Local potential fluctuation of topological surface states in Bi1.5Sb0.5Te1.7Se1.3 observed by Landau level spectroscopy

Abstract

We report the local observation of the band structure of topological surface states in Bi1.5Sb0.5Te1.7Se1.3 using scanning tunneling microscopy/spectroscopy (STM/STS). The energy-momentum dispersion relation is locally deduced by extracting the Landau level (LL) energies, which are formed in a high magnetic field, from the STS data. Spatial variation of LLs revealed a shift of the Dirac point energy at the nanometer scale. The structure of the potential fluctuation was not correlated with the topography, which indicated that the Te/Se substitution did not induce the potential shift because of their same valence. The results show that disorders from the Te/Se substitution at the surface do not induce any localized charged states and do not affect topological surface states. (C) 2016 AIP Publishing LLC.