Effect of charge doping on the electronic structure, orbital polarization, and structural distortion in nickelate superlattice

Using first-principles density functional theory calculations, we investigated the effect of charge doping in a ${\mathrm{LaNiO}}_{3}/{\mathrm{SrTiO}}_{3}$ superlattice. The detailed analysis based on two different doping simulation methods clearly shows that the electronic and structural properties change in a systematic way, and that the orbital polarization (i.e., relative occupation of two $\mathrm{Ni}\ensuremath{-}{e}_{g}$ orbitals) is reduced and the Ni to apical oxygen distance is enlarged as the number of doped electrons increases. Also, the rotation angles of the ${\mathrm{NiO}}_{6}/{\mathrm{TiO}}_{6}$ octahedra strongly and systematically depend on the doping. Our results not only suggest a possible way to control the orbital and structural properties by means of charge doping, but also provide useful information for understanding experiments under various doping situations such as oxygen vacancy.