Observation of the superconducting proximity effect in the surface state of SmB6 thin films

TL;DR

This paper demonstrates the superconducting proximity effect in the surface state of SmB6 thin films with bulk insulation, revealing high interface transparency and enabling exploration of exotic quantum phenomena in topological insulator-superconductor systems.

Contribution

It provides the first clear observation of the proximity effect in SmB6 surface states, highlighting the importance of high interface transparency for topological superconductor research.

Findings

Superconducting proximity effect observed in SmB6 surface states.

Fermi velocity in the surface state is approximately 10^5 m/s.

High transparency interfaces are crucial for the proximity effect.

Abstract

The proximity effect at the interface between a topological insulator (TI) and a superconductor is predicted to give rise to chiral topological superconductivity and Majorana fermion excitations. In most TIs studied to date, however, the conducting bulk states have overwhelmed the transport properties and precluded the investigation of the interplay of the topological surface state and Cooper pairs. Here, we demonstrate the superconducting proximity effect in the surface state of SmB6 thin films which display bulk insulation at low temperatures. The Fermi velocity in the surface state deduced from the proximity effect is found to be as large as 10^5 m/s, in good agreement with the value obtained from a separate transport measurement. We show that high transparency between the TI and a superconductor is crucial for the proximity effect. The finding here opens the door to investigation of exotic quantum phenomena using all-thin-film multilayers with high-transparency interfaces.