Backscattering Between Helical Edge States via Dynamic Nuclear Polarization

TL;DR

This paper demonstrates how dynamic nuclear polarization induced by helical edge states in topological insulators causes backscattering and conductance reduction, revealing new mechanisms affecting edge state transport.

Contribution

It introduces a novel backscattering mechanism via nuclear polarization influenced by inhomogeneous Rashba coupling in topological insulators.

Findings

Nuclear polarization can induce backscattering in helical edge states.

Conductance reduction persists to zero temperature.

Distinct current noise spectrum signatures are identified.

Abstract

We show that that the non-equilibrium spin polarization of one dimensional helical edge states at the boundary of a two dimensional topological insulator can dynamically induce a polarization of nuclei via the hyperfine interaction. When combined with a spatially inhomogeneous Rashba coupling, the steady state polarization of the nuclei produces backscattering between the topologically protected edge states leading to a reduction in the conductance which persists to zero temperature. We study these effects in both short and long edges, uncovering deviations from Ohmic transport at finite temperature and a current noise spectrum which may hold the fingerprints for experimental verification of the backscattering mechanism.