Nonlinear current-induced forces in Si atomic wires

We report first-principles calculations of current-induced forces in Si atomic wires as a function of bias and wire length. We find that these forces are strongly nonlinear as a function of bias due to the competition between the force originating from the scattering states and the force due to bound states. We also find that the shorter the wire, the larger the average force in the wire, suggesting that the wires are more difficult to break under current flow with increasing length. The last finding is in agreement with recent experimental data.