Yu-Shiba-Rusinov bound states versus topological edge states in Pb/Si(111)

TL;DR

This study uses STM/STS to compare in-gap states from magnetic impurities in Pb/Si(111) in ordered and disordered phases, demonstrating that certain in-gap states have a topological origin, relevant for understanding Majorana fermions.

Contribution

It provides experimental evidence distinguishing topological from non-topological in-gap states in a superconductor using phase-dependent spectroscopic analysis.

Findings

In-gap states around magnetic clusters in disordered Pb/Si(111) are topological.

Comparison between ordered and disordered phases reveals phase-dependent spectroscopic features.

The results help clarify the origin of zero-bias peaks related to Majorana fermions.

Abstract

There is presently a tremendous activity around the field of topological superconductivity and Majorana fermions. Among the many questions raised, it has become increasingly important to establish the topological or non-topological origin of features associated with Majorana fermions such as zero-bias peaks. Here, we compare in-gap features associated either with isolated magnetic impurities or with magnetic clusters strongly coupled to the atomically thin superconductor Pb/Si(111). We study this system by means of scanning tunneling microscopy and spectroscopy (STM/STS). We take advantage of the fact that the Pb/Si(111) monolayer can exist either in a crystal-ordered phase or in an incommensurate disordered phase to compare the observed spectroscopic features in both phases. This allows us to demonstrate that the strongly resolved in-gap states we found around the magnetic clusters in the disordered phase of Pb have a clear topological origin.