On the nature of the spin polarization limit in the warped Dirac cone of the Bi2Te3

TL;DR

This study combines experimental and theoretical methods to analyze the spin polarization in Bi2Te3 topological surface states, revealing in-plane and out-of-plane spin components and their relation to the warped Dirac cone.

Contribution

It provides a detailed quantitative analysis of spin polarization in Bi2Te3, integrating spin-resolved photoemission with ab initio calculations to understand spin textures.

Findings

In-plane spin polarization up to 45% near the Fermi level.

Out-of-plane spin polarization of approximately 15%.

Spin reversal occurs in the surface atomic layer.

Abstract

The magnitude of electron spin polarization in topologically protected surface states is an important parameter with respect to spintronics applications. In order to analyze the warped spin texture in Bi$_2$Te$_3$ thin films, we combine angle- and spin-resolved photoemission experiments with theoretical \textit{ab initio} calculations. We find an \textit{in-plane} spin polarization of up to $\sim$~45\% in the topologically protected Dirac cone states near the Fermi level. The Fermi surface of the Dirac cone state is warped and shows an \textit{out-of-plane} spin polarization of $\sim$~15\%. These findings are in quantitative agreement with dedicated simulations which find electron density of the Dirac cone delocalized over the first quintuple layer with spin reversal occurring in the surface atomic layer.