In this talk, I will first introduce our discovery that 2DEGs can be simply realized at the surface of various insulating TMOs, such as the quantum paraelectric SrTiO3 [1], the strong spin-orbit coupled KTaO3 [2], or the photo-catalyst TiO2 [3]. 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 oxygen-deficient surface of SrTiO3 [6]. I will then describe our recent development of a simple universal method to fabricate these 2DEGs in several other oxides, such as the ferroelectric BaTiO3 [7] or the binary semiconductor ZnO [8]. This novel technique allows engineering functional interfaces between the 2DEG and, e.g., tunable magnetic layers [9], and measuring their transport characteristics [10] –and is thus promising for applications.

[1] A. F. Santander-Syro et al., Nature 469, 189 (2011). [2] A. F. Santander-Syro et al., Phys. Rev. B 86, 121107(R) (2012). [3] T. C. Rödel et al., Phys. Rev. B 92, 041106(R) (2015). [4] C. Bareille et al., Sci. Rep. 4, 3586 (2014). [5] T. C. Rödel et al., Phys. Rev. Applied 1, 051002 (2014). [6] T. Taniuchi et al, Nat. Commun. doi : 10.1038/NCOMMS11781 (2016). [7] T. C. Rödel et al., Adv. Mater. doi:10.1002/adma.201505021 (2016). [8] T. C. Rödel et al., Phys. Rev. Materials (Rapid Comms), Accepted (2018). arXiv:1802.06907. [9] P. Lömker et al., Phys. Rev. Mater. 1, 062001(R) (2017). [10] S. Sengupta et al. submitted (2018).