Electronic structure and thermoelectric transport properties of Tellurium from Boltzmann transport theory

Tellurium has a trigonal structure consisting of isolated helical chains parallel to c axis. Density functional theory combined with Boltzmann transport theory was applied to investigate the electronic and thermoelectric transport properties of Tellurium in the rigid band model. Calculation results showed that $p$-type doping gives a higher \textit{ZT} and larger anisotropic behavior than $n$-type doping does. From the electronic structure, we find that the light band spitted from the spin-orbit coupling can contribute high mobility, while the drastically increased density from the heavy band bring a large asymmetry for the transport distribution function, which is benefit for the Seebeck coefficient. Besides, the band near the valence band maximum $H$ point have a saddle-shape band structure along c direction, and smaller effective mass along this direction than other two directions. The overall result is good thermoelectric property for $p$-type doping tellurium along c direction. So, our calculation results suggest that in experiment, people can get a high \textit{ZT} in tellurium by doping with small covalent electrons elements with a texture along [001] direction.