Current noise on the helical edge
We theoretically study the process of backscattering of electrons by a single magnetic impurity located near the edge of a two-dimensional topological insulator. We neglect electron-electron interactions and magnetic anisotropy of the impurity. Moreover, we suppose that Kondo renormalization of the electron-impurity coupling is weak. Assuming that finite voltage is applied to the edge we calculate the cumulants of the number of backscattered electrons in a given time interval. In certain cases, we determine the full counting statistics of the backscattering current. In the other cases, we restrict ourselves to the calculation of the average backscattering current and of its zero-frequency noise.