The response of oxide thin films to polar discontinuities at interfaces and surfaces has generated enormous activity due to the variety of interesting effects that it gives rise to. A case in point is the discovery of the electron gas at the interface between LaAlO3 and SrTiO3, which has since been shown to be quasi-two-dimensional, switchable, magnetic and/or superconducting. Despite these findings, the origin of the two-dimensional electron gas is highly debated and several possible mechanisms remain. Here we review the main proposed mechanisms and attempt to model expected effects in a quantitative way with the ambition of better constraining what effects can/cannot explain the observed phenomenology.

The origin of two-dimensional electron gases at oxide interfaces: insights from theory, N. C. Bristowe, P. Ghosez, P. B. Littlewood and E. Artacho, topical review in J. Phys.: Condens. Matter 26 p. 143201 (2014).