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Scattering of phonons by density fluctuations and thermal conductivity of amorphous solids
Author(s) -
Joshi Y. P.
Publication year - 1979
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220950137
Subject(s) - condensed matter physics , scattering , thermal conductivity , phonon , phonon scattering , amorphous solid , relaxation (psychology) , materials science , conductivity , density of states , quantum tunnelling , physics , chemistry , optics , quantum mechanics , crystallography , social psychology , composite material , psychology
Phonon relaxation time due to the scattering by spatial density fluctuations is studied in amorphous solids. The relaxation time τ f is found to vary with frequency ω as ω −4 in the case of phonons with frequencies small compared with ω 0 , which is a parameter characteristic of the density fluctuations. When ω is large in comparison with ω 0 , τ f is found to vary as ω −2 , and thus it undergoes a transition from a strong to a comparatively weak frequency dependence as ω increases and crosses ω 0 . It is discussed that the thermal conductivity of a typical amorphous solid can be explained in terms of the scattering by low lying tunnelling states and scattering by fluctuations in density and elasticity. The plateau in conductivity is interpreted as defining a temperature region where the former scattering mechanism with its comparatively weaker frequency dependence starts losing dominance over the latter. Finally the conductivity of vitreous silica is analysed, obtaining a good agreement between theoretical and experimental results.