Two-component anomalous Hall effect in a magnetically doped topological insulator

Nan Liu,Yongqing Li,Jing Teng

doi:10.1038/s41467-018-03684-0

Abstract

The anomalous Hall (AH) effect measurement has emerged as a powerful tool to gain deep insights into magnetic materials, such as ferromagnetic metals, magnetic semiconductors, and magnetic topological insulators (TIs). In Mn-doped Bi2Se3, however, the AH effect has never been reported despite a lot of previous studies. Here we report the observation of AH effect in (Bi,Mn)2Se3 thin films and show that the sign of AH resistances changes from positive to negative as the Mn concentration is increased. The positive and negative AH resistances are found to coexist in a crossover regime. Such a two-component AH effect and the sign reversal can also be obtained by electrical gating of lightly doped samples. Our results provide an important basis for understanding the puzzling interplay between the surface states, the bulk states, and various magnetic doping effects, as well as competing magnetic orders in magnetically doped TIs.

Highlights

Anomalous Hall (AH) effect is one of the most fundamental transport properties of magnetic materials, in which the interplay between magnetism and spin-orbit coupling produces a transverse Hall voltage perpendicular to the applied current and the magnetization[1,2]
Study of the AH effect has since become a valuable tool to understand the electronic properties of magnetic metals and semiconductors, interpretations of the experimental results are often complicated by the details of band structures as well as the existence of extrinsic sources of AH effect[1,2], namely skew scattering[5] and side jump[6]
The magnetically doped topological insulators (TIs) have received intensive experimental efforts[13], and the work on ferromagnetic (FM) order in Cr-doped (Bi,Sb)2Te3 thin films has led to the seminal discovery of quantum anomalous Hall effect (QAHE)[14]

Summary

Introduction

Anomalous Hall (AH) effect is one of the most fundamental transport properties of magnetic materials, in which the interplay between magnetism and spin-orbit coupling produces a transverse Hall voltage perpendicular to the applied current and the magnetization[1,2]. A recent study combining ARPES and other techniques has strongly suggested a non-magnetic origin for the surface energy gap in the Mn-doped Bi2Se3, in contradiction to the earlier findings[15,20]. It remains an open question how the non-magnetic gap, or more generally, the non-magnetic scattering effect of the magnetic impurities competes with magnetic interactions in the Mn-doped Bi2Se3 and other magnetically doped TIs. very few experimental techniques can probe the magnetic order in both the surface and bulk states at very low temperatures. Our results suggest that the nonmagnetic scattering effects of the magnetic dopants can have a profound impact on the transport properties of magnetic TIs, and should be taken into account in seeking high quality TI-based magnetic materials

Methods

Results

Conclusion