First principles calculation of topological invariants by means of the photonic green’s function

Abstract

The Chern topological numbers of a material platform are usually written in terms of the Berry curvature which depends on the normal modes of the system. Here, we use a gauge invariant Green’s function method to determine from “first principles” the topological invariants of photonic crystals. The proposed formalism does not require the calculation of the photonic band-structure, and can be easily implemented using the operators obtained with a standard plane-wave expansion.