Emerging properties of the two-dimensional electron gas at LaAlO₃/TiO₂ heterointerfaces on piezoelectric 0.7PbMg_1/3Nb_2/3O₃-0.3PbTiO₃ substrates

Understanding and controlling the emergent electronic transport properties at interfaces of oxides has been a major issue in condensed matter physics for both fundamental science and technological applications. In this work, we report a two-dimensional electron gas (2DEG) formed at the interfaces of amorphous-LaAlO₃/TiO₂ (a-LAO/TiO₂) thin film heterostructures on piezoelectric 0.7PbMg_1/3Nb_2/3O₃-0.3PbTiO₃ (PMN-PT) substrates, where the conductive layer is about 2.48 nm. The Kondo behaviors below 50 K are observed depending on TiO₂ thickness. In addition, unique negative magnetoresistance (MR) and asymmetry planar angular MR imply the presence of Rashba spin-orbit interactions. Furthermore, the electric-field-controlled hysteresis loop-like resistance changes were obtained in a-LAO/TiO₂/PMN-PT heterostructures. A resistance enhancement of ∼8% at room temperature was achieved at an electric field of −1 kV/cm, which indicates that such 2DEG is rather sensitive to the strain in the TiO₂ layer. Thus, this work creates a path to exploring the physics of low-dimensional oxide electronics and nonvolatile memory and logic devices.