Phase separation induced by density-spin interaction in one-dimensional extended t-J model

t-J model is one of important theoretical models in the study of high temperature superconductivity. Recent cold molecule experiments indicate that t-J model can be simulated by ultracold polar molecules. In the simulated t-J model, besides long-range dipolar interaction, density-spin interaction has also been introduced. In the present paper we study the effect of density-spin interaction in the one-dimensional extended t-J model by using the density matrix renormalization group method. We choose three sets of representative parameters, which correspond to three different phases in the ground state phase diagram of t-J model, to calculate the charge and spin density distribution in real space and the structure factor of density-density and spin-spin correlation functions. The results indicate that the nature of the system will not change if the intensity of the density-spin interaction is small, however if the intensity is large enough, the system enters the phase separation, in which the character is quiet different form that of the phase separation in the traditional t-J model.