Spin, Orbital and Charge Order at the Interface between Correlated Oxides

The collective behavior of correlated electrons in the VO${}_2-$interface layer of LaVO${}_3$/SrTiO${}_3$ heterostructure is studied within a quarter-filled $t_{2g}$-orbital Hubbard model on a square lattice. We argue that the ground state is ferromagnetic driven by the double exchange mechanism, and is orbitally and charge ordered due to a confined geometry and electron correlations. The orbital and charge density waves open gaps on the entire Fermi surfaces of all orbitals. The theory explains the observed insulating behavior of the $p$-type interface between LaVO${}_3$ and SrTiO${}_3$.