Influence of trigonal deformation on band structure and Seebeck coefficient of tellurium. (December 2019) - Han, J.C.
Abstract: Effects of trigonal deformation ( c/a ) on electronic structure and Seebeck coefficient of tellurium have been studied using first principles calculation combined with Boltzmann transport theory. Tellurium is found to be an indirect-gap semiconductor when 1.174 ≤ c/a <1.274, a direct-gap semiconductor when 1.274 ≤ c/a ≤1.372, and a typical semimetal when 1.372 < c/a ≤1.444. Moreover, a semiconductor-semimetal transition of tellurium is discovered at the critical c/a of 1.372, which is mainly because of the transition of the conduction band bottom and valence band top near the high-symmetry point of H . Calculations also reveal the significant impact of trigonal deformation on the Seebeck coefficient of tellurium, i.e., the highest Seebeck coefficient of tellurium can be achieved at the c/a ratio of 1.274, and seems much better than that of equilibrium tellurium ( c/a = 1.324). The present calculated results agree well with experimental measurements and theoretical predictions and could provide in-depth understanding of the intrinsic relationship among trigonal deformation, electronic band structure, semiconductor-semimetal transition, and Seebeck coefficient of tellurium. Highlights: Pin orbit coupling is not included to describe ground state property of Te. Te maintains the trigonal structure within the c/a range of 1.174–1.444 Semiconductor-semimetal transition of Te is discovered at the c/a of 1.372. The highest Seebeck coefficient of Te is achieved at the c/a ratio of 1.274. Results agree with theoretical and experimental observations in literature.