Unique surface polaritons and their transitions in metamaterials.

We investigated surface polaritons in a metamaterial composed of polar-crystal layers and antiferromagnetic layers. In a specific geometry, two surface polaritons were predicted, which are a unique ghost surface polariton (GSP) and surface hybrid-polarization polariton (SHP). The two surface polaritons occupy different segments of one smooth dispersion curve and are magnetically tunable. An external magnetic field along the antiferromagnetic easy axis can bring about the switch or transition between the two surface polaritons and meanwhile performs the necessary condition for the existence of two surface polaritons. In the metamaterial, either surface polariton consists of two branch waves. The branch waves of the GSP are coherent and have the same amplitude and different phases, but those of the SHP are not coherent and have different amplitudes and phases. The main characteristic of the GSP is that its fields oscillate and attenuate with the distance away from the metamaterial surface and exhibit interferent fringes on the plane normal to the surface.