Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity

Abstract

The present article reviews recent experimental investigations of spin dynamics in iron-based superconductors and their parent compounds by means of inelastic neutron scattering. It mainly focuses on the most contemporary developments in this field, pertaining to the observations of magnetic resonant modes in new superconductors, spin anisotropy of low-energy magnetic fluctuations that has now been observed in a wide range of chemical compositions and doping levels, as well as their momentum-space anisotropy incurred by the spin-nematic order. The implications of these new findings for our understanding of the superconducting state, along with the remaining unsettled challenges for neutron spectroscopy, are discussed.

Invited review article for a focus issue of Comptes Rendus Physique: 40 pages, 22 figures, 389 references

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• Pseudo-Goldstone magnons in the frustrated S=3/2 Heisenberg helimagnet ZnCr2Se4 with a pyrochlore magnetic sublattice
• Non-Fermi-liquid behaviors associated with a magnetic quantum-critical point in Sr(Co{1-x}Ni{x})2As2 single crystals
• Rise and fall of shape resonances in thin films of BCS superconductors
• Enhanced moments of Eu in single crystals of the metallic helical antiferromagnet EuCo{2-y}As2
• Metallic behavior induced by potassium doping of the trigonal antiferromagnetic insulator EuMn2As2
• Spin resonance in the superconducting state of Li${}_{1-x}$Fe${}_x$ODFe${}_{1-y}$Se observed by neutron spectroscopy
• Local and collective magnetism of EuFe${}_2$As${}_2$
• Intra-layer doping effects on the high-energy magnetic correlations in NaFeAs
• Transition from sign-reversed to sign-preserved Cooper-pairing symmetry in sulfur-doped iron selenide superconductors
• Electron doping evolution of the magnetic excitations in NaFe${}_{1-x}$Co${}_x$As
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• Numerical Investigation of Spin Excitations in a Doped Spin Chain
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• Superconducting Order Parameters in overdoped BaFe${}_{1.86}$Ni${}_{0.14}$As${}_2$ Revealed by Multiple Andreev Reflection Spectroscopy of Planar Break-Junctions
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• Temperature and polarization dependence of low-energy magnetic fluctuations in nearly-optimal-doped NaFe${}_{0.9785}$Co${}_{0.0215}$As
• First-principles perspective on magnetic second sound
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• Effect of the additional Se layer on the electronic structure of iron-based superconductor FeSe/SrTiO${}_3$
• Direct observation of the spin exciton in Andreev spectroscopy of iron-based superconductors
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• Bogoliubov quasiparticles coupled to the antiferromagnetic spin mode in a vortex core
• Spin dynamics in itinerant antiferromagnet SrCr${}_2$As${}_2$
• Acoustic lattice instabilities at the magneto-structural transition in Fe${}_{1.057(7)}$Te
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