Two-Coupled Chains with Spin-Anisotropic Backward Scattering
  By applying renormalization group method to the bosonized Hamiltonian of two-coupled chains with repulsive intrachain interaction, we have examined a role of backward scattering with a spin-anisotropy which competes with interchain hopping. From calculation of a dominant state in the limit of low energy, it is found that superconducting state moves into spin density wave state when the anisotropy becomes larger than a critical value. Further phase diagram is shown on the plane of g-ology. 
Masahisa Tsuchiizu and Yoshikazu Suzumura