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arXiv · 1402.3714

Identifying the `Fingerprint' of Antiferromagnetic Spin-Fluctuations on Iron-Pnictide Superconductivity

Milan P. Allan·Kyungmin Lee·Andreas W. Rost·Mark H. Fischer·Freek Massee·Kunihiro Kihou·Chul-Ho Lee·Akira Iyo·Hiroshi Eisaki·Tien-Ming Chuang·J. C. Davis·Eun-Ah Kim
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Abstract

Cooper pairing in the iron-based high-Tc superconductors is often conjectured to involve bosonic fluctuations. Among the candidates are antiferromagnetic spin-fluctuations and d-orbital fluctuations amplified by phonons. Any such electron-boson interaction should alter the electron's `self-energy', and then become detectable through consequent modifications in the energy dependence of the electron's momentum and lifetime. Here we introduce a theoretical/experimental approach aimed at identifying the relevant fluctuations of iron-based superconductors by measuring effects of their self-energy. We use quasiparticle interference (QPI) imaging techniques in LiFeAs to reveal strongly momentum-space anisotropic self-energy signatures that are focused along the Fe-Fe (interband scattering) direction, where the spin fluctuations of LiFeAs are concentrated. These effects coincide in energy with perturbations to the density-of-states N(ω) usually associated with the Cooper pairing interaction. We show that all the measured phenomena comprise the predicted QPI `fingerprint' of a self-energy due to antiferromagnetic spin-fluctuations, thereby distinguishing them as the predominant electron-boson interaction.

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Milan P. Allan, Kyungmin Lee, Andreas W. Rost, Mark H. Fischer, Freek Massee, Kunihiro Kihou, Chul-Ho Lee, Akira Iyo, Hiroshi Eisaki, Tien-Ming Chuang, J. C. Davis, Eun-Ah Kim. 2014-10-19. Identifying the `Fingerprint' of Antiferromagnetic Spin-Fluctuations on Iron-Pnictide Superconductivity. https://doi.org/10.1038/nphys3187

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