3D Acoustic Zero Index Metamaterial*

In this talk, I will report our design of a three-dimensional (3D) acoustic double-zero-index medium (DZIM) made of a cubic lattice of metal rods. Despite of several realizations of 2D DZIM in the past, achieving such a medium in 3D has remained an elusive challenge. Here, we show how a four-fold degenerate point with conical dispersion can be induced at the Brillouin zone center, such that the material becomes a 3D DZIM with the effective mass density and compressibility simultaneously acquiring near zero values. To demonstrate the features of the DZIM, we have fabricated an acoustic waveguide filled with 3D DZIM to form a “periscope” with two 90° turns and observed nearly perfect tunneling of a normally incident planar wave through the waveguide.