Absence of non-chiral edge states in Cr-doped (Bi, Sb)₂Te₃

The realization of the ohm at zero magnetic field has motivated the study of the quantum anomalous Hall effect. Magnetically doped topological insulators have received the most attention for their high quantization, a requirement for metrology applications. A significant limitation hindering their application has been the low temperature at which metrological level quantization occurs, on the order of tens of mK. Previous works have suggested that dissipation from non-chiral edge states may contribute to the low activation energies common in this system. To explore this possibility, we present a systematic study of transport in a 6 quintuple layer Cr-doped (Bi, Sb)₂Te₃ device near breakdown temperatures (T = 2 K). We acquired several independent dc measurements of Hall and non-local resistance and compared the results to various transport models. We determined that this system is best described by a continuum Ohm’s law model and that the addition of non-chiral edge states to the model does not significantly improve the fitting. Moreover, we highlight the methodology used in this work, where measurement configuration is the main experimental “knob”, instead of the commonly used temperature or gate voltage.