Experimental Observation of the Quantum Anomalous Hall Effect in a Magnetic Topological Insulator

TLDR

The quantized anomalous Hall effect was predicted in magnetic topological insulators, but experimental realization had been difficult. The authors observe the quantum anomalous Hall effect in Cr‑doped (Bi,Sb)₂Te₃ thin films, with zero‑field gate‑tuned Hall resistance reaching the quantized value h/e² and longitudinal resistance dropping, and under strong magnetic field the longitudinal resistance vanishes while the Hall resistance stays quantized, suggesting prospects for low‑power electronics.

Abstract

The quantized version of the anomalous Hall effect has been predicted to occur in magnetic topological insulators, but the experimental realization has been challenging. Here, we report the observation of the quantum anomalous Hall (QAH) effect in thin films of Cr-doped (Bi,Sb)2Te3, a magnetic topological insulator. At zero magnetic field, the gate-tuned anomalous Hall resistance reaches the predicted quantized value of h/e^2,accompanied by a considerable drop of the longitudinal resistance. Under a strong magnetic field, the longitudinal resistance vanishes whereas the Hall resistance remains at the quantized value. The realization of the QAH effect may lead to the development of low-power-consumption electronics.