“…Plasmon materials are a type of metamaterials that are artificially engineered to allow the presence of negative material parameters. We refer to [3,4,8,21], [1,2,5,12,13,14,23,28,31,32,33,34,37,38,39,40,41,42,43] and [6,7,9,10,15,25,26,29,22,24] and the references therein for the relevant studies in acoustics, electromagnetism and elasticity, respectively.…”