Orbital control of metal-to-insulator transition in high-entropy nickelates

High-entropy materials have emerged as a promising platform for exploring unique electronic and structural properties. In this study we investigated the orbital control of the metal-to-insulator transition in thin films of high-entropy nickelates, which are composed of five rare-earth elements in equiatomic concentrations. By manipulating the levels of misfit strain through substrate choice and film thickness, we modulated the electronic properties and examined the intricate interplay between strain, orbital interactions, and the metal-to-insulator transition. Compared to other nickelate thin films such as $\mathrm{NdNi}{\mathrm{O}}_{3}$ and $\mathrm{SmNi}{\mathrm{O}}_{3}$, thin films of high-entropy nickelates exhibited remarkable resilience in maintaining control over their transport properties and orbital polarization, even in the presence of considerable A-site disorder. This finding suggests that the electronic properties of A-site disordered high-entropy nickelates are still governed by the electronic bandwidth, primarily influenced by the Ni-O bonding geometry. This study provides valuable insights into the complex interplay among composition, structure, and electronic properties in perovskite oxides. These insights have the potential to guide the development of perovskite oxide materials with tailored electronic properties for a wide range of applications.