Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe<sub>0.55</sub>Se<sub>0.45</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33436594.
- Also identified by DOI 10.1038/s41467-020-20529-x and PMC identifier 7804303.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe<sub>0.55</sub>Se<sub>0.45</sub>, 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<sub>0.55</sub>Se<sub>0.45</sub>, 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.