Materials Science

Tuning Valley Degeneracy with Band Inversion



Valley degeneracy is a key feature of the electronic structure that benefits the thermoelectric performance of a material. Despite recent studies which claim that high valley degeneracy can be achieved with inverted bands, our survey of rock-salt IV-VI compounds demonstrates that mere band inversion is an insufficient condition for high valley degeneracy; rather, there is a critical degree to which the bands must be inverted to induce multiple carrier pockets. The so-called “band inversion parameter” is a chemically-tunable parameter, offering a design route to achieving high valley degeneracy in compounds with inverted bands. We predict that the valley degeneracy of rock-salt IV-VI compounds can be increased from NV = 4 to NV = 24, which could result in a corresponding increase in the thermoelectric figure of merit zT.


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Supplementary material

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Supporting Information
Content: 1) Electronic Band Structures of IV-VI Compounds; 2) Close-Up View of the SnSe Fermi Surface; 3) 12 Carrier Pockets from -3m Symmetry