@article {2350,
	title = {Simultaneous occurrence of structure-directed and particle-resonance-induced phononic gaps in colloidal films},
	journal = {Physical Review Letters},
	volume = {100},
	year = {2008},
	pages = {194301 (4 pages)},
	abstract = {<p>We report on the observation of two hypersonic phononic gaps of different nature in three-dimensional colloidal films of nanospheres using Brillouin light scattering. One is a Bragg gap occurring at the edge of the first Brillouin zone along a high-symmetry crystal direction. The other is a hybridization gap in crystalline and amorphous films, originating from the interaction of the band of quadrupole particle eigenmodes with the acoustic effective-medium band, and its frequency position compares well with the computed lowest eigenfrequency. Structural disorder eliminates the Bragg gap, while the hybridization gap is robust.</p>},
	author = {T. Still and W. Cheng and M. Retsch and R. Sainidou and J.J. Wang and U. Jonas and N. Stefanou and G. Fytas}
}
