Conductance histograms and conducting channels in atomic-scale metallic contacts

Properties of the conductance and transport channels of atomic-scale contac ts are discussed within the free electron model. In agreement with recent e xperiments, we find that, owing to the contribution of evanescent channels, even when the conductance is close to an integer number N of conductance q uanta more than N channels may contribute significantly to the current. We show that the observation of peaks at integer multiples of G(0) in conducta nce histograms is not a signature of conductance quantization of individual contacts. However, the observed peaks can still be associated to the quant um nature of electron transport in metallic contacts. (C) 1999 Elsevier Sci ence B.V. All rights reserved.