Superconducting pairing symmetries in anisotropic triangular quantum antiferromagnets

Motivated by the recent discovery of a low temperature spin liquid phase in layered organic compound kappa-(ET)(2)Cu-2(CN)(3) which becomes a superconductor under pressure, we examine the phase transition of Mott insulating and superconducting (SC) states in a Hubbard-Heisenberg model on an anisotropic triangular lattice. We use a renormalized mean field theory to study the Gutzwiller projected BCS wave functions. The half filled electron system is a Mott insulator at large onsite repulsion U, and is a superconductor at a moderate U. The symmetry of the SC state depends on the anisotropy, and is gapful with d(x2-y2)+id(xy) symmetry near the isotropic limit and is gapless with d(x2-y2) symmetry at small anisotropy ratio.