Enhanced elastodynamic resonance via co-dipole metaclusters

Metamaterials exploit sub-wavelength microstructure to yield novel macroscopic material properties. Recently the notion of a metacluster has emerged, which is a collection of resonators that interact in order to modify, and possibly enhance, the resonance. They can also be employed to modify and tune the far field scattered response. This is particularly important with regard to metamaterals design. In the context of elastodynamics, Cotterill et al.1 considered the case of void metaclusters, thus permitting the modification of the so-called giant monopole resonance in elastodynamics. Here we consider one of the original resonant configurations of metamaterials science, that of Liu et al.2; this structure consists of coated cylinders of circular cross-section and gives rise to strong dipole resonance for sufficiently soft coatings. We consider the nature of the interaction of two such identical resonators in close proximity, which we term the co-dipole metacluster. We show that, contrary to the giant monopole case, the frequency at which occurs the resonance is unchanged with respect to the case of a single resonator. The resonance itself is enhanced significantly and although the nature of the resonance remains dominated by a dipole response, both the enhancement and the far-field scattered response is now significantly affected by the angle of incidence, in strong contrast to an isolated single resonator.