  Barrier planes described by the Ionic Hubbard model and sandwiched between
metallic planes on both sides are studied using unrestricted Hartree Fock. For
zero onsite correlation, the presence of the metallic interface generates an
additional gap in the energy spectrum away from half filling, if the chemically
modulated potential in the barrier planes exceed a critical value. There is
reentrant behaviour and an insulator-metal-insulator transition as we tune
onsite correlation for fixed site potential. The metal is thus able to
penetrate the barrier planes due to proximity effect, in a system that is
otherwise an insulator throughout.
