Waveguiding properties of two parallel defects under conditions of two-channel scattering

It is shown that a pair of parallel planar defects in a crystal can act as a waveguide for a quantum particle or wave having two branches of the dispe rsion relation. The energies (or frequencies) for which the excitations are localized between the defects and propagate freely along them are determin ed. In a two-dimensional system there exists a discrete set of energies at which two-dimensional excitations can be "held in" between two parallel lin ear defects. (C) 2000 American Institute of Physics. [S1063-777X(00)01306-2 ].