2024/09/12 by Dipti Jasrasaria, Timothy C. Berkelbach, Jasrasaria, Dipti +1
Engineering · Materials Science · #Acoustic Wave Resonator Technologies #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Ferroelectric and Piezoelectric Materials #Materials Science (cond-mat.mtrl-sci) #Thermography and Photoacoustic Techniques
paper · pdf · doi:10.48550/arxiv.2409.08242
openalex publication_date 2024/09/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Type-I clathrate solids have attracted significant interest due to their ultralow thermal conductivities and subsequent promise for thermoelectric applications, yet the mechanisms underlying these properties are not well understood. Here, we extend the framework of vibrational dynamical mean-field theory (VDMFT) to calculate temperature-dependent thermal transport properties of X8Ga16Ge30, where X= Ba, Sr, using a many-body Green's function approach. We find that nonresonant scattering between cage acoustic modes and rattling modes leads to a reduction of acoustic phonon lifetimes and thus thermal conductivities. Moreover, we find that the moderate temperature dependence of conductivities above 300 K, which is consistent with experimental measurements, cannot be reproduced by standard perturbation theory calculations, which predict a T-1 dependence. Therefore, we conclude that nonperturbative anharmonic effects, including four- and higher-phonon scattering processes, are responsible for the ultralow thermal conductivities of type-I clathrates.