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Phase Separation Based on U(1) Slave-boson Functional Integral Approach to the t-J Model

We investigate the phase diagram of phase separation for the hole-doped two dimensional system of antiferromagnetically correlated electrons based on the U(1) slave-boson functional integral approach to the t-J model. We show that the phase separation occurs for all values of J/t, that is, whether $0 < J/t < 1$ or $J/t \geq 1$ with J, the Heisenberg coupling constant and t, the hopping strength. This is consistent with other numerical studies of hole-doped two dimensional antiferromagnets. The phase separation in the physically interesting J region, $0 < J/t \lesssim 0.4$ is examined by introducing hole-hole (holon-holon) repulsive interaction. We find from this study that with high repulsive interaction between holes the phase separation boundary tends to remain robust in this low $J$ region, while in the high J region, J/t > 0.4, the phase separation boundary tends to disappear.