Chern number in Ising models with spatially modulated real and complex   fields
  We study an one-dimensional transverse field Ising model with additional periodically modulated real and complex fields. It is shown that both models can be mapped on a pseudo spin system in the k space in the aid of an extended Bogoliubov transformation. This allows us to introduce the geometric quantity, the Chern number, to identify the nature of quantum phases. Based on the exact solution, we find that the spatially modulated real and complex fields rearrange the phase boundaries from that of the ordinary Ising model, which can be characterized by the Chern numbers defined in the context of Dirac and biorthonormal inner products, respectively. 
C. Li, G. Zhang, and Z. Song
quant-ph cond-mat.str-el