The quantum J₁-J₁′-J₂ spin-1/2 Heisenberg model: Influence of the interchain coupling on the ground-state magnetic ordering in two dimensions

We study the phase diagram of the two-dimensional (2D) J₁-J₁′-J₂ spin-1/2 Heisenberg model by means of the coupled cluster method. The effect of the coupling J₁′ on the Néel and stripe states is investigated. We find that the quantum critical points for the Néel and stripe phases increase as the coupling strength J₁′ is increased, and an intermediate phase emerges above the region at J₁′ ≈ 0.6 when J₁ = 1. We find indications for a quantum triple point at J₁′≈0.60 ± 0.03, J₂ ≈ 0.33 ± 0.02 for J₁ = 1.