Pure spin current in a two-dimensional topological insulator

TL;DR

This paper predicts a method to generate pure spin currents in 2D topological insulators by introducing magnetic impurities, which open a gap in edge states while preserving others, leading to robust spin current conduction.

Contribution

It introduces a novel mechanism for generating pure spin currents in 2D topological insulators via magnetic impurities, with robustness against weak disorder.

Findings

Pure spin currents can be induced by magnetic impurities in 2D topological insulators.

Conductance plateaus with half-integer values $e^2/h$ are observed in the impurity-induced gap.

The pure spin current remains insensitive to weak disorder.

Abstract

We predict a mechanism to generate a pure spin current in a two-dimensional topological insulator. As the magnetic impurities exist on one of edges of the two-dimensional topological insulator, a gap is opened in the corresponding gapless edge states but another pair of gapless edge states with opposite spin are still protected by the time-reversal symmetry. So the conductance plateaus with the half-integer values $e^2/h$ can be obtained in the gap induced by magnetic impurities, which means that the pure spin current can be induced in the sample. We also find that the pure spin current is insensitive to weak disorder. The mechanism to generate pure spin currents is generalized for two-dimensional topological insulators.