title: Entropy and kinetics of point defects in two-dimensional dipolar crystals.
abstract: We study in experiment and with computer simulation the free energy and the kinetics of vacancy and interstitial defects in two-dimensional dipolar crystals. The defects appear in different local topologies, which we characterize by their point group symmetry; Cn is the n-fold cyclic group and Dn is the dihedral group, including reflections. The frequency of different local topologies is not determined by their almost degenerate energies but is dominated by entropy for symmetric configurations. The kinetics of the defects is fully reproduced by a master equation in a multistate Markov model. In this model, the system is described by the state of the defect and the time evolution is given by transitions occurring with particular rates. These transition rate constants are extracted from experiments and simulations using an optimization procedure. The good agreement between experiment, simulation, and master equation thus provides evidence for the accuracy of the model.
authors: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, 6020 Innsbruck, Austria.|Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria.
authors: Wolfgang
authors: W
authors: Lechner
authors: Department of Physics, University of Konstanz, D-78457 Konstanz, Germany.
authors: David
authors: D
authors: Polster
authors: Department of Physics, University of Konstanz, D-78457 Konstanz, Germany.
authors: Georg
authors: G
authors: Maret
authors: Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
authors: Christoph
authors: C
authors: Dellago
authors: Department of Physics, University of Konstanz, D-78457 Konstanz, Germany.
authors: Peter
authors: P
authors: Keim