Magnetoelectric Response of the Time-Reversal Invariant Helical Metal

TL;DR

This paper derives analytical formulas for spin-charge interactions in topological insulator surface states, revealing unconventional magnetic couplings and electric current generation, with implications for spintronics and magnetic control.

Contribution

It provides the first compact analytical expressions for the coupled spin-charge susceptibility in helical metals, enabling new insights into magnetic interactions on TI surfaces.

Findings

Unconventional non-collinear RKKY interactions are predicted.

Electric currents can be generated by time-dependent magnetic moments.

Gate and bias voltages influence interlayer exchange coupling.

Abstract

We derive compact analytical expressions for the coupled spin-charge susceptibility of a clean helical metal at the surface of a three dimensional topological insulator (TI). These expressions lead to unconventional non-collinear RKKY interactions between two impurity magnetic moments placed on the surface of a TI, and predict the generation of electric currents by time-dependent magnetic moments. We determine the influence of gate and bias voltages on the interlayer exchange coupling between two single-domain ferromagnetic monolayers deposited on top of a TI.