Rotating spacetime modulation: Topological phases and spacetime Haldane model

Topological photonics has recently emerged as a very general framework for the design of unidirectional edge waveguides immune to backscattering and deformations, as well as other platforms that feature extreme nonreciprocal wave phenomena. While the topological classification of time-invariant crystals has been widely discussed in the literature, the study of spacetime crystals formed by time-variant materials remains largely unexplored. Here, we extend the methods of topological band theory to photonic crystals formed by inclusions that are subject to a spacetime rotating-wave modulation that imitates a physical rotating motion. By resorting to an approximate nonhomogeneous effective description of the electromagnetic response of the inclusions, it is shown that they possess a bianisotropic response that breaks the time-reversal symmetry and may give rise to nontrivial topologies. In particular, we propose an implementation of the Haldane model in a spacetime modulated photonic crystal.

Automated summary

Topological photonics is a general framework for designing unidirectional edge waveguides and other platforms with extreme nonreciprocal wave phenomena. This study focuses on the topological classification of photonic crystals formed by inclusions subjected to spacetime rotating-wave modulation. The results show that these crystals have a bianisotropic response that breaks time-reversal symmetry and can lead to nontrivial topologies. A proposal for implementing the Haldane model in a spacetime modulated photonic crystal is also presented.