Quantum Anomalous Hall effect in Cr-doped (Bi, Sb)₂Te₃ multilayer magnetic topological insulators.

Quantum anomalous Hall effect (QAHE) in magnetic ion-doped topological insulators (TIs) has been actively researched with great attention by virtue of its fascinating phenomena of quantized Hall resistance at zero external magnetic field. Even though various approaches have been reported so far to increase the QAHE temperature, the observable temperature of the QAHE has been limited below 500 mK without the help of gating.  

In this presentation, we investigate the QAHE with tuning Cr and Bi doping concentrations in multilayer magnetic TIs. As a platform, we employed a trilayer Cr-doped (Bi, Sb)₂Te₃ structure with heavy Cr doping at outer (top and bottom) layers. To increase the QAHE temperature, we systematically tune Bi and Cr concentrations in inner and outer MTI layers and, in a sample with optimized doping, observe close to the fully quantized value at 2 K without the external electric field for gating. We believe that this finding might be helpful for further study in high-temperature QAHE.