Regensburg 2007 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 15: Internal Symposium: Finite size effects at phase transitions
DY 15.5: Invited Talk
Tuesday, March 27, 2007, 16:15–16:45, H2
Spin Dynamics Simulations of Excitations and Critical Dynamics in a Heisenberg Antiferromagnet: Resolution of a controversy via finite size scaling — •David P. Landau — Center for Simulational Physics, The University of Georgia, Athens, GA , U.S.A.
The classic Halperin-Hohenberg classification of “dynamic” universality classes separates models with stochastic and deterministic behavior. Stochastic, e.g. Ising, models have long been studied using Monte Carlo simulations but research on magnetic systems with true dynamics is less detailed because of limitations in both computer speed and algorithms. Spin dynamics simulation methods have developed sufficiently that they now provide a powerful tool for the examination of excitations and dynamic critical behavior in magnetic models. From the Fourier transform of the space-displaced, time-displaced correlation functions the dynamics structure factor S(q,ω) can be extracted. After briefly describing modern decomposition methods for the time integration we shall present results for a classical, Heisenberg antiferromagent on a simple cubic lattice. This model is an excellent “testing ground” since it is expected to describe the magnetic behavior of RbMnF3 quite well. The estimation of the dynamic critical exponent z is non-trivial and relies on finite size scaling of the dynamic structure factor. We shall compare our results with theoretical predictions as well as with detailed neutron scattering data.
+Work performed in collaboration with S.-H. Tsai and A. Bunker
* Research supported by the National Science Foundation