Néel and disordered phases of coupled Heisenberg chains with S = ½ to S = 4

Abstract

We use the two-step density-matrix renormalization group method to study the effects of frustration in Heisenberg models for S = ½ to 4 in a two-dimensional anisotropic lattice. We find that as for S = ½ studied previously, the system is made up of nearly disconnected chains at the maximally frustrated point, Jd/J⊥ = 0.5, i.e., the transverse spin–spin correlations decay exponentially. This leads to the following consequences: (i) all half-integer spins systems are gapless, behaving like a sliding Luttinger liquid as for S = ½; (ii) for integer spins, there is an intermediate disordered phase with a spin gap, with the width of the disordered state roughly proportional to the 1D Haldane gap.