Supercurrent in atomic point contacts and Andreev states

We have measured the supercurrent in aluminum atomic point contacts containing a small number of well characterized conduction channels. For most contacts, the measured supercurrent is adequately described by the opposite contributions of two thermally populated Andreev bound states per conduction channel. However. far contacts containing an almost perfectly transmitted channel 0.9 less than or equal to tau less than or equal to 1 the measured supercurrent is higher than expected, a fact that Eve attribute to nonadiabatic transitions between hound states.