Diffusion thermoelectric power of bismuth in a magnetic field

Abstract

The diffusion thermoelectric power of bismuth in a magnetic field is calculated assuming a two-band model with parabolic dispersion for the holes and either parabolic or non-parabolic dispersion for the electrons. The scattering is described by a relaxation time which is assumed to be either dependent on energy as for intravalley acoustic scattering or independent of energy. Below 80K the density of charge carriers is only weakly temperature dependent and the Bethe-Sommerfeld expansion is used to derive expressions for the weak-field thermomagnetic coefficients. Above 80K a re-evaluation of earlier mobility data is performed to take into account the thermal smearing of the Fermi surfaces, and numerical integrations of the transport integrals are used. The results give a good agreement with experimental data, but this agreement is not compatible with the existence of an energy gap in the electron spectrum, such as is found in magneto-reflection experiments.