N ov 1 99 7 Doping induced metal - insulator transition in two - dimensional Hubbard , t − U , and extended Hubbard , t − U − W , models

Doping induced metal-insulator transition in two-dimensional Hubbard, t − U , and extended Hubbard, t − U − W , models. Abstract We show numerically that the nature of the doping induced metal-insulator transition in the two-dimensional Hubbard model is radically altered by the inclusion of a term, W , which depends upon a square of a single-particle nearest-neighbor hopping. This result is reached by computing the localiza-tion length, ξ l , in the insulating state. At finite values of W we find results consistent with ξ l ∼ |µ − µ c | −1/2 where µ c is the critical chemical potential. In contrast, ξ l ∼ |µ − µ c | −1/4 for the Hubbard model. At finite values of W , the presented numerical results imply that doping the antiferromagnetic Mott insulator leads to a d x 2 −y 2 superconductor.