Bound-states and polarized charged zero modes in three-dimensional topological insulators induced by a magnetic vortex

By coating a three-dimensional topological insulator (TI) with a ferromagnetic filmsupporting an in-plane magnetic vortex, one breaks the time-reversal symmetry (TRS)without generating a mass gap. It rather yields electronic states bound to the vortexcenter which have different probabilities associated with each spin mode. In addition, itsassociate current (around the vortex center) is partially polarized with an energy gapseparating the most excited bound state from the scattered ones. Charged zero-modes alsoappear as fully polarized modes localized near the vortex center. From the magnetic pointof view, the observation of such a special current in a TI-magnet sandwich comes about asan alternative technique for detecting magnetic vortices in magnetic thin films.