Highly-confined spin-polarized two-dimensional electron gas in   SrTiO$_{3}$/SrRuO$_{3}$ superlattices
  We report first principles characterization of the structural and electronic properties of (SrTiO$_{3}$)$_{5}$/(SrRuO$_{3}$)$_{1}$ superlattices. We show that the system exhibits a spin-polarized two-dimensional electron gas, extremely confined to the 4$d$ orbitals of Ru in the SrRuO$_{3}$ layer. Every interface in the superlattice behaves as a minority-spin half-metal ferromagnet, with a magnetic moment of $\mu$ = 2.0 $\mu_{\rm B}$/SrRuO$_{3}$ unit. The shape of the electronic density of states, half metallicity and magnetism are explained in terms of a simplified tight-binding model, considering only the $t_{2g}$ orbitals plus (i) the bi-dimensionality of the system, and (ii) strong electron correlations. 
Marcos Verissimo-Alves, Pablo Garc\'ia-Fern\'andez, Daniel I. Bilc,   Philippe Ghosez, and Javier Junquera
cond-mat.mtrl-sci