Display of Spin–Orbit Coupling at ReAlO₃/SrTiO₃ (Re = La, Pr, Nd, Sm, and Gd) Heterointerfaces

Complex oxide heterointerfaces provide a platform to manipulate spin–orbit coupling under the broken inversion symmetry. Moreover, their weak antilocalization (WAL) effect displays quantum coherent behavior due to the strong spin–orbit coupling. Herein, we break through the limitation of lattice mismatch at ReAlO3/STO (Re = La, Pr, Nd, Sm, and Gd) heterointerfaces and obtain their two-dimensional electric gas (2DEG) by spin coating. The effect of different Re elements in the resulting quantum corrections on the conductivity is investigated. It is observed that the conductivity of heterointerfaces is reduced with larger atomic numbers due to the ionization potential of Re elements. Moreover, magnetoresistance (MR) measurements in a perpendicular or a parallel field distinctly uncover strong Rashba spin–orbit coupling (SOC) in ReAO/STO samples besides SAO/STO (Re = Sm) and GAO/STO (Re = Gd), and the effective fields of the SOC (Hso) gradually increase from LAO/STO (Re = La, Hso = 0.82 T) to NAO/STO (Re = Nd, Hso = 1.37 T) at 2 K. The competition between SOC scattering and inelastic scattering is revealed through a temperature-dependence study of MR, and the WAL–weak localization transition is at about 6 K. Furthermore, unambiguous results of the Kondo effect, nonlinear Hall, hysteresis loop, and Rashba SOC suggest the coexistence of WAL at the PAO/STO (Re = Pr) heterointerface with exchange coupling between the localized magnetic moment and the itinerant electron. These results pave a unique route for the exploration of spin-polarized 2DEGs at oxide heterointerfaces.