Spin Hall Insulator

TL;DR

This paper predicts a dissipationless spin Hall effect in certain band insulators, where spin currents flow without charge dissipation, revealing a new topological phenomenon in non-magnetic materials.

Contribution

It introduces the first example of a topological spin Hall effect in band insulators without magnetic fields, expanding understanding of spin transport in insulators.

Findings

Dissipationless spin current predicted in specific band insulators.

Spin Hall conductance is non-quantized in these systems.

First demonstration of topological structure in non-magnetic band insulators.

Abstract

Recent theories predict dissipationless spin current induced by an electric field in doped semiconductors. Nevertheless, the charge current is still dissipative in these systems. In this work, we theoretically predict the dissipationless spin Hall effect, without any accompanying charge current, in some classes of band insulators, including zero-gap semiconductors such as HgTe and narrow-gap semiconductors such as PbTe. This effect is similar to the quantum Hall effect in that all the states below the gap contribute and there occurs no dissipation. However the spin Hall conductance is not quantized even in two dimensions. This is the first example of a nontrivial topological structure in a band insulator without any magnetic field.