Published April 11, 2020 | Version v1
Dataset Open

Vibrational hierarchy leads to dual-phonon transport in low thermal conductivity crystals

  • 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

* Contact person

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.

Files

File preview

files_description.md

All files

Files (91.9 MiB)

Name Size
md5:7fbb851e0ec9b1a941bf294f1a288fef
319 Bytes Preview Download
md5:79f47d958709006e7d4b33cda4c72e4d
1.1 KiB Preview Download
md5:032c991fbd12fcc1e820a10469568351
91.9 MiB Preview Download

References

Journal reference (Computational work)
Y. Luo, X. Yang, T. Feng, J. Wang, X. Ruan, Nature Communications, 11, 2554 (2020), doi: 10.1038/s41467-020-16371-w