Impurity-induced bound states inside the superconducting gap of FeSe

Abstract

We investigate the local density of states in the vicinity of a native dumbbell defect arising from an Fe vacancy in FeSe single crystals. The tunneling spectra close to the impurity display two bound states inside the superconducting gap, equally spaced with respect to zero energy but asymmetric in amplitude. Using spin-polarized density functional theory (DFT) calculations on realistic slab models with Fe vacancy, we show that such a defect does not induce a local magnetic moment. Therefore, the dumbbell defect is considered as non-magnetic. Thus, the in-gap bound states emerging from a non-magnetic defect-induced pair-breaking suggest a sign changing pairing state in this material.

arXiv comment8 pages, 6 figures

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• Vortex-lattice melting and paramagnetic depairing in the nematic superconductor FeSe
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• Impact of topology on the impurity effects in extended $s$-wave superconductors with spin-orbit coupling
• Influence of disorder on the signature of pseudogap and multigap superconducting behavior in FeSe
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• Disorder-sensitive node-like small gap in FeSe
• Stoichiometry and defect superstructures in epitaxial FeSe films on SrTiO3
• The study of intrinsic defect state of FeSe with scanning tunneling microscopy
• Impurity induced magnetic ordering in Sr${}_2$RuO${}_4$
• Atomic-scale analysis of disorder by similarity learning from tunneling spectroscopy
• Impact of Disorder on the Superconducting Properties and BCS-BEC Crossover in FeSe Single Crystals