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| VOLUME 90 | ISSUE 10 |
PAGE 746
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| Percolation with excluded small clusters and Coulomb blockade in a granular system
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A. S. Ioselevich, D. S. Lyubshin
Landau Institute for Theoretical Physics RAS, 117940 Moscow, Russia
Moscow Institute of Physics and Technology, 141700 Moscow, Russia
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PACS: 72.23.Hk, 72.80.Tm, 73.22.-f
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Abstract
We consider dc-conductivity σ of a mixture of small
conducting and insulating grains slightly below the percolation
threshold, where finite clusters of conducting grains are
characterized by a wide spectrum of sizes. The charge transport is
controlled by tunneling of carriers between neighboring conducting
clusters via short «links» consisting of one insulating grain.
Upon lowering temperature small clusters (up to some T-dependent
size) become Coulomb blockaded, and are avoided, if possible, by
relevant hopping paths. We introduce a relevant percolational
problem of next-nearest-neighbors (NNN) conductivity with excluded
small clusters and demonstrate (both numerically and analytically)
that σ decreases as power law of the size of excluded
clusters. As a physical consequence, the conductivity is a
power-law function of temperature in a wide intermediate
temperature range. We express the corresponding index through
known critical indices of the percolation theory and confirm this
relation numerically.
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