Diagnostics of functional materials with closed Fermi surfaces described by the Fivaz model and some aspects of their application

Abstract

The results of theoretical studies of the influence of a nonparabolicity in the Fivaz model on the properties of functional materials with closed Fermi surfaces are presented. Theoretical calculations of the longitudinal kinetic coefficients in the relaxation time approximation in a quantizing magnetic field perpendicular to layers and in the absence of a magnetic field are performed for two cases, such as the Fivaz model and the effective mass approximation. It is shown that the nonparabolicity effects may be well observed not only for highly open Fermi surfaces, as the majority of researchers believe, but for transient or closed Fermi surfaces. This is favorable factor for the diagnostics of such materials by the temperature and field dependences of their kinetic coefficients. Additionally, we investigated the nonparabolicity influence in the Fivaz model on the properties of thermoelectric materials in single crystals and powders. On this basis, some thermoelectric materials optimized by a powder grain size composition and a band spectrum are proposed.