SGM 6

Imaging backscattering through impurity-induced antidots in quantum Hall constrictions

We exploit the biased tip of a scanning gate microscope to induce a controlled backscattering between counterpropagating edge channels in a wide constriction in the quantum Hall regime. We compare our detailed conductance maps with a numerical percolation model and demonstrate that conductance fluctuations observed in these devices as a function of the gate voltage originate from backscattering events mediated by localized states pinned by potential fluctuations. Our imaging technique allows us to identify the necessary conditions for the activation of these backscattering processes and also to reconstruct the constriction confinement potential profile and the underlying disorder.

Fig1
Fig. 1: (a) SGM scan over a 1.2 μm wide and 2.5 μm long constriction defined in a ν = 2 quantum Hall system. The map displays the transmitted conductance G plotted as a function of the tip position. As a reference, the middle of the G = G0 plateau is indicated with a dashed white line. (b) Gradient map of G which emphasizes short scale modulations of the G signal. A fine pattern of arc structures is observed, indicating the occurrence of peculiar backscattering processes.

Publications:

  1. Nicola Paradiso, Stefan Heun, Stefano Roddaro, Giorgio Biasiol, Lucia Sorba, Davide Venturelli, Fabio Taddei, Vittorio Giovannetti, and Fabio Beltram: Imaging backscattering through impurity-induced antidots in quantum Hall constrictions, arXiv:1209.2438 [cond-mat.mes-hall].
  2. Nicola Paradiso, Stefan Heun, Stefano Roddaro, Giorgio Biasiol, Lucia Sorba, Davide Venturelli, Fabio Taddei, Vittorio Giovannetti, and Fabio Beltram: Imaging backscattering through impurity-induced antidots in quantum Hall constrictions, Phys. Rev. B 86, 085326 (2012).