The electronic structure of clean and adsorbate-covered Bi2Se3: an angle-resolved photoemission study

TL;DR

This study uses angle-resolved photoemission spectroscopy to analyze the electronic structure and surface states of Bi2Se3, revealing time-dependent band bending, quantum well states, and Rashba splitting influenced by surface contamination and adsorbates.

Contribution

It provides detailed insights into how surface contamination and adsorbates affect the electronic structure and surface states of Bi2Se3, including the formation of quantum well states and Rashba splitting.

Findings

Time-dependent band bending observed on Bi2Se3 surface.

Formation of quantised conduction band states with strong Rashba splitting.

Surface contamination accelerates band bending and state formation.

Abstract

Angle-resolved photoelectron spectroscopy is used for a detailed study of the electronic structure of the topological insulator Bi2Se3. Nominally stoichiometric and calcium-doped samples were investigated. The pristine surface shows the topological surface state in the bulk band gap. As time passes, the Dirac point moves to higher binding energies, indicating an increasingly strong downward bending of the bands near the surface. This time-dependent band bending is related to a contamination of the surface and can be accelerated by intentionally exposing the surface to carbon monoxide and other species. For a sufficiently strong band bending, additional states appear at the Fermi level. These are interpreted as quantised conduction band states. For large band bendings, these states are found to undergo a strong Rashba splitting. The formation of quantum well states is also observed for the valence band states. Different interpretations of similar data are also discussed.