Complete phase diagram of the spin-½ J₁-J₂-J₃ model (with J₃ = J₂) on the honeycomb lattice

We use the coupled cluster method (CCM) to investigate the ground-state (GS) properties of the frustrated spin-1/2 J1-J2-J3 model on the honeycomb lattice, with nearest-neighbor exchange coupling J1 plus next-nearest-neighbor (J2) and next-next-nearest-neighbor (J3) exchanges of equal strength. In particular we find a direct first-order phase transition between the Néel-ordered antiferromagnetic phase and the ferromagnetic phase at a value J2/J1=-1.17±0.01 when J1 > 0, compared to the corresponding classical value of -1. We find no evidence for any intermediate phase. From this and our previous CCM studies of the model we present its full zero-temperature GS phase diagram.