Disordered phase of a two-dimensional Heisenberg model with S=1

We use the two-step density-matrix renormalization group method to study an anisotropic version of the J(1)-J(2) model with S = 1. We find a second order transition from a Neel Q = (pi, pi) phase to a disordered phase with a spin gap. This result which is contrasted to our previous finding on S = 1/2 systems suggests the importance of topological effects in the disordered phases of Heisenberg models. 2 (c) 2005 Elsevier B.V. All rights reserved.