We’ve explored the proximity effect from superconducting niobium into topological insulators using ARPES and Josephson junction-based transport samples. While superconductivity penetrates via bulk carriers across a thin enough sample of Bi2Se3 which has bulk carriers to show up on the surface opposite a niobium substrate, in samples without bulk carriers no sign of superconductivity is observed there. This was done using the alloy (BiSb)Te3 for various Bi:Sb ratios, where the Fermi Energy can be tuned through the bulk gap so that it cuts only topological surface states. We have made Josephson junction nano-island arrays with both types of materials with the aim to make a topological superconductor capable of holding Majorana zero modes as suggested by Fu and Kane. Superconductivity occurs in both cases and without bulk carriers present the topological superconductivity is not contaminated by non-topological pairs. Interestingly, we see evidence for a small gap in the Josephson characteristics of the samples without bulk carriers
Recordings of Condensed Matter Seminar events can be found on mediaspace: https://mediaspace.illinois.edu/channel/Condensed%2BMatter%2BSeminar%2BTalks%2BFall%2B2020/178724052
