Spin-Momentum Locked Topological Surface States, non-trivial Berry's phase and magnetoelectric quantization in topological insulators

TL;DR

This paper discusses the unique spin-momentum locking and Berry's phase in topological insulator surface states, highlighting their role in quantized magnetoelectric responses and topological properties.

Contribution

It elucidates the connection between spin-momentum locking, Berry's phase, and the quantized magnetoelectric effect in 3D topological insulators.

Findings

Surface states exhibit spin-momentum locking.

Berry's phase is non-trivial in these states.

Magnetoelectric response is exactly quantized.

Abstract

The surface of a 3D topological insulator is a new type of two dimensional electron gas (2DEG). The exactly quantized magneto-optical or axionic response of a 3D topological insulator is a direct result of the Berry's phase protected spin-momentum locked states on its surface. (PRL Viewpoint http://physics.aps.org/node/3810).