Spin-orbit coupling induced semi-metallic state in the 1/3 hole-doped hyper-kagome NaIrO

1/3ホールドープされたハイパーカゴメNaIrOにおけるスピン軌道結合に誘起された半金属状態

高山 知弘*; Yaresko, A.*; 松本 章代*; Nuss, J.*; 石井 賢司; 吉田 雅洋*; 水木 純一郎; 高木 英典*

Takayama, Tomohiro*; Yaresko, A.*; Matsumoto, Akiyo*; Nuss, J.*; Ishii, Kenji; Yoshida, Masahiro*; Mizuki, Junichiro; Takagi, Hidenori*

The complex iridium oxide NaIrO with a B-site ordered spinel structure was synthesized in single crystalline form, where the chiral hyper-kagome lattice of Irions, as observed in the spin-liquid candidate NaIrO, was identified. The average valence of Ir is 4.33+ and, therefore, NaIrO can be viewed as a doped analogue of the hyper-kagome spin liquid with Ir. The transport measurements, combined with the electronic structure calculations, indicate that the ground state of NaIrO 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 orbitals on Ir triangles with strong spin-orbit coupling inherent to heavy Ir ions.