  The slave boson mean-field studies of the ground state of the Hubbard model
with correlated hopping were performed. The approach qualitatively recovers the
exact results for the case of the hopping integral t equal to the correlated
hopping integral X. The phase diagram for the strongly correlated state with
only singly occupied sites, the weakly correlated state, where single and
double occupation is allowed, and for the superconducting state, was determined
for any values of X and any electron concentration n. At the half-filled band
(n=1) a direct transition from the superconductor to the Mott insulator was
found. In the region of strong correlations the superconducting solution is
stable for n close to 1, in contrast to the case of weak correlations, in which
superconductivity occurs at n close to 0 and n close to 2. We found also that
strong correlations change characteristics of the superconducting phase, e.g.
the gap in the excitation spectrum has a nonexponential dependence close to the
point of the phase transition.
