Quantum confinement in double perovskite multilayers: Sr$_{2}$FeMoO$_{6}$/La$_{2}$CoMnO$_{6}$

We have examined the interfacial electronic structure of multilayers grown along [001] out of half metallic ferrimagnet Sr$_{2}$FeMoO$_{6}$ (SFMO) and insulating ferromagnet La$_{2}$CoMnO$_{6}$ (LCMO) using the density functional theory calculations. The half-metallic nature arises due to the partial occupancy of xz, yz and x$^{2}$-y$^{2}$ states of SFMO in the spin minority channel. We find that LCMO provides a confinement potential along z the direction to the spin-polarized free electrons at the interface. The confinement potential ensures further quantization of the delocalized states, namely xz and yz of SFMO, lying on the Fermi level. The x$^{2}$-y$^{2}$ states remain unaffected and therefore, spin-polarized two dimensional electron gas (2DEG) is intrinsically formed. The formation of 2DEG is very distinct from that of the widely studied LAO/STO and LMO/SMO heterostructures. In these compounds, the 2DEG is formed via interfacial electron reconstruction to quench the polar catastrophe.