Elastic Waves Scattering without Conversion in Metamaterials with Simultaneous Zero Indices for Longitudinal and Transverse waves

TL;DR

This paper explores elastic wave behavior in metamaterials with simultaneous zero indices for longitudinal and transverse waves, demonstrating perfect transmission and scattering without mode conversion, which is unlike conventional elastic media.

Contribution

The study introduces a theoretical analysis and design of metamaterials with unique zero index properties that prevent mode conversion during elastic wave scattering.

Findings

Elastic waves mostly transmit through the metamaterials with cloaking effect.

Elastic waves become totally blocked at resonances, indicating scattering.

No mode conversion occurs despite scattering, contrasting conventional media.

Abstract

We theoretically investigate elastic waves propagating in metamaterials with simultaneous zero indices for both the longitudinal and transverse waves. With scattering objects (here cylinders) present in the metamaterials slabs, while the elastic waves can mostly transmit through the metamaterials slabs perfectly, exhibiting the well-known cloaking effect of zero index metamaterials, they nevertheless become totally blocked at resonances, indicating strong elastic waves scattering by the objects in the cases. However, despite the occurrence of the elastic waves scattering, there is, counter-intuitively, no mode conversion between the longitudinal and transverse waves in the process, completely in contrast with that in conventional elastic media. A design of two-dimensional phononic crystal with these peculiar properties is presented.