Properties of the U>>t 2-electrons in two dimensions using the Hubbard model

We examine the behaviour of 2 electrons on a 2 x 2 square lattice sites. The Hubbard model was used to model the system and was diagonalized using the configuration interaction method which is a variational method. The variations of the ground state energy E/t ground state double occupied sites D, and the ground state kinetic energy E(kin)/t with the interaction strength u/t (u < 0 and u > 0) were examined. The functions E/t and E(kin)/t were found to be parabolic functions of u/t u. This suggests that superconductivity is driven by both electron and hole doping.