Highly Confined Spin-Polarized Two-Dimensional Electron Gas in SrTiO3/SrRuO3 Superlattices

Phys Rev Lett. 2012 Mar 9;108(10):107003. doi: 10.1103/PhysRevLett.108.107003. Epub 2012 Mar 8.


We report first-principles characterization of the structural and electronic properties of (SrTiO3)5/(SrRuO3)1 superlattices. We show that the system exhibits a spin-polarized two-dimensional electron gas, extremely confined to the 4d orbitals of Ru in the SrRuO3 layer. Every interface in the superlattice behaves as a minority-spin half-metal ferromagnet, with a magnetic moment of μ=2.0μ(B)/SrRuO3 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 bidimensionality of the system and (ii) strong electron correlations.