Unexpected superconductivity at nanoscale junctions made on the topological crystalline insulator Pb$_{0.6}$Sn$_{0.4}$Te

TL;DR

This paper reports the discovery of a localized, high-temperature superconducting phase induced by point-contacts on the surface of a topological crystalline insulator, Pb$_{0.6}$Sn$_{0.4}$Te, revealing new physics in topological materials.

Contribution

It demonstrates that nanoscale point-contacts can induce superconductivity in topological crystalline insulators, a novel finding in the field.

Findings

Superconductivity is locally induced under point-contacts.

The induced superconducting phase has a transition temperature between 3.7 K and 6.5 K.

Superconductivity occurs as a nano-droplet on the surface of Pb$_{0.6}$Sn$_{0.4}$Te.

Abstract

Discovery of exotic phases of matter from the topologically non-trivial systems not only makes the research on topological materials more interesting but also enriches our understanding of the fascinating physics of such materials. Pb$_{0.6}$Sn$_{0.4}$Te was recently shown to be a topological crystalline insulator. Here we show that by forming a mesoscopic point-contact using a normal non-superconducting elemental metal on the surface of Pb$_{0.6}$Sn$_{0.4}$Te a novel superconducting phase is created locally in a confined region under the point-contact. This happens while the bulk of the sample remains to be non-superconducting and the superconducting phase emerges as a nano-droplet under the point-contact. The superconducting phase shows a high transition temperature $T_c$ that varies for different point-contacts and falls in a range between 3.7 K and 6.5 K. Therefore, this Letter presents the discovery of a new superconducting phase on the surface of a topological crystalline insulator and the discovery is expected to shed light on the mechanism of induced superconductivity in topologically non-trivial systems in general.