Effective field theory for the bulk-edge correspondence in a   two-dimensional Z_2 topological insulator with Rashba interactions
  We determine the effective field theory in (2+1)-dimensional space and time that captures the long wave length and low-energy limit of fermions hopping on a honeycomb lattice at half-filling when both a dominant intrinsic and subdominant Rashba spin-orbit couplings are present. This effective field theory for a Z_2 topological insulator (the Kane-Mele model at vanishing uniform and staggered chemical potentials) is a perturbation around a double Chern-Simons theory, with the U(1) gauge invariance associated to spin conservation explicitly broken due to the Rashba spin orbit coupling. Nonetheless, we find that the effective field theory has a BRST symmetry that allows us to construct the bulk-edge correspondence. 
Pedro R. S. Gomes, Po-Hao Huang, Claudio Chamon, Christopher Mudry
cond-mat.str-el hep-th