Spontaneous staggered magnetization in antiferromagnetic Heisenberg-Ising chains

Abstract
We calculate numerically the spontaneous staggered magnetization and susceptibility of the ground state of quantum antiferromagnetic Heisenberg-Ising chains. We use a zero-temperature Monte Carlo method and consider the cases of spin 1 and 2. As a function of the anisotropy parameter, the magnetization vanishes continuously at a critical point whose critical exponents for both cases are found to be in agreement with those of the two-dimensional Ising model.