Emerging weak localization effects on a topological insulator–insulating ferromagnet (Bi2Se3-EuS) interface

Abstract

Thin films of topological insulator Bi${}_{2}$Se${}_{3}$ were deposited directly on insulating ferromagnetic EuS. Unusual negative magnetoresistance was observed near the zero field below the Curie temperature ${T}_{C}$, resembling the weak localization effect; whereas the usual positive magnetoresistance was recovered above ${T}_{C}$. Such negative magnetoresistance was only observed for Bi${}_{2}$Se${}_{3}$ layers thinner than $t\ensuremath{\sim}4$ nm, when its top and bottom surfaces are coupled. These results provide evidence for a proximity effect between a topological insulator and an insulating ferromagnet, laying the foundation for future realization of the half-integer quantized anomalous Hall effect in three-dimensional topological insulators.