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DY: Fachverband Dynamik und Statistische Physik

DY 30: Nonlinear stochastic systems

DY 30.9: Vortrag

Freitag, 27. März 2009, 12:15–12:30, ZEU 118

The nonlinear ion transport mechanism in disordered systems — •Lars Lühning and Andreas Heuer — Institute of Physical Chemistry, University of Münster, Germany

The conduction mechanism which leads to nonlinear transport effects in disordered nonmetallic solids like ionic conductive glasses is still poorly understood but widely accepted to be due to hopping dynamics. Comparison of theoretical analysis and experimental data indicates that the random-energy model can serve as a realistic model to understand nonlinear ion transport. In this model the hopping of ions which occurs between localized sites in the glass matrix is projected on a square lattice with a characteristic hopping distance representing the typical distance between adjacent ionic sites. We analyze the evolution of the conductivity with increasing field strength. The strength of the nonlinear effects is strongly correlated with the properties of the sites with the lowest energies. First, the presence of very low-energy sites on average gives rise to stronger non-linear effects. Second, even for a fixed set of energies variation of the spatial arrangement gives rise to significant variations of the degree of non-linearity. Thus, also topological information is contained in the non-linear response. Bond-percolation current pathways are laid on the top of node-percolation energy cluster and the percolation calculations are extended to a more general cluster analysis. Surprisingly, there is no strict overlap of the current- with the energy percolation cluster. But the current cluster which carries up to 95% of the whole system current spans quasi-homogeneous the disordered energy landscape.