title: Universal conductance correction in a tunable strongly coupled nanogranular metal.
abstract: We present temperature-dependent conductivity data obtained on a sample set of nanogranular Pt-C with finely tuned intergrain tunnel coupling strength g. For samples in the strong-coupling regime g > g(C), characterized by a finite conductivity for T→0, we find a logarithmic behavior at elevated temperatures and a crossover to a √T behavior at low temperatures over a wide range of coupling strengths g(C) ≈ 0.25 < g ≤ 3. The experimental observation for g > 1 is in very good agreement with recent theoretical findings on ordered granular metals in three spatial dimensions. The results indicate a validity of the predicted universal conductivity behavior that goes beyond the immediate range of the approach used in the theoretical derivation.
authors.affiliation: Physikalisches Institut, Goethe-Universität, Frankfurt am Main, Germany. sachser@physik.uni-frankfurt.de
authors.forename: Roland
authors.initials: R
authors.lastname: Sachser
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Porrati
authors.forename: Christian H
authors.initials: CH
authors.lastname: Schwalb
authors.forename: Michael
authors.initials: M
authors.lastname: Huth