Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na2IrO3

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Authors

CHUN Sae Hwan 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 Jiří JACKELI George KHALIULLIN Giniyat KIM B.J.

Year of publication 2015
Type Article in Periodical
Magazine / Source Nature Physics
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://www.nature.com/nphys/journal/v11/n6/full/nphys3322.html
Doi http://dx.doi.org/10.1038/NPHYS3322
Field Solid matter physics and magnetism
Keywords spin interactions; frustrated magnetism; iridates; spin models
Description 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. Herewe 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 Neel temperature, with the three spin components exhibiting short-range correlations along distinct crystallographic directions. 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.
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