Quantum Spin Hall Effect

TL;DR

This paper predicts a quantized spin Hall effect in semiconductors without magnetic fields, driven by spin-orbit coupling and strain, revealing a new topological state with potential for novel electronic applications.

Contribution

It introduces a new topological quantum state exhibiting quantized spin Hall conductance without magnetic fields, expanding the understanding of topological insulators.

Findings

Quantized spin Hall conductance in units of 2e/4π

Degenerate Landau levels created by spin-orbit coupling

Topological field theory describes correlated properties

Abstract

The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of $2 \frac{e}{4\pi}$. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.