Weak-link Josephson Junctions Made from Topological Crystalline Insulators

TL;DR

This paper demonstrates the fabrication of Josephson junctions using topological crystalline insulators, revealing unique AC Josephson effects linked to topologically nontrivial surface states, distinct from trivial materials.

Contribution

It introduces a method to create Josephson junctions with topological crystalline insulators and identifies novel AC Josephson phenomena associated with their surface states.

Findings

Rich subharmonic structure in AC Josephson effect for topological insulator junctions

Absence of such structure in trivial material junctions

Indication of topologically driven novel behavior in superconducting junctions

Abstract

We report on the fabrication of Josephson junctions using the topological crystalline insulator Pb$_{0.5}$Sn$_{0.5}$Te as the weak link. The properties of these junctions are characterized and compared to those fabricated with weak links of PbTe, a similar material yet topologically trivial. Most striking is the difference in the AC Josephson effect: junctions made with Pb$_{0.5}$Sn$_{0.5}$Te exhibit rich subharmonic structure consistent with a skewed current-phase relation. This structure is absent in junctions fabricated from PbTe. A discussion is given on the origin of this effect as an indication of novel behavior arising from the topologically nontrivial surface state.