Helical edge transport in the presence of a magnetic impurity.

We consider the effects of electron scattering off a quantum magnetic impurity on the current-voltage characteristics of the helical edge of a two-dimensional topological insulator. We compute the backscattering contribution to the current along the edge for a general form of the exchange interaction matrix and arbitrary value of the magnetic impurity spin. We find that the differential conductance may exhibit a nonmonotonic dependence on the voltage with several extrema. [ABSTRACT FROM AUTHOR]