Topological invariants for interacting topological insulators with   inversion symmetry
  For interacting Z_2 topological insulators with inversion symmetry, we propose a simple topological invariant expressed in terms of the parity eigenvalues of the interacting Green's function at time-reversal invariant momenta. We derive this result from our previous formula involving the integral over the frequency-momenta space. This formula greatly simplifies the explicit calculation of Z_2 topological invariants in inversion symmetric insulators with strong interactions. 
Zhong Wang, Xiao-Liang Qi, Shou-Cheng Zhang
cond-mat.str-el