THE SPIRAL PHASE AND THE SPIN-LIQUID STATE IN THE T-J-J' MODEL

The possible spin-liquid state and phase separation are studied in the framework of the t-J-J' model (frustrated t-J model) by using the Schwinger boson mean-field theory. It is shown that both doping and the quantum fluctuation of spins, which are treated on the same footing, favour the spin-liquid state. Away from half filling, the phase separation is still present for any values of t/J and J'/J in the case of spin S = 1/2, but a tendency to diminish the range of the phase separation is induced due to quantum fluctuation of the spins.