Electronic correlation and strain effects at the interfaces between polar and nonpolar complex oxides

The interface between the polar LaAlO ₃ and nonpolar SrTiO ₃ layers has been shown to exhibit various electronic and magnetic phases such as two-dimensional electron gas (2DEG), superconductivity, magnetism, and electronic phase separation. These rich phases are expected due to the strong interplay between charge, spin, and orbital degree of freedom at the interface between these complex oxides, leading to the electronic reconstruction in this system. However, until now all of these new properties have been studied extensively based on the interfaces which involve a polar LaAlO ₃ layer. To investigate the role of the ABO ₃ polar layer, here we study various combinations of polar/nonpolar oxide (NdAlO ₃/SrTiO ₃, PrAlO ₃/SrTiO ₃, and NdGaO ₃/SrTiO ₃) interfaces which are similar in nature to the LaAlO ₃/SrTiO ₃ interface. Our results show that all of these new interfaces can also produce 2DEG at their interfaces, supporting the idea that the electronic reconstruction could be the driving mechanism for the creation of the 2DEG at these oxide interfaces. Furthermore, the electrical properties of these interfaces are shown to be governed by the interface strain and the type of cations in the polar overlayers. Our observations may provide an approach to further tune the properties of the 2DEG at the selected polar/nonpolar oxide interfaces.