Logarithmic temperature dependence of Hall transport in granular metals

TL;DR

This study demonstrates a logarithmic temperature dependence of Hall coefficient and conductivity in granular indium tin oxide films, confirming theoretical predictions about electron-electron interactions and Coulomb effects in such systems.

Contribution

It provides experimental evidence for the ln T dependence of Hall coefficient and conductivity in granular metals, supporting recent theoretical models.

Findings

Hall coefficient R_H ∝ ln T observed from 2 to 120 K

Electrical conductivity σ ∝ ln T observed from 3 K to several tens K

Results support theories of charge transport involving electron-electron and Coulomb interactions in granular systems

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 $R_H$\,$\propto$\,ln$T$ law is observed in a considerably wide temperature range of 2 and $\sim$120 K. This ln$T$ dependence is explained as originated from the electron-electron interaction effect in the presence of granularity, as newly theoretically predicted. Furthermore, we observed a $\sigma$\,$\propto$\,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 supports for the current theoretical concepts for charge transport in granular metals with intergrain tunneling conductivity $g_T$$\gg$1.