Thermal transport exceeding bulk heat conduction due to nonthermal micro/nanoscale phonon populations
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APL19-AR-10223.pdf
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Author(s)
Chiloyan, Vazrik
Huberman, Samuel
Maznev, Alexei A.
Nelson, Keith A.
Chen, Gang
Date Issued
April 2020
Journal
Applied Physics Letters
Publisher
AIP Publishing
Citation
Chiloyan, Vazrik et al. "Thermal transport exceeding bulk heat conduction due to nonthermal micro/nanoscale phonon populations." Applied Physics Letters 116, 16 (April 2020): 163102 © 2020 Author(s)
Version
Author's final manuscript
Abstract
While classical size effects usually lead to a reduced effective thermal conductivity, we report here that nonthermal phonon populations produced by a micro/nanoscale heat source can lead to enhanced heat conduction, exceeding the prediction from Fourier's law. We study nondiffusive thermal transport by phonons at small distances within the framework of the Boltzmann transport equation (BTE) and demonstrate that the transport is significantly affected by the distribution of phonons emitted by the source. We discuss analytical solutions of the steady-state BTE for a source with a sinusoidal spatial profile, as well as for a three-dimensional Gaussian “hot spot,” and provide numerical results for single crystal silicon at room temperature. If a micro/nanoscale heat source produces a thermal phonon distribution, it gets hotter than that predicted by the heat diffusion equation; however, if the source predominantly produces low-frequency acoustic phonons with long mean free paths, it may get significantly cooler than that predicted by the heat equation, yielding an enhanced heat transport beyond bulk heat conduction.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Massachusetts Institute of Technology. Department of Chemistry
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1063/1.5139069
