Spatially resolved Landau level spectroscopy of the topological Dirac cone of bulk-type Sb_2Te_3(0001): Potential fluctuations and quasiparticle lifetime

摘要

Using low-temperature scanning tunneling spectroscopy, we probe the Landau levels of the topologically protected state of Sb_2Te_3(0001) after in situ cleavage of a single crystal. Landau levels are visible for magnetic fields B ≥ 2 T at energies, which confirm the Dirac type dispersion including the zeroth Landau level. We find different Dirac velocities for the lower and the upper part of the Dirac cone in reasonable agreement with previous density functional theory data. The Dirac point deduced from the zeroth Landau level shifts by about 40 meV between different areas of the sample indicating long-range potential fluctuations. The local potentials are correlated to different local defect densities varying slightly stronger than expected from a statistical distribution. Moreover, the width of the Landau level peaks is analyzed. It is found to increase, mostly linearly, with the energy distance to the Fermi level. Consequently, we attribute the peak width to a dominating scattering of the hot quasiparticles by electron-electron interaction.