  We study the transport properties of a hybrid junction made of a
ferromagnetic lead in electrical connection with the helical edge modes of a
two-dimensional topological insulator. In this system, the time reversal
symmetry, which characterizes the ballistic edge modes of the topological
insulator, is explicitly broken inside the ferromagnetic region. This conflict
situation generates unusual transport phenomena at the interface which are the
manifestation of the interplay between the spin polarization of the injected
current and the spin-momentum locking mechanism operating inside the
topological insulator. We show that the spin polarized current originated in
the ferromagnetic region is asymmetrically divided in spatially separated
branch currents sustained by edge channels with different helicity inside the
topological insulator. The above findings provide the working principle of a
topological current divider in which the relative intensity of the branch
currents is determined by the polarization of the incoming current. We discuss
the relevance of this effect in spintronics where, for instance, it offers an
alternative way to measure the current polarization generated by a
ferromagnetic electrode.
