ETD

• scanning gate microscopy
• semiconductor-superconductor hybrids
• superconductivity

In this Master’s thesis work we report the first Scanning Gate Microscopy experiments on superconducting weak links, demonstrating the possibility of manipulating the supercurrent flow across a semiconductor-superconductor heterostructure through the charged tip of an atomic force microscope at a local level. To this end, we have employed a new generation of Nb-contacted ballistic InSb nanoflag-based Josephson junctions. We performed a full magneto-transport characterization of these devices at 300mK. Fully gate-tunable Josephson effect as well as larger switching currents with respect to the previous Nb/Ti contact design have been observed. Furthermore, we report evidence of fully developed Fraunhofer side lobes, as well as observation of Multiple Andreev Reflections, demonstrating the high transparency of the superconductor/semiconductor
interfaces. Scanning Gate Microscopy measurements on superconducting junctions clearly show tip-induced modulation of critical current due to the local charge carrier depletion of the semiconducting region. Our experimental findings are consistent with theoretical simulations and establish a new way of investigating the behavior of superconducting weak links, with a view to supercurrent flow imaging and local investigation of topological samples.