Artificial Gauge Field for Photons in Coupled Cavity Arrays
  We propose and characterize solid-state photonic structures where light experiences an artificial gauge field. A suitable coupling of the propagation and polarization degrees of freedom introduces a geometrical phase for photons tunneling between adjacent sites of a coupled cavity array. We then discuss the feasibility of observing strong gauge field effects in the optical spectra of realistic systems, including the Hofstadter butterfly spectrum. 
R. O. Umucalilar and I. Carusotto
cond-mat.quant-gas