Theory of Mott insulator-band insulator heterostructures

A theory of heterostructures comprised of LaTiO3 (a Mott insulator) and SrTiO3 (a band insulator) is presented. The band structure of the Ti d-electrons is treated with a nearest neighbor tight-binding approximation; the electric fields arising from the La3+/Sr2+ charge difference and the carriers are treated within a Hartree approximation; and the on-site interactions are treated by unrestricted Hartree-Fock. The phase diagram as a function of interaction strength and layer number is determined and predictions are made for optical conductivity experiments. A noteworthy finding is that the edges of the heterostructure are generally metallic.