Conductance of atomic-scale gold contacts under high-bias voltages

The conductance of atomic-scale gold contacts has been studied experimentally as a function of bias voltage. At low voltages, the conductance histogram shows a pronounced peak at G₀=2e^2/h and broad peaks near 2G₀ and 3G₀. With increasing the bias voltage, these peaks decrease in height and disappear at some critical voltage. The 1G₀ peak is found to disappear at 1. 9 V at room temperature, which corresponds to a critical current of 137. At liquid-nitrogen temperature, the critical voltage and current slightly increases to 2. 2 V and 165, respectively. The observed disappearance of the conductance peaks can be interpreted as a contact instability due to the electromigration of contact atoms induced by a high current density.