Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor $\mathrm{FeTe}_{0.55}\mathrm{Se}_{0.45}$

摘要: By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor $\mathrm{FeTe}_{0.55}\mathrm{Se}_{0.45}$, a material that exhibits signatures of topological superconductivity, Majorana bound at vortex cores or impurity locations. We use superconducting STM tip for enhanced energy resolution, which enables us to show can be tuned through Fermi level with varying tip-sample distance. state is Yu-Shiba-Rusinov (YSR) type, argue shift caused by low superfluid density allows electric field slightly penetrate sample. model newly introduced tip-gating scenario within single-impurity Anderson good agreement experimental data.