Two-dimensional superconductivity at a Mott insulator/band insulator interface LaTiO₃/SrTiO₃

Abstract

Transition metal oxides show a great variety of quantum electronic behaviours where correlations often have an important role. The achievement of high-quality epitaxial interfaces involving such materials gives a unique opportunity to engineer artificial structures where new electronic orders take place. One of the most striking result in this area is the recent observation of a two-dimensional electron gas at the interface between a strongly correlated Mott insulator LaTiO₃ and a band insulator SrTiO₃. The mechanism responsible for such a behaviour is still under debate. In particular, the influence of the nature of the insulator has to be clarified. In this article, we show that despite the expected electronic correlations, LaTiO₃/SrTiO₃ heterostructures undergo a superconducting transition at a critical temperature T_c^onset~300mK. We have found that the superconducting electron gas is confined over a typical thickness of 12nm and is located mostly on the SrTiO₃ substrate.