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arXiv · 1704.07024

Hopping Processes Explain T-linear Rise of Thermal Conductivity in Thermoelectric Clathrates above the Plateau

Qing Xi·Zhongwei Zhang·Jie Chen·Jun Zhou·Tsuneyoshi Nakayama·Baowen Li
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Abstract

Type-I clathrate compounds with off-center guest ions realize the phonon-glass electron-crystal concept by exhibiting almost identical lattice thermal conductivities $κ_{\rm L}$ to those observed in network-forming glasses. This is in contrast with type-I clathrates with on-center guest ions showing $κ_{\rm L}$ of conventional crystallines. Glasslike $κ_{\rm L}$ stems from the peculiar THz frequency dynamics in off-center type-I clathrates where there exist three kinds of modes classified into extended(EX), weakly(WL) and strongly localized(SL) modes as demonstrated by Liu $et.\,al.$, Phys. Rev. B $\textbf{93}$, 214305(2016). Our calculated results based on the hopping mechanism of SL modes via anharmonic interactions show fairly good agreement with observed ${\it T}$-linear rise of $κ_{\rm L}$ above the plateau. We emphasize that both the magnitude and the temperature dependence are in accord with the experimental data of off-center type-I clathrates.

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Qing Xi, Zhongwei Zhang, Jie Chen, Jun Zhou, Tsuneyoshi Nakayama, Baowen Li. 2017-07-31. Hopping Processes Explain T-linear Rise of Thermal Conductivity in Thermoelectric Clathrates above the Plateau. https://doi.org/10.1103/physrevb.96.064306

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