Emerging two-dimensional conductivity at Mott-band insulator interface

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 LaTiO_3 Mott- and large band gap KTaO_3 insulators. Based on first-principles calculations, we reveal a mechanism of interfacial conductivity, which is distinct from a formerly studied one applicable to interfaces between polar wide band insulators. Here the key factor causing conductivity is the matching of oxygen octahedra tilting in KTaO_3 and LaTiO_3 which, due to a small gap in the LaTiO_3 results in its sensitivity to the crystal structure, yields metalization 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 LaTiO_3/KTaO_3 (110) where the ”polar“ arguments are not applicable and on the emergence of superconductivity in these structures.