G. Chiappe et al., GROUND-STATE PROPERTIES OF THE U=INFINITY HUBBARD-MODEL ON A 4X4 CLUSTER, Physical review. B, Condensed matter, 48(22), 1993, pp. 16539-16546
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.