New York University
Missing Shapiro steps in InAs-based Josephson junctions with epitaxial Al contacts
Semiconductor-based Josephson junction provide a platform to study the proximity effect and can serve as a platform for the realization of topological superconductivity. Recently our group has demonstrated the possibility to have a highly transparent contact between the superconductor and the semiconductor by combining InAs high mobility surface 2D-dimensional electron gases with epitaxially grown aluminium. The interplay between the induced superconducting gap and the spin-orbit coupling in those structure is still an on-going field of research. While DC measurements can allow to access the current-phase relation of those structure, some details could be masked by relaxation processes. We utilize microwave radiation on Josephson junctions to unmask the periodicity of the current phase relation. We study Shapiro steps that appear in the IV characteristic of a junction under microwave irradiation. Depending on the microwave frequency, we observe a rich set of features: suppression of odd steps, suppression of the first two steps, fractional steps at high frequency. In the absence of a magnetic field our junction are not expected to be topological and the origin of the observed signature is most likely related to Landau-Zener transitions in our InAs structures.
Pizza lunch: 12 - 12:30pm
Seminar: 12:30 - 1:30pm