Original Title: Quantum transport in superconductor-semiconductor nanowire hybrid devices with axially built-in quantum dots as spectrometers

Abstract: 

The project is motivated by the recent excitement of the appearance of topological phases and Majorana bound states (MBSs) in semiconducting nanowires (NWs) with strong spin-orbit interaction (SOI) coupled to a superconductor (SC) in magnetic field. To unravel the emergence of MBSs in single and coupled NWs, we develop new probes with which the proximity gap and proximity-induced bound states can be quantified. Our approach is based on measuring both DC and AC transport, the latter also at GHz frequencies using reflectometry. As a complementary test, we can also study the microwave radiation in the GHz domain emitted by the quantum device. With the current project we aim to deepen our understanding of the superconductive proximity effect in a NW with strong SOI by studying the evolution of the gap spectroscopically. For the latter we exploit quantum dots (QDs) as spectrometers. Here, the QDs are established by heteroepitaxy during growth. This is done in collaboration with Prof. Lucia Sorba from CNR-Nano at Pisa, where the InAs NWs are grown (see figure). These QDs are very promising due to the large confinement potential. We further plan to test different SCs beyond Al, e.g. Pd and MoRe, and optimize the evaporation together with collaborators from the Niels-Bohr Institute in Copenhagen.

p.s. in the meantime the material system was changed to 2D InAs quantum proximitized from above by a thin Al layer. This material is provided by the Mafra group (Purdue Univ. USA).