Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe_0.55Se_0.45

Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe_0.55Se_0.45

Chatzopoulos, Damianos (Universiteit Leiden)
Cho, Doohee (Universiteit Leiden; Yonsei University)
Bastiaans, Koen M. (Universiteit Leiden)
Steffensen, Gorm O. (University of Copenhagen)
Bouwmeester, D. (TU Delft QN/van der Zant Lab; Universiteit Leiden; Kavli institute of nanoscience Delft)
Akbari, Alireza (Max Planck Institute for Chemical Physics of Solids)
Gu, Genda (Brookhaven National Laboratory)
Paaske, Jens (University of Copenhagen)
Andersen, Brian M. (University of Copenhagen)
Allan, Milan P. (Universiteit Leiden)

2021

By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe_0.55Se_0.45, 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 FeTe_0.55Se_0.45, 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.

http://resolver.tudelft.nl/uuid:b24aef9f-3c39-4218-9958-99108194b925

https://doi.org/10.1038/s41467-020-20529-x

2041-1723

Nature Communications, 12 (1)

Institutional Repository

journal article

© 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