Some aspects of electrical conduction in
granular systems of various dimensions
M. Creyssels1, S. Dorbolo2, A.
Merlen1, C. Laroche1, B. Castaing1
and E. Falcon1,*
1 Laboratoire de Physique,
Ecole Normale Supérieure de Lyon, CNRS UMR 5672, 69 007 Lyon,
France
2 GRASP Photopôle, Physics Department,
Université de
Liège, B-4000 Liège, Belgium
* Present address: MSC, Université Paris Diderot - Paris 7, CNRS
UMR 7057, 75 013 Paris, France
Reference:
European Physical Journal E 23, 255 - 264
(2007)
DOI: 10.1140/epje/i2006-10186-9
Abstract:
We report on measurements of the electrical
conductivity in both a 2D triangular lattice of metallic beads and in a
chain of beads. The voltage/current characteristics are qualitatively
similar in both experiments. At low applied current, the voltage is
found to increase logarithmically in a good agreement with a model of
widely distributed resistances in series. At high enough current, the
voltage saturates due to the local welding of microcontacts between
beads. The frequency dependence of the saturation voltage gives an
estimate of the size of these welded microcontacts. The DC value of the
saturation voltage ( ~ 0.4 V per contact) gives an indirect measure of
the number of welded contact carrying the current within the 2D
lattice. Also, a new measurement technique provides a map of the
current paths within the 2D lattice of beads. For an isotropic
compression of the 2D granular medium, the current paths are localized
in few discrete linear paths. This quasi-onedimensional nature of the
electrical conductivity thus explains the similarity between the
characteristics in the 1D and 2D systems.
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