Elastodynamical resonances and cloaking of negative material structures beyond quasistatic approximation

Abstract

Given the flexibility of choosing negative elastic parameters, we construct material structures that can induce two resonance phenomena, referred to as the elastodynamical resonances. They mimic the emerging plasmon/polariton resonance and anomalous localized resonance in optics for subwavelength particles. However, we study the peculiar resonance phenomena for linear elasticity beyond the subwavelength regime. It is shown that the resonance behaviours possess distinct characters, with some similar to the subwavelength resonances, but some sharply different due to the frequency effect. It is particularly noted that we construct a core-shell material structure that can induce anomalous localized resonance as well as cloaking phenomena beyond the quasi-static limit. The study is boiled down to analyzing the so-called elastic Neumann-Poincáre (N-P) operator in the frequency regime. We provide an in-depth analysis of the spectral properties of the N-P operator beyond the quasi-static approximation, and these results are of independent interest to the spectral theory of layer potential operators.

Modal approximation for time-domain elastic scattering from metamaterial quasiparticles

“…Due to the rapid technological advancement, elastic metamaterials with negative bulk moduli and/or negative density have been realised via many means [26,29,39]. Moreover, striking applications have been proposed and realised by using elastic metamaterial structures including super-focusing and superlensing [11,19,40] and invisibility cloaking [5,16,19,21,24,25,27]. The fundamental basis for those applications is the polariton resonances induced by the metamaterial structures (in the subwavelength scale), which have also received considerable attention in the mathematical literature [15,16,21].…”