Electrical conductance of a 2D packing of metallic beads under thermal perturbation

¹ Service de Physique de l'Etat Condensé, CEA Saclay 91191 Gif-sur-Yvette Cedex, France
² Technion, Israel Institute of Technology, Physics Department - Haifa 32000, Israel

Received: 4 April 2000
Accepted: 14 July 2000

Abstract

Electrical conductivity measurements on a 2D packing of metallic beads have been performed to study internal rearrangements in weakly perturbed granular materials. Small thermal perturbations lead to large non-Gaussian conductance fluctuations. These fluctuations are found to be intermittent in time, with peaks gathered in bursts. The distribution of the waiting time between two peaks is found to be a power law inside bursts. The exponent is independent of the bead network, the intensity of perturbation and external stress. These bursts are interpreted as the signature of individual bead creep rather than collective vault reorganisations. We propose a simple model giving , where ζ is the roughness exponent of the surface of the beads.