Low-temperature magnetoresistance of (111) ( La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3

The two-dimensional conducting interfaces in ${\mathrm{SrTiO}}_{3}$-based systems are known to show a variety of coexisting and competing phenomena in a complex phase space. Magnetoresistance measurements, which are typically used to extract information about the various interactions in these systems, must be interpreted with care, since multiple interactions can contribute to the resistivity in a given range of magnetic field and temperature. Here we review all the phenomena that can contribute to transport in ${\mathrm{SrTiO}}_{3}$-based conducting interfaces at low temperatures. We apply this understanding to the perpendicular magnetoresistance data of the high-mobility system of (111) oriented $({\mathrm{La}}_{0.3}{\mathrm{Sr}}_{0.7})({\mathrm{Al}}_{0.65}{\mathrm{Ta}}_{0.35}){\mathrm{O}}_{3}/\mathrm{STO}$ heterostructures, and find an excess negative magnetoresistance contribution which cannot be explained by weak localization alone. We argue that contributions from magnetic scattering as well as electron-electron interactions, combined with weak localization/antilocalization, can provide a possible explanation for the observed magnetoresistance.