Our paper about relation between the tunneling current and the chemical force has been published 5 Jan 2011 in Phys. Rev. Lett. This work has been done in collaboration with Almaden IBM Laboratory, MPI Stuttgart and University of Regensburg.

The coupling between two atomically sharp nanocontacts provides tunable access to a fundamental underlying interaction: the formation of the bond between two atoms as they are brought into contact. Here we report a detailed experimental and theoretical analysis of the relation between the chemical force and the tunneling current during bond formation in atom-scale metallic junctions and their dependence on distance, junction structure, and material. We found that the short-range force as well as the conductance in atomic metal junctions depend exponentially on the distance with the same decay constant.

Fig. Dependence of the tunneling current and the chemical force on tip-sample distance using simultaneous AFM/STM measurements and DFT simulations.

M. Ternes et al, Phys. Rev. Lett. 106, 016802 (2011).