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arXiv · 1204.4471

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

R. Comin·G. Levy·B. Ludbrook·Z. -H. Zhu·C. N. Veenstra·J. A. Rosen·Yogesh Singh·P. Gegenwart·D. Stricker·J. N. Hancock·D. van der Marel·I. S. Elfimov·A. Damascelli
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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.

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R. Comin, G. Levy, B. Ludbrook, Z. -H. Zhu, C. N. Veenstra, J. A. Rosen, Yogesh Singh, P. Gegenwart, D. Stricker, J. N. Hancock, D. van der Marel, I. S. Elfimov, A. Damascelli. 2012-11-12. Na2IrO3 as a spin-orbit-assisted antiferromagnetic insulator with a 340 meV gap. https://doi.org/10.1103/physrevlett.109.266406

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