ATiO₃/TiO (A=Pb, Sn) superlattice: Bridging ferroelectricity and conductivity

We propose a superlattice structure by repeating TiO and perovskite ATiO₃ layers and use first-principles calculations to investigate its physical properties. Our computational analysis shows that the structure, which consists of repeated ATiO₃ and TiO layers, has strong anisotropic conductivity. The electronic structure immediately suggests a possible control of its conductivity by ion displacements related to its intrinsic ferroelectricity. Moreover, the flat bands observed in the electronic structure strongly resemble that of MgB₂ (a superconductor) and twisted bilayer systems with unconventional superconductivity. The implication of such similarity is discussed. In addition, we have obtained the structural information of its low-energy phases with the aid of phonon calculation and examined their evolution with epitaxial strain. Since the number of possible combinations is huge, we have therefore suggested an approach to mix perovskites and simpler metal-oxides to build materials with novel properties.