Investigation of low-temperature <i>I</i>-<i>V</i> curves of high-quality Nb/Al-AlO<i>x</i>/Nb Josephson junctions

Abstract

A detailed experimental temperature dependence of the subgap current of high-quality Nb/Al-AlOx/Nb Josephson tunnel junctions is reported. The presence of a pronounced current rise at V≂Δ/e is observed. Comparison with the theoretical model for two-particle tunneling is performed, but a substantial disagreement is found. At V&amp;lt;Δ/e the measured current is in remarkably good agreement with the single particle tunneling predictions down to 2 K.