Phase diagram, correlations, and quantum critical point in the periodic Anderson model
Yang Jian-Wei, Chen Qiao-Ni
       

Schematic plot of Fermi surface in the three different phases. In the AF2 phase, the Fermi surface has an electron pocket. The Fermi surface of the AF1 phase has a hole pocket, it can be obtained by folding the Fermi surface in the PKS phase.