Metal–insulator transition in Honeycomb lattice due to electronic correlation

The role of electronic correlation in metallicity and insulating behavior of Honeycomb (HC) lattice is investigated via the Hubbard model. It is shown that the HC lattice suffers an evolution from an ionic band insulator to a metal on increasing the electronic interaction, U. There is no critical value Uc1 for onset of metallic state and each of two common van Hove singularities splits into two extra singularities. The metallic state is enhanced with further increasing the interaction strength U  , and the characteristic Kondo peak develops. The height of Kondo peak completely vanishes at U≃6.15tU≃6.15t, and then a Mott insulator develops at Uc2≃6.5tUc2≃6.5t.