Metallic phase in the two-dimensional ionic Hubbard model

Abstract

We investigate the phases of the ionic Hubbard model in a two-dimensional square lattice using determinant quantum Monte Carlo (DQMC). At half-filling, when the interaction strength or the staggered potential dominate we find Mott and band insulators, respectively. When these two energies are of the same order we find a metallic region. Charge and magnetic structure factors demonstrate the presence of antiferromagnetism only in the Mott region, although the externally imposed density modulation is present everywhere in the phase diagram. Away from half-filling, other insulating phases are found. Kinetic energy correlations do not give clear signals for the existence of a bond-ordered phase.

Short-range Coulomb correlations render massive Dirac fermions massless

“…The ionic-Hubbard model has been studied extensively in one dimension [21], and two dimensions, and the nature of interim phase has been debated [22]. In addition to various low-dimensional techniques employed to study such model, the DMFT technique has also been employed to study the nature of intermediate phase of this model for metallic parent systems [9,23].…”

Electronic and magnetic properties of the ionic Hubbard model on the striped triangular lattice at34filling

“…21,22 These studies all suggested that a phase with nonzero spectral weight at the Fermi energy exists between the band insulator and Mott insulator phases, at least in some of the phase diagram. However, there has been some debate over whether this phase is metallic 21,22 or bond ordered. 20 There has been far less work on the ionic Hubbard model away from half-filling.…”

“…This model has been studied using both cluster DMFT 20 and determinant quantum Monte Carlo ͑DQMC͒. 21,22 These studies all suggested that a phase with nonzero spectral weight at the Fermi energy exists between the band insulator and Mott insulator phases, at least in some of the phase diagram. However, there has been some debate over whether this phase is metallic 21,22 or bond ordered.…”

“…However, Penc et al 23 studied the quarter-filled ionic Hubbard model on the zigzag ladder and found a competition between ferromagnetism and a paramagnetic phase with strong antiferromagnetic correlations. Bouadim et al 22 studied the ionic Hubbard model on a square lattice with a checkerboard potential across all possible fillings with DQMC. The most interesting features they found, away from half filling, were Mott insulation at quarter and three quarters filling ͑which are related by the particlehole symmetry of this model͒.…”

Ionic Hubbard model on a triangular lattice forNa0.5CoO2,Rb0.5Powell1, Merino2, McKenzie3 2009Phys. Rev. B9020View full textAdd to dashboardCite

“…The ionic Hubbard model on half-filled bipartite lattices has attracted interest because it undergoes a transition from a Mott insulator to a band insulator. [12][13][14][15][16][17][18] Furthermore, away from halffilling and on frustrated lattices the ionic Hubbard model shows a subtle interplay between charge and spin ordering and metallic and insulating phases. [19][20][21][22][23][24] The Hamiltonian of the ionic Hubbard model is…”