Doping-induced metal-insulator transition in two-dimensional Hubbard and extended Hubbard models

We show numerically that the nature of the doping-induced metal-insulator transition in the two-dimensional Hubbard model with hopping matrix element (Formula presented) and Coulomb repulsion (Formula presented) is radically altered by the inclusion of a term (Formula presented) that depends upon a square of a single-particle nearest-neighbor hopping. This result is reached by computing the localization length (Formula presented) in the insulating state. At (Formula presented) and (Formula presented), we find results consistent with (Formula presented) where (Formula presented) is the critical chemical potential. In contrast, (Formula presented) for the Hubbard model at (Formula presented). At half-filling, we calculate the density of states (Formula presented). The large value of (Formula presented) in the vicinity of (Formula presented) present at (Formula presented) is suppressed with growing values of (Formula presented). At finite doping, the (Formula presented)-wave pair-field correlations are enhanced with growing values of (Formula presented). The numerical results imply that at finite values of (Formula presented) doping the antiferromagnetic Mott insulator leads to a (Formula presented) superconductor.