Possible phase diagram of a t-J ladder model

We investigate a t-J ladder model by using the numerical diagonalization method. By calculating correlation functions and assuming the Luttinger liquid relation, we obtained a possible phase diagram of the ground state as a function of J/t and electron density n. We also found that behavior of correlation functions seems to be consistent with the prediction based on the Luttinger liquid relation. The result suggests that the superconducting phase appears in the region of J/t greater than or similar to 0.5 for high electron density and J/t greater than or similar to 2.0 for low electron density.