Orbital order and possible superconductivity in LaNiO3/LaMO3 superlattices

A hypothetical layered oxide La2NiMO6 where NiO2 and MO2 planes alternate along the c axis of ABO(3) perovskite lattice is considered theoretically. Here, M denotes a trivalent cation Al, Ga,... such that MO2 planes are insulating and suppress the c-axis charge transfer. We predict that correlated e(g) electrons in the NiO2 planes develop a planar x(2)-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-t(')-J model, suggesting favorable conditions for high-T-c superconductivity.