Structural periodicity dependent scattering behavior in parity-time symmetric elastic metamaterials

We investigate the effect of structural periodicity on elastic longitudinal and flexural wave propagation in parity-time (PT) symmetric prototypical elastic metamaterial rods and beams. Through theoretical analysis and numerical demonstration, we reveal the link between the observed band structure of infinite periodic PT symmetric elastic metamaterials and the unique scattering properties of the corresponding finite periodic PT symmetric systems. In particular, we study the coherent perfect absorber and laser (CPAL). There is an observed periodic-like occurrence of the CPAL formation when varying the cell number in the finite periodic metamaterial that correlates to the band structure of the infinite periodic system. For this, we provide simple equations to estimate the periodicity and the minimum cell number. Using a piezoelectric-aided elastic metamaterial consist-ing of piezoelectric patches and active circuits, we propose a feasible configuration to realize tunable flexural wave CPALs in a periodic-structured PT symmetric metamaterial beam, and demonstrate that the CPAL can be induced in the Bragg's bandgap.

Automated summary

This study investigates the effect of structural periodicity on wave propagation in elastic metamaterials and reveals the connection between finite and infinite periodic PT symmetric systems. Particularly, the formation of coherent perfect absorbers and lasers in elastic metamaterials is studied, providing simple equations to estimate periodicity and minimum cell number.