The electric-field tunable Rashba spin-orbit coupling at the LaAlO3/SrTiO3 interface shows potential applications in spintronic devices. However, different gate dependence of the coupling strength... Show moreThe electric-field tunable Rashba spin-orbit coupling at the LaAlO3/SrTiO3 interface shows potential applications in spintronic devices. However, different gate dependence of the coupling strength has been reported in experiments. On the theoretical side, it has been predicted that the largest Rashba effect appears at the crossing point of the dxy and dxz,yz bands. In this work, we study the tunability of the Rashba effect in LaAlO3/SrTiO3 by means of backgating. The Lifshitz transition was crossed multiple times by tuning the gate voltage so that the Fermi energy is tuned to approach or depart from the band crossing. By analyzing the weak antilocalization behavior in the magnetoresistance, we find that the maximum spin-orbit coupling effect occurs when the Fermi energy is near the Lifshitz point. Moreover, we find strong evidence for a single spin winding at the Fermi surface. Show less
In LaAlO3/SrTiO3 heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent... Show moreIn LaAlO3/SrTiO3 heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent Schrödinger-Poisson calculations, we obtain an empirical relation between the amount of trapped electrons and the gate voltage. The amount of trapped electrons decays exponentially away from the interface. However, contrary to earlier observations, we find that the Fermi level remains well within the quantum well. The enhanced trapping of electrons induced by the gate voltage can therefore not be explained by a thermal escape mechanism. Further gate sweeping experiments strengthen that conclusion. We propose a new mechanism which involves the electromigration and clustering of oxygen vacancies in SrTiO3 and argue that such electron trapping is a universal phenomenon in SrTiO3-based two-dimensional electron systems. Show less
