Stop Gaps and Single Defect States of Acoustic Waves in Two-Dimensional Lattice of Liquid Cylinders

The acoustic wave band structures and single defect states of the two-dimensional periodic composite media of water (mercury) cylinders with circular cross section in mercury (water) host was studied by using the plane-waves method and supercell calculations. We find that the numbers of gaps in the first 50 bands versus the filling fraction have similar results as gap/midgap ratio of the lowest gap in the period systems. Only one band gap exhibits in the wide range of filling fraction, and several defect states are created inside the band gaps in single defect systems. The influences of the filling fraction and defect radius on the band structure are investigated.