Quantum tunneling analogue in real-time-controlled mechanical metamaterials

The Klein tunneling phenomenon, describing an unimpeded crossing of particles through higher potential barriers, is supported in graphene due to its unique form of wavefunctions and dispersion. Recently, a classical analogue of this quantum phenomenon was suggested in an acoustic metamaterial, which was not constrained by a graphene-like structure, but had a specific form of effective constitutive parameters, obtained by a targeted design of its unit cells. Here I present a realization of this analogue in a basic mechanical mass-spring metamaterial, where the tunneling parameters are obtained in a programmed real-time control operation.