In-gap Bound States Induced by Interstitial Fe Impurities in Iron-based Superconductors

Abstract

Based on a two-orbit four-band tight binding model, we investigate the low-lying electronic states around the interstitial excess Fe ions in the iron-based superconductors by using T-matrix approach. It is shown that the local density of states at the interstitial Fe impurity (IFI) possesses a strong resonance inside the gap, which seems to be insensitive to the doping and the pairing symmetry in the Fe-Fe plane, while a single or two resonances appear at the nearest neighboring (NN) Fe sites. The location and height of the resonance peaks only depend on the hopping $t$ and the pairing parameter ${\Delta }_I$ between the IFI and the NN Fe sites. These in-gap resonances are originated in the Andreev's bound states due to the quasiparticle tunneling through the IFI, leading to the change of the magnitude of the superconducting order parameter. When both $t$ and ${\Delta }_I$ are small, this robust zero-energy bound state near the IFI is consistent with recent scanning tunneling microscopy observations.

4 pages, 5 figures

References in corpus (20)

• Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeO${}_{1-x}$F${}_x$FeAs
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Superconductivity at 25 K in hole doped $(L{a}_{1-x}S{r}_x)OFeAs$
• A minimal two-band model for the superconducting Fe-pnictides
• Electronic structure of the iron-based superconductor LaOFeP
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Observation of a Robust Zero-energy Bound State in Iron-based Superconductor Fe(Te,Se)
• Spin-triplet p-wave pairing in a 3-orbital model for iron pnictide superconductors
• Momentum dependence of the superconducting gap in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Superconducting gap symmetry of Ba0.6K0.4Fe2As2 studied by angle-resolved photoemission spectroscopy
• (pi,pi)-electronic order in iron arsenide superconductors
• Observation of Lattice and Andreev Bound States of Vortices in Ba0.6K0.4Fe2As2 Single Crystals with Scanning Tunneling Microscopy/Spectroscopy
• Electronic structure of heavily electron-doped BaFe${}_{1.7}$Co${}_{0.3}$As${}_2$ studied by angle-resolved photoemission
• Homogeneous vs. inhomogeneous coexistence of magnetic order and superconductivity probed by NMR in Co and K doped iron pnictides
• Bound States of Defects in Superconducting LiFeAs Studied by Scanning Tunneling Spectroscopy
• Domain Walls in Normal and Superconducting States of Iron Pnictides
• Magnetic domain walls induced by twin boundaries in low doped Fe-pnictides

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• Tunneling interstitial impurity in iron-chalcogenide based superconductors
• Edge states and local electronic structure around an adsorbed impurity in a topological superconductor
• Zero Energy Bound States on Nano Atomic Line Defect in Iron-based High Temperature Superconductors
• Nesting-induced Local Electronic Patterns around a Single As (Te, Se) Vacancy in Iron-based Superconductors