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Phase transitions in anisotropic two‐dimensional quantum antiferromagnets
Author(s) -
Roscilde T.,
Cuccoli A.,
Verrucchi P.
Publication year - 2003
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200301697
Subject(s) - anisotropy , condensed matter physics , physics , antiferromagnetism , ising model , isotropy , phase diagram , quantum , quantum phase transition , quantum monte carlo , phase transition , quantum fluctuation , universality (dynamical systems) , monte carlo method , renormalization group , statistical physics , quantum mechanics , phase (matter) , mathematics , statistics
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 2 d ‐XXZ antiferromagnet in the region of small anisotropies is then presented.