Phase separation based on a U(1) slave-boson functional integral approach to the t-J model

Based on the U(1) slave-boson functional integral approach to the t-J model Hamiltonian, we investigate the phase diagram of phase separation for the hole-doped two-dimensional system of antiferromagnets. We discuss the phase separation (into a hole-rich and a hole-free phase) as a function of J/t where J is the Heisenberg (antiferromagnetic) coupling constant and t the hopping energy. For the physically interesting region of relatively small Heisenberg coupling, 0<J/t<0.2, we find that the phase separation occurs in a region of hole doping concentration below x(c)similar to0.1 and that in the same region the critical hole doping concentrations remain robust with nearest-neighbor hole-hole repulsive interactions. On the other hand, in the region of larger J/t the phase separation boundary is found to be highly sensitive to the variation of the repulsive hole-hole interactions. In agreement with other studies, we find that the phase separation occurs at a critical value of J, approximate to3.4t corresponding to the critical hole concentration x(c)=1.