Strongly frustrated triangular spin lattice emerging from triplet dimer formation in honeycomb Li2IrO3
journal contributionposted on 06.08.2018 by Satoshi Nishimoto, Vamshi M. Katukuri, Viktor Yushankhai, Hermann Stoll, Ulrich K. Roessler, Liviu Hozoi, Ioannis Rousochatzakis, Jeroen van den Brink
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Iridium oxides with a honeycomb lattice have been identified as platforms for the much anticipated Kitaev topological spin liquid: the spin-orbit entangled states of Ir4+in principle generate precisely the required type of anisotropic exchange. However, other magnetic couplings can drive the system away from the spin-liquid phase. With this in mind, here we disentangle the different magnetic interactions in Li2IrO3, a honeycomb iridate with two crystallographically inequivalent sets of adjacent Ir sites. Our ab initio many-body calculations show that, while both Heisenberg and Kitaev nearest-neighbour couplings are present, on one set of Ir-Ir bonds the former dominates, resulting in the formation of spin-triplet dimers. The triplet dimers frame a strongly frustrated triangular lattice and by exact cluster diagonalization we show that they remain protected in a wide region of the phase diagram.
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Partial financial support from the German Research Foundation (HO-4427 and SFB 1143) is gratefully acknowledged.