Skrutinizing the phonon Kondo effect in thermoelectrc clathrates
Intermetallic clathrates are of great interest, not only for their potential as thermoelectric materials but also for fundamental interest in their unusual lattice dynamics. It is now well documented that these materials exhibit energetically low-lying optical phonon so-called Einstein corresponding to the rattling motion of the guest atoms in the structural cages. However, how these interact with the heat-transporting acoustic modes to produce ultralow lattice thermal conductivities is an open question. Recently, a phonon-Kondo effect was proposed to explain striking deviations between lattice dynamics predictions and experimental observations for various thermal transport and thermodynamic quantities. The proposed experiment sets out to scrutinize this model. We will study the temperature dependence of the low-energy phonon dispersion in the vicinity of the optic-acoustic mode interaction ("anticrossing") on the type-I clathrate Ba8Cu4.8Ge40.2Ga, a particularly well pre-characterized compound available as large single crystal. We expect a characteristic disentanglement of the two modes above the phonon Kondo temperature.
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MAZZA Federico; BEAUVOIS Ketty; BOEHM Martin; EGUCHI Gaku; Dmytro Inosov; PASCHEN Silke; Andrey Prokofiev and STEFFENS Paul. (2021). Skrutinizing the phonon Kondo effect in thermoelectrc clathrates. Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.7-01-547
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