Neutron scattering evidence on the nature of the boson peak

U. Buchenau; A. Wischnewski; M. Ohl; E. Fabiani

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Neutron scattering evidence on the nature of the boson peak

U. Buchenau·A. Wischnewski·M. Ohl·E. Fabiani

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Abstract

A close inspection of neutron spectra of glass formers in the frequency region above the boson peak does not show the constant eigenvalue density expected for a random dynamical matrix, but a slow decrease towards higher eigenvalues. In 1,4-polybutadiene and selenium, the slope becomes steeper with increasing temperature in the undercooled liquid, suggesting an influence of the vibrational entropy. One can describe the behaviour quantitatively in terms of a balance between level repulsion (from the randomness of the dynamical matrix) and vibrational entropy. On the basis of this evidence, the boson peak must be a crossover from such a balance at higher frequencies to a mixture of sound waves and additional excitations at low frequency.

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U. Buchenau, A. Wischnewski, M. Ohl, E. Fabiani. 2004-07-06. Neutron scattering evidence on the nature of the boson peak. https://arxiv.org/abs/cond-mat/0407136

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