High-bias conductance of atom-sized Cu contacts

We have measured the conductance of Cu nanocontacts for biases Vb=0.1-0.8 V and investigated the bias dependence of the formation probability pCu of Cu single-atom contacts (SACs). We found that pCu decreases with increasing Vb and vanishes at a critical bias Vbc ∼0.7 V, contrary to Vbc ∼2.3 V for pAu of Au SACs. Both pCu and pAu, however, show the same bias dependence when plotted against the reduced bias Vb/Vbc