Effect of disorder on the conductance of a Cu atomic point contact

We present a systematic study of the effect of the disorder in copper point contacts. We show that peaks in the conductance histogram of copper point contacts shift upon addition of nickel impurities. The shift increases initially linearly with the nickel concentration, thus confirming that it is due to disorder in the nanowire, in accordance with predictions. In general, this shift is modeled as a resistance R-s which is placed in series with the contact resistance R-c. However, we obtain different R-s values for the two peaks in the histogram, R-s being larger for the peak at higher conductance.