Microscopic understanding of the orbital splitting and its tuning at   oxide interfaces
  By means of a Wannier projection within the framework of density functional theory, we are able to identify the modified c-axis hopping and the energy mismatch between the cation bands as the main source of the $t_{2g}$ splitting around the $\Gamma$ point for oxide heterostructures, excluding previously proposed mechanisms such as Jahn-Teller distortions or electric field asymmetries. Interfacing LaAlO$_3$, LaVO$_3$, SrVO$_3$ and SrNbO$_3$ with SrTiO$_3$ we show how to tune this orbital splitting, designing heterostructures with more $d_{xy}$ electrons at the interface. Such an "orbital engineering" is the key for controlling the physical properties at the interface of oxide heterostructures. 
Zhicheng Zhong, Philipp Wissgott, Karsten Held and Giorgio Sangiovanni
cond-mat.str-el cond-mat.mtrl-sci