Double-Negative Pillared Elastic Metamaterial

Elastic metamaterials exhibiting negative values of both effective mass density and Young's modulus in certain frequency ranges are important for controlling the propagation and path of elastic waves. However, a description of the vibrations involved in this ``double negativity'' is still needed. In this numerical study, the authors bring to light the microscopic mechanisms that lead to the double negativity of a double-sided metamaterial with pillars. The results will promote the computational design of devices to control waves guided in membranes and plates, such as acoustic lenses and ``inaudibility'' cloaks.