Distortion of the perfect lattice structure in bilayer graphene
  We consider the instability of bilayer graphene with respect to a distorted configuration in the same spirit as the model introduced by Su, Schrieffer and Heeger. By computing the total energy of a distorted bilayer, we conclude that the ground state of the system favors a finite distortion. We explore how the equilibrium configuration changes with carrier density and an applied potential difference between the two layers. 
Vitor M. Pereira, R. M. Ribeiro, N. M. R. Peres, A. H. Castro Neto