Orbital-dependent effects of electron correlations in microscopic models for iron-based superconductors

Abstract

The bad metal behavior in the normal state of the iron-based superconductors suggests an intimate connection between the superconductivity and a proximity to a Mott transition. At the same time, there is strong evidence for the multi-orbital nature of the electronic excitations. It is then important to understand the orbital-dependent effects of electron correlations. In this paper we review the recent theoretical progresses on the metal-to-insulator transition in multiorbital models for the iron-based superconductors. These include studies of models that contain at least the 3d xy and 3d xz/yz models, using a slave-spin technique. For commensurate filling corresponding to that of the parent iron pnictides and chalcogenideds, a Mott transition generally exists in all these models. Near the Mott transition, a strongly correlated metal exhibiting bad metal features and strong orbital selectivity is stabilized due to the interplay of Hund's coupling and orbital-degeneracy breaking. Particularly for the alkaline iron selenides, the ordered vacancies effectively reduce the kinetic energy, thereby pushing the system further into the Mott-insulating regime; in the metallic state, there exists an orbital-selective Mott phase in which the iron 3d xy orbital is Mott localized while the other 3d orbitals are still itinerant. An overall phase diagram for the alkaline iron selenides has been proposed, in which the orbital-selective Mott phase connects between the superconducting phase and the Mott-insulating parent state.

20 pages, 7 figures, to appear in a special issue of Current Opinion in Solid State & Materials Science on "Fe-based superconductors"

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Cited by in corpus (19)

• High Temperature Superconductivity in Iron Pnictides and Chalcogenides
• Orbital-selective superconductivity, gap anisotropy and spin resonance excitations in a multiorbital t-J1-J2 model for iron pnictides
• Quantum criticality in AFe2As2 with A = K, Rb, and Cs suppresses superconductivity
• A Mott insulator continuously connected to iron pnictide superconductors
• Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides
• Orbital selectivity in electron correlations and superconducting pairing of iron-based superconductors
• Temperature-induced band selective localization and coherent-incoherent crossover in single-layer FeSe/Nb:BaTiO3 /KTaO3
• Nearly-critical spin and charge fluctuations in KFe2As2 observed by high-pressure NMR
• Broken mirror symmetry, incommensurate spin correlations, and $B_{2g}$ nematic order in iron pnictides
• Evolution of quasiparticle excitations with critical mass enhancement in superconducting AFe2As2 (A = K, Rb, and Cs)
• Breakdown of single spin-fluid model in heavily hole-doped superconductor CsFe2As2
• Genuine Electronic Structure and Superconducting Gap Structure in (Ba${}_{0.6}$K${}_{0.4}$)Fe${}_2$As${}_2$ Superconductor
• Orbital-selective bad metals due to Hund's rule and orbital anisotropy: a finite-temperature slave-spin treatment of the two-band Hubbard model
• Emergence of Superconductivity from Fully Incoherent Normal State in an Iron-Based Superconductor (Ba${}_{0.6}$K${}_{0.4}$)Fe${}_2$As${}_2$
• Stripe Antiferromagnetism and Disorder in the Mott Insulator NaFe${}_{1-x}$Cu${}_x$As ($x\lesssim 0.5$)
• Emergent spin-glass state in the doped Hund's metal CsFe2As2
• Orbital-selective correlations and renormalized electronic structure in LiFeAs
• Toward the Mott state with Magnetic Cluster Formation in Heavily Cu-Doped NaFe${}_{1-x}$Cu${}_x$As
• Orbital-selective electron correlations in high-$T_{\mathrm{c}}$ bilayer nickelates: from a global phase diagram to implications for spectroscopy