Semimetal and Topological Insulator in Perovskite Iridates

The two-dimensional layered perovskite Sr2IrO4 was proposed to be a spin-orbit Mott insulator, where the effect of Hubbard interaction is amplified on a narrow Jeff=1/2band due to strong spin-orbit coupling. On the other hand, the three-dimensional orthorhombic perovskite (Pbnm) SrIrO3 remains metallic. To understand the physical origin of the metallic state and possible transitions to insulating phases, we construct a tight-binding model for SrIrO3. The band structure possesses a line node made ofJeff=1/2 bands below the Fermi level. As a consequence, instability toward magnetic ordering is suppressed, and the system remains metallic. This line node, originating from the underlying crystal structure, turns into a pair of three-dimensional nodal points on the introduction of a staggered potential or spin-orbit coupling strength between alternating layers. Increasing this potential beyond a critical strength induces a transition to a strong topological insulator, followed by another transition to a normal band insulator. We propose that materials constructed with alternating Ir- and Rh-oxide layers along the (001) direction, such as Sr2IrRhO6, are candidates for a strong topological insulator.

Jean-Michel Carter1, V. Vijay Shankar1, M. Ahsan Zeb2, and Hae-Young Kee1,3,*
1Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7 Canada
2Cavendish Laboratory, Cambridge University, Cambridge, United Kingdom
3Canadian Institute for Advanced Research, Toronto, Ontario, Canada