Modulation doping in LaNiO₃/SrIrO₃ superlattices from first principles

Doping is commonly used to tune and optimize material properties such as conductivity and optical properties. Doping at extremely high concentrations, at the level of an electron per formula unit, can stabilize novel phases. Here we study lanthanum nickelate (LaNiO₃)/strontium iridate (SrIrO₃) superlattices using the first-principles density functional theory (DFT) +U method, focusing on the 1/1 superlattice. For this superlattice we find that there is a modulation doping effect where electrons are transferred from the SrIrO₃ layers to the LaNiO₃ layers, converting nickels from Ni³⁺ to Ni²⁺ in the electron-doped LaNiO₃ layers and and iridiums from Ir⁴⁺ to Ir⁵⁺ in the hole-doped SrIrO₃ layers. We will present results on the orbital occupations and low energy structures, with the possibility for charge ordering, as well as the electronic and magnetic structures. To elucidate the behavior of the interfaces within these heterostructures, we present and analyze results for additional superlattices, including the 1/2 and 1/3 superlattices.