Superconductivity in a Quasi One Dimensional Spin Liquid
  The single rung t-J ladder is analyzed in a mean field theory using Gutzwiller renormalization of the matrix elements to account for strong correlation. The spin liquid (RVB) state at half-filling evolves into a superconducting state upon doping. The order parameter has a modified d-wave character. A lattice of weakly coupled ladders should show a superconducting phase transition. 
M. Sigrist, T.M. Rice and F.C. Zhang