Superconductivity in Hubbard Model with Correlated Hopping

Using the slave-boson method in its spin- and charge-rotational invariant representation we determine stability of the superconducting state in the Hubbard model with correlated hopping. In general the term with correlated hopping violates electron-hole symmetry, however, in the special case when the correlated hopping integral X is equal to the uncorrelated hopping integral t the electron-hole symmetry remains. We investigate this case and show that correlations induced by onsite Coulomb interactions U yield to the normal state with exactly single occupied sites (corresponding to |U=∞⟩). The phase diagram of the superconducting state is determined for the different electron concentration n. At the half-filled band (n=1) a direct transition from the Mott insulator to the superconducting state occurs.