Conductance eigenchannels in nanocontacts

The electronic conductance of metal nanocontacts is analyzed in terms of eigenchannels for the transmission. The transmission through individual eigenchannels is calculated numerically for realistic models of gold point contacts based on molecular-dynamics simulation of the elongation of a contact. The conductance as a function of contact elongation exhibits a step structure. For the smallest contact areas of one or a few atom diameters, the conductance is typically quantized, and a specific number of almost open eigenchannels can be ascribed. For larger contact areas the scattering leads to partly open channels, but plateaus in the conductance can still be present. We also show that the finite stiffness of the experimental setup can significantly affect the step structure of the conductance curves.