Mass Reduction in Low Carrier Density Systems

Abstract

The cyclotron masses observed by the de Haas-van Alphen effect in semimetallic LaSb and particularly in small flat pockets in LaB₆, are substantially smaller than those evaluated by band calculations. As a common mechanism for low-carrier-density-systems, the mass reduction mechanism by the exchange interaction was first studied for an electron gas based on a simple model including Wigner crystal type screening. This model reproduces the result of high-density expansion and extends the result to the much lower density region of the Wigner liquid. The model was applied to the band electrons by dividing the band state into a plane wave part and a core part within a muffin-tin-sphere. It is shown that the mass reduction effect is enhanced particularly in the case of a small Fermi surface with strong anisotropy, which is in good agreement with the results obtained for the above materials.