Role of heating and current-induced forces in the stability of atomic wires

We investigate the role of local heating and forces on ions in the stability of current-carrying aluminum wires. For a given bias, we find that heating increases with wire length due to a redshift of the frequency spectrum. Nevertheless, the local temperature of the wire is relatively low for a wide range of biases provided good thermal contact exists between the wire and the bulk electrodes. On the contrary, current-induced forces increase substantially as a function of bias and reach bond-breaking values at about 1 V. These results suggest that local heating promotes low-bias instabilities if dissipation into the bulk electrodes is not efficient, while current-induced forces are mainly responsible for the wire breakup at large biases. We compare these results to experimental observations.

Figure 1

Total current-induced forces as a function of bias in atomic wires containing (a) one, (b) two, (c) three, and (d) four atoms. The inset shows a schematic of one of the wires investigated. The atoms are labeled from the left electrode. The left electrode is positively biased. Positive force pushes the atom against electron flow.

Figure 2

(a) Average force on ions as a function of bias for Al wires of different length. (b) Total current divided by the number of atoms in the wire as a function of bias.

Figure 3

Local temperature as a function of bias for Al wires of different lengths. No heat dissipation into the bulk electrodes is taken into account.

Figure 4

Local temperature as a function of bias for Al wires of different lengths. Heat dissipation into the bulk electrodes is taken into account.