Transition-metal oxides (TMOs) show remarkable properties, not found in standard semiconductors, such as high-temperature superconductivity, large magnetoresistance, metalto-insulator transitions, or photo-catalytic behavior. The realization of two-dimensional electron gases (2DEGs) in TMOs is crucial for harnessing the functionalities of these materials for future applications. Additionally, such 2DEGs offer the possibility to explore new physics emerging from the combined effects of electron correlations and low-dimensional confinement.
In this talk, I will first introduce our discovery that 2DEGs can be simply realized at the surface of various insulating transparent TMOs, such as the quantum paraelectric SrTiO3 [1], the strong spin-orbit coupled KTaO3 [2], or the photo-catalyst TiO2 [3]. Then, I will show how the choice of the surface termination allows tailoring the electronic structure and symmetries of these 2DEGs [4-5], paving the way for the quest of topological states in correlated oxides.
Furthermore, I will discuss our studies of magnetism in the 2DEG at the surface of oxygendeficient SrTiO3 [6]. These results show that confined electronic states at oxide surfaces can be endowed with novel properties, not present in the bulk, which are promising for technological applications. Finally, I will describe our recent development of a universal, simple and cheap, method to fabricate these 2DEGs in several other oxides, such as the ferroelectric BaTiO3, which simultaneously protects the 2DEG from passivation in air and allows measuring its transport characteristics –and is thus promising for the realization of oxide devices [7].
