Shapiro Steps and Microwave Tunable Diode Effect in Novel Josephson Junctions

The discovery of materials with non-trivial topological properties has led to the realization of novel Josephson junctions with anomalous properties. In particular, it has been proposed that in some conditions such junctions can be in a superconducting topological state. In this work we present results for Josephson junctions based on three different heterostructures: Al/InAs, W/BiSb, and Al/Cd₃As₂. Junctions based on each of these heterostructures are predicted to have unique properties, and can in principle be tuned into a topological state, due to the fact that InAs has a very strong spin-orbit coupling, BiSb is a topological insulator, and Cd₃As₂ is a Dirac semimetal. We show how features of the Shapiro steps of the current-voltage characteristic under microwave radiation can be used, in realistic conditions, to extract detailed information on the microscopic electronic properties of the junctions, such as their topological state, and the presence of Leggett modes in the superconducting leads. We then discuss how in SQUIDs formed by some of the studied Josephson junctions a microwave-tunable diode effect might be present.