Spin liquid versus dimer phases in an anisotropic J1-J2 frustrated square antiferromagnet

The spin-1/2 J1-J2 antiferromagnet is a prototypical model for frustrated magnetism and one possible candidate for a realization of a spin liquid phase. The generalization of this system on the anisotropic square lattice is given by the J1-J2-J1'-J2' Heisenberg model, which can be treated by a renormalization group (RG) analysis of coupled frustrated chains. The J1-J2-J1'-J2'-model shows an interesting interplay of N\'eel order, dimerization, and spin liquid behavior. The analytical findings supported by numerical results indicate that for the isotropic model the phase at intermediate coupling strength 0.4 J1 < J2 < 0.6 J1 is not a spin liquid, but has instead a spontaneously staggered dimer order.