Phase separation effect in cuprate superconductors

In terms of the Ginzburg-Landau theory, we investigate the effect of coupli ng between the paramagnetantiferromagnet (AF) phase transition, superconduc ting (SC) phase transition, and phase separation (PS) of doping holes in cu prate superconductors. It is found that in the presence of PS, the hole-ric h metallic phase can coexist with the hole-poor insulating AF phase, and th ere is a metal-insulator transition with increasing doping concentration n beyond a percolation threshold. The occurrence of PS will lead to significa nt changes in the phase diagram: the SC phase appearing at lower n and the step dependence of T-c on n. These results are qualitatively consistent wit h experiments of photodoped and oxygen-doped cuprate perovskites.