Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)+1 plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~ 7E14 cm-2
@article{arxiv.1404.2556,
title = {High-density two-dimensional small polaron gas in a delta-doped Mott insulator},
author = {Daniel G. Ouellette and Pouya Moetakef and Tyler A. Cain and Jack Y. Zhang and Susanne Stemmer and David Emin and S. James Allen},
journal= {arXiv preprint arXiv:1404.2556},
year = {2014}
}