Mott Transition in Multi-Orbital Models for Iron Pnictides

Abstract

The bad-metal behavior of the iron pnictides has motivated a theoretical description in terms of a proximity to Mott localization. Since the parent compounds of the iron pnictides contain an even number of 3d-electrons per Fe, it is important to determine whether a Mott transition robustly exists and the nature of the possible Mott insulating phases. We address these issues in a minimal two-orbital model and a more realistic four-orbital model for the parent iron pnictides using a slave-spin approach. In the two-orbital model with two electrons per Fe, we identify a transition from metal to Mott insulator. The critical coupling, $U_c$, is greatly reduced by the Hund's coupling. Depending on the ratio between the inter- and intra-orbital Coulomb repulsions, the insulating state can be either a spin-Mott insulator or an orbital-Mott insulator. In the four-orbital model with four electrons per Fe, we find an orbitally selective metal-to-insulator transition in the case of zero Hund's coupling; the transition to a Mott insulator in the $xz$ and $yz$ orbitals takes place at the same critical coupling as the transition to a band insulator in the $xy$ and $x^2-y^2$ orbitals. In the presence of a finite Hund's coupling, however, the localization transition is into a spin-Mott state.

12 pages, 11 figures, to appear in Phys. Rev. B

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• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
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• Experimental Observation of Incoherent-Coherent Crossover and Orbital Dependent Band Renormalization in Iron Chalcogenide Superconductors
• Microscopic nature of correlations in multi-orbital AFe2As2 (A=K, Rb, Cs): Hund's coupling versus Coulomb repulsion
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• Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides
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• Tuning a Strain-Induced Orbital Selective Mott Transition in Epitaxial VO${}_2$
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• Orbital-dependent effects of electron correlations in microscopic models for iron-based superconductors
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• Electron Correlation and Spin Dynamics in Iron Pnictides and Chalcogenides
• Orbital-selective bad metals due to Hund's rule and orbital anisotropy: a finite-temperature slave-spin treatment of the two-band Hubbard model
• Revisit of Antiferromagnetism in Hubbard Model by A Cluster Slave-Spin Method
• Two-Fluid Description for Iron-Based Superconductors
• Orbital-selective correlations and renormalized electronic structure in LiFeAs
• Influence of electronic correlations on orbital polarizations in the parent and doped iron pnictides
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• Semiconductor of spinons: from Ising band insulator to orthogonal band insulator
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• Comment on "Z2-slave-spin theory for strongly correlated fermions" + Reply to the Reply to the "Comment on ?Z2-slave-spin theory for strongly correlated" fermions?
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