Nonlocal Transport in Cr-doped (Bi,Sb)2Te3: Absence of Nonchiral Edge States

TL;DR

This study investigates non-chiral edge states in magnetically doped topological insulators and finds no significant evidence for their presence, supporting a simple Ohm's law description of transport at low temperatures.

Contribution

It provides extensive experimental evidence that non-chiral edge states are absent in Cr-doped (Bi,Sb)2Te3, simplifying the understanding of dissipation mechanisms in these materials.

Findings

Transport behavior is well-described by Ohm's law.

No significant improvement in model fit with non-chiral edge states.

Implications for high-temperature quantized anomalous Hall effect.

Abstract

The quantum anomalous Hall effect shows great promise for realization of the ohm without the need for an external magnetic field. The most mature material platform is magnetically doped topological insulators. In these materials, precise quantization is limited to low temperatures, with the activation energy for dissipative transport typically in the range of 1 K. One potential source of dissipative transport is non-chiral edge states. These states are expected to be present in sufficiently thick samples. In this work, we perform extensive Hall and non-local resistance measurements in a Hall bar geometry at 2 K. By comparing 15 independent transport measurements to different transport models, we find that the system behavior is well-described by a simple continuum Ohm's law model. The addition of non-chiral edge states into the model does not significantly improve the fitting, and we conclude that there is not strong evidence for these states. We discuss the implications of our results for the prospect of high temperature quantized anomalous Hall effect in these materials.