Defect-controlled transport phenomena at complex oxide interfaces

Electric-field control of 2-dimensional electron systems (2DES) in oxide heterostructures is a key tool for tuning properties such as carrier density, magnetism, and superconductivity. There remain open questions however if in all cases gate-tunable properties can be ascribed to electronic phenomena deriving directly from varying the charge accummulated in the interfacial potential well. Here, we discuss that various gate-tunable properties observed in 2DES can also be mimicked by controlling the ionic defect structure and lattice disorder in the vicinity of the interface. As we will show accumulation of scatter centers at the interface can result in diminished charge transfer, while the magnetic response of the electron system is enhanced and quantum interference phenomena (weak-anti-localization) arise. Additionally, we discuss how a controlled and homogenous defect background in thin film SrTiO₃ intrinsically yields a transition from positive to negative magnetoresistance, at comparable carrier concentration. Our results yield an ionic-electronic perspective on electrical gating experiments frequently conducted in the oxide electronics community. We provide a comprehensive discussion of the coupling of electronic gating and gradual defect profiles.