Onset of nondiffusive phonon transport in transient thermal grating decay
Name
Maznev-2011-Onset of nondiffusive phonon transport in transient.pdf
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Author(s)
Maznev, Alexei
Nelson, Keith Adam
Johnson, Jeremiah A.
Date Issued
November 2011
Journal
Physical Review B
Publisher
American Physical Society (APS)
Citation
Maznev, A., Jeremy Johnson, and Keith Nelson. “Onset of Nondiffusive Phonon Transport in Transient Thermal Grating Decay.” Physical Review B 84.19 (2011): n. pag. Web. 2 Mar. 2012. © 2011 American Physical Society
Version
Final published version
Abstract
The relaxation of a spatially sinusoidal temperature perturbation in a dielectric crystal at a temperature comparable to or higher than the Debye temperature is investigated theoretically. We assume that most phonons contributing to the specific heat have a mean free path (MFP) much shorter than the thermal transport distance and can be described by the thermal diffusion model. Low-frequency phonons that may have MFP comparable to or longer than the grating period are described by the Boltzmann transport equation. These low-frequency phonons are assumed to interact with the thermal reservoir of high-frequency phonons but not with each other. Within the single mode relaxation time approximation, an analytical expression for the thermal grating relaxation rate is obtained. We show that the contribution of “ballistic” phonons with long MFP to the effective thermal conductivity governing the grating decay is suppressed compared to their contribution to thermal transport at long distances. The reduction in the effective thermal conductivity in Si at room temperature is found to be significant at grating periods as large as 10 μm.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1103/PhysRevB.84.195206
