Evidence for 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 inter-grain 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 sqrt(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.

References in corpus (3)

• Nature of the superconductor-insulator transition in disordered superconductors
• Tuning the electrical conductivity of Pt-containing granular metals by postgrowth electron irradiation
• An inhomogeneous Josephson phase in thin-film and High-Tc superconductors

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