The dispersion relation obtained from the OPAL codes by defining a 25 Angstrom diameter sphere of aluminium arranged in a simple cubic lattice (with spacing 53 Angstroms) as the unit cell. Also shown on the graph is the free space dispersion line for photons. The structure consists of a series of flat bands, implying a small group velocity, which strongly interact with the free space photon line. These flat bands are the coupled surface plasmons of the aluminium spheres. They are split over a wide range of energies by sphere-sphere interactions and are of a strongly resonant nature.
last updated Wed Apr 08 14:49 bst 1998 by RAE