  We propose a method of controlling the metal-insulator transition of one
perovskite material at its interface with a another ferroelectric material
based on first principle calculations. The operating principle is that the
rotation of oxygen octahedra tuned by the ferroelectric polarization can
modulate the superexchange interaction in this perovskite. We designed a
tri-color superlattice of (BiFeO$_3$)$_N$/LaNiO$_3$/LaTiO$_3$, in which the
BiFeO$_3$ layers are ferroelectric, the LaNiO$_3$ layer is the layer of which
the electronic structure is to be tuned, and LaTiO$_3$ layer is inserted to
enhance the inversion asymmetry. By reversing the ferroelectric polarization in
this structure, there is a metal-insulator transition of the LaNiO$_3$ layer
because of the changes of crystal field splitting of the Ni $e_g$ orbitals and
the bandwidth of the Ni in-plane $e_g$ orbital. It is highly expected that a
metal-transition can be realized by designing the structures at the interfaces
for more materials.
