Cutoff dependence of a configuration-interaction approach to the two-dimensional Hubbard model

Abstract

The two-dimensional Hubbard model near half-filling is studied using a configuration-interaction method with kinetic energy cutoffs of $4t,$ $5t,$ and $6t.$ D-wave superconducting order parameter and spin-spin correlation functions are calculated as functions of distance to probe for superconductivity and antiferromagnetism. These calculations do not show indications of d-wave superconductivity in the ground state of the two-dimensional repulsive Hubbard model for the $5t$ and $6t$ cutoffs. To understand these results, in particular the enhancement of d-wave correlations at a cutoff of $4t,$ we implement a different cutoff scheme. In this second scheme we introduce a cutoff in the single particle energies relative to the Fermi surface. Using this second scheme, we obtain a significant enhancement for g-wave superconductivity.