Conductance of atomic-scale metallic contacts with controllable interface hopping integrals

We study the conductance of metallic point contacts between two external leads. Landauer conductance has been computed under constraint of atomic charge neutrality. For Cu and Ni the conductance increases nonlinearly with the number of atoms within the contact layer (unlike the Sharvin conductance). Moreover, the current polarization of nickel turns out to be sensitive to interface conditions.