Logarithmic temperature dependence of Hall transport in granular metals

Abstract

We have measured the Hall coefficient R-H and the electrical conductivity sigma of a series of ultrathin indium-tin-oxide films between 2 and 300 K. A robust R-H proportional to ln T law is observed in a considerably wide temperature range of 2 and similar to 120 K. This ln T dependence is explained as originating from the electron-electron interaction effect in the presence of granularity as theoretically predicted. Furthermore, we observed sigma proportional to ln T law from 3 K up to several tens K, which also arose from the Coulomb interaction effect in inhomogeneous systems. These results provide strong experimental support for the current theoretical concepts for charge transport in granular metals with intergrain tunneling conductivity g(T) >> 1.