Electron transport in atomic-size metallic contacts proceed through a reduced number of conduction
channels. When the contact is in the superconducting state a quasi-particle current can be
established at subgap bias voltages thanks to the mechanism of Multiple Andreev Reflections. This
results in a highly non-linear current voltage characteristic which allows to extract information
on the channel distribution. We shall discuss several theoretical predictions for electron
transport properties that have been tested experimentally using atomic contacts including
shot-noise, Josephson currents and the Coulomb blockade effect.
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