Zero-Bias Anomalies in Normal Metal Tunnel Junctions

Abstract

We have investigated the current flow through thin chromium-oxide layers from 1\ifmmode^\circ\else\textdegree\fi{}K to 290\ifmmode^\circ\else\textdegree\fi{}K. We believe that current flows by means of a tunneling mechanism, but the dependence of the dynamic resistance of the junction on voltage and temperature is completely anomalous in terms of expected tunneling behavior. Some new results on other metal-oxide junctions strongly suggest that properties of the oxide layer are responsible for the anomaly observed by Wyatt in tantalum oxide junctions.