Spin and charge transport through helical Aharonov-Bohm interferometer with strong magnetic impurity

TL;DR

This paper analyzes how a strong magnetic impurity affects charge and spin transport in a helical edge state interferometer, revealing conditions for perfect spin filtering and novel quantum effects at high temperatures.

Contribution

It provides a closed-form analysis of conductance and spin polarization with strong magnetic impurities, highlighting new quantum effects absent in weak disorder scenarios.

Findings

Spin polarization can reach 100% under optimal conditions.

Strong magnetic impurities induce quantum effects not seen in weak disorder.

The conductance and spin polarization are derived in closed form for various parameters.

Abstract

We discuss transport through an interferometer formed by helical edge states of the quantum spin Hall insulator. Focusing on effects induced by a strong magnetic impurity placed in one of the arms of interferometer, we consider the experimentally relevant case of relatively high temperature as compared to the level spacing. We obtain the conductance and the spin polarization in the closed form for arbitrary tunneling amplitude of the contacts and arbitrary strength of the magnetic impurity. We demonstrate the existence of quantum effects which do not show up in previously studied case of weak magnetic disorder. We find optimal conditions for spin filtering and demonstrate that the spin polarization of outgoing electrons can reach 100%.