Fractional Charge and Quantized Current in the Quantum Spin Hall State

TL;DR

This paper demonstrates that magnetic domain walls in quantum spin Hall insulators carry fractional charge and that rotating magnetic fields can induce quantized electric currents, revealing novel topological phenomena.

Contribution

It shows fractional charge at magnetic domain walls and proposes an experiment to measure it, along with the link between rotating magnetic fields and quantized currents in quantum spin Hall states.

Findings

Magnetic domain walls carry half an electron charge.

Rotating magnetic fields induce quantized dc electric currents.

Proposed experimental method for direct measurement of fractional charge.

Abstract

A profound manifestation of topologically non-trivial states of matter is the occurrence of fractionally charged elementary excitations. The quantum spin Hall insulator state is a fundamentally novel quantum state of matter that exists at zero external magnetic field. In this work, we show that a magnetic domain wall at the edge of the quantum spin Hall insulator carries one half of the unit of electron charge, and we propose an experiment to directly measure this fractional charge on an individual basis. We also show that as an additional consequence, a rotating magnetic field can induce a quantized dc electric current, and vice versa.