Kagome Flat-Band Acoustic Metamaterials

The search for electronic flat bands in atomic lattices is difficult and time-consuming. Acoustic metamaterials, on the other hand, can be easily simulated, cheaply fabricated, and quickly measured, allowing us to search the phase space more rapidly and thoroughly for lattices that host acoustic flat bands. Here, we investigate an acoustic analogue to the kagome lattice made of air cavities in solid materials. We present both COMSOL Multiphysics simulations and experimental data imaging the dispersive bands of the kagome metamaterial in momentum space and the localized modes of the kagome flat band in real space. Taking advantage of the flexibility of metamaterials, we also designed a new set of lattice structures, the “n-extended kagome lattices,” by adding n additional cavities between kagome supercells. These modified kagome lattices host a singly degenerate, frequency isolated flat band with a significantly higher Q-factor than that of the kagome lattice. Such artificial lattices may be interesting candidates for developing strongly-correlated electron systems.