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- ItemEngineering Kitaev exchange in stacked iridate layers: Impact of inter-layer species on in-plane magnetism(Cambridge : Royal Society of Chemistry, 2019) Yadav, R.; Eldeeb, M.S.; Ray, R.; Aswartham, S.; Sturza, M.I.; Nishimoto, S.; Van Den Brink, J.; Hozoi, L.Novel functionalities may be achieved in oxide electronics by appropriate stacking of planar oxide layers of different metallic species, MOp and M′Oq. The simplest mechanism allowing the tailoring of the electronic states and physical properties of such heterostructures is of electrostatic nature - charge imbalance between the M and M′ cations. Here we clarify the effect of interlayer electrostatics on the anisotropic Kitaev exchange in H3LiIr2O6, a recently proposed realization of the Kitaev spin liquid. By quantum chemical calculations, we show that the precise position of H+ cations between magnetically active [LiIr2O6]3- honeycomb-like layers has a strong impact on the magnitude of Kitaev interactions. In particular, it is found that stacking with straight interlayer O-H-O links is detrimental to in-plane Kitaev exchange since coordination by a single H-ion of the O ligand implies an axial Coulomb potential at the O site and unfavorable polarization of the O 2p orbitals mediating the Ir-Ir interactions. Our results therefore provide valuable guidelines for the rational design of Kitaev quantum magnets, indicating unprecedented Kitaev interactions of ≈40 meV if the linear interlayer linkage is removed.
- ItemV4 tetrahedral units in AV4X8 lacunar spinels: Near degeneracy, charge fluctuations, and configurational mixing within a valence space of up to 21 d orbitals(2020) Hozoi, L.; Eldeeb, M.S.; Rößler, U.K.All properties of a given molecule or solid are determined by the way valence electrons are distributed over single-particle energy levels. For multiple, closely spaced single-particle levels, different occupation patterns may provide many-electron quantum states that are close in energy, interact, and admix. We address such near-degeneracy electron correlation effects for V4 vanadium tetrahedral units as encountered in the lacunar spinel GaV4S8, explicitly taking into account up to 21 vanadium valence orbitals, and find effective orbital occupation numbers much different as compared to the picture previously laid out on the basis of mean-field calculations. In light of these results, a modified theoretical frame seems necessary to explain the peculiar magnetic properties of lacunar spinels and of related compounds.