Hopping thermopower in FEGA<sub>3</sub>
Yasutomo Kajikawa
Abstract
A narrow-gap semiconductor FeGa 3 has attracted much interest for its unusual physical properties, in particular, for its colossal thermopower at low temperatures for which the origin has not been elucidated yet. In this study, the temperature-dependence data of the conductivity, the Hall coefficient, and the Seebeck coefficient on FeGa 3 samples reported by Wagner-Reetz et al. [Phys. Rev. B 90, 195206 (2014)] have been analyzed with including the effects of impurity Hubbard bands. As a result, it is shown that, contrary to the claim by Wagner-Reetz et al., the large negative peak of the Seebeck coefficient is not due to the phonon-drag effect but due to hopping conduction in the impurity Hubbard bands. The significant effect of nonpolar-optical-phonon scattering on free-electron conduction is also pointed out.