Electronic structure ofBi2X3(X=S,Se,T)compounds: Comparison of theoretical calculations with photoemission studies

Abstract

In recent years electronic structures of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ 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 ${\mathrm{Bi}}_{2}{X}_{3}$ $(X=\mathrm{S},\mathrm{Se},\mathrm{Te})$ obtained within density-functional theory. While several electronic structure calculations for ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ and ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ have been reported in the literature, there have been no published calculations for ${\mathrm{Bi}}_{2}{\mathrm{S}}_{3}$ or ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}\mathrm{Se}.$ Recent photoemission and inverse-photoemission measurements in these systems, performed by four separate groups (including our photoemission measurements of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ and ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}),$ 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.