Circular dichroism in angle-resolved photoemission spectroscopy of topological insulators

TL;DR

This paper reviews how circularly polarized light influences photoemission in topological insulators, revealing insights into their spin textures and potential for spin manipulation using optical methods.

Contribution

It provides a comprehensive review of experimental and theoretical studies on circular dichroism effects in topological insulators' photoemission, highlighting the role of light polarization and geometry.

Findings

Polarization affects photocurrent and spin polarization in topological surface states.

A spin-orbit coupled matrix element model explains experimental observations.

Circularly polarized light can be used to map and manipulate spin textures.

Abstract

Topological insulators are a new phase of matter that exhibits exotic surface electronic properties. Determining the spin texture of this class of material is of paramount importance for both fundamental understanding of its topological order and future spin-based applications. In this article, we review the recent experimental and theoretical studies on the differential coupling of left- versus right-circularly polarized light to the topological surface states in angle-resolved photoemission spectroscopy. These studies have shown that the polarization of light and the experimental geometry plays a very important role in both photocurrent intensity and spin polarization of photoelectrons emitted from the topological surface states. A general photoemission matrix element calculation with spin-orbit coupling can quantitatively explain the observations and is also applicable to topologically trivial systems. These experimental and theoretical investigations suggest that optical excitation with circularly polarized light is a promising route towards mapping the spin-orbit texture and manipulating the spin orientation in topological and other spin-orbit coupled materials.