Localization and Magnetotransport at the LaAlO$_{3}$/SrTiO$_{3}$ Heterointerface

Low-temperature electrical transport experiments of the metallic LaAlO$_{3}$/SrTiO$_{3}$ heterointerface have revealed a vast array of physical phenomena, including superconductivity, weak localization, and possible magnetic ordering. Through a study of LaAlO$_{3}$ films ranging from 1.6 to 15 nm grown on TiO$_{2}$-terminated (001) SrTiO$_{3}$ substrates, we show that there is an evolution of transport that converges when the film thickness reaches to 5-6 nm. In general, thicker samples have larger carrier densities, but lower low-temperature mobility values. In addition, field-dependent magnetoresistance data show that higher carrier density samples exhibit antilocalization effects. Together these results suggest greater disorder-induced elastic scattering and strong spin-orbit coupling, which may arise from large electric fields at the heterointerface. In contrast, lower carrier density samples exhibit large in-plane negative magnetoresistance and no features of antilocalization. Carrier density and disorder play prominent roles in determining the field-dependent carrier transport in the metallic conduction regime.