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Title: Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na 2IrO 3

We show that heisenberg interactions are ubiquitous in magnetic materials and play a central role in modelling and designing quantum magnets. Bond-directional interactions offer a novel alternative to Heisenberg exchange and provide the building blocks of the Kitaev model, which has a quantum spin liquid as its exact ground state. Honeycomb iridates, A 2IrO 3 (A = Na, Li), offer potential realizations of the Kitaev magnetic exchange coupling, and their reported magnetic behaviour may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-directional interactions has so far been indirect. Here we present direct evidence for dominant bond-directional interactions in antiferromagnetic Na 2IrO 3 and show that they lead to strong magnetic frustration. Diffuse magnetic X-ray scattering reveals broken spin-rotational symmetry even above the Néel temperature, with the three spin components exhibiting short-range correlations along distinct crystallographic directions. Lastly, this spin- and real-space entanglement directly uncovers the bond-directional nature of these interactions, thus providing a direct connection between honeycomb iridates and Kitaev physics.
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [3] ;  [2] ;  [2] ;  [4] ;  [4] ;  [4] ;  [5] ;  [6] ;  [7] ;  [7]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  3. Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City (India)
  4. European Synchrotron Radiation Facility (France)
  5. Masaryk University (Czech Republic). Central European Institute of Technology
  6. Max Planck Institute for Solid State Research (Germany); University of Stuttgart (Germany). Institute for Functional Matter and Quantum Technologies
  7. Max Planck Institute for Solid State Research (Germany)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Nature Physics
Additional Journal Information:
Journal Volume: 11; Journal Issue: 6; Journal ID: ISSN 1745-2473
Publisher:
Nature Publishing Group (NPG)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Magnetic properties and materials
OSTI Identifier:
1355347

Hwan Chun, Sae, Kim, Jong-Woo, Kim, Jungho, Zheng, H., Stoumpos, Constantinos C., Malliakas, C. D., Mitchell, J. F., Mehlawat, Kavita, Singh, Yogesh, Choi, Y., Gog, T., Al-Zein, A., Sala, M. Moretti, Krisch, M., Chaloupka, J., Jackeli, G., Khaliullin, G., and Kim, B. J.. Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na2IrO3. United States: N. p., Web. doi:10.1038/nphys3322.
Hwan Chun, Sae, Kim, Jong-Woo, Kim, Jungho, Zheng, H., Stoumpos, Constantinos C., Malliakas, C. D., Mitchell, J. F., Mehlawat, Kavita, Singh, Yogesh, Choi, Y., Gog, T., Al-Zein, A., Sala, M. Moretti, Krisch, M., Chaloupka, J., Jackeli, G., Khaliullin, G., & Kim, B. J.. Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na2IrO3. United States. doi:10.1038/nphys3322.
Hwan Chun, Sae, Kim, Jong-Woo, Kim, Jungho, Zheng, H., Stoumpos, Constantinos C., Malliakas, C. D., Mitchell, J. F., Mehlawat, Kavita, Singh, Yogesh, Choi, Y., Gog, T., Al-Zein, A., Sala, M. Moretti, Krisch, M., Chaloupka, J., Jackeli, G., Khaliullin, G., and Kim, B. J.. 2015. "Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na2IrO3". United States. doi:10.1038/nphys3322. https://www.osti.gov/servlets/purl/1355347.
@article{osti_1355347,
title = {Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na2IrO3},
author = {Hwan Chun, Sae and Kim, Jong-Woo and Kim, Jungho and Zheng, H. and Stoumpos, Constantinos C. and Malliakas, C. D. and Mitchell, J. F. and Mehlawat, Kavita and Singh, Yogesh and Choi, Y. and Gog, T. and Al-Zein, A. and Sala, M. Moretti and Krisch, M. and Chaloupka, J. and Jackeli, G. and Khaliullin, G. and Kim, B. J.},
abstractNote = {We show that heisenberg interactions are ubiquitous in magnetic materials and play a central role in modelling and designing quantum magnets. Bond-directional interactions offer a novel alternative to Heisenberg exchange and provide the building blocks of the Kitaev model, which has a quantum spin liquid as its exact ground state. Honeycomb iridates, A2IrO3 (A = Na, Li), offer potential realizations of the Kitaev magnetic exchange coupling, and their reported magnetic behaviour may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-directional interactions has so far been indirect. Here we present direct evidence for dominant bond-directional interactions in antiferromagnetic Na2IrO3 and show that they lead to strong magnetic frustration. Diffuse magnetic X-ray scattering reveals broken spin-rotational symmetry even above the Néel temperature, with the three spin components exhibiting short-range correlations along distinct crystallographic directions. Lastly, this spin- and real-space entanglement directly uncovers the bond-directional nature of these interactions, thus providing a direct connection between honeycomb iridates and Kitaev physics.},
doi = {10.1038/nphys3322},
journal = {Nature Physics},
number = 6,
volume = 11,
place = {United States},
year = {2015},
month = {5}
}