Electronic Structure of the Topological Insulator Bi2Se3 Using Angle-Resolved Photoemission Spectroscopy: Evidence for a Nearly Full Surface Spin Polarization

TL;DR

This study uses high-resolution spin- and angle-resolved photoemission spectroscopy to reveal that the surface state of Bi2Se3, a topological insulator, exhibits nearly full spin polarization, surpassing previous reports and highlighting extrinsic factors as primary limitations.

Contribution

The paper provides the first high-resolution measurements showing nearly full spin polarization of Bi2Se3 surface states, clarifying the role of extrinsic factors in limiting polarization.

Findings

Surface state is well separated from bulk states near the Z point.

Surface state spin polarization is approximately 0.75, higher than previously reported.

Extrinsic factors mainly limit the surface state spin polarization.

Abstract

We performed high-resolution spin- and angle-resolved photoemission spectroscopy studies of the electronic structure and the spin texture on the surface of Bi$_2$Se$_3$, a model topological insulator. By tuning the photon energy, we found that the topological surface state is well separated from the bulk states in the vicinity of $k_z=Z$ plane of the bulk Brillouin zone. The spin-resolved measurements in that region indicate a very high degree of spin polarization of the surface state, $\sim 0.75$, much higher than previously reported. Our results demonstrate that the topological surface state on Bi$_2$Se$_3$ is highly spin polarized and that the dominant factors limiting the polarization are mainly extrinsic.