Viscous Maxwell-Chern-Simons theory for topological electromagnetic phases of matter

Chern-Simons theories, initially developed for high-energy physics, have been very successful in explaining integer and fractional quantum Hall phases of matter, topological insulators, and Weyl semimetals. However, it was an open question as to whether Chern-Simons theories can be adapted to topological photonics. Here, the authors develop a viscous Maxwell-Chern-Simons theory to capture the fundamental physics of a topological electromagnetic phase of matter. The theory applies to viscous Hall fluids and predicts the existence of unique spin-1 photonic skyrmions in momentum space.