Growth and transport properties of topological insulator Bi_2Se_3 thin film on a ferromagnetic insulating substrate

Exchange coupling between topological insulator and ferromagnetic insulator through proximity effect is strongly attractive for both fundamental physics and technological applications. Here we report a comprehensive investigation on the growth behaviors of prototype topological insulator Bi_2Se_3 thin film on a single-crystalline LaCoO_3 thin film on SrTiO_3 substrate, which is a strain-induced ferromagnetic insulator. Different from the growth on other substrates, the Bi_2Se_3 films with highest quality on LaCoO_3 favor a relatively low substrate temperature during growth. As a result, an inverse dependence of carrier mobility with the substrate temperature is found. Moreover, the magnetoresistance and coherence length of weak antilocalization also have a similar inverse dependence with the substrate temperature, as revealed by the magnetotransport measurements. Our experiments elucidate the special behaviors in Bi_2Se_3/LaCoO_3 heterostructures,which provide a good platform for exploring related novel quantum phenomena, and are inspiring for device applications.     

Electron localization in ultrathin films of three-dimensional topological insulators

The recent discovery of three-dimensional(3D) topological insulators(TIs) has provided a fertile ground for obtaining further insights into electron localization in condensed matter systems.In the past few years,a tremendous amount of research effort has been devoted to investigate electron transport properties of 3D TIs and their low dimensional structures in a wide range of disorder strength,covering transport regimes from weak antilocalization to strong localization.The knowledge gained from these studies not only offers sensitive means to probe the surface states of 3D TIs but also forms a basis for exploring novel topological phases.In this article,we briefly review the main experimental progress in the study of the localization in 3D TIs,with a focus on the latest results on ultrathin TI films.Some new transport data will also be presented in order to complement those reported previously in the literature.