Temperature- and doping-dependent roles of valleys in thermoelectric performance of SnSe: a first-principles study

Abstract

We theoretically investigate how each orbital and valley play a role for high thermoelectric performance of SnSe. In the hole-doped regime, two kinds of valence band valleys contribute to its transport properties: one is the valley near the U-Z line, mainly consisting of the Se-$p_z$ orbitals, and the other is the one along the $\Gamma$-Y line, mainly consisting of the Se-$p_y$ orbitals. Whereas the former valley plays a major role in determining the transport properties at room temperature, the latter one also offers comparable contribution and so the band structure exhibits multi-valley character by increasing the temperature. In the electron-doped regime, the conduction band valley around the $\Gamma$ point solely contributes to the thermoelectric performance, where the quasi-one-dimensional electronic structure along the $a$-axis is crucial. This study provides an important knowledge for the thermoelectric properties of SnSe, and will be useful for future search of high-performance thermoelectric materials.

arXiv comment9 pages, 8 figures

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• Direct observation of double valence-band extrema and anisotropic effective masses of the thermoelectric material SnSe
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• Exact dynamics of a one dimensional Bose gas in a periodic time-dependent harmonic trap
• Thermoelectric performance of materials with Cu$C{h}_4$ ($Ch=$ S, Se) tetrahedra: Similarities and differences among their low-dimensional electronic structure from first principles