Real-Space Observation of Drift States in a Two-Dimensional Electron System at High Magnetic Fields

Abstract

The local density of states of the adsorbate-induced two-dimensional electron system is studied in magnetic fields up to B=6 T. Landau quantization is observed and drift states with a width of about the magnetic length are found in agreement with theoretical predictions. At the tails of the Landau levels the states form closed paths indicating localization. These states show the expected energy dependence. A multifractal analysis applied to the data results in a nice parabolic shape of the characteristic f(alpha) spectra, but we find only a slight displacement of the origin from alpha=2.0 for the states in the center of the Landau level.

Robust Nodal Structure of Landau Level Wave Functions Revealed by Fourier Transform Scanning Tunneling Spectroscopy

“…The 2DESs are usually deeply buried in semiconducting heterostructures, which prevents the use of high resolution scanning tunneling spectroscopy (STS). Recently, the advent of surface 2DESs in doped semiconductors [7][8][9], graphene [10,11], and on the surface of topological insulators [12,13] has in principle opened the way to such direct high resolution measurements. This should allow probing the internal structure of the LL wave functions.…”

Visualizing Landau Levels of Dirac Electrons in a One-Dimensional Potential

“…One of the most powerful methods to probe these effects on a local scale is to measure Landau levels in an inhomogeneous system 4 with scanning tunneling microscopy (STM). Landau levels appear as a sequence of peaks in STM spectra and have been observed in many systems including graphene, 5, 6, 7 conventional 2DEGs 8,9 , and topological insulators 10,11 .However, although a few experiments have discussed the effects of spatial inhomogeneity on Landau level energies, 7, 9 there have been no experiments directly probing the systematic effects of the increasing wavefunction size on the electronic structure.We have recently discovered that the prototypical topological insulator Bi 2 Te 3 is susceptible to a periodic buckling, which results in a periodic potential variation superimposed on the Dirac electrons. The linear dispersion and the well-defined potential variation make this an ideal system to study size effects of Landau level wavefunctions.…”

“…One of the most powerful methods to probe these effects on a local scale is to measure Landau levels in an inhomogeneous system 4 with scanning tunneling microscopy (STM). Landau levels appear as a sequence of peaks in STM spectra and have been observed in many systems including graphene, 5,6,7 conventional 2DEGs 8,9 , and topological insulators 10,11 .…”

Scanning Tunneling Spectroscopy

“…More interestingly, the transformation of the wave functions in a magnetic field could be observed in real space. While 0D and 1D systems did not show pronounced changes due to the relatively large confinement, a distinct change has been observed for 2D [29] and 3D [30]. In both cases, serpentine structures exhibiting strong corrugation appear as shown in Fig.…”