Precise quantization of anomalous Hall effect near zero magnetic field

A. J. Bestwick, E. J. Fox, Xufeng Kou, Lei Pan, Kang L. Wang, D. Goldhaber-Gordon

Published 2014-12-10Version 1

The discovery of the quantum Hall effect (QHE) led to a new understanding of electronic behavior in which topology plays a central role. Since then, researchers have been tantalized by the possibility of producing a similar phenomenology without the need for an external magnetic field to break time-reversal symmetry (TRS). In the past decade, the development of 2D and 3D topological insulators (TIs), in which conduction is restricted to topologically-protected boundary states, has provided one possible avenue. If a 3D TI is made ferromagnetic, a gap opens in its surface states and the remaining edge conduction is quantized. Here, we study this so-called quantum anomalous Hall effect (QAHE) in the limit of zero applied magnetic field, and measure Hall resistance quantized to $h/e^2$, where $h$ is Planck's constant and $e$ is the electron charge, to within one part per 10,000. Deviation from quantization is due primarily to thermally activated carriers, which can be nearly eliminated through adiabatic demagnetization cooling. This result demonstrates an important step toward dissipationless electron transport in technologically relevant conditions.