Manipulation of orbital occupancy by ferroelectric polarization in LaNiO3/BaTiO3−δ heterostructures

We investigate the control of orbital occupancy by ferroelectric polarization in LaNiO3/BaTiO3−δ heterostructures. It is achieved by the ferroelectric displacement of Ti ions polarized downward (upward) to form (break) Ni–O–Ti covalent bonding at the interface, accompanied by charge transfer between them and the modulation of the conductivity of ultrathin LaNiO3. This electrically switchable and bi-direction control of orbital polarization in LaNiO3 is up to 25%, different from the manipulation by epitaxial strain or quantum confinement. Our finding opens a window for electrical control of orbital polarization at an oxide interface.