Current and noise in 2D topological insulator with 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 microscopic form of the exchange interaction matrix and arbitrary value of the magnetic impurity spin We find that the differential conductance is a non monotonous function of the voltage with several extrema We discuss the effects of the local anisotropy on the current voltage characteristics Also we present the result for the full counting statistics of the backscattering current for the case of spin