Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 34: Correlated Electrons: Spin Systems and Itinerant Magnets

TT 34.2: Talk

Friday, March 31, 2006, 10:30–10:45, HSZ 301

Phase diagram of the two-dimensional quantum Heisenberg antiferromagnet with an easy-axis anisotropy — •Martin Holtschneider¹, Stefan Wessel², and Walter Selke¹ — ¹Institut für Theoretische Physik, RWTH Aachen — ²Institut für Theoretische Physik, Universität Stuttgart

The square lattice spin-1/2 Heisenberg antiferromagnet with an easy-axis anisotropy is studied in an external magnetic field, using Quantum Monte Carlo simulations based on the stochastic series expansions with a directed loop update. The model displays long range ordered antiferromagnetic, algebraically ordered spin-flop, and paramagnetic phases. The low-temperature phase diagram is determined by studying both thermodynamic quantities such as the (staggered) suszeptibility and the staggered magnetization as well as histograms of e.g. the order parameter distribution. The numerical results are compared to previous findings on this model (being equivalent to a hard core boson Hubbard model), in particular G. Schmid et al., Phys. Rev. Lett. 88, 167208 (2002), and the results on the corresponding classical model in M. Holtschneider et al., Phys. Rev. B 72, 064443 (2005).