Exotic spin-orbital Mott insulating states in BaIrO3

Electronic structures of 5d transition-metal oxide BaIrO3 are investigated by using a first-principles method. The system is found to be an exotic spin-orbital Mott insulator in multiple Jeff = 1/2 states, achieved only after spin-orbit coupling and a modest on-site Coulomb interaction are taken into account simultaneously. The multiplicity of Jeff=1/2 states is associated with the unique Ir3O12 structural units in the crystal. These results explain well the nonmetallic behavior of the system observed in experiments. The magnetic state is found to be weak and noncollinear. Our work provides essential understandings on the electronic states of this type of 5d transition-metal oxide.