Spin exchange and superconductivity in a $t-J'-V$ model for   two-dimensional quarter-filled systems
  The effect of antiferromagnetic spin fluctuations on two-dimensional quarter-filled systems is studied theoretically. An effective $t-J'-V$ model on a square lattice which accounts for checkerboard charge fluctuations and next-nearest-neighbors antiferromagnetic spin fluctuations is considered. From calculations based on large-N theory on this model it is found that the exchange interaction, $J'$, increases the attraction between electrons in the d$_{xy}$ channel only, so that both charge and spin fluctuations work cooperatively to produce d$_{xy}$ pairing. 
Andres Greco, Jaime Merino, Adriana Foussats and Ross H. McKenzie