Bulk band structure of Sb$_2$Te$_3$ determined by angle-resolved photoemission spectroscopy

TL;DR

This study uses angle-resolved photoemission spectroscopy to map the bulk band structure of Sb$_2$Te$_3$, revealing the valence band maximum at the bulk $ ext{Γ}$ point and clarifying its relation to the topological surface state.

Contribution

First direct experimental determination of the bulk valence band maximum position in Sb$_2$Te$_3$ using ARPES, clarifying previous theoretical predictions.

Findings

Valence band maximum is at the bulk $ ext{Γ}$ point.

Surface alkali adsorption enables full valence band observation.

Low-symmetry position predictions are ruled out.

Abstract

The bulk band structure of the topological insulator \sbte~ is investigated by angle-resolved photoemission spectroscopy. Of particular interest is the dispersion of the uppermost valence band with respect to the topological surface state Dirac point. The valence band maximum has been calculated to be either near the Brillouin zone centre or in a low-symmetry position in the $\bar{\Gamma}-\bar{M}$ azimuthal direction. In order to observe the full energy range of the valence band, the strongly p-doped crystals are counter-doped by surface alkali adsorption. The data show that that the absolute valence band maximum is likely to be found at the bulk $\Gamma$ point and predictions of a low-symmetry position with an energy higher than the surface Dirac point can be ruled out.