Interface dipole induced by asymmetric exchange effect in Mott-insulator/Mott-insulator heterojunction

We study theoretically the interfacial electronic property of aheterojunction made from two Mott insulators (MI) with differentmagnetic structures. By means of unrestricted Hartree-Fockcalculations in real space, we find that a charge dipole can formspontaneously near the interface of the MI/MI heterojunction. Themagnitude of this charge dipole depends strongly on the magneticstates of both sides of the heterojunction. Combining with theresult from an exactly solvable two-site toy model, we argue thatthe interface dipole arises from exchange effects as well as itsasymmetry intrinsic to the heterojunction near the interface. Ourstudy may shed light on the fabrication of ultrathin ferroelectricand magnetoelectric devices.