Filling of magnetic-impurity-induced gap in topological insulators by potential scattering

TL;DR

This paper demonstrates that potential scattering from non-magnetic impurities can fill the magnetic-impurity-induced gap in topological insulators, explaining experimental inconsistencies regarding the gap's existence.

Contribution

It reveals that potential scattering can close the magnetic gap in topological insulators, combining continuum and lattice models to explain experimental observations.

Findings

Weak potential scattering fills the magnetic gap with impurity resonances.

The gap disappears at weak scattering due to spectral weight at the Dirac point.

Results reconcile conflicting experimental reports on the gap presence.

Abstract

We show that the energy gap induced by ferromagnetically aligned magnetic impurities on the surface of a topological insulator can be filled, due to scattering off the non-magnetic potential of the impurities. In both a continuum surface model and a three-dimensional tight-binding lattice model, we find that the energy gap disappears already at weak potential scattering as impurity resonances add spectral weight at the Dirac point. This can help explain seemingly contradictory experimental results as to the existence of a gap.