Quantum electrical transport and superconducting proximity effects in topological Dirac materials

Abstract

Topological materials are characterized by their unique band topology, which guarantees the existence of topologically protected conducting states at edges or surfaces. When interfaced with conventional superconductors, these materials can realize engineered topological superconductivity capable of hosting Majorana zero modes (MZMs). MZMs are fundamental building blocks for fault-tolerant topological quantum computation due to their non-Abelian statistics and topological protection. However, experimental confirmation of MZMs remains challenging, as reported signatures of MZMs have been shown to be mimicked by non-topological origins. This thesis investigates topological superconductivity in the Josephson junctions made of topological materials and conventional superconductors, focusing on establishing reliable experimental signatures of MZMs in Josephson junctions. Prior to investigation of topological superconductivity, the experimental characterizations of Josephson junctions demonstrates high-quality proximity-induced superconductivity with showing clear Josephson effects. We have investigated systematically various signatures of MZMs such as node lifting in Fraunhofer pattern, first Shapiro step missing, and bimodal switching current distribution behaviors using nano-hybrid Josephson junctions. In conclusion, we suggest the complementary measurements of bimodal switching current distribution and first Shapiro step missing as a reliable method to probe the existence of MZMs in topological Josephson junctions.