Electron Correlation and Spin Dynamics in Iron Pnictides and Chalcogenides

Abstract

Superconductivity in the iron pnictides and chalcogenides is closely connected to a bad-metal normal state and a nearby antiferromagnetic order. Therefore, considerable attention has been focused on the role of electron correlations and spin dynamics. In this article, we summarize some key experiments that quite directly imply strong electron correlations in these materials, and discuss aspects of the recent theoretical studies on these issues. In particular, we outline a $w$-expansion, which treats the correlation effects using the Mott transition as the reference point. For the parent systems, it gives rise to an effective J1-J2 model that is coupled to the itinerant electrons in the vicinity of the Fermi energy; this model yields an isoelectronically-tuned quantum critical point, and allows a study of the distribution of the spin spectral weight in the energy and momentum space in the paramagnetic phase. Within the same framework, we demonstrate the Mott insulating phase in the iron oxychalcogenides as well as the alkaline iron selenides; for the latter system, we also consider the role of an orbital-selective Mott phase. Finally, we discuss the singlet superconducting pairing driven by the short-range J1-J2 interactions. Our considerations highlight the iron pnictides and chalcogenides as exemplifying strongly-correlated electron systems at the boundary of electronic localization and itinerancy.

v2. Discussion extended on several points, including the expected effect of the reduced/suppressed vacancy order on the spin spectral weight at temperatures above the Neel/structural transitions in the insulating alkaline iron selenides. 14 pages, 9 figures, to appear in the Proceedings of Materials and Mechanisms of Superconductivity Conference (M2S 2012, Washington D.C.)

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Cited by in corpus (8)

• Antiferromagnetic order and spin dynamics in iron-based superconductors
• Orbital selective pairing and gap structures of iron-based superconductors
• Electron pairing in the presence of incipient bands in iron-based superconductors
• Orbital-selective superconductivity, gap anisotropy and spin resonance excitations in a multiorbital t-J1-J2 model for iron pnictides
• Strong electronic correlations in iron pnictides: Comparison of the optical spectra for BaFe2As2-related compounds
• Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors
• Magnetic and Structural Properties of the Iron Oxychalcogenides La${}_2$O${}_2$Fe${}_2$O$M_2$ ($M$= S, Se)
• Anisotropic magnetic excitations of a frustrated bilinear-biquadratic spin model -- Implications for spin waves of detwinned iron pnictides