Unidirectional phase singularity in ultrathin metamaterials at exceptional points

Scattering properties of light in metamaterials are similar to those in open quantum systems. Here we propose an ultrathin tailored metamaterial designed to show that one-way zero reflection yielding to topologically stable phase dislocation is responsible for the exceptional point, one of the most important degeneracies in the non-Hermitian Hamiltonian. In order to bridge the exotic macroscopic optical phenomenon occurring in metamaterials, a phenomenological model under microscopic view is developed and good agreement with the full-blown numerical simulation is found. Our investigation uncovers the capabilities of metamaterials to exhibit extreme optical properties and to provide us with many potential applications such as the suppression of undesired scattering signals in the spectral band ranging from microwaves to visible light.