Effects of correlations on honeycomb lattice in ionic-Hubbard model

•The ionic-Hubbard model at half-filling is studied by DMFT method.•The competition between U and Δ created three separate phases.•The Fermi velocity is decreased by increasing U.•The differences in occupancy didn't have smooth change in large Delta.

In a honeycomb lattice the symmetry has been broken by adding an ionic potential and a single-particle gap was generated in the spectrum. We have employed the iterative perturbation theory (IPT) in dynamical mean field approximation method to study the effects of competition between U and Δ on energy gap and renormalized Fermi velocity. As we found, the competition between the single-particle gap parameter and the Hubbard potential closed the energy gap and restored the semi-metallic phase, then the gap was opened again in Mott insulator phase. For a fixed Δ by increasing U  , the renormalized Fermi velocity v˜F is decreased, but change in Δ, for a fixed U  , has no effects on v˜F. The difference in filling factor is calculated for various numbers of U, Δ. The results of this study can be implicated for gapped graphene e.g. hydrogenated graphene.