Evidence for a phase transition in the zero-temperature anisotropic two-dimensional Heisenberg antiferromagnet

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Abstract
We describe a Monte Carlo study of the ground state of of the two-dimensional anisotropic Heisenberg antiferromagnet. Values of the energy per spin and the rms z^-staggered magnetization are determined for a range of transverse couplings. At zero temperature the isotropic point g=1 apparently separates two phases having nonzero and zero z^-staggered magnetization for g and g>1, respectively. This may imply that the isotropic Heisenberg antiferromagnet is unsuitable as a model of the precursor insulators of the high-temperature superconductors. We also compare our results with previous conjectures regarding the ground state of the anisotropic system.