We analyze the ground-state properties of the U=∞ Hubbard model on a 4×4 cluster using a Lanczos technique. The quantum numbers of the ground-state, its momentum distribution, the magnetic structure factor, some 〈n${\mathrm{⁁}}_{\mathbf{k}}$n${\mathrm{⁁}}_{\mathbf{k}\prime }$〉 dynamic correlation functions, and the overlap of the ground state with the noninteracting one (both before and after 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 noninteracting one to a new ground state that shows local ferromagnetic correlations and negligible overlap with the corresponding U=0 ground state. A detailed analysis of the wave function corresponding to the ground state of 14 electrons (two holes) proves the existence of a finite shift of the Fermi surface. Our results support the existence of a stable magnetic phase at small but finite hole doping. This new magnetic phase is locally ferromagnetic although the total spin is not maximum.

• Received 26 February 1993

DOI:https://doi.org/10.1103/PhysRevB.48.16539