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arXiv · 1403.6698

Strongly frustrated triangular spin lattice emerging from triplet dimer formation in honeycomb Li2IrO3

Satoshi Nishimoto·Vamshi M. Katukuri·Viktor Yushankhai·Hermann Stoll·Ulrich K. Roessler·Liviu Hozoi·Ioannis Rousochatzakis·Jeroen van den Brink
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Abstract

In quantum magnetism spin dimers are typically associated with spin-singlet states. To date, $triplet$ $dimerization$ has not been observed in any 3D or quasi-2D material. With this in mind we here discuss the electronic structure of the spin-orbit driven $5d^5$ Mott insulator Li$_2$IrO$_3$, a honeycomb-lattice system with two crystallographically inequivalent Ir-Ir bonds. From $ab$ $initio$ many-body calculations we find that, while both Heisenberg and Kitaev couplings are present, the magnetic interactions are dominated by a strong isotropic ferromagnetic exchange on only one set of bonds. This causes the formation of triplet spin dimers effectively placed on a strongly frustrated triangular lattice. The triplet dimers remain protected in a large region of the phase diagram, suggesting that Li$_2$IrO$_3$ has a long-range incommensurate magnetic ground state that is pushed by the Kitaev exchange interactions beyond a standard planar helix configuration.

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Satoshi Nishimoto, Vamshi M. Katukuri, Viktor Yushankhai, Hermann Stoll, Ulrich K. Roessler, Liviu Hozoi, Ioannis Rousochatzakis, Jeroen van den Brink. 2014-03-26. Strongly frustrated triangular spin lattice emerging from triplet dimer formation in honeycomb Li2IrO3. https://doi.org/10.1038/ncomms10273

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