Hopping Time Scales and the Phonon-Liquid Electron-Crystal Picture in Thermoelectric Copper Selenide

David Voneshen, Helen Walker, Keith Refson, Jonathan Goff

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The suppression of transverse phonons by liquidlike diffusion in superionic conductors has been proposed as a means to dramatically reduce thermal conductivity in thermoelectric materials [H. Lui et al. Nat. Mater. 11, 422 (2012)]. We have measured the ion transport and lattice dynamics in the original phonon-liquid electron-crystal Cu2Se using neutron spectroscopy. We show that hopping time scales are too slow to significantly affect lattice vibrations and that the transverse phonons persist at all temperatures. Substantial changes to the phonon spectrum occur well below the transition to the superionic phase, and the ultralow thermal conductivity is instead attributed to anharmonicity.
Original languageEnglish
Article number145901
Pages (from-to)1-5
Number of pages5
JournalPhysical Review Letters
Issue number14
Publication statusPublished - 5 Apr 2017

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