Interface-induced ferromagnetism and superconductivity in two-dimensional electron gases

Abstract

Interface is a device,” as Herbert Kroemer stated, highlighting how interfaces can drastically alter material properties. Oxide thin films offer a rich platform for such engineering, especially due to strong electron correlations in Mott insulators. Oxide interfaces host two-dimensional electron gases (2DEGs) with high carrier densities, enabling functionalities like ferromagnetism, superconductivity, and strong spin-orbit coupling. This thesis investigates 2DEGs at KTaO₃/LaTiO₃ interfaces grown by MBE. Ferromagnetism with high mobility is observed via Hall and XMCD measurements. Density functional theory attributes magnetism to TiO₆ tilting. KTO(111)/LTO also shows superconductivity (~1 K) coexisting with ferromagnetism, with a dome-like Tc dependence on LTO thickness. Additionally, proximity effects with TiN overlayers reveal new superconducting behavior, suggesting unconventional mechanisms at oxide/nitride interfaces.