Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45

Journal article (2021)

Authors

Damianos Chatzopoulos Universiteit Leiden
Doohee Cho Yonsei University, Universiteit Leiden
Koen M. Bastiaans Universiteit Leiden
Gorm O. Steffensen University of Copenhagen
D. Bouwmeester QN/van der Zant Lab - AS , Universiteit Leiden, Kavli institute of nanoscience Delft
Alireza Akbari Max Planck Institute for Chemical Physics of Solids
Genda Gu Brookhaven National Laboratory
Jens Paaske University of Copenhagen
Brian M. Andersen University of Copenhagen
Milan P. Allan Universiteit Leiden
Research Group
QN/van der Zant Lab (AS) (TU Delft)
Copyright: © 2021 Damianos Chatzopoulos, Doohee Cho, Koen M. Bastiaans, Gorm O. Steffensen, D. Bouwmeester, Alireza Akbari, Genda Gu, Jens Paaske, Brian M. Andersen, Milan P. Allan
DOI: https://doi.org/10.1038/s41467-020-20529-x
More Info
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Published Date

2021

Language

English

Faculty

Applied Sciences

Department

QN/Quantum Nanoscience

Research Group

QN/van der Zant Lab

Abstract

By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe0.55Se0.45, a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTe0.55Se0.45, which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.