Phase Separation in the Two-Dimensional Systems of Strongly Correlated electrons; the Role of Spin Singlet Pairs on Hole Pairing Contribution to Hole-rich Phase

By paying attention to the hole-doped two-dimensional systems of antiferromagnetically (strongly) correlated electrons, we discuss the cause of hole-rich phase formation in association with phase separation. We show that the phase diagram obtained from the Maxwell's construction in the plane of temperature vs. hole density is consistent with one derived from the evaluation of hole-rich and electron-rich phases in real space. We observe that the formation of a hole-rich phase is attributed to the aggregation of hole pairs induced by spin singlet pairs present in the pseudogap phase and that a direct involvement of correlations between hole pairs are not essential for phase separation.