Figure 1

Results of the m = 4 SL with n-p type interfaces.

(a) Schematic crystal structure. (b) The local displacements between anions and cations. Both the PE and FE initial conditions give the same profiles. The vertical dash lines denote the two interfaces. For reference, the red and blue dot lines denote the Ti-O and Pb-O relative displacements of PTO bulk on LAO substrate, respectively. (c) Sketch of the mechanism. No matter the initial condition is PE or FE, the internal built electric field from the n-p interfaces can polarize the PTO layers. Circle with sign stands for the center of positive/negative charge. (d) The PDOS of each TiO₂ layer, which shows a clear band shift (1.5 eV) due to the polar n-p termination pair and depolarization field. The Fermi energy is positioned at zero, as indicated by the vertical dash line.