Parabolic metamaterials and Dirac bridges

A new class of multi-scale structures, referred to as 'parabolic metamaterials', is introduced and studied in this paper. For an elastic two-dimensional triangular lattice, we identify dynamic regimes, which correspond to so-called 'Dirac bridges' on the dispersion surfaces. Such regimes lead to a highly localised and focussed unidirectional beam when the lattice is excited. We also show that the flexural rigidities of elastic ligaments are essential in establishing the 'parabolic metamaterial' regimes.