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Title: Thermal transport exceeding bulk heat conduction due to nonthermal micro/nanoscale phonon populations

Journal Article · · Applied Physics Letters
DOI:https://doi.org/10.1063/1.5139069· OSTI ID:1801477
 [1];  [1];  [2];  [2]; ORCiD logo [1]
  1. Massachusetts Institute of Technology, Cambridge, MA (United States). Department of Mechanical Engineering
  2. Massachusetts Institute of Technology, Cambridge, MA (United States). Department of Chemistry
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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.

Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
SC0001299; SC0001299/DE-FG02-09ER46577
OSTI ID:
1801477
Alternate ID(s):
OSTI ID: 1615419
Journal Information:
Applied Physics Letters, Vol. 116, Issue 16; ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 6 works
Citation information provided by
Web of Science

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Related Subjects

42 ENGINEERING
Physics
Thermodynamic states and processes
Nonequilibrium statistical mechanics
Phonons
Thermal transport