Topological effect in plasmonic system

In this work, we extend the scope of the metallic and dielectric states by treating a pure metal or dielectric as the limiting case of a metal-dielectric layered metamaterial. The metamaterial with metal filling ratio larger than one-half shares the same topological invariant as a pure metal and thus exhibits some metallic behaviors. In contrast, the dielectric-rich metamaterial and a pure dielectric are topologically equivalent and display dielectric properties. This new understanding gives surface plasmon polariton (SPP) at a metal/dielectric interface a new physical meaning: the limiting case of a topological edge state. Finally, a complex structure also supports hidden topological effects if it is transformed from a layered metamaterial possessing an edge state.