Tuning Rashba spin-orbit coupling at LaAlO3/SrTiO3 interfaces by band filling

Abstract

The electric-field tunable Rashba spin-orbit coupling at the ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ 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 ${d}_{\text{xy}}$ and ${d}_{\text{xz},\text{yz}}$ bands. In this work, we study the tunability of the Rashba effect in ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ 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.