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 LaTio 3 and a band insulator srTio 3 . 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, LaTio 3 /srTio 3 heterostructures undergo a superconducting transition at a critical temperature T c onset~3 00 mK.We have found that the superconducting electron gas is confined over a typical thickness of 12 nm and is located mostly on the srTio 3 substrate.

The electrical conductivity of the two‐dimensional (2D) electron gas at the interface of epitaxially grown ultrathin films of LaTiO3 on SrTiO3 shows a large gain upon near‐UV excitation. The gain in conductivity can be turned on or off by the application of a gate voltage of correct polarity. This feature of the 2D gas should allow realization of optoelectronic devices whose functionality can be enhanced by sequential application of an electric field and light.

We have investigated the temperature driven first order metal-insulator transition in thin films of NdNiO3 and have compared it with the bulk behavior. The M-I transition of thin films is sensitive to epitaxial strain and a partial relaxation of epitaxial strain creates an inhomogeneous strain field in the films which broadens the M-I transition. Both the thin film and the bulk samples exhibit non equilibrium features in the transition regime which are attributed to the presence of high temperature metallic phases in their supercooled state. The degree of supercooling in the thin films is found to be much smaller than in the bulk which suggests that the metal insulator transition in the thin film occurs through heterogeneous nucleation.

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