# Elastostatics with multi-layer metamaterial structures and an algebraic framework for polariton resonances

## TL;DR

This paper develops a mathematical framework for elastostatics in multi-layer metamaterial structures, analyzing their spectral properties and establishing an algebraic approach to study polariton resonances relevant for advanced metamaterial applications.

## Contribution

It introduces a general algebraic framework for analyzing elastostatics and polariton resonances in multi-layer elastic metamaterials with arbitrary layers and materials.

## Key findings

- Derived exact perturbed field expressions using elastic momentum matrices.
- Analyzed spectral properties of the elastic momentum matrix.
- Established a comprehensive algebraic framework for polariton resonances.

## Abstract

Multi-layer structures are ubiquitous in constructing metamaterial devices to realise various frontier applications including super-resolution imaging and invisibility cloaking. In this paper, we develop a general mathematical framework for studying elastostatics within multi-layer material structures in $\mathbb{R}^d$, $d=2,3$. The multi-layer structure is formed by concentric balls and each layer is filled by either a regular elastic material or an elastic metamaterial. The number of layers can be arbitrary and the material parameters in each layer may be different from one another. In practice, the multi-layer structure can serve as the building block for various material devices. Considering the impingement of an incident field on the multi-layer structure, we first derive the exact perturbed field in terms of an elastic momentum matrix, whose dimension is the same as the number of layers. By highly intricate and delicate analysis, we derive a comprehensive study of the spectral properties of the elastic momentum matrix. This enables us to establishe a handy algebraic framework for studying polariton resonances associated with multi-layer metamaterial structures, which forms the fundamental basis for many metamaterial applications.