Electronic States on Bi₂Te₃ Studied by Angle-Resolved Photoelectron Spectroscopy Using Synchrotron Radiation

Abstract

We have studied the electronic structure within the topmost two quintuple layers (QL) on vacuum-cleaved n- and p-type Bi₂Te₃(111) at 10 K by angle-resolved photoelectron spectroscopy. Tunable synchrotron radiation maximized the surface sensitivity of photoelectrons. The gapless surface-state band (SSB) in the angle-resolved photoelectron spectra clearly demonstrates the topological nature of the samples. Below the SSB, the bulk valence bands (BVB) is observed. Against the three-fold symmetry of the crystal structure, the k_|| dispersion of the BVB is highly symmetrical around the Γ, which indicates the six-fold symmetry. Moreover, most of the BVB show almost flat k_⊥ dispersion perpendicular to the surface. These facts are the experimental evidence of a strong modification of the valence bands within the topmost two QLs into highly two-dimensional states by the advent of the surface. [DOI: 10.1380/ejssnt.2012.117]