Ferroelectricity and tunneling electroresistance effect driven by asymmetric polar interfaces in all-oxide ferroelectric tunnel junctions

By constructing asymmetric polar interfaces, all-oxide ferroelectric tunnel junctions (FTJs) are proposed that can achieve a sizable tunneling electroresistance (TER) effect. Based on first-principles quantum transport calculations on a prototypical LaNiO3/BaTiO3/LaNiO3 junction, we predict that TER reaches 103% under a finite bias. Driven by the asymmetric polar interfaces, the resultant intrinsic electric field causes a highly asymmetric electrostatic potential in comparison to that of the FTJ with symmetric polar interfaces. As a result, the tunneling resistance changes significantly upon polarization reversal leading to sizable TER. The physical origin of the TER effect can be well understood in terms of local density of states, transport in momentum space, real-space scattering states and a free-electron tunneling model. Our results provide an insight into the understanding of ferroelectricity and the TER mechanism in FTJs and will be useful for FTJ-based devices design.