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TT: Fachverband Tiefe Temperaturen
TT 49: CE: Spin Systems and Itinerant Magnets 2
TT 49.6: Talk
Thursday, March 17, 2011, 15:15–15:30, HSZ 03
Thermodynamics of quantum magnets at large S — •Andreas Honecker1, Mike Zhitomirsky2, Johannes Richter3, and Moritz Härtel3 — 1Institut für Theoretische Physik, Georg-August-Universität Göttingen, Germany — 2Commissariat à l’Energie Atomique, DSM/INAC/SPSMS, Grenoble, France — 3Institut für Theoretische Physik, Otto-von-Guericke-Universität Magdeburg, Germany
Experiments demand efficient methods to compute thermodynamic properties of quantum magnets in arbitrary dimensions and with arbitrary interaction geometries as well as spin quantum numbers S at moderate to high temperatures. Using the example of the square lattice, we start by generating reference data for S≤5/2 by Quantum Monte Carlo simulations and for S=∞ by classical Monte Carlo simulations. Next, we perform a phenomenological scaling analysis with spin quantum number S. We then explore other, mainly semiclassical methods, which avoid expensive numerical simulations. The methods investigated include linearized spin-wave theory, equations of motion for the Green functions, and a Monte-Carlo evaluation of a cumulant expansion in a spin-coherent-states representation. We compare advantages and shortcomings of the different methods.