Electronic structure of Bi2X3 (X=S, Se, T) compounds: Comparison of theoretical calculations with photoemission studies

In recent years electronic structures of Bi₂Te₃ and related materials have been studied theoretically through ab initio band-structure calculations and experimentally through photoemission experiments, but to the best of our knowledge, a detailed comparison between experiment and theory has not been attempted so far. In this paper we discuss the density of states (DOS) of the narrow-gap semiconductors Bi₂X₃ (X=S, Se, Te) obtained within density-functional theory. While several electronic structure calculations for Bi₂Te₃ and Bi₂Se₃ have been reported in the literature, there have been no published calculations for Bi₂S₃ or Bi₂Te₂Se. Recent photoemission and inverse-photoemission measurements in these systems, performed by four separate groups (including our photoemission measurements of Bi₂Te₃ and Bi₂Se₃), allows for a comparison of the general features of the calculated DOS for both valence- and conduction-band states with photoemission and inverse-photoemission spectra. The agreement between the positions of the prominent peaks in the calculated DOS and photoemission spectra continues to improve with better energy resolution in the experiment.