J. Phys. II France
Volume 1, Numéro 3, March 1991
Page(s) 259 - 263
DOI: 10.1051/jp2:1991166
J. Phys. II France 1 (1991) 259-263

On the nature of the order parameter in quantum antiferromagnets

Joseph D. Reger

Institut für Physik, Universtät Mainz, D-6500 Mainz, Germany

(Received 14 January 1991, accepted 17 January 1991)

The first moments of the magnetization mz of the d=2, $S=\frac{1}{2}$ 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 $R=\langle m^4_z \rangle / \langle m^2_z \rangle^2$ show a cross-over at a system size of $N \approx 100$ to the classical behavior, $\lim_{N\to \infty} R = 9/5$. 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.

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