Mesoscopic fluctuations of conductance of a helical edge contaminated by magnetic impurities

TL;DR

This paper investigates how magnetic impurities induce mesoscopic conductance fluctuations in helical edges, revealing interference effects and unique statistical behavior despite time-reversal symmetry constraints.

Contribution

It introduces a model for TRS-preserving backscattering caused by magnetic impurities and predicts distinctive conductance fluctuation statistics in helical edge states.

Findings

Magnetic impurities cause interference effects in conductance.

Backscattering energy transfer is suppressed exponentially with impurity number.

Conductance fluctuation statistics differ from quenched disorder cases.

Abstract

Elastic backscattering of electrons moving along the helical edge is prohibited by time-reversal symmetry (TRS). We demonstrate, however, that an ensemble of magnetic impurities may cause TRS-preserving quasi-elastic backscattering, resulting in interference effects in the conductance. The characteristic energy transferred in a backscattering event is suppressed due to the RKKY interaction of localized spins (the suppression is exponential in the total number of magnetic impurities). We predict the statistics of conductance fluctuations to differ from those in the conventional case of a one-dimensional system with quenched disorder.