On the nature of the order parameter in quantum antiferromagnets

(Received 14 January 1991, accepted 17 January 1991)

Abstract
The first moments of the magnetization m_z of the d=2, quantum Heinsenberg antiferromagnet with nearest neighbor interactions on the square lattice are computed for T=0 via path integral Monte Carlo Simulations. The results for the ratio show a cross-over at a system size of to the classical behavior, . This supports the arguments that the long range order in the ground state is reached by a spontaneous symmetry breaking, just as in the classical case.