Sammendrag
The interface between a topological insulator and a ferromagnetic insulator exhibits an interesting interplay of
topological Dirac electrons and magnetism. As has been shown recently, the breaking of time-reversal invariance
by magnetic order generates a Chern-Simons term in the action, that in turn leads to a Berry phase and a
magnetoelectric effect of topological origin. Here, we consider the system in the presence of a long-range
Coulomb interaction between the Dirac electrons, and find that the magnetoelectric effect of the fluctuating
electric field becomes nonlocal. We derive a Landau-Lifshitz equation for the fluctuation-induced magnetization
dynamics and the Euler-Lagrange equation of the Coulomb field by explicit one-loop calculations. Via the
Coulomb interaction, divergences in the in-plane magnetization affect the magnetization dynamics over large
distances in a topologically protected way.
Vis fullstendig beskrivelse