Spin-polarized Yu-Shiba-Rusinov states in an iron based superconductor

TL;DR

This study uses spin-resolved spectroscopy to investigate magnetic impurity states in an iron-based superconductor, revealing spin signatures of Yu-Shiba-Rusinov states and their relation to potential Majorana states.

Contribution

It provides the first spin-resolved measurements of YSR states in FeTe0.55Se0.45, distinguishing between finite-energy and zero-energy states and their spin properties.

Findings

Finite-energy YSR states exhibit opposite spin polarization.

Zero-energy bound states lack spin signature, indicating no Majorana states.

Spin signatures align with theoretical predictions for magnetic impurity states.

Abstract

Yu-Shiba-Rusinov (YSR) bound states appear when a magnetic atom interacts with a superconductor. Here, we report on spin-resolved spectroscopic studies of YSR states related with Fe atoms deposited on the surface of the topological superconductor FeTe0.55Se0.45 using a spin-polarized scanning tunneling microscope. We clearly identify the spin signature of pairs of YSR bound states at finite energies within the superconducting gap having opposite spin polarization as theoretically predicted. In addition, we also observe zero-energy bound states for some of the adsorbed Fe atoms. In this case, a spin signature is found to be absent indicating the absence of Majorana bound states associated with Fe adatoms on FeTe0.55Se0.45.