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Demystifying umklapp vs normal scattering in lattice thermal conductivity
| Title: | Demystifying umklapp vs normal scattering in lattice thermal conductivity |
| Authors: | Maznev, A. A. Browse this author | | Wright, O. B. Browse this author |
| Issue Date: | Nov-2014 |
| Publisher: | American Association of Physics Teachers |
| Journal Title: | American journal of physics |
| Volume: | 82 |
| Issue: | 11 |
| Start Page: | 1062 |
| End Page: | 1066 |
| Publisher DOI: | 10.1119/1.4892612 |
| Abstract: | We discuss the textbook presentation of the concept of umklapp vs normal phonon-phonon scattering processes in the context of lattice thermal conductivity. A simplistic picture, in which the "momentum conservation" in a normal process leads to the conservation of the heat flux, is only valid within the single-velocity Debye model of phonon dispersion. Outside this model, the simple "momentum conservation" argument is demonstrably inaccurate and leads to conceptual confusion. Whether or not an individual scattering event changes the direction of the energy flow is determined by the phonon group velocity, which, unlike the quasimomentum, is a uniquely defined quantity independent of the choice of the primitive cell in reciprocal space. Furthermore, the statement that normal processes do not lead to a finite thermal conductivity when umklapp processes are absent is a statistical statement that applies to a phonon distribution rather than to individual scattering events. It is also important to understand that once umklapp processes are present, both normal and umklapp processes contribute to thermal resistance. A nuanced explanation of the subject would help avoid confusion of the student and establish a connection with cutting edge research. (C) 2014 American Association of Physics Teachers. |
| Rights: | Copyright 2014 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in American journal of physics 82, 1062 (2014) and may be found at
http://dx.doi.org/10.1119/1.4892612 |
| Type: | article |
| URI: | http://hdl.handle.net/2115/57644 |
| Appears in Collections: | 工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: WRIGHT O. B.
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