Na2IrO3 as a spin-orbit-assisted antiferromagnetic insulator with a 340 meV gap

Abstract

We study Na2IrO3 by ARPES, optics, and band structure calculations in the local-density approximation (LDA). The weak dispersion of the Ir 5d-t2g manifold highlights the importance of structural distortions and spin-orbit coupling (SO) in driving the system closer to a Mott transition. We detect an insulating gap Δ_gap = 340 meV which, at variance with a Slater-type description, is already open at 300 K and does not show significant temperature dependence even across T_N ~ 15 K. An LDA analysis with the inclusion of SO and Coulomb repulsion U reveals that, while the prodromes of an underlying insulating state are already found in LDA+SO, the correct gap magnitude can only be reproduced by LDA+SO+U, with U = 3 eV. This establishes Na2IrO3 as a novel type of Mott-like correlated insulator in which Coulomb and relativistic effects have to be treated on an equal footing.

Accepted in Physical Review Letters. Auxiliary and related material can be found at: http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/articles.html

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• Kitaev-Heisenberg Hamiltonian for High-Spin $d^7$ Mott Insulators
• Monte Carlo study of an unconventional superconducting phase in Ir-oxide J_{eff}=1/2 Mott insulators induced by carrier doping
• Importance of anisotropic exchange interactions in honeycomb iridates. Minimal model for zigzag antiferromagnetic order in Na${}_2$IrO${}_3$
• Spin-orbit physics of j=1/2 Mott insulators on the triangular lattice
• Spiral order in the honeycomb iridate Li2IrO3
• Theory of Magnetic Phase Diagrams in Hyperhoneycomb and Harmonic-honeycomb Iridates
• Unified theory of spiral magnetism in the harmonic-honeycomb iridates α, β, γ Li2IrO3
• Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects
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• Confinement-Deconfinement Transition as an Indication of Spin-Liquid-Type Behavior in Na${}_2$IrO${}_3$
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• Emergent ultrafast phenomena in correlated oxides and heterostructures
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• Analysis of the optical conductivity for A2IrO3 (A = Na, Li) from first principles
• Probing spinon nodal structures in three-dimensional Kitaev spin liquids
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• Electronic excitations and structure of Li2IrO3 thin films grown on ZrO${}_2$:Y (001) substrates
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• Frustration and Entanglement in Compass and Spin-Orbital Models
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• Thermal conductivity of local moment models with strong spin-orbit coupling
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• Topological property of a $t_{2g}^5$ system with a honeycomb lattice structure
• Experimental percolation studies of two-dimensional honeycomb lattice: Li2Mn1-xTixO3