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The Central Peak in SbSI
Author(s) -
Steigmeier E. F.,
Auderset H.,
Harbeke G.
Publication year - 1975
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.2220700231
Subject(s) - condensed matter physics , phonon , scattering , light scattering , chemistry , soft modes , mode (computer interface) , phonon scattering , optics , physics , atomic physics , molecular physics , quantum mechanics , dielectric , computer science , ferroelectricity , operating system
New measurements of light scattering in SbSI as a function of temperature are reported which extend the previous results to lower frequencies by improving the spectral purity of the spectrometer. The light is found to couple to the central peak in SbSI only indirectly via the soft mode. Using this fact as a condition, from a two‐coupled‐oscillator analysis of the soft‐mode/central‐mode system all the oscillator parameters are determined. Within the first 10 deg below the phase transition the central mode turns out to be a strongly overdamped oscillator of width Γω 1 2 /2γ 1 of 0.4 to 4 cm −1 . This width compares very well with the value obtained from the hydrodynamic theory of light scattering; using measured thermal conductivity and specific heat data of SbSI one obtains a width of 0.3 to 1 cm −1 for a Δ T of 2 to 10 deg. Thus, the central peak in SbSI has been directly spectrally resolved and it seems justified to assign this feature to light scattering by phonon density fluctuations.