Bulk dissipation in the quantum anomalous Hall effect

TL;DR

This study demonstrates that bulk conduction is the primary source of dissipation in the quantum anomalous Hall effect, with breakdown phenomena occurring in the bulk, guiding future material development for higher temperature QAH realization.

Contribution

It provides a comparative analysis of Hall bar and Corbino devices, establishing bulk conduction as the main dissipation mechanism in QAH systems.

Findings

Bulk conduction dominates dissipation at all temperatures.

Breakdown phenomena are identical in different device geometries.

Methodology can identify dissipation mechanisms in new QAH materials.

Abstract

Even at the lowest accessible temperatures, measurements of the quantum anomalous Hall (QAH) effect have indicated the presence of parasitic dissipative conduction channels. There is no consensus whether parasitic conduction is related to processes in the bulk or along the edges. Here, we approach this problem by comparing transport measurements of Hall bar and Corbino geometry devices fabricated from Cr-doped (BiSb)$_2$Te$_3$. We identify bulk conduction as the dominant source of dissipation at all values of temperature and in-plane electric field. Furthermore, we observe identical breakdown phenomenology in both geometries, indicating that breakdown of the QAH phase is a bulk process. The methodology developed in this study could be used to identify dissipative conduction mechanisms in new QAH materials, ultimately guiding material development towards realization of the QAH effect at higher temperatures.