Electron transport in mesoscopic conductors with superconducting contacts

As the dimensions of a normal ( N ) metallic conductor are reduced, the resistance of the conductor begins to increase when the contacts go into the superconducting ( S ) state. Likewise, the amplitude of the Aharonov-Bohm effect is strongly enhanced in mesoscopic wires and rings with superconducting contacts. We propose an explanation based on a quantization of electron energies resulting from Andreev reflections at N/S interfaces.