Topological Josephson Junctions on Magnetically-Doped Topological Insulators*

Topological superconductors (TSCs) hosting Majorana fermions at their edges have been a topic of intense debate in condensed matter physics. A large number of experimental trials to detect the evidence of TSCs have been performed using topological Josephson junctions composed of nanowires and topological insulators (TIs). In contrast to successful observation of the signatures of TSCs in InSb nanowires, the results are rather unclear in 3D TI junctions so far.
Here we present transport properties of a topological Josephson junction fabricated on a magnetically-doped 3D TI with high insulating properties in the bulk. We expect that the amplitude of the p-wave component in the proximity-induced superconductivity is enhanced by the magnetic moment due to the doping. In fact, three types of distinct features: anomalous temperature dependence of critical currents, the zero-bias conductance peaks, and dominant 4π-periodic Josephson supercurrent without conventional Shapiro-steps in microwave responses, suggest the dominant p-wave component in the proximity effect. Therefore, the Josephson junction on magnetic 3D TIs is a promising platform to investigate the basic physics of the TSCs.