Abstract
We have studied a disordered plaquette Hubbard model on a two-dimensional square lattice at half-filling using a coherent potential approximation (CPA) in combination with a single-site dynamical mean field theory (DMFT) approach with a paramagnetic bath. Such a model conveniently interpolates between the ionic Hubbard model at and the Anderson model at and enables the analysis of the various limiting properties. We confirmed that within the CPA approach a band insulator behavior appears for noninteracting strongly disordered systems with a small plaquette size , while the paramagnetic Anderson insulator with nearly gapless density of states is present for large plaquette sizes . When the interaction is turned on in the strongly fluctuating random potential regions, the electrons on the low energy states push each other into high energy states in DMFT in a paramagnetic bath and correlated metallic states with a quasiparticle peak and Hubbard bands emerge, though a larger critical interaction is needed to obtain this state from the paramagnetic Anderson insulator () than from the band insulator (). Finally, we observe a Mott insulator behavior in the strong interaction regions for both and independent of the disorder strength. We discuss the application of this model to real materials.
- Received 2 February 2016
- Revised 25 May 2016
DOI:https://doi.org/10.1103/PhysRevB.93.224203
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