Topological Phases in Oxide Heterostructures with Light and Heavy   Transition Metal Ions
  Using a combination of density functional theory, tight-binding models, and Hartree-Fock theory, we predict topological phases with and without time-reversal symmetry breaking in oxide heterostructures. We consider both heterostructures containing light transition metal ions, and those containing heavy transition metal ions. We find the (111) growth direction naturally leads to favorable conditions for topological phases in both perovskite structures and pyrochlore structures. For the case of light transition metal elements, Hartree-Fock theory predicts the spin-orbit coupling is effectively enhanced by on-site multiple-orbital interactions and may drive the system through a topological phase transition, while heavy elements with intrinsically large spin-orbit coupling require much weaker, or even vanishing electron interactions to bring about a topological phase. 
Gregory A. Fiete, Andreas R\"uegg
cond-mat.str-el