Emerging Two-Dimensional Conductivity at the Interface between Mott and Band Insulators

Intriguingly, conducting perovskite interfaces between ordinary band insulators are widely explored, whereas similar interfaces with Mott insulators are still not quite understood. Here, we address the (001), (110), and (111) interfaces between the LaTiO3 Mott, and large band gap KTaO3 insulators. Based on firstprinciples calculations, we reveal a mechanism of interfacial conductivity, which is distinct from a formerly studied one applicable to interfaces between polar wideband insulators. Here, the key factor causing conductivity is the matching of oxygen octahedra tilting in KTaO3 and LaTiO3 which, due to a small gap in the LaTiO3 results in its sensitivity to the crystal structure, yields metallization of its overlayer and following charge transfer from Ti to Ta. Our findings, also applicable to other Mott insulators interfaces, shed light on the emergence of conductivity observed in LaTiO3/KTaO3 (110) where the "polar" arguments are not applicable and on the emergence of superconductivity in these structures.