Landau level spectroscopy of Bi2Te3

Abstract

Here we report on Landau level spectroscopy in magnetic fields up to 34 T performed on a thin film of the topological insulator Bi2Te3 epitaxially grown on a BaF2 substrate. The observed response is consistent with the picture of a direct-gap semiconductor in which charge carriers closely resemble massive Dirac particles. The fundamental band gap reaches Eg=(175±5) meV at low temperatures and it is not located on the trigonal axis, thus displaying either sixfold or twelvefold valley degeneracy. Interestingly, our magneto-optical data do not indicate any band inversion at the direct gap. This suggests that the fundamental band gap is relatively distant from the Γ point where profound inversion exists and gives rise to the relativisticlike surface states of Bi2Te3.