Volume 103, Number 1, July 2013
|Number of page(s)||6|
|Section||Condensed Matter: Structural, Mechanical and Thermal Properties|
|Published online||24 July 2013|
Waves in microstructured solids and negative group velocity
1 Department of Mathematics, City University of Hong Kong - 83 Tat Chee Avenue, Kowloon Tong, Kowloon, Hong Kong
2 Centre for Nonlinear Studies, Institute of Cybernetics at Tallinn University of Technology Akadeemia tee 21, Tallinn 12618, Estonia, EU
(a) On a leave from Institute of Cybernetics at Tallinn University of Technology - Tallinn, Estonia, EU; email@example.com
Received: 29 April 2013
Accepted: 27 June 2013
Waves with negative group velocity (NGV) were discovered in optics by Sommerfeld and Brillouin, and experimentally verified in many cases, for example in left-handed media. For waves in solids, such an effect is described mostly in layered media. In this paper, it is demonstrated that in microstructured solids, waves with NGV may also exist leading to backwards pulse propagation. Two physical cases are analysed: a Mindlin-type hierarchical (a scale within a scale) material and a felt-type (made of fibres) material. For both cases, the dispersion analysis of one-dimensional waves shows that there exists certain ranges of physical parameters which lead to NGV. The results can be used in dispersion engineering for designing materials with certain properties.
PACS: 62.30.+d – Mechanical and elastic waves; vibrations / 46.40.Cd – Mechanical wave propagation (including diffraction, scattering, and dispersion) / 43.20.+g – General linear acoustics
© EPLA, 2013
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