Phase transitions in anisotropic two‐dimensional quantum antiferromagnets
Tommaso Roscilde, Alessandro Cuccoli, Paola Verrucchi
Abstract We study the thermodynamic properties of anisotropic two‐dimensional quantum antiferromagnets, with both easy‐plane and easy‐axis anisotropy. We make use of the Quantum Monte Carlo (QMC) method based on the continuous‐time loop algorithm. For S = 1/2 and very small anisotropies our QMC data reveal that both the Ising and Berezinskii–Kosterlitz–Thouless universality class (for the easy‐axis and easy‐plane models, respectively) are well observed and that the critical temperature remains finite even for anisotropies as small as 10–3, i.e. comparable to the anisotropies measured in real layered compounds; this result rules out the possibility of quantum fluctuations to destroy the finite‐temperature transition before the isotropic limit is reached. The phase diagram of the S = 1/2 2d‐XXZ antiferromagnet in the region of small anisotropies is then presented.
physica status solidi (b)•Mar 1, 2003•6 citations