Landau levels in a topological insulator

Two recent experiments successfully observed Landau levels in the tunneling spectra of the topological insulator Bi2Se3. To mimic the influence of a scanning tunneling microscope tip on the Landau levels we solve the two-dimensional Dirac equation in the presence of a localized electrostatic potential. We find that the STM tip not only shifts the Landau levels, but also suppresses for a realistic choice of parameters the negative branch of Landau levels.