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

TL;DR

This paper demonstrates that magnetic vortices in a ferromagnetic film on a 3D topological insulator induce bound states and polarized zero modes, providing a new method to detect magnetic vortices.

Contribution

It introduces a novel way to generate and detect bound states and zero modes in topological insulators via magnetic vortices without opening a mass gap.

Findings

Bound states are localized at the vortex center.

Charged zero modes are fully polarized and localized.

The vortex-induced current can be used to detect magnetic vortices.

Abstract

By coating a three-dimensional topological insulator (TI) with a ferromagnetic film supporting 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 vortex center which have different probabilities associated with each spin mode. In addition, its associate current (around the vortex center) is partially polarized with an energy gap separating the most excited bound state from the scattered ones. Charged zero-modes also appear as fully polarized modes localized near the vortex center. From the magnetic point of view, the observation of such a special current in a TI-magnet sandwich comes about as an alternative technique for detecting magnetic vortices in magnetic thin films.