Giant negative magnetoresistance driven by spin-orbit coupling at the LAO/STO interface

The LAO/STO interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70\%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with Kondo-screened magnetic impurities. Here we report on experiments over a broad temperature range, showing the persistence of the magnetoresistance up to the 20~K range --- indicative of a single-particle mechanism. Motivated by a striking correspondence between the temperature and carrier density dependence of our magnetoresistance measurements we propose an alternative explanation. Working in the framework of semiclassical Boltzmann transport theory we demonstrate that the combination of spin-orbit coupling and scattering from finite-range impurities can explain the observed magnitude of the negative magnetoresistance, as well as the temperature and electron density dependence.
Comment: new updates from feedback and review process. main text: improved discussion of the mechanisms of the MR; a discussion of a rescaling of the MR with a characteristic field B*(n). supplemental: theoretical estimate of the "sweet spot" density and window; effect of an out-of-plane B-field component on the MR; discussion of spin-orbit corrections to Boltzmann transport. 6+4 pages, 4+4 figures