Precise quantization of anomalous Hall effect near zero magnetic field

TL;DR

This paper demonstrates nearly perfect quantum anomalous Hall effect in a topological insulator thin film with ferromagnetic doping, achieving precise quantization near zero magnetic field and identifying thermal effects as deviations.

Contribution

It reports the first near-ideal quantization of the quantum anomalous Hall effect at zero magnetic field in a three-dimensional topological insulator with ferromagnetic doping.

Findings

Exact quantization within 1 part in 10,000

Longitudinal resistivity under 1 ohm per square

Thermally-activated carriers cause deviations, mitigated by magnetocaloric effect

Abstract

We report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in Hall resistance to within a part per 10,000 and longitudinal resistivity under 1 ohm per square, with chiral edge transport explicitly confirmed by non-local measurements. Deviations from this behavior are found to be caused by thermally-activated carriers, which can be eliminated by taking advantage of an unexpected magnetocaloric effect.