# Photoemission Circular Dichroism and Spin Polarization of the Topological Surface States in Ultrathin Bi2Te3 Films

## TL;DR

This study investigates the circular dichroism and spin polarization of topological surface states in ultrathin Bi2Te3 films, revealing complex behaviors explained by comprehensive theoretical modeling of photoemission mechanisms.

## Contribution

It provides a detailed experimental and theoretical analysis of CD in topological insulator films, clarifying the connection between spin-orbit texture and photoemission signals.

## Key findings

- Complex CD variations with film thickness and photon energy
- Sign reversals in CD explained by multiple photoemission mechanisms
- Theoretical model accurately describes experimental data

## Abstract

Circular dichroism (CD) observed by photoemission, being sensitive to the orbital and spin angular momenta of the electronic states, is a powerful probe of the nontrivial surface states of topological insulators, but the experimental results thus far have eluded a comprehensive description. We report a study of Bi2Te3 films with thicknesses ranging from one quintuple layer (two-dimensional limit) to twelve layers (bulk limit) over a wide range of incident photon energy. The data show complex variations in magnitude and sign reversals, which are nevertheless well described by a theoretical calculation including all three photoemission mechanisms: dipole transition, surface photoemission, and spin-orbit coupling. The results establish the nontrivial connection between the spin-orbit texture and CD.

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Source: https://tomesphere.com/paper/1705.09720