Materials with periodic variations in their elastic properties currently receive much interest as phononic crystals. Analogue to light propagation in photonic crystals, the transmitted spectrum of sound waves traveling through phononic crystals exhibit band gaps whose frequency is determined by the length scale on which the elastic properties are modulated. Here, we experimentally investigate the phononic properties of a two-dimensional crystal of colloidal particles immersed in a liquid and being subjected to a periodic substrate potential. Depending on the substrate strength and particle interactions, the phononic band structure and thus the position and width of phononic band gaps can be largely tuned. Because the concept applies not only to micron-sized colloids but also to much smaller particles, this suggests tailoring the phononic properties of atoms or molecules confined to extended optical lattices.
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|||Phonon dispersion curves of two-dimensional colloidal crystals: On the wavelength dependence of friction|
|J. Baumgartl, J. Dietrich, J. Dobnikar, C. Bechinger, H.H.v. Grünberg|
Soft Matter 4, 2199 (2008)
|||Tailoring of phononic band structures in colloidal crystals|
|J. Baumgartl, M. Zvyagolskaya, C. Bechinger|
Phys. Rev. Lett. 99, 205503 (2007)