Part-per-million quantization and current-induced breakdown of the quantum anomalous Hall effect

TL;DR

This study demonstrates near-perfect quantization of the Hall resistance in magnetic topological insulator films at zero magnetic field, revealing breakdown mechanisms due to electron heating and bulk dissipation effects.

Contribution

It provides the first precise measurement of quantum anomalous Hall effect quantization at ppm level and investigates the breakdown mechanisms in detail.

Findings

Hall resistance quantized to within one part per million

Breakdown occurs due to electron heating at high current densities

Evidence of bulk dissipation mechanisms like thermal activation

Abstract

In the quantum anomalous Hall effect, quantized Hall resistance and vanishing longitudinal resistivity are predicted to result from the presence of dissipationless, chiral edge states and an insulating 2D bulk, without requiring an external magnetic field. Here, we explore the potential of this effect in magnetic topological insulator thin films for metrological applications. Using a cryogenic current comparator system, we measure quantization of the Hall resistance to within one part per million and longitudinal resistivity under 10 m$\Omega$ per square at zero magnetic field. Increasing the current density past a critical value leads to a breakdown of the quantized, low-dissipation state, which we attribute to electron heating in bulk current flow. We further investigate the pre-breakdown regime by measuring transport dependence on temperature, current, and geometry, and find evidence for bulk dissipation, including thermal activation and possible variable-range hopping.