Origin of Landau oscillations observed in scanning tunneling spectroscopy on n-InAs(110)

The magnetic field induced oscillations in dI/dV curves recorded with a low-temperature scanning tunneling microscope on n-InAs(110) are analyzed in detail. It is found that the previous interpretation of the oscillations as due to the Landau quantization of the bulk conduction band of InAs has to be reconsidered. While the distance between the maxima of the oscillation corresponds to the effective mass of the InAs conduction band, the energetic positions of the maxima depend on the individual tip and can only be understood if the tip induced quantum dot is taken into account. A comparison of measured quantities (spatial fluctuations of the Landau level energies and spin splittings) with Hartree-Fock calculations of the tip induced quantum dot reveals quantitative correspondence. From this comparison, we conclude that the tunneling experiment detects the (m = 0) states of different Landau and spin levels of the quantum dot, which are only marginally influenced by their resonant coupling to the bulk conduction band.