Yixiu Luo^1*, Xiaolong Yang², Tianli Feng³, Jingyang Wang¹, Xiulin Ruan⁴

1 Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

2 Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China

3 Energy and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States

4 School of Mechanical Engineering and the Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA

* Corresponding authors emails: yxluo13s@imr.ac.cn

DOI10.24435/materialscloud:2020.0036/v1 [version v1]

Publication date: Apr 11, 2020

How to cite this record

Yixiu Luo, Xiaolong Yang, Tianli Feng, Jingyang Wang, Xiulin Ruan, Vibrational hierarchy leads to dual-phonon transport in low thermal conductivity crystals, Materials Cloud Archive 2020.0036/v1 (2020), doi: 10.24435/materialscloud:2020.0036/v1.

Description

Many low-thermal-conductivity (κL) crystals show intriguing temperature (T) dependence of κL: κL∝T-1 (crystal-like) at intermediate temperatures whereas weak T-dependence (glass-like) at high temperatures. It has been in debate whether thermal transport can still be described by phonons at the Ioffe-Regel limit. In this work, we propose that most phonons are still well defined for thermal transport, whereas they carry heat via dual channels: “normal” phonons described by the Boltzmann transport equation theory and “diffuson-like” phonons described by the diffusion theory. Three physics-based criteria are incorporated into first-principles calculations to judge mode-by-mode between the two phonon channels. Case studies on La2Zr2O7 and Tl3VSe4 show that normal phonons dominate low temperatures while diffuson-like phonons dominate high temperatures. Our present dual-phonon theory enlightens the physics of hierarchical phonon transport as approaching the Ioffe-Regel limit, and provides a numerical method that should be practically applicable to many materials with vibrational hierarchy.

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Keywords

Dual-phonon theory thermal conductivity theoretical calculation