Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect

TL;DR

This paper demonstrates that magnetic modulation doping in topological insulators significantly raises the temperature at which the quantum anomalous Hall effect can be observed, from below 300 mK to 2 K, by reducing surface state disorder.

Contribution

The study introduces a novel magnetic-Cr modulation doping technique in topological insulators to enhance the observable temperature of QAHE, achieving a substantial increase to 2 K.

Findings

QAHE observed up to 2 K with modulation doping

Suppression of surface state disorder improves QAHE stability

Superlattice design enables higher-temperature dissipation-less conduction

Abstract

Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs), such as Cr- and V-doped (Bi,Sb)2Te3. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb)2Te3 films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of the both surfaces based on non-Cr-doped (Bi,Sb)2Te3 films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the highertemperature and zero magnetic-field quantum conduction.