Disordered surface vibrations in jammed sphere packings.
basic_science · Level V
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- Record sourced from PubMed, PMID 25690151.
- Also identified by DOI 10.1039/c4sm02905d.
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Abstract
We study the vibrational properties near a free surface of disordered spring networks derived from jammed sphere packings. In bulk systems, without surfaces, it is well understood that such systems have a plateau in the density of vibrational modes extending down to a frequency scale ω*. This frequency is controlled by ΔZ = 〈Z〉 - 2d, the difference between the average coordination of the spheres and twice the spatial dimension, d, of the system, which vanishes at the jamming transition. In the presence of a free surface we find that there is a density of disordered vibrational modes associated with the surface that extends far below ω*. The total number of these low-frequency surface modes is controlled by ΔZ, and the profile of their decay into the bulk has two characteristic length scales, which diverge as ΔZ(-1/2) and ΔZ(-1) as the jamming transition is approached.