Anomalous superconducting state in LiFeAs implied by the ${}^{75}$As Knight shift measurement

Abstract

${}^{75}$As NMR investigation of a single crystal of superconducting LiFeAs is presented. The Knight shift and the \textit{in situ} ac susceptibility measurements as a function of temperature and external field are indicative of two superconducting (SC) transition temperatures, each of which is associated with its own upper critical field. Strikingly, the Knight shift maintains its normal state value over a temperature range in the SC state before it drops abruptly being consistent with spin-singlet pairing. Together with our previous NMR study, the anomalous SC state featured by the constant Knight shift is attributed to the extremely sensitive SC properties of LiFeAs, probably stemming from its proximity to a critical instability.

The title and text were modified; accepted in J. Physics: Condensed matter

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Cited by in corpus (12)

• Superconductivity from emerging magnetic moments
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference
• Spin-Fluctuation-Induced Non-Fermi-Liquid Behavior with suppressed superconductivity in LiFe${}_{1-x}$Co${}_x$As
• Incommensurate antiferromagnetic fluctuations in single-crystalline LiFeAs studied by inelastic neutron scattering
• Hedgehog Spin-vortex Crystal Antiferromagnetic Quantum Criticality in CaK(Fe1-xNix)4As4 Revealed by NMR
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• Towards a Microscopic Theory of the Knight Shift in an Anisotropic, Multiband Type-II Superconductor