to be 2.6+or-0.9%. The method of analysis is verified by similar measurements in dispersion of sodium. The results for lithium are consistent with the most recent positron annihilation, Compton scattering and optical absorption data, but yield a Fermi surface distortion which is significantly less than that given by typical bandstructure calculations. This discrepancy lends support to the suggestion of Rasolt, Nickerson and Vosko that non-local exchange and correlation effects may cause a substantial reduction of the Fermi surface anisotropy (see Solid State Commun., vol.16, p.827 (1975)).