Defect states of homogeneity dislocation structures in two-dimensional phononic crystal

The defect states in two-dimensional phononic crystal homogeneity dislocation structures has been studied by means of the plane-wave expansion method in combination with a supercell technique. Transverse dislocation structures and longitudinal dislocation structures are investigated respectively. The results show that, acting as a line defect, transverse dislocation structures can mold the flow of sound in the bandgap along the dislocation channel and form the so called waveguides; while longitudinal dislocation structures, which act just as point defects, can form a cavitylike void surrounded by the three nearest cylinders around the dislocation line to create a localized state. In addition, the number and the position of defect bands strongly depend on the transverse and longitudinal dislocation displacement, so we can artificially control the defect bands by adjusting the transverse and longitudinal dislocations of lattices in a homogeneity dislocation structures.