Impurity states and cooperative magnetic order in Fe-based superconductors

Abstract

We study impurity bound states and impurity-induced order in the superconducting state of LiFeAs within a realistic five-band model based on the band structure and impurity potentials obtained from density functional theory. In agreement with recent experiments, we find that Co impurities are too weak to produce subgap bound states, whereas stronger impurities like Cu do. We also obtain the bound-state spectrum for magnetic impurities, such as Mn, and show how spin-resolved tunneling may determine the nature of the various defect sites in iron pnictides, a prerequisite for using impurity bound states as a probe of the ground-state pairing symmetry. Lastly, we show how impurities pin both orbital and magnetic order, providing an explanation for a growing set of experimental evidence for unusual magnetic phases in doped iron pnictides.

Source-reported materials — not catalogue approval

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