Quantum phase transition in the one-dimensional extended Peierls-Hubbard   model
  We consider the one-dimensional extended Hubbard model in the presence of an explicit dimerization $\delta$. For a sufficiently strong nearest neighbour repulsion we establish the existence of a quantum phase transition between a mixed bond-order wave and charge-density wave phase from a pure bond-order wave phase. This phase transition is in the universality class of the two-dimensional Ising model. 
H.Benthien, F.H.L.Essler, A.Grage