Self-doping and emergent conductance at Mott interfaces via internal charge transfer

We use $ab$ $initio$ calculations to show that internal charge transfer can induce spatially separated electron-hole pairs at interfaces between two Mott insulators. DFT+ $U$ studies of multilayer systems consisting of Sr$_2$VO$_4$ and Sr$_2$MnO$_4$ (both Mott insulators) reveal that conductance emerges at their interface with electrons residing dominantly on the Mn $d_{x^2-y^2}$ orbital and holes on the V $d_{xy}$ orbital. With the transferred electron coupled to the core spin on Mn sites, ferromagnetism is significantly favored in the Sr$_2$MnO$_4$ layer, although this material is antiferromagnetic in bulk. Our work establishes internal charge transfer as a powerful method of tailoring correlation effects and that superlattices composed of Ruddlesden-Popper type oxides provide new possibilities for materials design, complementary to perovskite oxide heterostructures.