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Institute: search.filters.UBSInstitut.Institut für Funktionelle Materie und QuantentechnologieSubject: search.filters.subject.540

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Now showing 1 - 4 of 4
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    Spin-orbital entanglement and molecular orbital formation in 4d and 5d transition metal oxides
    (2020) Krajewska, Aleksandra; Takagi, Hidenori (Prof. Dr.)
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    Monoclinic SrIrO3 : a Dirac semimetal produced by non-symmorphic symmetry and spin-orbit coupling
    (2018) Takayama, Tomohiro; Yaresko, Alexander N.; Takagi, Hidenori
    SrIrO3 crystallizes in a monoclinic structure of distorted hexagonal perovskite at ambient pressure. The transport measurements show that the monoclinic SrIrO3 is a low-carrier density semimetal, as in the orthorhombic perovskite polymorph. The electronic structure calculation indicates a semimetallic band structure with Dirac bands at two high-symmetry points of Brillouin zone only when spin-orbit coupling is incorporated, suggesting that the semimetallic state is produced by the strong spin-orbit coupling. We argue that the Dirac bands are protected by the non-symmorphic symmetry of lattice.
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    Heteroepitaxial tuning of resonant forbidden reflections in a spinel
    (2024) Oka, Ryosuke; Kim, Minu; Wochner, Peter; Francoual, Sonia; Palstra, Thomas T. M.; Takagi, Hidenori; Huang, Dennis
    In resonant elastic X-ray scattering (REXS), low site symmetries in a crystal may be revealed through resonant Bragg reflections that are normally forbidden in conventional X-ray diffraction due to screw axes and/or glide planes. These resonant forbidden reflections have been observed in spinel compounds, but to better understand and utilize their connection to microscopic material parameters and possible charge and/or orbital ordering, a systematic study of their dependence on growth conditions and applied strain is desired. We performed REXS at the V K edge and examined the resonant forbidden (002) reflection in thin films of the spinel LiV2O4 grown on three substrates: MgAl2O4, SrTiO3, and MgO. The energy dependence of the (002) reflection shows a systematic evolution as epitaxial strain modifies the local anisotropy of the V site. More strikingly, the integrated intensity of the (002) reflection varies by more than an order of magnitude in films on different substrates. We speculate that the large variation in integrated intensity reflects the varying degree of antiphase domains that arise during the epitaxy.
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    Robust quantum spin liquid state in the presence of giant magnetic isotope effect in D3LiIr2O6
    (2025) Takayama, Tomohiro; Gibbs, Alexandra; Kitagawa, Kentaro; Matsumoto, Y.; Ishii, K.; Kato, A.; Takano, R.; Bette, Sebastian; Dinnebier, Robert E.; Takagi, Hidenori
    The deuterium isotope effect on the honeycomb iridate H3LiIr2O6, a quantum spin-orbit-entangled liquid, was examined by synthesizing D3LiIr2O6. The structural refinements indicate the different character of the interlayer OH and OD bonds, which results in a giant isotope effect on the magnetic interactions; the antiferromagnetic Curie-Weiss temperature |θCW| of D3LiIr2O6 increases to ~ 170 K from ~ 100 K of H3LiIr2O6. Nevertheless, the quantum liquid state is robust against the deuterium isotope exchange in contrast to the theoretical prediction that the Kitaev spin liquid is stable only for a limited phase space of magnetic interactions. The bond- and site disorders associated with disordered OD(H) bonds, in combination with Kitaev physics, may play a role in realizing the quantum liquid state.