Bound states and controllable currents on Topological Insulator surfaces with extended magnetic defects

TL;DR

This paper demonstrates that magnetic line defects on topological insulator surfaces support tunable, spin-polarized bound states and currents, which can be controlled via magnetic fields and electrostatic potentials, with implications for spintronics.

Contribution

It reveals the existence of two distinct bound state branches on TI surfaces and shows how their properties can be independently tuned by magnetic fields and scattering potentials.

Findings

Bound states support spin-polarized, current-carrying modes.

Bound state velocities and spin textures are tunable by in-plane magnetic fields.

Net spin polarization and currents vary stepwise with scattering potentials.

Abstract

We show that a magnetic line defect on the surface of a topological insulator generically supports two distinct branches of spin-polarized and current carrying one-dimensional bound states. We identify the components of magnetic scattering that lead to the bound states. The velocity, and hence spin texture, of each of those branches can be independently tuned by a magnetic field rotated in the plane of the surface. We compute the local net and spin-resolved density of states as well as spin accumulation and charge currents. The net spin polarization and current due to both bound and scattering states vary stepwise as a function of the electrostatic and magnetic components of the scattering potential, and can be tuned by an applied field. We discuss stability of the bound states with respect to impurity scattering.