First-principles study of intermixing and polarization at the DyScO$_3$ /SrTiO$_3$ interface

Exploring oxide interfaces is an attractive challenge, due to the emerging novel behaviors which don't exist in the corresponding parent bulk compounds. E. g. joining two simple band insulators LaAlO$_3$ and SrTiO$_3$ with different polarity can induce conductivity at the interface. We carried out density functional theory (DFT) calculations based on the full potential linearized augmented planewave (FLAPW) method as implemented in the {\tt FLEUR} code (www.flapw.de) for studying the polar to non-polar interface of DyScO$_3$ and SrTiO$_3$. Due to the polar discontinuity, arising from nominally charged DyO or ScO$_2$ layers, sharp interfaces induce a strong ferroelectric-like polarization in the SrTiO$_3$ , while in off-stoichiometric interfaces this discontinuity is avoided and no such polarization can be found. In both scenarios the interface remains insulating with only a small reduction of the bandgap. Our calculations show that chemically mixed interfaces are energetically more favorable than sharp ones. Our DFT calculations explore also different configurations of the Dy and Sr atoms within the mixed interface plane. The calculated ground state configuration is confirmed by experimental observations.