GROUND-STATE PROPERTIES OF THE U=INFINITY HUBBARD-MODEL ON A 4X4 CLUSTER

We analyze the ground-state properties of the U = infinity Hubbard mod el on a 4 x 4 cluster using a Lanczos technique. The quantum numbers o f the ground-state, its momentum distribution, the magnetic structure factor, some [n(k)n(k')] dynamic correlation functions, and the overla p of the ground state with the noninteracting one (both before and aft er a Gutzwiller projection) are given for all fillings. As the number of electrons approaches half-filling the system undergoes a transition from a conventional ground state that overlaps appreciably with the n oninteracting one to a new ground state that shows local ferromagnetic correlations and negligible overlap with the corresponding U = 0 grou nd state. A detailed analysis of the wave function corresponding to th e ground state of 14 electrons (two holes) proves the existence of a f inite shift of the Fermi surface. Our results support the existence of a stable magnetic phase at small but finite hole doping. This new mag netic phase is locally ferromagnetic although the total spin is not ma ximum.