Spin fluctuations & superconducting pairing in new iron-based systems

Alice Taylor (University of Oxford)

The iron-based superconductors discovered in 2008 present a new test bed for understanding unconventional superconductivity. It is widely believed that magnetic fluctuations are intimately linked to the superconducting mechanism, but there is currently no complete understanding of the microscopic origin of magnetism or of its detailed relationship with superconductivity in these materials.

Inelastic neutron scattering is a key tool for unraveling the interactions in iron-based superconductors. In this talk I will focus on the magnetic resonance feature that is observed in the inelastic neutron scattering spectrum of these systems below Tc. I will explain how this feature sheds light on the links between magnetism and superconductivity, and focus on new insights gained by studying the recently discovered materials Cs(x)Fe2Se2[1] and molecular-intercalated FeSe [2]. I show evidence that in both these materials the magnetic resonance occurs at the wave vector (0.5, 0.25), and explain the significance of this result in terms of the superconducting pairing symmetry.

[1] A. E. Taylor et al., Phys. Rev. B, 86, 094528, (2012). [2] A. E. Taylor et al., arXiv:1305.4898, accepted for publication in PRB Rapid Comm.

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