Dresden 2006 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 46: Poster
DY 46.125: Poster
Donnerstag, 30. März 2006, 16:00–18:00, P1
Excitations and percolation phenomena in 3D random field Ising magnets — •Martin Zumsande and Alexander K. Hartmann — University of Göttingen, Institute for Theoretical Physics, Friedrich-Hund-Platz 1, 37077 Göttingen
The ground-state structure of the three-dimensional Gaussian random field Ising magnet (RFIM) is known to show a rich behaviour, especially since there occurs a disorder-driven phase transition in 3D. For small random fields the 3D RFIM is ferromagnetic, at high fields the spins align with the random fields leading to a paramagnetic phase. We compute ground states of very large systems (L ≈ 1003 spins) using a mapping of the problem to the maximum-flow minimum-cut problem of graph theory which can be solved by efficient algorithms.
We create small excitations by freezing one spin of the system opposite to its ground state direction and recalculating the ground state. Doing this, we generate clusters that have a maximum extension at criticality where the correlation length diverges. We numerically determine geometrical and energetical properties of these clusters.
We also study percolation properties of the ground state at different random fields. There is a transition from the ferromagnetic phase where one spin direction percolates to the paramagnetic phase, where both of them do. We determine the properties of the percolation transition of this and related types of percolation and discuss the influence of the phase transition on this.