title: Spin-orbit coupling induced semi-metallic state in the 1/3 hole-doped hyper-kagome Na3Ir3O8.
abstract: The complex iridium oxide Na3Ir3O8 with a B-site ordered spinel structure was synthesized in single crystalline form, where the chiral hyper-kagome lattice of Ir ions, as observed in the spin-liquid candidate Na4Ir3O8, was identified. The average valence of Ir is 4.33+ and, therefore, Na3Ir3O8 can be viewed as a doped analogue of the hyper-kagome spin liquid with Ir(4+). The transport measurements, combined with the electronic structure calculations, indicate that the ground state of Na3Ir3O8 is a low carrier density semi-metal. We argue that the semi-metallic state is produced by a competition of the molecular orbital splitting of t2g orbitals on Ir3 triangles with strong spin-orbit coupling inherent to heavy Ir ions.
authors.affiliation: 1] Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany [2] Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Takayama
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Yaresko
authors.affiliation: Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Akiyo
authors.initials: A
authors.lastname: Matsumoto
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Nuss
authors.affiliation: SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ishii
authors.affiliation: 1] SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan [2] School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: 1] SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan [2] School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Mizuki
authors.affiliation: 1] Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany [2] Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan [3] RIKEN Advanced Science Institute, Wako 351-0195, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Takagi