Preparation and characterization of a possible topological insulator BiYO3: experiment versus theory

Abstract

The Bi–Y–O system has been investigated by X-ray powder diffraction, electron diffraction, UV-vis and IR experiments. A metastable cubic high temperature phase of BiYO₃ with fluorite-type structure has been structurally characterized for the first time and shows a large band gap of ∼5.9 eV. A unified description for the numerous structural variants discovered in the Bi–Y–O system is established within the symmetry breaking approach. This rich structural phenomenon makes the Bi–Y–O system a promising candidate in the search for new topological insulators for applications. On this basis, a long standing controversy on the phase diagram of the Bi–Y–O system has been solved. Our DFT calculations predict a high pressure phase for BiYO₃ with perovskite (ABO₃) structure and ordering of Bi and Y on the A and B sites, respectively. However, our analysis of the nature of the low energy electronic structure shows that this phase is not a suitable candidate for a topological insulator.