Influence of Topological Edge States on the Properties of Al/Bi2Se3/Al Hybrid Josephson Devices

TL;DR

This study demonstrates ballistic topological edge state transport in Al/Bi2Se3/Al Josephson junctions, providing insights into Majorana fermions and the influence of edge states on superconducting properties.

Contribution

It provides systematic evidence of ballistic edge state transport in topological insulator-based Josephson junctions, highlighting the role of topological edge states in superconducting behavior.

Findings

Evidence of ballistic transport through topological edge states.

Bulk effects influence only normal transport, not edge states.

Signature of 2D Dirac electron transport in Bi2Se3 flakes.

Abstract

In superconductor-topological insulator-superconductor hybrid junctions, the barrier edge states are expected to be protected against backscattering, to generate unconventional proximity effects, and, possibly, to signal the presence of Majorana fermions. The standards of proximity modes for these types of structures have to be settled for a neat identification of possible new entities. Through a systematic and complete set of measurements of the Josephson properties we find evidence of ballistic transport in coplanar Al-Bi2Se3-Al junctions that we attribute to a coherent transport through the topological edge state. The shunting effect of the bulk only influences the normal transport. This behavior, which can be considered to some extent universal, is fairly independent of the specific features of superconducting electrodes. A comparative study of Shubnikov - de Haas oscillations and Scanning Tunneling Spectroscopy gave an experimental signature compatible with a two dimensional electron transport channel with a Dirac dispersion relation. A reduction of the size of the Bi2Se3 flakes to the nanoscale is an unavoidable step to drive Josephson junctions in the proper regime to detect possible distinctive features of Majorana fermions.