Orbital Order and Possible Superconductivity inLaNiO3/LaMO3Superlattices

Abstract

A hypothetical layered oxide ${\mathrm{La}}_{2}\mathrm{Ni}M{\mathrm{O}}_{6}$ where ${\mathrm{NiO}}_{2}$ and $M{\mathrm{O}}_{2}$ planes alternate along the $c$ axis of $AB{\mathrm{O}}_{3}$ perovskite lattice is considered theoretically. Here, $M$ denotes a trivalent cation Al, Ga,\dots{} such that $M{\mathrm{O}}_{2}$ planes are insulating and suppress the $c$-axis charge transfer. We predict that correlated ${e}_{g}$ electrons in the ${\mathrm{NiO}}_{2}$ planes develop a planar ${x}^{2}\mathrm{\text{\ensuremath{-}}}{y}^{2}$ orbital order driven by the reduced dimensionality and further supported by epitaxial strain from the substrate. Low-energy electronic states can be mapped to a single-band $t\ensuremath{-}{t}^{\ensuremath{'}}\ensuremath{-}J$ model, suggesting favorable conditions for high-${T}_{c}$ superconductivity.