Majorana Edge States for Z2 Topological Orders of the Wen-plaquette   Model and the Toric-code Model
  In this paper we study the symmetry protected Majorana edge states for the Z2 topological order of the Wen-plaquette model and the toric-code model and calculate the dispersion of the Majorana edge states. For the system with translational symmetry, the Majorana edge states are gapless and have the nodal points at k=0 and k=pi. For the edge states of the toric-code model without translational symmetry, the edge modes become gapped. 
Jing Yu, Xing-Hai Zhang, and Su-Peng Kou
cond-mat.str-el quant-ph