Structural Diversity in Oxoiridates with 1D IrO Chain Fragments and Flat Bands.

A previously unreported series of hexagonal-perovskite-based Rb-oxoiridates, RbIrO, RbIrO, and RbIrO, have been synthesized and structurally analyzed via N-protected single-crystal X-ray diffraction (SC-XRD). These materials exhibit different 1D IrO chain fragments along their axes. IrO octahedra and RbO ( = 6, 8, and 10) polyhedra are their basic building blocks. The IrO octahedra are linked via face-sharing, forming IrO dimers, IrO trimers, and IrO heptamers. The nonmagnetic RbO ( = 6, 8, and 10) polyhedra serve as both bridging units and spacers. Temperature-dependent SC-XRD shows all three to display positive thermal expansion and rules out structural transitions from their triangular symmetries down to 100 K. Density functional theory results suggest semiconducting-like behavior for the title compounds. The flatness of the electronic bands and our structural analysis are of potential interest for understanding and designing 1D quantum materials.