Density-Functional Study of the Two-Dimensional Electron Gas at the Perovskite Titanate Interface

Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies$^{1}$ of the recently fabricated, lattice-matched perovskite titanates$^{2}$ (SrTiO$_{3})_{n}$/(LaTiO$_{3})_{m}$ reveal a classic wedge-shaped potential well for the monolayer structure, originating from the Coulomb potential of a charged La sheet. The potential in turn confines the electrons in the Airy-function-localized states. This resulting two-dimensional electron gas may be described in terms of the simplified jellium model$^{3}$ and it describes reasonably well the observed charge modulation of the Ti atoms near the interface. Concerning magnetism, it is suppressed for the monolayer LaTiO$_{3}$ structure, while in structures with a thicker LaTiO$_{3}$ part, bulk antiferromagnetism is recovered, with a narrow transition region separating the magnetic LaTiO$_{3}$ and the non-magnetic SrTiO$_{3}$. 1. Z. S. Popovic and S. Satpathy, Phys. Rev. Lett. \underline {94}, 176805 (2005) 2. A. Ohtomo et al., Nature \underline {419}, 378 (2002) 3. S. Thulasi and S. Satpathy, Phys. Rev. B (2006)