Stoichiometry Control, Electronic and Transport Studies of Pyrochlore Iridate Thin Films*

Pyrochlore iridate thin films are predicted to host a variety of exotic magnetic and topological states. Experimental probing of the emergent quantum states strongly relies on the synthesis of high-quality thin film samples. In this work, we demonstrate the epitaxial growth and stoichiometry control of pyrochlore Bi₂Ir₂O₇ thin films via pulsed laser deposition followed by a post annealing process. The as-deposited films form a bilayer-like structure consisting of an Ir-deficient top-surface and an Ir metal layer at the bottom. Post annealing in iridium oxide atmosphere significantly improves the stoichiometry and homogeneity throughout the film thickness. Density functional theory calculation shows a fourfold degenerate Dirac node slightly below the Fermi energy at the X point, coexisting with some trivial bands around the Γ point. Transport studies revealed a transition from a weakly-metallic to weakly-insulating behavior at around 150 K, accompanied by positive magnetoresistance at low temperatures.