Two iridates, two models, and two approaches: A comparative study on magnetism in three-dimensional honeycomb materials

Eric Kin-Ho Lee, Jeffrey G. Rau, and Yong Baek Kim
Phys. Rev. B 93, 184420 – Published 17 May 2016

Abstract

Two recent theoretical works studied the role of Kitaev interactions in the newly observed incommensurate magnetic order in the hyper-honeycomb (βLi2IrO3) and stripy-honeycomb (γLi2IrO3) iridates. Each of these works analyzed a different model (JKΓ versus coupled zigzag chain model) using a contrasting method (classical versus soft-spin analysis). The lack of commonality between these works precludes meaningful comparisons and a proper understanding of these unusual orderings. In this study, we complete the unfinished picture initiated by these two works by solving both models with both approaches for both three-dimensional (3D) honeycomb iridates. Through comparisons between all combinations of models, techniques, and materials, we find that the bond-isotropic JKΓ model consistently predicts the experimental phase of βLi2IrO3 regardless of the method used, while the experimental phase of γLi2IrO3 can be generated by the soft-spin approach with eigenmode mixing irrespective of the model used. To gain further insights, we solve a one-dimensional (1D) quantum spin-chain model related to both 3D models using the density matrix renormalization group method to form a benchmark. We discover that in the 1D model, incommensurate correlations in the classical and soft-spin analysis survive in the quantum limit only in the presence of the symmetric-off-diagonal exchange Γ found in the JKΓ model. The relevance of these results to the real materials is also discussed.

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  • Received 22 September 2015
  • Revised 17 April 2016

DOI:https://doi.org/10.1103/PhysRevB.93.184420

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Eric Kin-Ho Lee1, Jeffrey G. Rau2, and Yong Baek Kim1,3,4

  • 1Department of Physics and Center for Quantum Materials, University of Toronto, Toronto, Ontario, Canada M5S 1A7
  • 2Department of Physics and Astronomy, University of Waterloo, Ontario, Canada N2L 3G1
  • 3Canadian Institute for Advanced Research/Quantum Materials Program, Toronto, Ontario, Canada MSG 1Z8
  • 4School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea

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Issue

Vol. 93, Iss. 18 — 1 May 2016

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