Chiral Surface Modes in Three-Dimensional Topological Insulators

TL;DR

This paper demonstrates that in ferromagnetic three-dimensional topological insulators, the quantum anomalous Hall effect induces a single chiral surface mode on side faces, revealing new surface conduction phenomena.

Contribution

It reveals the existence of chiral surface modes in ferromagnetic 3DTIs due to the QAH effect, and compares with helical modes in nonmagnetic 3DTIs.

Findings

Chiral surface modes appear on side faces of ferromagnetic 3DTIs.

Delocalized helical modes exist in nonmagnetic 3DTIs due to quantum spin Hall effect.

The QAH effect induces a single chiral mode in 3DTI slabs.

Abstract

Where chiral modes should appear is an essential question for the quantum anomalous Hall (QAH) effect in three-dimensional topological insulators (3DTIs). In this Letter, we show that in a slab of ferromagnetic 3DTI subjected to a uniform exchange field normal to its top and bottom surfaces, the QAH effect creates a single chiral surface mode delocalized on the side faces. In a nonmagnetic 3DTI, analogously, delocalized helical modes consisting of a pair of oppositely propagating chiral surface modes are produced by the quantum spin Hall effect.