Quantum transport at oxide interfaces

Abstract

The realization of interfaces between different transition metal oxides has heralded a new era of materials and physics research. Notably, it enabled a uniquely diverse set of coexisting physical properties to be combined with an ever-increasing degree of experimental control. The primary focus of this thesis is the celebrated interface between the two wide band-gap insulators LaAlO3 and SrTiO3, which exhibits a variety of phenomena such as conductivity, superconductivity and spin–orbit coupling—all of which are gate-tunable, demonstrating the promise of this system for fundamental research and technological applications alike. We start by discussing the role of spin–orbit coupling in the magnetotransport properties of the system. Namely, we show how it can drive a giant in-plane magnetoresistance. On a more technically challenging perspective, we realize tunable Josephson junctions by means of lateral confinement and local side-gating. This technique, due to its simplicity, can be expanded to a broad group of interfacial systems. We then investigate LaAlO3/SrTiO3 interfaces along the (111) crystallographic direction, discovering that it condenses into a superconducting ground state and elucidating the important role played by electronic correlations. Finally, this thesis ends with a twist to the story. Moving away from epitaxial interfaces, we employ an innovative technique to obtain free-standing oxide films by etching a water-soluble sacrificial buffer layer. This exciting development paves the way to integrating complex oxides with van der Waals materials and engineering new phases in hybrid devices.