Electronic structure and transport in the low-temperature thermoelectricCsBi4Te6: Semiclassical transport equations

Abstract

The band structure of the low-temperature thermoelectric material, $\mathrm{Cs}{\mathrm{Bi}}_{4}{\mathrm{Te}}_{6}$, is calculated and analyzed using the semiclassic transport equations. It is shown that to obtain a quantitative agreement with measured transport properties, a band gap of $0.08\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ must be enforced. A gap in reasonable agreement with experiment was obtained using the generalized gradient functional of Engel and Vosko [E. Engel and S. H. Vosko, Phys. Rev. B 47, 13164 (1993)]. We found that the experimental $p$-type sample has a carrier concentration close to optimal. Furthermore, the conduction bands have a form equally well suited for thermoelectric properties and we predict that an optimally doped $n$-type compound could have thermoelectric properties exceeding those of the $p$ type.