Demonstration of robust quantum anomalous Hall effect (QAHE) in macroscopic and 3D ferromagnetic topological insulator system
Wei-Li Lee1*, Xufeng Kou2, Shih-Ting Guo1, Yabin Fan2, Lei Pan2, Murong Lang2, Ying Jiang3, Qiming Shao2, Tianxiao Nie2, Koichi Murata2, Jianshi Tang2, Yong Wang3, Liang He2, Ting-Kuo Lee1, Kang L. Wang2
1Institute of Physics, Academia Sinica, Taipei, Taiwan
2Department of Electrical Engineering, University of California, Los Angeles, California, United States of America
3Department of Materials Science and Engineering, Zhejiang University, Hangzhou, China
* presenting author:Wei-Li Lee,
Anomalous Hall effect refers to the phenomenon of linear proportionality between the anomalous Hall resistance and its magnetic moment in a magnetic system. In normal magnetic metal and semiconductor, there is no universal value for the anomalous Hall resistance. Nevertheless, in a ferromagnetic topological insulator (FM TI) under zero external magnetic field, the Dirac surface states, originating from the non-trivial bulk band topology, attain different effective masses on different surfaces. This results in a dissipationless chiral edge channel forming at the Dirac fermion mass domain-wall and gives rise to the quantization of the anomalous Hall resistance. We report the observation of (QAHE) in our 10-quintuple layer Cr-doped (BiSb)₂Te₃ film grown by MBE technique. The Hall resistance Rxy attains quantized value of h/e2 (25.8 kΩ) as temperature drops below 85 mK. Unlike previous report in a thinner Cr-doped (BiSb)₂Te₃ film, a finite longitudinal resistance is found in QAHE regime and remains non-zero up to 15 Tesla suggesting the coexistence of the chiral edge channel and certain dissipative conduction channel. From macroscopic non-local transport measurements with leads separated by few millimeters, we further identify the dissipationless nature of the chiral edge channel associated with the QAHE. This may provide a new direction for resolving the heat dissipation problem in electronics using dissipationless chiral edge channel in a topological material.

Keywords: topological insulator, Anomalous Hall effect, Quantum anomalous Hall effect , Magnetism