Thin-Film Magnetization Dynamics on the Surface of a Topological Insulator

TL;DR

This paper theoretically investigates the interaction between magnetization dynamics in a thin ferromagnetic film and electronic zero modes on a topological insulator surface, revealing reciprocal effects mediated by chiral modes and domain walls.

Contribution

It introduces a thermodynamic framework for understanding the coupled dynamics of magnetic textures and electronic zero modes on topological insulators, proposing an experimental setup for observation.

Findings

Chiral modes act as dissipative interconnects controlling magnetization dynamics.

Reciprocal hydrodynamic equations describe the interaction between domain walls and electronic spin torques.

Proposed experimental realization involves a ferromagnetic strip on a topological insulator surface.

Abstract

We theoretically study the magnetization dynamics of a thin ferromagnetic film exchange-coupled with a surface of a strong three-dimensional topological insulator. We focus on the role of electronic zero modes imprinted by domain walls (DW's) or other topological textures in the magnetic film. Thermodynamically reciprocal hydrodynamic equations of motion are derived for the DW responding to electronic spin torques, on the one hand, and fictitious electromotive forces in the electronic chiral mode fomented by the DW, on the other. An experimental realization illustrating this physics is proposed based on a ferromagnetic strip, which cuts the topological insulator surface into two gapless regions. In the presence of a ferromagnetic DW, a chiral mode transverse to the magnetic strip acts as a dissipative interconnect, which is itself a dynamic object that controls (and, inversely, responds to) the magnetization dynamics.