High-Mobility Carriers in Epitaxial IrO 2 Films Grown using Hybrid Molecular Beam Epitaxy.

Binary rutile oxides of 5d metals such as IrO 2 stand out in comparison to their 3d and 4d counterparts due to limited experimental studies, despite rich predicted quantum phenomena. Here, we investigate the electrical transport properties of IrO 2 by engineering epitaxial thin films grown using hybrid molecular beam epitaxy. Our findings reveal phonon-limited carrier transport and thickness-dependent anisotropic in-plane resistance in IrO 2 (110) films, the latter suggesting a complex relationship between strain relaxation and orbital hybridization. Magnetotransport measurements reveal a previously unobserved nonlinear Hall effect. A two-carrier analysis of this effect shows the presence of minority carriers with mobility exceeding 3000 cm 2 /(V s) at 1.8 K. These results point toward emergent properties in 5d metal oxides that can be controlled using dimensionality and epitaxial strain.