Quantum Transition between an Antiferromagnetic Mott Insulator and   $d_{x^2 - y^2}$ Superconductor in Two Dimensions
  We consider a Hubbard model on a square lattice with an additional interaction, $W$, which depends upon the square of a near-neighbor hopping. At half-filling and a constant value of the Hubbard repulsion, increasing the strength of the interaction $W$ drives the system from an antiferromagnetic Mott insulator to a $d_{x^2 -y^2}$ superconductor. This conclusion is reached on the basis of zero temperature quantum Monte Carlo simulations on lattice sizes up to $16 \times 16$. 
F.F. Assaad (Dept. Phys. UCSB), M. Imada (ISSP. Univ. Tokyo) and D.J.   Scalapino (Dept. Phys. UCSB)