Two-dimensional electron gases (2DEGs) at interfaces between two insulating oxides have attracted significant attention because they can exhibit unique properties, such as strong electron correlations, superconductivity and magnetism. In this presentation, we will discuss emergent properties at interfaces and quantum wells formed between Mott insulating rare earth titanates (SmTiO3 and GdTiO3), and the band insulator SrTiO3. Such interfaces exhibit a high-density 2DEG, of approximately ½ electron per surface unit cell, providing ~ 3×1014 cm-2 mobile charge per interface. We will start with an overview of the basic properties of these materials, their physics, and recent advances in controlling growth and interface properties. We show that the subband structure can be probed using quantum oscillations and resonant

tunneling studies. We investigate electron correlation effects due to short-range Coulomb interactions and metal-insulator transitions in narrow quantum wells bound by two such interfaces, and the role of coupling to the lattice. 

This work was performed in collaboration with Clayton Jackson, Santosh Raghavan, Pouya Moetakef, Jack Zhang, Jinwoo Hwang, Evgeny Mikheev, Adam Kajdos, Leon Balents, and Jim Allen.