Spiral phases and time-reversal-violating resonating-valence-bond states of doped antiferromagnets

The phase diagram of the t-t'-J model is investigated with use of a slave-fermion mean-field approach. States with spiral antiferromagnetic order are found to be stable for small t/J and hole concentration. For larger t/J and, corresponding more closely to the physical parameter values of the oxide superconductor, a flux phase exhibiting a uniform chiral order is found to be more stable than the spiral states. This state breaks parity and time-reversal symmetry.