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

Abstract

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, 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 ${\mathrm{FeTe}}_{0.55}{\mathrm{Se}}_{0.45}$, 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.

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• Direct Transport between Superconducting Subgap States in a Double Quantum Dot
• Single-electron charge transfer into putative Majorana and trivial modes in individual vortices
• Nanoscale Control of Quantum States in Radical Molecules on Superconducting Pb(111)
• Yu-Shiba-Rusinov states in 2D superconductors with arbitrary Fermi contours
• Exactly solving the Kitaev chain and generating Majorana-zero-modes out of noisy qubits
• Observation of robust zero-energy state and enhanced superconducting gap in a tri-layer heterostructure of MnTe/Bi2Te3/Fe(Te, Se)
• Tracking a Spin-Polarized Superconducting Bound State across a Quantum Phase Transition
• Diamagnetic property and optical absorption in conventional superconductors with magnetic impurities
• Observation of Yu-Shiba-Rusinov-like states at the edge of CrBr3/NbSe2 heterostructure
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• Shiba states in systems with density of states singularities
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• Direct visualization of quasiparticle concentration around superconducting vortices
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• Control of nonreciprocal charge transport in topological insulator/superconductor heterostructures with Fermi level tuning and superconducting-layer thickness
• Signatures of Amorphous Shiba State in FeTe${}_{0.55}$Se${}_{0.45}$
• Direct observation of intrinsic surface magnetic disorder in amorphous superconducting films
• Visualizing Pair-breaking Scattering Interference in Bulk FeSe
• Dual Enhancement of Superconductivity in FeSe/SrTiO3 via Orbital and Correlation Synergy