# Current-driven instability of quantum anomalous Hall effect in ferromagnetic topological insulators

## TL;DR

This study investigates the current-driven breakdown of the quantum anomalous Hall effect in ferromagnetic topological insulators, revealing the role of Hall electric fields and variable range hopping in the stability of the QAH state.

## Contribution

It demonstrates that the breakdown current scales with Hall-bar width and identifies variable range hopping as the dominant transport mechanism at low temperatures.

## Key findings

- Breakdown current proportional to Hall-bar width.
- Electron transport dominated by variable range hopping at low temperatures.
- Localization length of QAH state estimated to be about 5 μm.

## Abstract

Instability of quantum anomalous Hall (QAH) effect has been studied as function of electric current and temperature in ferromagnetic topological insulator thin films. We find that a characteristic current for the breakdown of the QAH effect is roughly proportional to the Hall-bar width, indicating that Hall electric field is relevant to the breakdown. We also find that electron transport is dominated by variable range hopping (VRH) at low temperatures. Combining the current and temperature dependences of the conductivity in the VRH regime, the localization length of the QAH state is evaluated to be about 5 $\mu$m. The long localization length suggests a marginally insulating nature of the QAH state due to a large number of in-gap states.