Landau level spectroscopy of Bi2Te3

Bismuth telluride is a widely explored material in the condensed matter community and one of the first experimentally identified as a topological insulator. Nevertheless, despite considerable effort, the bulk electronic band structure of Bi${}₂$Te${}₃$ is known only partially. Here, the authors present a magneto-optical study of Bi${}₂$Te${}₃$, which provides one with compelling evidence that bismuth telluride is a direct-gap semiconductor, with a multiple valley degeneracy and charge carriers that closely resemble massive Dirac electrons.