Issue |
Europhys. Lett.
Volume 33, Number 7, March I 1996
|
|
---|---|---|
Page(s) | 533 - 538 | |
Section | Condensed matter: structure, thermal and mechanical properties | |
DOI | https://doi.org/10.1209/epl/i1996-00374-9 | |
Published online | 01 September 2002 |
Cross-over to incoherent tunnelling of substitutional defects in alkali halide crystals
1
Institut Laue-Langevin - B.P. 156X, 38042 Grenoble, France
2
Institut für Angewandte Physik, Universität Heidelberg Albert-Ueberle-Str. 3-5, 69120 Heidelberg, Germany
Received:
22
September
1995
Accepted:
11
January
1996
The dielectric susceptibility of substitutional defects in alkali halides shows a surprising dependence on concentration c. In the dilute case ppm, the susceptibility is proportional to the number of defects. It reaches a maximum at a concentration where the average dipole-dipole interaction is equal to the bare tunnelling amplitude of a single defect and for still higher concentrations ppm it strongly decreases. The data for various defect systems are in quantitative agreement with a parameter-free master curve derived from a continued fraction expansion for the relevant correlation function. With increasing defect concentration a universal cross-over from coherent tunnelling to incoherent relaxation is driven by a novel relaxation mechanism, based on the dipolar interaction.
PACS: 61.72.Yx – Interaction between different crystal defects; gettering effect / 77.22.Gm – Dielectric loss and relaxation
© EDP Sciences, 1996
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