Re-entrance during nonequilibrium relaxation

¹ Institute of Theoretical Physics, Szeged University - H-6720 Szeged, Hungary
² Institut für Theoretische Physik I, Universität Erlangen-Nürnberg D-91058 Erlangen, Germany
³ Research Institute for Solid State Physics and Optics - P.O. Box 49 H-1525 Budapest, Hungary

Received: 14 September 2005
Accepted: 23 November 2005

Abstract

We consider nonequilibrium critical dynamics of the two-dimensional Ising model for which the initial state is prepared by switching on random fields with zero mean and variance H. In the initial state there is no magnetic order but the clusters of parallel spins have a percolation transition for small enough H. Using heat-bath dynamics we measure the relaxation of the magnetization which shows a re-entrance in time. Due to cluster dissolution in the early time regime there is a decrease of the magnetization, followed by an increase due to nonequilibrium domain growth which itself turns to a decrease due to equilibrium relaxation. The power law decay of the nonequilibrium autocorrelation function is not influenced by the percolation in the initial state.