Josephson junctions (JJs) fabricated on a three-dimensional (3D) topological insulator (TI) can be used to probe signatures of Majorana bound states (MBSs) at Josephson vortices. In this talk, I will present our recent advancements for such observations using Corbino-geometry JJs fabricated on a single surface of a bulk-insulating 3D TI. We successfully fabricated high-quality Nb JJs on Sn-doped Bi1.1Sb0.9Te2S single crystals with extremely low bulk carrier concentrations, with their pristine surfaces preserved by Te films grown via molecular beam epitaxy. Utilizing different Corbino-style geometries enabled Josephson interferometry within a single junction, revealing the skewed current-phase relation of our highly transparent junctions. Strikingly, we observed a superconducting diode effect alternating its sign for even- and odd-fluxoid states. Our analysis attributes this phenomenon to a topological phase, with diode polarity directly reflecting the sign reversal in periodic boundary conditions for even/odd numbers of Josephson vortices. Lastly, I will discuss our latest efforts to probe the non-Abelian statistics of MBSs in Corbino–Josephson trijunction hybrid devices, where Josephson vortices can be exchanged, collided, and split.

Contact. Prof. Heung Sun Sim (hs_sim@kaist.ac.kr)