CONDUCTION CHANNEL TRANSMISSIONS OF ATOMIC-SIZE ALUMINUM CONTACTS

We have determined the individual transmission coefficients of Al quan tum point contacts containing up to six conduction channels. The deter mination is based on a comparison of the highly nonlinear current-volt age characteristics in the superconducting state with the predictions of the theory for a single channel superconducting contact. We find th at at least two channels contribute to the transport even for contacts with conductance lower than the conductance quantum.