Appearance of above the gap resonances in dirty Josephson junctions with epitaxial contact*

In Josephson junctions, when the separation of the superconducting contacts is made long enough, the system can be approximated with two superconducting-normal metal junctions connected with a normal link. In devices fabricated on InAs-Al materials, we observe oscillations of conductance with driving bias above the superconducting gap. The frequency of conductance oscillations as a function of the bias is determined by the geometric properties of the junction. We interpret these geometric oscillations (GO) in interference of quasi-particles with energies above the superconductivity gap. This can be compared with a simple quantum mechanical problem involving a particle in the box where the states with energy above the box wall solely gain a phase shift as they pass over the box potential. In the case of GO the variation of the superconducting gap size affect the phase of the quasi-particles as they pass through. We compare our data with our theoretical model and find agreement in dependence of the data to bias, magnetic field and temperature.