Weak localization effect in topological insulator micro flakes grown on insulating ferrimagnet BaFe12O19

TL;DR

This study demonstrates that magnetic proximity effect in topological insulator micro flakes grown on ferrimagnetic insulator BaFe12O19 can open a surface state gap, evidenced by weak localization effects, with potential for spintronics applications.

Contribution

It provides experimental evidence of a 10 meV surface state gap in topological insulators induced by magnetic proximity to BaFe12O19, using van der Waals epitaxy.

Findings

Weak localization observed below 50 K in micro flakes.

Surface state gap estimated at 10 meV.

Magnetic proximity effect can open a topological surface gap.

Abstract

Many exotic physics anticipated in topological insulators require a gap to be opened for their topologica surface states by breaking time reversal symmetry. The gap opening has been achieved by doping magnetic impurities, which however inevitably create extra carriers and disorder that undermine the electronic transport. In contrast, the proximity to a ferromagnetic/ferrimagnetic insulator may improve the device quality, thus promises a better way to open the gap while minimizing the side-effects. Here, we grow thin single-crystal Sb1.9Bi0.1Te3 micro flakes on insulating ferrimagnet BaFe12O19 by using the van der Waals epitaxy technique. The micro flakes show a negative magnetoresistance in weak perpendicular fields below 50 K, which can be quenched by increasing temperature. The signature implies the weak localization effect as its origin, which is absent in intrinsic topological insulators, unless a surface state gap is opened. The surface state gap is estimated to be 10 meV by using the theory of the gap-induced weak localization effect. These results indicate that the magnetic proximity effect may open the gap for the topological surface attached to BaM insulating ferrimagnet. This heterostructure may pave the way for the realization of new physical effects as well as the potential applications of spintronics devices.