Indications of d_(x² - y²) Superconductivity in the Two Dimensional t-J Model

Superconducting correlations in the two dimensional ${\rm t-J}$ model at zero temperature are evaluated using numerical techniques. At the fermionic density $\langle n \rangle \sim 1/2$, strong signals of $\dx2y2$ superconductivity were observed in the ground state. These conclusions are based on a study of static pairing correlations, the Meissner effect, flux quantization, and other indicators of superconductivity. It is argued that these results can be explained using a spin dimer ``liquid'' state. A phase diagram of the two dimensional ${\rm t-J}$ model is presented.