Transport Properties ofBi2Te3

Abstract

Measurements of the low-field magnetoresistance coefficients for both $n$- and $p$-type ${\mathrm{Bi}}_2$ ${\mathrm{Te}}_3$ have been made at 77 and 4.2 K as a function of carrier concentration. Results for samples with low carrier densities are satisfactorily interpreted in terms of a previously proposed multiellipsoidal model of the valence- and conduction-band minima. Comparison of the observed galvanomagnetic coefficients with those predicted from de Haas-van Alphen (dHvA) experiments indicates that the relaxation time is anisotropic for both holes and electrons. Formulas which allow for anisotropic scattering are presented and the results combined with dHvA data to determine the relaxation-time tensor as a function of carrier concentration. For $n$-type samples with a carrier density greater than 4 × ${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$, the observed behavior is explained in terms of a simple two-band model and the anisotropy of the second band is shown to be relatively small. The presence of the second band appears to affect the scattering rates for the lower conduction band. A similar analysis is carried out for $p$-type ${\mathrm{Bi}}_2$ ${\mathrm{Te}}_3$, but the results are less satisfactory.