Enhancement of Rashba spin-orbit coupling by electron confinement at the LaAlO/SrTiO interface.

Electrical transport property is closely related to the dimensionality of carriers' distribution. In this work, we succeed in tuning the carriers' distribution and the Rashba spin-orbit coupling at LaAlO/SrTiO interface by varying the oxygen pressure (c-P ) adopted in crystalline LaAlO growth. Measurements of the in-plane anisotropic magnetoresistance and the conducting-layer thickness indicate that the carriers' distribution changes from three to two dimensions with c-P increasing, i.e. the electron confinement gets stronger. Importantly, by measuring the low-temperature out-of-plane magnetoresistance and analyzing the weak localization/weak anti-localization, we find that the strength of Rashba spin-orbit coupling can be enhanced by electron confinement. The electron confinement is a manifestation of breaking of spatial inversion symmetry. Therefore, our work reveals the intimate relationship between spatial inversion symmetry breaking and Rashba spin-orbit coupling at the LaAlO/SrTiO interface, and provides a new method to tune the Rashba spin-orbit coupling, which is valuable in the application of oxide-spintronics.