Hopping processes explain linear rise in temperature of thermal conductivity in thermoelectric clathrates with off-center guest atoms
Abstract
Type-I clathrate compounds with off-center guest ions can be used to realize the concept of phonon-glass electron-crystal because they exhibit lattice thermal conductivities κL that are almost identical to those observed in network-forming glasses. This is in contrast with type-I clathrates with on-center guest ions, which show κL of conventional crystalline structures. Glasslike κL stems from the peculiar THz frequency dynamics in off-center type-I clathrates, in which there appear three kinds of modes classified as extended, weakly localized (WL) and strongly localized (SL) modes, as demonstrated by Liu et al. [Phys. Rev. B 93, 214305 (2016), 10.1103/PhysRevB.93.214305]. Our calculated results based on the hopping mechanism of SL modes via anharmonic interactions show fairly good agreement with the observed T -linear rise of κL above the plateau at a few tens Kelvin. We emphasize that both the magnitude and the temperature dependence are in accord with the experimental data of off-center type-I clathrates.
- Publication:
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Physical Review B
- Pub Date:
- August 2017
- DOI:
- 10.1103/PhysRevB.96.064306
- arXiv:
- arXiv:1704.07024
- Bibcode:
- 2017PhRvB..96f4306X
- Keywords:
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- Condensed Matter - Other Condensed Matter
- E-Print:
- Phys. Rev. B 96, 064306 (2017)