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

TL;DR

This study uses first-principles calculations to show how charge doping systematically alters the electronic structure, orbital polarization, and octahedral rotations in a LaNiO3/SrTiO3 superlattice, offering a way to control these properties.

Contribution

It provides a detailed analysis of charge doping effects on orbital and structural properties in nickelate superlattices using two simulation methods, revealing systematic property changes.

Findings

Orbital polarization decreases with increased doping.

Ni to apical oxygen distance enlarges as doping increases.

Octahedral rotation angles depend systematically on doping.

Abstract

Using first-principles density functional theory calculations, we investigated the effect of charge doping in a LaNiO$_3$/SrTiO$_3$ superlattice. The detailed analysis based on two different simulation methods for doping clearly shows that the electronic and structural properties change in a systematic way that the orbital polarization ({\it i.e.} relative occupation of two Ni-$e_g$ orbitals) is reduced and the Ni to apical oxygen distance enlarged as the number of doped electrons increases. Also, the rotation angles of the NiO$_6$/TiO$_6$ octahedra strongly and systematically depend on the doping so that the angle $\gamma$ gradually decreases whereas the $\alpha$ and $\beta$ increase as a function of electron doping. Further analysis shows that the electron (hole) doping can play a similar role with the compressive (tensile) strain for the octahedral rotations. Our results not only suggest a possible way to control the orbital and structural property by means of charge doping, but also provide useful information to understand the experiments under various doping situations such as oxygen vacancy.