Spin filtering by helical edge states of topological insulator

R. A. Niyazov, D. N. Aristov, V. Yu. Kachorovskii

Published 2019-04-29Version 1

We study spin filtering properties of interferometer formed by helical edge states of two dimensional topological insulators. We find that unpolarized incoming electron beam entering interferometer through one of the metallic leads acquires a finite polarization after transmission through the setup provided that interferometer contains magnetic impurities. The finite polarization appears even in the fully classical regime and therefore robust to dephasing. There also exists quantum contribution to polarization which survives at relatively large temperature and is tunable by magnetic flux piercing the interferometer. Specifically, the quantum contribution shows sharp identical resonances as a function of magnetic flux with maxima (in the absolute value) at integer and half-integer values of the flux. For interferometer containing a single strong magnetic impurity, which blocks the transmission in one shoulder of interferometer, the spin polarization of transmitted electrons can achieve 100%. We also show that polarization reverses sign when impurity is moved from one shoulder of interferometer to another. The obtained results open wide avenue for applications in the area of quantum networking.