Anomalous Hall Response in Two Dimensional Topological Insulators due to the Stark Effect

It is shown that the presence of matrix dipole moments induced by external electric fields can modify the Hall response in two dimensional Topological insulators. In the case of the Quantum Anomalous Hall effect the induced transverse currents acquire an extra term being proportional to the Hall conductance and the time derivative of the applied electric field. In the case of the Quantum Spin Hall effect both a spin and charge transverse currents appear simultaneously. In virtue of the bulk-edge correspondence the coupling between the chiral edge channels and the electromagnetic field changes allowing for an extra non minimal coupling term. Both effects can be measured through transport and tunnelling experiments.Comment: Version published in PR

Domain Wall Motion in Thin-Film Magnets/ Topological Insulator Junctions

We derive the equations of motion of a Domain Wall in a thin-film magnet coupled to the surface states of a Topological Insulator in the presence of of both an electric field along the Domain Wall and a magnetic field perpendicular to the junction. We show how the electric field acts as a chirality stabilizer holding off the appearance of Walker breakdown and enhancing the terminal velocity. We also propose a mechanism to reverse the Domain Wall chirality in a controllable manner by tuning the chiral current flowing through the Wall. An input from a weak perpendicular magnetic field is required in order to break the reflection symmetry that protects the degeneracy of the chirality vacuum.Comment: Enlarged and revised version accepted in PR