Neutron-Diffraction Measurements of an Antiferromagnetic Semiconducting Phase in the Vicinity of the High-Temperature Superconducting State of K${}_x$Fe${}_{2-y}$Se${}_2$

Abstract

The recently discovered K-Fe-Se high temperature superconductor has caused heated debate regarding the nature of its parent compound. Transport, angle-resolved photoemission spectroscopy, and STM measurements have suggested that its parent compound could be insulating, semiconducting or even metallic [M. H. Fang, H.-D. Wang, C.-H. Dong, Z.-J. Li, C.-M. Feng, J. Chen, and H. Q. Yuan, Europhys. Lett. 94, 27009 (2011); F. Chen et al. Phys. Rev. X 1, 021020 (2011); and W. Li et al.,Phys. Rev. Lett. 109, 057003 (2012)]. Because the magnetic ground states associated with these different phases have not yet been identified and the relationship between magnetism and superconductivity is not fully understood, the real parent compound of this system remains elusive. Here, we report neutron-diffraction experiments that reveal a semiconducting antiferromagnetic (AFM) phase with rhombus iron vacancy order. The magnetic order of the semiconducting phase is the same as the stripe AFM order of the iron pnictide parent compounds. Moreover, while the root5*root5 block AFM phase coexists with superconductivity, the stripe AFM order is suppressed by it. This leads us to conjecture that the new semiconducting magnetic ordered phase is the true parent phase of this superconductor.

1 table, 4 figures,5 pages

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• Phase diagram of (Li1-xFex)OHFeSe: a bridge between iron selenide and arsenide superconductors
• Structure, magnetic order and excitations in the 245 family of Fe-based superconductors
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Superconductivity and phase instability of NH3-free Na-intercalated FeSe1-zSz
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• Quantum Monte Carlo Study of Pairing Symmetry and Correlation in Iron-based Superconductors
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• Orbital-dependent effects of electron correlations in microscopic models for iron-based superconductors
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• Two spatially separated phases in semiconducting Rb${}_{0.8}$Fe${}_{1.5}$S${}_2$
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• Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides
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• Annealing Effect on Microstructure and Superconductivity of KxFeySe2 Synthesized by an Easy One-step Method
• Suppression of the antiferromagnetic order when approaching the superconducting state in a phase-separated crystal of K${}_x$Fe${}_{2-y}$Se${}_2$
• Paramagnetic spin excitations in insulating Rb${}_{0.8}$Fe${}_{1.6}$Se${}_2$
• Indirect K-edge bimagnon resonant inelastic X-ray scattering spectrum of $\alpha$-FeTe
• Spin fluctuations and pairing symmetry in A${}_x$Fe${}_{2-y}$Se${}_2$: dual effect of the itinerant and the localized nature of electrons
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