Ranjani Ramachandran Dissertation Defense

Thesis Title: Hybrid quantum transport in complex oxide 2D electron gases: LaAlO$_3$/SrTiO$_3$ and LaAlO$_3$/KTaO$_3$ Abstract: Two-dimensional electron gases (2DEGs) at complex oxide interfaces have emerged as a versatile platform for exploring novel quantum transport phenomena. Unlike conventional semiconductor 2DEGs, interfaces such as LaAlO$_3$/SrTiO$_3$ (LAO/STO) and LaAlO$_3$/KTaO$_3$ (LAO/KTO) combine gate-tunable electronic transport with intrinsic superconductivity, offering unique opportunities for investigating mesoscopic quantum devices. In this talk, I will present these oxide interfaces as a versatile platform for hybrid quantum transport, highlighting their properties through acoustic, microwave, thermoelectric, and magnetotransport measurements. I will first discuss the generation and characterization of surface acoustic waves in LAO/STO and LAO/KTO. I demonstrate acoustoelectric transport in LAO/KTO, which can be used to shuttle charge carriers across quantum devices. I will then explore superconducting microwave resonators fabricated on LAO/KTO, highlighting their potential for parametric amplification. Next, I will present thermoelectric measurements of the superconducting state through the Nernst effect, providing new insights into superconductivity in LAO/KTO. Finally, I will discuss magnetotransport in coupled nanowire arrays fabricated in LAO/STO, illustrating the rich quantum transport phenomena that emerge in confined oxide nanostructures.