Gauge fields at the surface of topological insulators
  We study the emergence of gauge couplings in the surface states of topological insulators. We show that gauge fields arise when a three dimensional strong topological insulator is coated with an easy-plane ferromagnet with magnetization parallel to the surface. We analyze the modification induced by the gauge fields on the surface spectrum for some specific magnetic configurations. 
M. I. Katsnelson, F. Guinea, and M. A. H. Vozmediano
cond-mat.mtrl-sci cond-mat.other