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arXiv:cond-mat/9711172 · Physical review. B, Condensed matter

Doping-induced metal-insulator transition in two-dimensional Hubbard t−U and extended Hubbard t−U−W models

Fakher F. Assaad, Masatoshi Imada

Published Jul 15, 1998• 20 citations
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Abstract

We show numerically that the nature of the doping-induced metal-insulator transition in the two-dimensional Hubbard model with hopping matrix element $t$ and Coulomb repulsion $U$ is radically altered by the inclusion of a term $W$ that depends upon a square of a single-particle nearest-neighbor hopping. This result is reached by computing the localization length ${\ensuremath{\xi}}_{l}$ in the insulating state. At $W/t=0.05$ and $U/t=4$, we find results consistent with ${\ensuremath{\xi}}_{l}\ensuremath{\sim}|\ensuremath{\mu}\ensuremath{-}{\ensuremath{\mu}}_{c}{|}^{\ensuremath{-}1/2}$ where ${\ensuremath{\mu}}_{c}$ is the critical chemical potential. In contrast, ${\ensuremath{\xi}}_{l}\ensuremath{\sim}|\ensuremath{\mu}\ensuremath{-}{\ensuremath{\mu}}_{c}{|}^{\ensuremath{-}1/4}$ for the Hubbard model at $U/t=4$. At half-filling, we calculate the density of states $N(\ensuremath{\omega})$. The large value of $N(\ensuremath{\omega})$ in the vicinity of $\ensuremath{\omega}={\ensuremath{\mu}}_{c}$ present at $W=0$ is suppressed with growing values of $W$. At finite doping, the $d$-wave pair-field correlations are enhanced with growing values of $W$. The numerical results imply that at finite values of $W$ doping the antiferromagnetic Mott insulator leads to a ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ superconductor.

DOI
10.1103/physrevb.58.1845

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