We explore the structural and electronic properties of the bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ on ${\mathrm{LaAlO}}_3\left(001\right)$ and ${\mathrm{SrTiO}}_3\left(001\right)$ by using density functional theory including a Coulomb repulsion term. For ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7/{\mathrm{LaAlO}}_3\left(001\right)$, we find that compressive strain and electron doping across the interface result in the unconventional occupation of the antibonding Ni $3d_{z^2}$ states. In sharp contrast, no charge transfer is observed for ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7/{\mathrm{SrTiO}}_3\left(001\right)$. Surprisingly, tensile strain drives a metallization of the bonding Ni $3d_{z^2}$ states, rendering a Fermi surface topology akin to superconducting bulk ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under high pressure, yet with spin fluctuations enhanced considerably beyond pressure effects. Concomitantly, significant octahedral rotations are retained. We discuss the fundamental differences between hydrostatic pressure versus epitaxial strain and establish that strain provides a much stronger control over the Ni $e_g$ orbital polarization. The results suggest epitaxial ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, particularly under tensile strain, as interesting system to provide novel insights into the physics of bilayer nickelates and possibly induce superconductivity without external pressure.

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• Electronic structure
• Fermi surface
• Superconductivity
• Complex oxides
• Nickelates
• Unconventional superconductors
• Density functional theory