Anomalous localization due to magnetic impurities in two-dimensional topological insulators

Two-dimensional topological insulators have attracted considerable interest due to their spin-polarized edge states, which are protected by time-reversal symmetry and expected to be robust against structural disorder. However, local magnetic moments can break this symmetry, leading to deviations in conductance. While the impact of a few magnetic impurities has been studied, the microscopic effects of localized accumulations of such impurities on macroscopic transport properties remain poorly understood.

In this work, we predict the onset of Anderson localization at sufficiently high impurity concentrations and identify the emergence of an anomalous localization regime, characterized by an exponential decay of conductance with the square root of the number of impurities. Furthermore, we show that the system exhibits universal behavior directly governed by the impurity concentration. Applying our model to HgTe-based 2DTIs doped with Mn, we find excellent agreement with experimental data quantitative addressing the observed reduction in conductance. These results pave the way for further experimental investigations into anomalous localization phenomena in electronic systems.