Modifying the electronic orbitals of nickelate heterostructures via structural distortions.

We describe a general materials design approach that produces large orbital energy splittings (orbital polarization) in nickelate heterostructures, creating a two-dimensional single-band electronic surface at the Fermi energy. The resulting electronic structure mimics that of the high temperature cuprate superconductors. The two key ingredients are (i) the construction of atomic-scale distortions about the Ni site via charge transfer and internal electric fields, and (ii) the use of three-component (tricomponent) superlattices to break inversion symmetry. We use ab initio calculations to implement the approach, with experimental verification of the critical structural motif that enables the design to succeed.