The atomic-level control achievable in artificially structured oxide superlattices provides a unique opportunity to explore interface phases of matter including high-density two-dimensional (2D) electron gases. Electronic-structure calculations show that the charge distribution introduced by ${\mathrm{LaTiO}}_3$ monolayers in ${\mathrm{SrTiO}}_3$ is strongly modulated by electron-phonon interactions with significant ionic polarization. Anharmonic finite-temperature effects must be included to reproduce experiment. Density functional perturbation theory is used to parametrize a simple model introduced to represent these effects and predict temperature dependencies.

• Received 12 January 2006

DOI:https://doi.org/10.1103/PhysRevB.73.195403