Wedge-Shaped Potential and Airy-Function Electron Localization in Oxide Superlattices

Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies of the recently fabricated, lattice-matched perovskite titanates (SrTiO₃)_n/(LaTiO₃)_m reveal a classic wedge-shaped potential well for the monolayer (m=1) structure, originating from the Coulomb potential of a two-dimensional charged La sheet. The potential in turn confines the electrons in the Airy-function-localized states. Magnetism is suppressed for the monolayer structure, while in structures with a thicker LaTiO₃ part, bulk antiferromagnetism is recovered, with a narrow transition region separating the magnetic LaTiO₃ and the nonmagnetic SrTiO₃.