$\eta$-pairing as a mechanism of superconductivity in models of strongly   correlated electrons
  We consider extended versions of the Hubbard model which contain additional interactions between nearest neighbours. In this letter we show that a large class of these models has a superconducting ground state in arbitrary dimensions. In some special cases we are able to find the complete phase diagram. The superconducting phase exist even for moderate repulsive values of the Hubbard interaction $U$. 
Jan de Boer, Vladimir E. Korepin and Andreas Schadschneider