paper

Novel Phase Between Band and Mott Insulators in Two Dimensions

arXiv:cond-mat/0607568 · doi:10.1103/PhysRevLett.98.016402

Abstract

We investigate the ground state phase diagram of the half-filled repulsive Hubbard model in two dimensions in the presence of a staggered potential , the so-called ionic Hubbard model, using cluster dynamical mean field theory. We find that for large Coulomb repulsion, , the system is a Mott insulator (MI). For weak to intermediate values of , on decreasing , the Mott gap closes at a critical value beyond which a correlated insulating phase with possible bond order (BO) is found. Further, this phase undergoes a first-order transition to a band insulator (BI) at with a finite charge gap at the transition. For large , there is a direct first-order transition from a MI to a BI with a single metallic point at the phase boundary.

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